Preparation and management of mass-participation endurance sporting events

INTRODUCTION — Mass-participation endurance sporting events have grown in popularity and number over the past several decades. These events vary widely, ranging from small-scale, local, 5-km run-walks whose participants are primarily recreational athletes and non-athletes to major international marathon and triathlon events with professional participants. Local clinicians may be called upon to help organize medical operations for such an event or to provide medical care during the event.

This topic will review mass-participation endurance sporting events from a medical perspective, including discussions of what injuries to anticipate and how to organize and equip medical facilities. Management of the endurance athlete who collapses is discussed separately. (See "Evaluation of the collapsed adult athlete".)

TERMINOLOGY — A mass-participation endurance sporting event can be loosely defined as any endurance competition that has the potential to generate a significant number of casualties due to the large number of participants or the potential injury risk [1,2]. A mass gathering is an organized event with over 1000 people at a given place and time [3], although a smaller-size event with high medical encounter rates would require similar strategies for providing medical care.

The "classic" mass-participation event is a running road race of 5 to 42 km (3 to 26 miles), which places participants at risk for a number of medical conditions, including sudden cardiac arrest (SCA), exertional heat stroke (EHS), exercise-associated hyponatremia (EAH), and exercise-associated collapse (EAC), where the number of affected runners could potentially overwhelm local emergency response systems. Other activities like ultra-marathons in remote environments, open-water swimming, triathlons, cross-country skiing, and bicycling races present similar problems for medical care, with some variation in the most likely medical conditions due to differences in the environment and nature of the race (eg, remote locations, cold weather, water exposure, and higher-speed collisions).

Alternative events such as obstacle course races (eg, Tough Mudder, Warrior Dash, Spartan Race, and Rugged Maniac) present additional medical challenges, such as injuries sustained from obstacles, less-trained participants, fire, and alcohol ingestion. Large youth tournaments for football (soccer) and other sports with simultaneous games played on 20 to 50 pitches, Special Olympics events with 5000-plus participants at multiple sites, and Paralympic competitions can also be viewed as mass-participation events with unique medical challenges for medical teams. The details of managing such alternative events will not be discussed here, but the general concepts for managing such events apply.

EPIDEMIOLOGY

General epidemiology of medical encounters — Factors that influence the number of medical encounters at a mass-participation endurance sporting event include (table 1):

●Weather (abnormally hot and humid or cold and damp weather increases encounters)

●Participant acclimatization (eg, heat and humidity, altitude)

●Event type (more strenuous races increase encounters)

●Distance and pace of race

●Participant health and fitness

●Safety preparations (eg, hydration strategies, medical triage, course evacuation)

A substantial percentage of race entrants ultimately do not participate due to acute illness, other medical conditions, or for other reasons. Based on the author's experience at Twin Cities in Motion (Minneapolis-St. Paul, US), it is common for 24 percent of marathon entrants, 10 percent of half-marathon entrants, and 12 percent of 10-mile (16-km) entrants not to arrive at the starting line due to intervening medical conditions, life events, or inclement weather. Up to 25 percent of entrants do not present to the starting line at the New York City Marathon [4]. Shorter races tend to have a lower percentage of no-shows.

Weather is a major factor in the number of medical casualties during endurance races [5-7]. In general, the higher the wet-bulb globe temperature (WBGT, an indicator of combined ambient temperature, radiant heat, and humidity), the greater the number of medical encounters, race dropouts (before and during the race), and cases of exertional heat stroke (EHS) and exercise-associated hyponatremia (EAH). This is especially true for participants who are not well acclimatized. On average, the number of starters who do not finish plus the number of medical encounters per 1000 finishers at the Twin Cities Marathon rises from the 40 to 60 range in cool conditions (start WBGT 30 to 55°F) to 160 in warmer conditions (start WBGT 72°F) [5]. (See "Exertional heat illness in adolescents and adults: Management and prevention" and "Exertional heat illness in adolescents and adults: Epidemiology, thermoregulation, risk factors, and diagnosis" and "Exercise-associated hyponatremia".)

Hot weather increases medical encounter rates and reduces the percent of starters who finish (at Twin Cities marathon, the usual 97 percent finish rate dropped to 89 percent during the hottest year) [8]. In a "hot" year, some marathons have 10 percent finish-area casualty rates [9]. In 2014, with a high temperature of 70°F (21°C), the Boston Marathon medical team had 3762 finish-area medical tent encounters during and after the race, which involved 34,208 starters and 31,805 finishers (11.8 percent of finishers required medical care, and only 93 percent of starters finished) [10]. Twenty racers required hospital admission. The day was "hot" compared with the weeks and days leading up to the event. In the fall of 2017, the Army 10-mile race held on an unseasonably hot day in October had 32 EHS victims and so many medical encounters that the area emergency medical services (EMS) system went to mass casualty status, initiating an area-wide mutual aid request to service the race and the community.

Medical conditions encountered at finish areas are relatively well defined [7,11]. Marathon finish-line encounter rates vary from 1 to 6 percent of finishers, with an average of 2 percent at the Twin Cities Marathon [12] and Houston Marathons [13]. At the 21- and 56-km distances, 0.54 and 13 percent of starters, respectively, require some level of medical management, according to a four-year prospective study of two races run on the same day and location [14]. A comparison of 10- and 21-km Singapore races over three years showed a greater likelihood of casualties in the longer-distance races, with a medical encounter rate of 1.6 to 2.6 per 1000 participants [15]. The United States Army Ten-Miler (16 km race) has 3.8 medical encounters per 1000 starters [16]. A six-year review of three Boston-area 10-km races reported 6.2 medical encounters per 1000 finishers (total of 19 races and 90,265 finishers), with heat-related illness (1.6 per 1000 finishers), musculoskeletal complaints (1.3 per 1000 finishers), and fluid–electrolyte imbalances (1.2 per 1000 finishers) the most common reasons for evaluation [17].

As expected, more extreme endurance events have higher casualty rates [18-20]. In a seven-day, 250-km, desert-based running race, 85 percent of the participants required some form of medical care, although 95 percent of the encounters were considered minor and were mainly skin related [18]. The medical encounter rate for the Ironman Triathlon (225 km total distance) is approximately 15 to 35 per 1000 finishers. Between 1995 and 2014, 13 to 21 per 1000 finishers of the Kona Ironman field have required medical assistance. Triathlon medical encounters at the Sprint, Olympic, and Fun race distances (≤5 km) are lower, at 2 to 3 per 1000 participants [19]. In a 55-km cross-county ski race, about 5 percent of finishers require assistance, and the same is true for cycling races across varying distances.

Obstacle races, such as Tough Mudder, Spartan Race, Warrior Dash, and others, are growing in popularity. These races incorporate obstacles and physical challenges along the running course that increase the risk for injury compared with traditional running road races. Data are limited, but the hospital transport rate from these events is in the range of 1 to 2 per 1000 participants [21,22].

Sudden cardiac arrest and mortality — Event-related deaths are relatively uncommon but usually due to sudden cardiac arrest (SCA), EHS, or EAH [7]. Drowning at triathlons may occur but is even less common. Participants with EHS or EAH can recover without sequelae if the condition is recognized and treated immediately. SCA occurs in races of all types and distances, and outcomes are better if an emergency action plan (EAP) is in place and both immediate, high-quality cardiopulmonary resuscitation (CPR) and early defibrillation are provided. The emergence of portable, easily applied automatic external defibrillators (AEDs) has improved the risk profile for participants of mass sporting events [23].

Of the potentially lethal events mentioned, SCA during marathons is the best studied. According to three studies, the rate of marathon-related SCA ranges from 1.01 to 2.6 per 100,000 finishers, while mortality rates range from 0.63 to 1.3 per 100,000 finishers [24-26]. A study using the London Marathon database reported that coronary artery disease and hypertrophic cardiomyopathy are the major causes [27]. A long-term study of two marathons (1982 through 2009 with approximately 600,000 finishers) tracking SCA with and without successful resuscitation reported 14 episodes of SCA with seven deaths (six men and one woman), yielding a rate of 3.4 of 100,000 in men and 0.6 of 100,000 in women [25]. The relative risk for men compared with women was 5.7 for SCA and 2.7 for death. The 2006 to 2012 Paris registry on acute cardiovascular events (RACE Paris registry) for half- and full-marathon races identified 17 SCAs (two fatal) in 511,880 runners, and 13 occurred in experienced male runners. Initial shockable rhythm compared with non-shockable rhythm (odds ratio [OR] 29.9, 95% CI 4.0-222.5) or nonischemic etiology (OR 6.4, 95% CI 1.4-28.8) was associated with survival [28]. Japanese researchers reported similar outcomes over 15 years, with SCA rates of 2.0 and 2.5 per 100,000 participants for the marathon and half marathon, respectively [29]. About half of the 63 participants with cardiac arrest survived. Although SCA occurs most often near the finish line, it may occur anywhere along the course [24,25,28].

The incidence of SCA during triathlons appears to be similar to marathons. According to a study of United States triathlon participants from 1985 through 2016 (approximately 4.8 million athletes), 1.74 fatal SCA events occur for every 100,000 participants [30]. Of the 135 cases of SCA reported, two-thirds (n = 90) occurred during the swimming competition. Most cases involved men (n = 78). Autopsy results were available for 61 victims, and most had some form of cardiovascular disease. Ten deaths occurred during the bicycle portion of the race from collisions with motor vehicles.

While SCA is the most discussed life-threatening medical event during marathons and comparable endurance races, EHS is more prevalent by a factor of ten in warmer conditions, according to several reports, including a seven-year retrospective study of endurance races in Tel Aviv, Israel [31]. The author's experience with the Twin Cities Marathon over 35 years supports this observation.

Medical encounters according to event type — The injuries and medical conditions that occur during mass-participation endurance sporting events vary by activity. The medical issues most often encountered fall into three basic categories: medical, musculoskeletal, and dermatologic (table 1) [7]. The most serious medical problems encountered include SCA, acute coronary syndrome, EHS, EAH, anaphylaxis, and insulin reaction (acute hypoglycemia). (See "Advanced cardiac life support (ACLS) in adults" and "Initial evaluation and management of suspected acute coronary syndrome (myocardial infarction, unstable angina) in the emergency department" and "Exertional heat illness in adolescents and adults: Management and prevention" and "Anaphylaxis: Emergency treatment" and "Anaphylaxis: Acute diagnosis" and "Hypoglycemia in adults with diabetes mellitus".)

The most common medical condition encountered during an endurance sporting event is exercise-associated collapse (EAC), also known as exercise-associated postural hypotension (EAPH), which is usually self-limited and benign [14,32,33]. EAC accounted for 60 percent of total medical encounters and 90 percent of encounters unrelated to musculoskeletal or skin issues at the Twin Cities Marathon from 1983 to 1994, and it continues to be the leading cause for evaluation in the finish-line medical tent. If widely adopted, international consensus statements about definitions and recording strategies for medical events during endurance events should improve our understanding of such encounters during races [34]. (See "Evaluation of the collapsed adult athlete".)

As one would expect, exertional heat illness is relatively common during any type of endurance event conducted in warm, humid conditions. In an analysis of nearly 100,000 finishers of 10-km races, roughly 600 medical encounters occurred, and about 25 percent were heat-related, most occurring among racers in the top and bottom quintiles [17]. The wet bulb globe temperature (WBGT) during these races ranged from 16.1 to 24.7°C. Ninety-four finishers with exertional heat stroke required ice water tub immersion for onsite cooling, but no cardiac arrests or deaths occurred.

In a three-year study of a 109-km, community-based bicycle tour with just over 102,000 starters and WBGTs ranging from 12 to 20°C, 50 life-threatening medical encounters per 100,000 participants were reported (22 trauma and 28 illness related), including three cardiac arrests and one death [35]. Approximately 500 serious medical encounters occurred per 100,000 participants, mostly related to dehydration, and just over 300 injury-related encounters occurred per 100,000 participants.

Most musculoskeletal injuries sustained during endurance events involve acute sprains and strains of muscles, tendons, and ligaments. Occasionally, chronic conditions such as stress fractures and overuse tendinopathies are exacerbated and manifest during an endurance race. Completed stress fractures can develop during a race and become unstable, requiring transport for care. While most musculoskeletal issues that arise during running-based races are predictable, obstacle races or races involving higher-velocity activities, such as bicycling, in-line skating, and Nordic skiing, may involve more severe trauma-related injuries (eg, fractures) from falls and collisions. High-speed collisions may also cause internal injury, including possibly intracranial hemorrhage and concussion. Collisions between participants and motor vehicles can occur, causing serious injuries or death [30]. (See "Initial management of trauma in adults" and "Running injuries of the lower extremities: Risk factors and prevention" and "Overview of stress fractures" and "Sideline evaluation of concussion" and "Acute mild traumatic brain injury (concussion) in adults".)

Skin-related problems during endurance sporting events consist mainly of blisters and abrasions. Trauma during higher-velocity activities can cause deep abrasions.

MEDICAL PLANNING

Key concepts and tasks — Medical coverage for a mass-participation event can be approached as a "planned disaster" (and used as a mass-casualty incident drill by the community emergency response system) [36]. The number and type of medical conditions and injuries likely to be encountered during the "disaster" can estimated based on the type of event (eg, running, bicycling, swimming, multi-activity [triathlon], obstacle course), number of participants, location, and expected weather conditions. Organizations like World Athletics Endurance Medicine have developed race management training materials and a race medicine handbook that can assist planners (table 2 and table 3). (See 'General epidemiology of medical encounters' above.)

Key concepts for the medical team and race administration planning the medical management of a mass-participation endurance sporting event include the following:

●Be aware of and plan for the potentially catastrophic risks to participants. Important conditions to consider include sudden cardiac arrest (SCA), exertional heat stroke (EHS), exercise-associated hyponatremia (EAH), high-speed collision, and drowning. (See 'Serious and common medical conditions encountered during endurance events' below.)

●Be aware of and plan for the common medical problems likely to require care at medical aid stations. Ensure that adequate personnel and resources are available to manage these conditions.

●Coordinate with community emergency medicine leaders and organizations. Notifying area hospitals long in advance allows them time to increase staffing on race day to accommodate anticipated increases in patient volume. Local emergency medical services (EMS) systems must be prepared to transport casualties from the course, and the logistics for such transport must be prepared in advance. Such planning is more complex in remote areas [37]. (See 'Integrating area emergency medical services and hospitals' below.)

●Develop or adopt standardized medical management protocols for common and important medical conditions likely to occur. Educate all medical personnel, local emergency clinicians, and race volunteers so all are using the same protocols and have the same expectations. (See 'Medical management protocols' below and 'Serious and common medical conditions encountered during endurance events' below.)

Well prior to the event, the medical team and race administration must create an event management document that establishes how important issues and potential problems will be handled. The following table provides a general timeline for developing the race medical safety and management plan (table 2). The event management document should address three general areas:

●Strategies and plans for race safety and injury reduction (see 'Race safety and injury reduction strategies' below)

●Survey of the race course, with an emergency action plan for events that occur anywhere along the course (see 'Course survey and emergency action plan' below)

●Medical protocols to standardize care for anticipated common and serious medical conditions (see 'Medical management protocols' below and 'Serious and common medical conditions encountered during endurance events' below)

Medical management protocols — In advance of a mass-participation endurance sporting event, the medical director and key members of the medical team should adapt or create medical management protocols for the serious and common medical problems most likely to be confronted. These medical conditions are discussed below, and sample protocols for select conditions are provided. Using medical protocol algorithms to standardize evaluation and treatment makes the delivery of care more efficient and improves outcomes. Sample medical management protocols from the Marine Corps Marathon can be found here (Marine Corps Marathon protocols). (See 'Serious and common medical conditions encountered during endurance events' below.)

All clinicians who will be providing direct care during the race should be educated about the management protocols in advance of the race. This can be accomplished during medical team meetings and with written materials or web-based modules.

Race safety and injury reduction strategies — Participant safety can be improved with appropriate scheduling and review. Races during cooler weather and with start times closer to sunrise reduce the heat load. Nordic ski races are best started early enough in the day to allow racers to complete the course prior to sunset unless the course has lighting. Course time limits should reflect the risks associated with ski racing in low-light or dark conditions. At triathlons, the number of swimmers entering the water at any time should be limited so participants who are struggling can be identified more easily, closely monitored, and extracted from the water if necessary [30]. Safety issues related to the course itself are discussed below. (See 'Course survey and emergency action plan' below.)

In most instances, individual pre-event screening to ensure adequate health and fitness to participate in an endurance race is the responsibility of the participant. Formal preparticipation evaluations are cumbersome for large events, and participants are expected to review and monitor their health status with their personal clinicians as needed. However, medical directors can request that important medical information be listed on the reverse side of the competitor's number sheet (ie, "bib") or in a computer-based medical information "app" accessible on race day to assist emergency medical personnel. Commonly listed information includes medications, drug allergies, and expected race day weight. Computer-based medical information "apps" that allow race medical personnel to access important participant health information are available and may supplant the "back of the bib" approach because they provide better information while maintaining confidentiality.

Some smaller, relatively high-risk events, such as back-country or ultra-distance races, require participants to be evaluated by a clinician at some specified interval prior to race day, but there are no standardized requirements. Recommendations for wilderness events and ultramarathons based on participant numbers and geography have been published [38,39]. Researchers have studied the Two Oceans Races (21 and 56 km) in South Africa and its process of embedding cardiac screening questions in the race application [14,40]. Positive responses from prospective participants to questions about chest pain or pressure, syncope, or other cardiovascular symptoms and signs trigger emails with additional inquiries. Over the four-year study, there was an increase in the number of applicants who chose not to participate in these races. In the weeks leading up to the event, race administrators also screened for recent illness using "neck check" questions (symptoms isolated above the neck such as nonproductive cough are considered acceptable; symptoms below the neck or systemic symptoms such as fever are considered unacceptable for participation). The rate of medical encounters decreased during the study period compared with the previous four years, suggesting the program was effective in reducing casualties [14].

Course survey and emergency action plan — The medical team should prepare a detailed map of the race course, with high-risk areas (areas where casualties are more likely) clearly marked for medical personnel and first responders. The map should include all the locations of medical aid stations and first aid sites. Entry and exit routes for EMS to the aid stations should be clearly delineated. In addition, the review should include any sites where there is a risk of automobile traffic intruding onto the course. Rail crossings should be noted and train schedules confirmed so as not to conflict with race times.

Race courses that include remote or wilderness areas (eg, Western States 100, American Birkebeiner ski race, Patagonian Expedition Race) present added logistical difficulties should a participant require emergency medical transfer [37,41]. Specific plans for such transfer must be arranged in advance. In rare instances, organizers may warn about the risk of wild animals and possible management strategies (eg, bear spray for the Le Grizz ultra marathon).

Rapid response to life-threating problems is critical, and mobile teams of clinicians or first responders can decrease the time to evaluation or defibrillation and cardiopulmonary resuscitation (CPR) if needed. The communications team is critical to successful dispatch of mobile units on bicycle, motorcycle, or motorized (golf) cart for rapid response to medical emergencies along the course. At the Twin Cities Marathon, we use the area Mountain Bike Patrol to form mobile teams of two to three members carrying an automatic external defibrillator (AED) and connected by radio to our communications center. Five to six teams are initially spaced 2 miles apart and move along the course, with the last team traveling just ahead of the course-closing team. The teams stop at aid stations, and all the teams advance as the stations close along the course. This puts an AED within a mile of every participant and within a half mile as slower finishers complete the course.

Placement of aid stations and AEDs — Medical aid stations are designated as either "major" or "minor" care sites based on their resources and capacity. Major care sites are typically located in the finish area and sometimes along the course at areas known to have higher casualty rates or limited access.

●Major care sites provide full medical care for the conditions anticipated at the event and possess the capacity to transfer participants with serious conditions beyond the available scope of care to the local EMS.

●Minor care stations are located along the course, usually in association with fluid stations, and provide first aid, shelter, and some basic emergency interventions for participants with more serious conditions awaiting transfer to the EMS system.

Medical aid stations should generally be placed downstream from fluid stations and are best spaced at 3 to 5 km intervals along a marathon running course, or about 20 to 30 minutes apart for other races based on the speed of average participants (a typical recreational runner averages about 8 to 10 km/hour, or 5 to 6 miles/hour) [42]. As another example, the average in-line skate race speed is about 21 km/hour (13 miles/hour), so fluid stations would be spaced every 7 to 10 km along the course.

Large marathon races (>20,000 starters) often place fluid and medical aid stations every mile to improve access; however, that strategy may increase the incidence of EAH. For instance, at the Houston Marathon 30, water stations were placed along the course and several cases of severe hyponatremia were reported over a three-year period. After cutting the number of fluid stations in half, no cases occurred. (See "Exercise-associated hyponatremia".)

Standard recommendations call for even distribution of fluid and aid stations, but some races (generally longer races such as marathons) distribute more stations over the final third or quarter of the course. At one relatively smaller marathon (up to 5000 racers), medical aid stations were distributed at miles: 5 (8 km), 10 (16 km), 15 (24 km), 19 (31 km), 22 (35 km), 24 (39 km), and the finish line (major medical station). There is no high-quality evidence that such increased distribution improves race safety. Based on individual race experience, fewer fluid and aid stations or changes in the distribution of stations may be needed. Stationary aid stations do little to reduce emergency response times and are used in part as drop-out points for participants who cannot continue. In events involving obstacles with the potential to cause injury, medical aid stations may be located near the areas of highest risk to speed access to care.

The location and staffing of major and minor medical stations often evolves over years as race directors and medical staff learn about the course and participant trends. Initial placement may follow the standard recommendations described above but change as the character of the race becomes clearer with experience. Available medical care at the starting line is generally limited to a response team for SCA, with an automated external defibrillator (AED), and an information station for medical advice. Staffing for minor aid stations varies, but training in CPR and first aid is all that is required for most personnel. (See 'Composition of the on-site medical team' below and 'Determining medical personnel needs based on environment and event' below.)

Medical teams for races whose participants will be at higher risk for EHS (eg, hot, humid conditions) may need to integrate whole-body cooling strategies into medical protocols, which may include placing cooling tubs at course aid stations, as immediate cooling can be lifesaving. Placing aid stations in close proximity to fluid stations makes it easier for medical personnel to obtain water and ice to fill tubs. (See "Exertional heat illness in adolescents and adults: Management and prevention" and "Exertional heat illness in adolescents and adults: Epidemiology, thermoregulation, risk factors, and diagnosis".)

Ideally, AEDs are available at all aid stations, but this may not be feasible. The accessibility of AEDs can be increased if they are mobile, using bicycles, motorcycles, or golf carts for transport. SCA can occur at any point along the course and has been documented at nearly every mile of a marathon, although most occur in the last quartile and finish area [24]. AEDs that are mobile, as opposed to stationary, have greater range and effectiveness [43]. If there is only one AED available, placing it with a mobile team paced to the middle of the pack would likely be the most effective strategy. (See "Automated external defibrillators".)

Integrating area emergency medical services and hospitals — The event team responsible for emergency medical planning should include a senior representative from local EMS. Ready access to the course and aid stations for EMS vehicles and staff is critical for emergency transport to the nearest or designated emergency medical facility. At a minimum, area medical facilities and their emergency medicine leadership should be notified of the event, dates and times, expected casualty numbers and types, and race protocols. Notification allows these facilities to increase their staffing and prepare needed equipment and supplies. The findings of a large retrospective study suggest that disruptions in emergency medical care during marathons in major cities can have adverse effects on ambulance transport times and overall patient mortality [44]. Careful planning and coordination with local EMS and hospitals is important to minimize disruptions to community medical care. The potential interruption to community medical services should be considered when creating the "do not start" policy [5].

Integrating local EMS directly into the race communications system effectively brings emergency responders and the local emergency department (ED) into the management team. In some systems, the race communications team becomes the dispatch for any race-related casualties. The process is more complicated when there are multiple hospitals in the race catchment area, but most EMS systems are adept at moving casualties to the appropriate site.

When event casualty numbers are large, the need for evaluation and advanced care affects the community emergency medical system, with potentially negative consequences for community members in need of care. Although relevant medical literature can be used to estimate potential casualties, prior data from the event itself provide the best guide for determining an event care plan. Integrating community resources appropriately into the care plan enables local EDs to continue to provide adequate medical care for the community and any event participants truly in need of advanced care. These "planned disasters" can be used as community disaster-training experiences for unanticipated events that may affect the community in the future [45].

SAFETY STRATEGIES FOR RACES DURING COVID-19 PANDEMIC OR COMPARABLE CIRCUMSTANCES — The global coronavirus disease 2019 (COVID-19) pandemic disrupted endurance mass-participations events, with cancellation or postponement of most major events during 2020 and 2021. Overall, the risk of transmission of COVID-19 or comparable illness during outdoor sporting events is low outside the starting pen, finish area, and medical tent [46]. Several strategies that may be used to improve safety for endurance athletes are summarized in the following table (table 4).

MEDICAL TEAM

Medical director — The medical director is a physician with an interest in the medical planning and medical conditions associated with mass-participation sporting events [1]. A background in sports medicine, family medicine, and/or emergency medicine provides a sound knowledge base for determining management protocols and staffing needs [1]. Management or administrative experience is helpful for organizing the medical team and managing finances. It is helpful for the medical director to work with an administrative coordinator with an allied health background who can fulfill many of the managerial functions, leaving the medical director to focus on medical protocols and safety issues.

The medical director must be a part of the race management decision-making process and should sit on the event's executive administration committee to ensure that all concerns related to participant safety and medical management are adequately addressed. The medical director is responsible for all major decisions affecting the medical plan and participant safety. In collaboration with the medical operations committee, the medical director is responsible for evaluating the event safety plan, developing race-day protocols for anticipated medical conditions, procuring needed supplies and equipment, and securing personnel to staff the race.

Medical operations committee — The medical operations committee or team works with the medical director to evaluate event safety plans, develop race-day protocols for anticipated medical conditions, procure needed supplies and equipment, and secure personnel to staff the race.

At Twin Cities in Motion, the medical operations committee is composed of coordinators representing the major areas of the medical team. Representatives from local emergency medical services (EMS) organizations, the emergency medicine residency, nurses, physical therapists and athletic trainers, ski and bicycle patrols, and communications specialists all assist with determining medical protocols, supplies, personnel staffing, and race-day assignments in addition to acting as area leaders on race day. Depending on the scale of the event, medical operations committees often extend beyond medical personnel and include public safety officers and, in some cases, representatives from law enforcement, public health, and homeland security, due in part to the soft-target terrorism status of large gatherings.

Should there be a natural or man-made disaster or some other occurrence that requires a community-wide response (eg, gas pipe explosion, major fire, large scale accident, bomb threat, bomb explosion), law enforcement officials assume control of the scene and may cancel or close the sporting event. The medical operations team may be integrated into the community disaster or adverse event plan. As an example, while the medical director may decide whether to cancel an event should unexpectedly hot or humid conditions increase race casualties or a lightning storm move into the area, the local police chief or Homeland Security director assumes leadership and control should an act of terrorism or some other incident occur that threatens the community.

Composition of the on-site medical team — The medical team for a mass sporting event should be interdisciplinary and span the full range of needed medical expertise, including clinicians capable of handling likely emergency medical conditions (eg, exertional heat stroke [EHS] and exercise-associated hyponatremia [EAH]), trauma, and musculoskeletal injury. Most teams include physicians, physicians in training (residents, medical students), clinician-extenders (physician assistants, nurse practitioners), athletic trainers, physical therapists, registered nurses (especially those with emergency department [ED] or intensive care experience), paramedics, emergency medical technicians (EMTs), and first aid providers. Establishing a medical team that can respond to worst-case casualty scenarios improves the safety profile for the participants and prevents some medical volunteers from providing care that extends beyond their medical training and license. Nonmedical volunteers can assist with tent maintenance, supply management, documentation, and other functions that do not require medical training.

Determining medical personnel needs based on environment and event — The number of medical personnel needed to cover a mass-participation endurance sporting event depends upon the number of entrants, the type of event and its duration, and the "surge" of participants at the finish area. The surge is when the largest group of runners arrives at the finish line, generally during the middle of the race.

Calculating the number of medical personnel needed for a new race is not an exact science. Most races have a major station at the finish area, and large races (eg, major city marathons) often have two or more major medical sites. The medical teams at the major medical tents often include clinicians with critical care training in addition to others with the skills needed to care for most other medical encounters. Staffing for minor aid stations varies, but training in cardiopulmonary resuscitation (CPR) and first aid is all that is required for most personnel. At a minimum, for marathon distances in good running conditions, one physician and two advanced response providers (eg, nurse, paramedic, medical resident) are needed for each aid station along the course, while two physicians and six advanced response providers are needed for every 1000 entrants to staff adequately the major medical station in place at the finish line.

Whenever possible, we use larger teams, especially for aid stations at the middle and later portions of the course. In addition, an automatic external defibrillator (AED)-equipped mobile (bicycle, motorcycle, or golf cart) team of EMTs is needed for every 1000 to 2000 entrants. Twice this minimum number of clinicians would likely be needed if conditions are hotter or more humid than seasonal norms, as caring for participants with exertional heat illness is time and personnel intensive (table 5 and table 6). Fewer personnel at the finish area may be adequate for shorter races, provided the participants are well trained and race day is not hot and humid.

The atmosphere at the finish area at the time of the surge can be challenging for clinicians trying to provide care to participants. Therefore, it is important to anticipate the surge time and prepare as best as possible. Surge times can vary by race and from year to year at the same event. Typically, the surge in medical encounters follows the surge in race finishers; data from similar races can help a medical director anticipate the timing of the surge for new events. As an example, the surge of medical encounters for the Twin Cities Marathon in the 1980s and 1990s was at the 3.5- to 4-hour mark, but in the last decade as finishing times have increased, the "surge" has drifted to the 4.5- to 5-hour mark.

The location and staffing of major and minor medical stations often evolve over years as race directors and medical staff learn about the course and participant trends. Initial placement may follow the standard recommendations described above but change as the character of the race becomes clearer with experience. Available medical care at the starting line is generally limited to a response team with an AED for treatment of sudden cardiac arrest (SCA) and an information station. (See 'Placement of aid stations and AEDs' above.)

Volunteers assisting with medical care — The number of volunteers (ie, not advanced medical practitioners) needed to assist with medical care at an event must be estimated unless race data are available to assist with decision-making. As a general guideline, minimum teams of two to three should be present at each medical aid station so effective CPR can be performed until additional help arrives. Under adverse conditions (eg, high temperature and humidity), the number of volunteers should be at least double the minimum. In addition to volunteers with some level of medical training, a group of volunteers who need not have medical expertise should be present at the finish line to assist finishers and keep them walking in order to prevent post-exercise collapse. The shift length for volunteers should range from four to six hours, as longer shifts lead to fatigue and attrition. (See 'Exercise-associated postural hypotension' below.)

As a case study, the author and his colleagues at the Twin Cities in Motion event manage two races simultaneously: a 10-mile (16 km) race starting at 7:00 AM and a marathon starting at 8:00 AM. These race courses join for the last 6 miles. As participation in the 10-mile event has grown, medical staffing needs have changed, requiring more volunteers to staff the latter part of the marathon course, which doubles as the second half of the 10-mile race. Finishers for the 10-mile race begin arriving at approximately 8:00 AM, while marathon finishers begin arriving at around 10:10 AM. In order to keep the finish area and the 19- through 26-mile aid stations open from the early morning until 2:30 PM, we have had to increase the time commitment for volunteers from four to six hours to six to eight hours. To keep the aid stations and finish area adequately staffed, we are experimenting with a shift model to rotate fresh volunteers into these areas, thereby reducing the total shift time commitment for all volunteers. On race day, we require just over 300 volunteers for 16,000 to 19,000 finishers (16 to 19 volunteers per 1000 finishers), with an additional 50 volunteers on our communications team (table 6).

Medical volunteers should be readily identifiable to participants and other nonmedical race volunteers. A distinctive t-shirt works well in mild weather. At the Twin Cities Marathon, where start temperatures have ranged from -4 to 22°C (24 to 72°F), volunteers are identified by orange vests with interchangeable panels that indicate the person's role (eg, EMS, triage, physician, nurse) (picture 1). Such vests are easily identified and can be worn over heavy apparel during cold or poor weather conditions, and they are reusable. An event t-shirt can be used to identify volunteers and may be kept as a souvenir. Volunteers in the medical tent at the Twin Cities Marathon are identified by different-colored vests: orange for team leaders, yellow for physical therapists, and blue for youth volunteers. Members of teams that care for cardiac arrest patients wear vests printed with "MD" or "RN" to distinguish them from other finish-area medical volunteers.

Scope of practice for the medical team — The scope of care to be provided by the medical team should be decided well in advance of any mass-participation endurance event. The potential range of care varies widely among races depending upon their size, location, and available resources. Some medical teams limit the care provided to basic first aid and transfer all other problems to local clinics and hospitals (note: these facilities should be notified of the race months in advance), while others provide comprehensive on-site care for serious medical problems commonly encountered at races, such as EHS and EAH. (See 'Serious and common medical conditions encountered during endurance events' below.)

When necessary resources and personnel with appropriate clinical expertise are available on site, outcomes are better for participants with conditions requiring immediate intervention, such as cardiac arrest, EHS, and EAH. On-site care also reduces the burden for local ED. Regardless of the resources available on site, some participants may require transport to the ED. In such cases, the medical director should be notified immediately to prepare for family and media inquiries.

The medical team and event administrators must assess carefully the capacity of local emergency medical facilities and their willingness to provide advanced field care for participants before finalizing any medical care protocols. Limiting factors for the transfer of care to local EDs, clinics, and hospitals include:

●Number of ambulances available for transport (taking into account community baseline needs)

●Number of ED beds and staffing levels

●Distance and transport time to the facility from course aid stations and primary medical station (finish line)

Medicolegal considerations — Medicolegal considerations vary by locale. A knowledgeable member or members of the event team should investigate relevant statutes and provide the medical team with their appraisal of the local medicolegal climate, which should provide peace of mind and enable clinicians to perform their duties without fear of legal repercussion. Medical liability is likely comparable to that of the medical office setting, as the medical plan is beyond most "Good Samaritan" statutes that involve unplanned emergency medical interventions. Race-day liability policies are available to cover the medical activities on behalf of clinicians. Some group malpractice policies cover an individual clinician outside the office or hospital for volunteer event coverage but require advance notification and approval. It is best to delineate the process clearly for each clinician. Many races in the United States now provide race-day medical liability coverage, which has helped with clinician recruitment.

EQUIPMENT, SUPPLIES, AND COMMUNICATIONS

Determining medical equipment and medication needs based on environment and event — Necessary medical equipment and supplies are determined based upon the number and type of casualties typical for a given event. Weather conditions are an important factor in determining supply needs, with more cooling materials needed on hot days and warming materials for cold days [47]. Necessary items include the following:

●Furniture and related amenities: Cots, drape partitions, tables, chairs, lights, heaters or fans, blankets, towels

●General equipment and material: Tubs for ice baths, microwaves for heating blankets, ice chest for ice and water, easily accessed and plentiful water supply

●Medical equipment: Automated external defibrillators (AEDs), medications, intravenous (IV) fluids, airway equipment, rectal thermometers, apparatus for measuring vital signs (sphygmomanometer and cuffs, pulse oximeter), bandages, tape, slings, crutches

●General supplies: Drinks, snacks, sanitary pads, contact lens solutions and containers

More comprehensive lists of supplies that may be needed are found in the following tables (table 7 and table 8).

Shelter for the primary medical station — Some form of shelter for the medical treatment site is needed in case of inclement weather and to provide privacy for injured participants during evaluation and treatment. The main medical facility should be located downstream from the flow of runners to the finish line and near an ambulance access site. Ideally, there should be a direct path of transport from the finish line area to the main medical station. Guidance for the organization of the main medical station is provided in the table (table 9).

The area of the shelter is determined by the season, size of the event, and the anticipated number of participants seeking care (ideally based upon data from prior races at the same event). Buildings near the finish line work well, but few events are situated near adequately sized, available facilities capable of housing all casualties and a large medical team.

At the Twin Cities Marathon, which has about 9000 starters and 8500 finishers, we use a 40 by 80 foot (12 by 24 m) treatment tent (picture 2) with a 10 by 30 foot (3 by 9 m) extension that serves as an entryway for runner check-in and check-out. The extension also serves as a communications tent for about 9000 marathon runners finishing between 10:10 AM and 2:15 PM and 9000 10-mile runners finishing between 8:00 AM and 10:00 AM. The 10-mile (16 km) race has few encounters, which could likely be accommodated in a 20 by 30 foot (6 by 9 m) tent. The Boston Marathon uses three large tents spread along six city blocks at the finish area to provide for runners in distress. Located near the entry to the main medical area at the Twin Cities Marathon is a 10 by 10 foot (3 by 3 m) self-help tent where runners can obtain simple self-care items like adhesive bandages and ice. Another small tent serves as our on-site central command station. (See 'Communications center' below.)

The interior of the medical tents used for the Twin Cities Marathon is shown in the accompanying photographs (picture 2). Care teams 1 through 10 each have four cots. Lighting is high intensity so clinicians can assess runners' skin color and other signs of perfusion. Supply tables are centrally located, and draping is used to block patient areas from storage. Draping is also used to cordon off the critical-care area.

Security — Physical barriers that limit access to the medical area are essential and should be incorporated into the secure finish-area plan. Security is improved when law enforcement personnel man the entrances and exits. Many races have enlisted local law enforcement agencies to police the race start and finish areas for potential threats to safety. For major races, direct race-day communication and continual close coordination with law enforcement is critical.

To reduce the number of spectators at the security entrances, the Twin Cities Marathon added a family waiting tent within the medical area that can be accessed without entering the secured medical area. The family area is connected to the medical check-in system to help families locate their "downed" or lost runners. A designated space gives relatives and friends a place to gather and wait for the runner to be released from the medical tent and a meeting place when discharge occurs. Except for rare circumstances, family members are not allowed in the medical treatment area to preserve privacy and confidentiality for other runners and to reduce the chances of inadvertent exposures to blood-borne pathogens.

Communication systems — An effective communications system that encompasses the entire event course is essential for medical management on race day. A back-up system is crucial should the primary system fail. Some combination of cell phones, handheld radios, and ham radios allows for rapid communication. Radio communications may not be confidential. (See 'What communications systems work best in a race environment?' below.)

Communications center — It is helpful to house the medical director and event administration leaders in the same location as the race communications hub (so-called Race Incident Command Center). This allows all leaders to monitor the event communications network continuously and enables critical information to reach key decision-makers quickly in the case of a disaster or some other problem requiring that the event be modified (eg, course change). Medical record "apps" for mobile smart phones that incorporate global positioning system (GPS) signals have the capacity to record medical encounters in real time and map the location of each incident. Twin Cities in Motion uses the RaceSafe (SportzPeak) app for medical records, race and family communication, and GPS location. The app has allowed us to transition from paper to electronic medical data collection. Other apps are being developed. A dedicated phone line or text message system that includes the medical director, head of safety, emergency medical technician (EMT) coordinator, and race director can speed emergency communication among race administrators. (See 'What communications systems work best in a race environment?' below.)

What communications systems work best in a race environment? — Mobile phones and text messaging work well for race communications among members of the medical team, provided battery life is longer than the event and the mobile phone network functions normally. Mobile phones are generally more private than other types of radio communications, allowing confidential medical information to be shared by voice or text message. While cell phones have become ubiquitous, mobile phone networks are often the first to become inoperable in an emergency situation, especially if a bombing or bomb threat occurs. The phone system may be shut down intentionally by public safety officials or unintentionally by the sheer volume of calls.

A dedicated ham radio network can be used for general communication or as a backup to mobile phones. While a reliable backup, handheld radio and ham radio systems are not as secure as mobile phones for transmitting confidential medical information. Radio frequencies are easily monitored by reporters and others. In addition, a ham network can be silenced by local law enforcement if necessary for security reasons. Handheld radios can be used for on-course and finish-area communications and can be tied into the emergency medical and law enforcement systems. These devices can be monitored by others, so they are not ideal for confidential communications regarding downed participants and are subject to battery life limits.

An increasingly common medical communication tool involves the use of "apps" for mobile phones and tablets. These can be connected with GPS to determine the location of medical personnel and casualties in real time while simultaneously recording such data and relevant medical information. When used on a mobile phone, such apps can be used to connect to race command, emergency medical services (EMS) dispatch, and a participant's emergency contact. In addition, these apps can be used by participants to record their personal medical data, including chronic health issues, medications, allergies, and usual training or pre-race weight. This information is invaluable to clinicians managing acute medical problems. Traditionally, such information has been collected on the back of competition bibs, when provided at all.

A dedicated, race-wide emergency phone number is useful. This number can be distributed to all volunteers, enabling anyone to report a medical incident.

In the event of race cancelations, delays, course changes, or disasters of some type, officials can use text messaging, email, and/or websites to relay information to key decision-makers, volunteers, and competitors. These networks can be announced to volunteers and participants in advance. Race registration software systems often have this function embedded in the program. Announcements about clothing, hydration, course risks, thermal stress, and locations of medical aid and fluid stations can also be made using such networks. Just prior to the start of the race, traditional public address systems may be used to make announcements about weather conditions or special precautions.

Cancellations immediately prior to or during an event are often signaled with a combination of coded flags (black flag indicates cancellation) and announcements over available public address systems, including megaphones in law enforcement vehicles. If cancellation becomes necessary, it is best to do so before the start of a race whenever possible.

Providing fluids to participants — Particularly during hot weather and longer races, it is important to provide appropriate fluids to participants along the race course to help them maintain reasonable hydration. For events that last 60 to 80 minutes for the slowest runners (10K), one water stop at the mid-point or two waters stops one-third and two-thirds of the course should be adequate. Most long races have water stops every 3 to 5 km, although large events may place fluid stations at more frequent (1.5 km) intervals to improve access. Educating runners to avoid overhydration is critical, particularly for longer races. Overhydration may lead to life-threatening dilutional hyponatremia. Participants in running races of 5 to 10 km or shorter who begin the race well hydrated may not require any fluid, unless they have a high sweat rate or conditions are hotter and more humid than usual. The risk factors, prevention, and treatment of exercise-associated hyponatremia (EAH) are reviewed in detail separately. (See "Exercise-associated hyponatremia".)

Determining an individual’s fluid needs and fluid recommendations for participants — Fluid losses during activity vary by sweat rate [48-50], which ranges from 400 mL/hour to >2500 mL/hour, making universal recommendations impossible [51,52]. The sodium concentration of sweat also varies among individuals. In addition to individual variation, sweating rates fluctuate with the environment and other factors. In general, hot and humid conditions increase sweating, but the acclimatization level of the participant, running pace, and level of exertion all affect the sweating rate. Thus, fluid requirements of runners are affected by the interplay among all these variables. To stay safely hydrated during prolonged activity, an athlete should consume enough fluid to replace most sweat losses but must avoid excessive fluid intake [42,53]. (See "Exercise-associated hyponatremia", section on 'Pathogenesis'.)

While either under- or overhydration during endurance activity can cause problems, overhydration combined with paradoxical nonosmotic stimulation of vasopressin (antidiuretic hormone) release (triggered by exercise, heat, or stress) can lead to fatal hyponatremia. Therefore, runners and medical volunteers must be educated about appropriate fluid replacement. Such education includes fluid-replacement strategies and calculating sweat fluid losses. Ideally, for longer races, several assessments of a participant's sweat rate should be performed under the environmental conditions anticipated for the race and at varying exercise intensities wearing race togs (ie, racing clothes). These calculations are used to develop an individualized fluid-replacement plan.

For competitors who have not developed an individualized plan, drinking to thirst or ad libitum (especially for slow runners) is probably the safest strategy to avoid both dehydration and EAH. For elite and high-level athletes striving for maximal performance, thirst may be delayed, and using a "drink when thirsty" strategy may compromise performance, but elite runners tend to tolerate some dehydration during races and often forgo maximal fluid replacement [54]. Appropriate fluid intake for the prevention of EAH is reviewed in detail separately. (See "Exercise-associated hyponatremia", section on 'Prevention'.)

Determining how much and where fluid should be available — Calculating fluid-replacement for large numbers of participants and placement of fluid stations for an endurance race is not an exact science [55]. Preliminary fluid calculations are based on the anticipated number of starters and race conditions, but the amounts of fluid needed are better estimated after several years of experience managing a particular race. One simple minimalist approach is as follows:

●At each aid station, assume every runner uses one cup of fluid (common cup sizes are 210 to 300 mL, or about 7 to 10 ounces), and there is one cup for each type of fluid provided (water or sports drink) for every runner. Every cup contains about 120 to 240 mL (about 4 to 8 ounces) of fluid.

●At the start and finish areas, the number of cups and fluid volume are double that of a typical on-course aid station.

Tables providing basic estimates and a case study are provided (table 10 and table 11). As a general rule, it is better to have excess supplies: Err on the side of having more water and cups than needed. The Road Race Water Planner (Sports Science Synergy, LLC), a science-based app for calculating fluid volume for races in various environments, has been released and is now commercially available [56]. The Road Race Water Planner may be useful for calculating water needs for a race.

If a sports drink is provided in addition to water, both should be available at each water stop, or the stations with sports drink fluid should be announced in advance of the race. The decision to provide sports drinks is primarily a budget issue at most races and is decided by the race administration. Although runners often expect sports drinks to be available at major races, administrators at many smaller races, including marathons, provide only water along the course. For participants in endurance events that last longer than an hour, sports drinks provide carbohydrates for active muscle, although the performance decrements for the average runner drinking only water are probably not significant [42].

If both water and a sports drink are to be provided, a minimum starting estimate for total fluid requirements would be two-thirds of the total water volume calculation for each fluid at each station, although this estimate entails a risk of running out of one fluid or the other at an individual station. If temperatures are expected to be hotter than normal, fluid volumes and the number of cups should be increased by 50 to 100 percent at the on-course fluid stations, as participants often drink one or two cups and dump one on their head or body. Sports drinks can be mixed on site using bulk powdered formulations.

Runner education should emphasize that it is the water in you, not on you, that affects body temperature. As tempting as it may be to put mist-producing machines on the course when it is hot, mist makers have minimal, if any, cooling effect unless a runner stops in the mist for an extended period.

An on-site potable water source provides for increased water needs, leaving the cup supply as the limiting factor. A military-style "water buffalo" (water tanker truck) is an option for transporting bulk potable water, but an adequate supply of cups is needed to meet increased demands for fluid. If bottled water is used, there should be a plan in place to increase water supplies at the aid stations and finish line when hot weather is expected on race day. Extra water can be dropped at each water station or loaded onto vehicles in advance of the race and ready for dispatch to stations that run low due to potential increased demand in the heat.

Immediately after the race, soup bullion is a good fluid to provide for runners, as it replaces fluid and salt losses. Providing a vegetarian option is helpful. Water and sports drinks should also be made available. Chocolate milk with 1 or 2 percent milkfat is another good post-event rehydration fluid.

HAZARDOUS CONDITIONS AND INDICATIONS TO CANCEL AN EVENT — Depending upon the time of year, location, and the nature of the event, hazardous conditions may arise that require that a mass-participation endurance sporting event be cancelled. Extreme temperatures, lightning in the event vicinity, ice-covered surfaces, strong winds, and poor air quality are examples of factors that put participants at risk and are reason for cancellation. The safety of event volunteers and staff must also be considered. Unforeseen natural events (eg, lightning storm, flooding) or man-made catastrophes (eg, Boston Marathon 2013 bombing) have caused cancellations of major events in past years.

When deciding whether to cancel or proceed with an event despite some increased risk (eg, temperatures higher or lower than anticipated), event organizers and the medical director must take into account the effect of the anticipated increase in the number of casualties on community medical capacity and care, in addition to the increased needs for on-site medical care.

During hot weather, race conditions, specifically the wet-bulb globe temperature (WBGT) and direct overhead sun, play a major role in determining the number and severity of medical encounters and race dropouts. Unseasonably warm weather, particularly for participants from cooler regions who may not be acclimated to the heat, increases the risk of heat-related medical problems [5,12,16,47,57]. In this setting, race administrators must determine an appropriate threshold for cancellation. Standard guidance for activities based on the WBGT is provided in the following table (table 12).

For the Twin Cities Marathon, the medical committee has used race weather conditions and race outcomes data (non-finishers plus medical tent encounters per 1000 finishers) to establish a "do not start" temperature (WBGT of 20.5°C or 69°F) that is specific to the heat stress at the start of the race and community medical capacity [5,58]. High temperatures and humidity during the 2007 Twin Cities Marathon pushed the emergency response system beyond its capacity to provide patient transport and medical care at race area hospitals, forcing the use of regional ambulance systems (mutual aid) and hospitals outside the usual catchment area (figure 1). Using data from that episode, race administrators subsequently calculated the "do not start" WBGT described above that is specific to the race and local medical system (the calculation, which incorporated a number of race data points to determine the interaction of casualties and area medical response capacity) [5]. These issues reinforce the importance of coordinating with local emergency medical services (EMS) and hospitals during planning and the race. (See 'Integrating area emergency medical services and hospitals' above.)

Cold temperatures do not generally cause increases in the rate of exercise-associated collapse (EAC) or other medical issues, provided participants are appropriately dressed and trained for the event. Nordic ski races set temperature and wind-chill thresholds for cancellation to reduce the risk of frostbite (including corneal injury), particularly during the faster downhill portions of the course. The International Ski Federation set a cancellation level at -20°C (-5°F) following the 1980 Olympics. The "do not start" level has been lowered to -25°C (-13°F), with a requirement to notify the athletes of the increased risk for cold injury for temperatures of -20 to -24°C. Volunteers may be at greater risk in cool wet or extreme cold conditions than seasoned event participants due to lack of proper clothing. (See "Frostbite: Emergency care and prevention" and "Accidental hypothermia in adults".)

Some increase in the risk to participants and volunteers occurs with wind speeds in excess of 32 mph (51 km/hour); risks accelerate with winds above 39 mph (63 km/hour). In the United States, the National Weather Service issues a high wind warning when sustained wind speeds of at least 40 mph (64 km/hour) or gusts of 58 mph (93 km/hour) or more are expected or occurring. Potential hazards stem from moving objects (start/finish banners, tents, tree limbs) and direct injury to race participants or personnel, especially those on bicycles. Higher wind speeds increase the wind chill, which raises the risk of hypothermia in participants and possibly frostbite if the ambient temperature is below freezing. Wind speeds can be predicted with reasonable accuracy, and information from a local or national weather service can be helpful. Event directors should consider wind speed in their race cancellation policy.

Poor air quality can adversely affect race participants with asthma or other pulmonary disorders, and is more of an issue in particular parts of the world. Air-quality guidelines are based on the air quality index (AQI), which reflects the particulate and chemical matter in the air. As the AQI rises above 100 to 150, athletes and volunteers can be adversely affected [59]. The AQI can be used to determine the need for event cancellation. If the AQI is above 100, it is prudent for race administrators to warn participants and volunteers, particularly those with lung conditions, about the potential risk. (See "Risk factors for asthma", section on 'Air pollution'.)

While not a factor that changes or can be modified, high altitude does pose a risk to participants, particularly those who have not acclimated. Altitude can precipitate acute mountain sickness (AMS), high altitude cerebral edema (HACE), or high altitude pulmonary edema (HAPE) in susceptible individuals. Some individuals can develop AMS at altitudes as low as 1500 to 1800 m (approximately 5000 to 6000 feet). While HACE and HAPE generally occur at altitudes above 3000 to 4000 m, both can be fatal, and rapid descent is the most effective intervention. Race medical teams operating at higher altitudes should be prepared to evaluate and manage participants with these disorders. The diagnosis and management of these conditions is reviewed in detail separately. (See "Acute mountain sickness and high-altitude cerebral edema" and "High-altitude pulmonary edema" and "High-altitude disease: Unique pediatric considerations".)

Other problems may require that a mass-participation sporting event be cancelled. Terrorism, or the threat of terrorism, and unanticipated course violations (eg, wayward cars, animals, political demonstrations) have disrupted or cancelled events. Close cooperation and advanced planning with community emergency and law enforcement officials is important for effective management and provides for an appropriate and recognized chain of command in the face of such natural or manmade disasters.

SERIOUS AND COMMON MEDICAL CONDITIONS ENCOUNTERED DURING ENDURANCE EVENTS

Medical emergencies and important conditions — The initial evaluation and management of a recreational or higher-level adult athlete who has collapsed during or following a sporting event are discussed in detail separately. (See "Evaluation of the collapsed adult athlete".)

The following table summarizes our approach to the initial evaluation and management of the collapsed athlete (table 13).

The serious medical conditions most likely to be encountered during an endurance event are listed below, along with links to the UpToDate topics that discuss the diagnosis and management of these conditions:

●Sudden cardiac arrest (SCA) (see "Advanced cardiac life support (ACLS) in adults" and "Adult basic life support (BLS) for health care providers")

●Exertional heat stroke (EHS) (see "Exertional heat illness in adolescents and adults: Management and prevention", section on 'Management of exertional heat stroke')

●Exercise-associated postural hypotension (EAPH) (ie, exercise-associated collapse [EAC]) (see "Evaluation of the collapsed adult athlete", section on 'Exercise-associated postural hypotension (EAPH)' and "Evaluation of the collapsed adult athlete", section on 'Management of exercise-associated postural hypotension')

●Exercise-associated hyponatremia (EAH) (see "Exercise-associated hyponatremia")

●Anaphylaxis (see "Anaphylaxis: Emergency treatment" and "Anaphylaxis: Acute diagnosis")

●Insulin shock (acute hypoglycemia) (see "Hypoglycemia in adults with diabetes mellitus")

●Acute severe asthma exacerbation (see "Acute exacerbations of asthma in adults: Home and office management")

●Hypothermia (see "Accidental hypothermia in adults" and "Frostbite: Emergency care and prevention" and "Nonfreezing cold water (trench foot) and warm water immersion injuries")

●Major trauma (See "Initial management of trauma in adults".)

Patients who sustain a SCA are managed according to standard advanced cardiac life support (ACLS) and basic life support (BLS) protocols and immediately transferred to an appropriate medical facility. Most community-based endurance races involve participants over age 40, who are at greater risk for SCA. The baseline risk of individuals may rise in conditions of extreme heat.

It is clear from anecdotes, published case reports, and race reports that warmer and more humid weather conditions (higher wet-bulb globe temperature [WBGT]) than are typical for the area increase the risk of EAPH (or EAC), EHS, EAH, and race dropouts [5,12,14-17]. For patients with EHS or EAH, immediate diagnosis and on-site treatment with rapid cooling or hypertonic (3 percent) saline, respectively, can be life-saving.

EAPH is by far the most common medical condition managed by medical personnel at endurance races. However, it remains a diagnosis of exclusion.

Depending upon the nature of the race, other serious medical problems may arise. Events that include bicycling, inline skating, and Nordic skiing entail the added risk of high-speed collisions and falls and associated injuries, including concussion, internal hemorrhage, and fracture. Nordic skiing and other cold-weather pursuits may lead to frostbite and hypothermia. Events that include swimming entail a risk of drowning [60]. Cold-water swims can cause hypothermia, despite the metabolic heat production from exercise. There are reports of EAH among participants in open-water swimming events [61]. (See "Frostbite: Emergency care and prevention" and "Accidental hypothermia in adults" and "Drowning (submersion injuries)".)

Exercise-associated postural hypotension — The most common medical condition encountered following an endurance race is exercise associated collapse (EAC) [32,62-64]. Runners with a normal or only mildly elevated body temperature who experience EAC are more accurately said to have exercise-associated postural hypotension (EAPH). Such patients are often described as "weak, wobbly, and dizzy." EAPH accounted for nearly 60 percent of the medical encounters at the Twin Cities Marathon from 1983 to 1994 and continues to be the leading cause for evaluation at the finish-line medical tent [12]. EAPH is treated with leg elevation (picture 3), rest, and oral fluids, and generally resolves within 10 to 30 minutes. The most important task for the clinician is distinguishing this benign process from the potentially life-threatening conditions of EHS and EAH. (See "Evaluation of the collapsed adult athlete", section on 'Initial management of the collapsed athlete without trauma'.)

Musculoskeletal and skin injuries — The initial care provided for musculoskeletal and skin trauma at mass-participation sporting events is generally straightforward. Protection, rest, ice, compression, and elevation (PRICE) is the standard approach for sprains and strains of muscles and tendons. An occasional race participant will require crutches for ambulation. Participants with stress fractures that develop into complete fractures during the event typically require transport to a hospital.

The most common skin trauma is a blister. Abrasions may require minor debridement prior to the application of a dressing. Deep abrasions embedded with road grit should be referred for more thorough cleaning and possibly additional care (eg, tetanus booster, antibiotics) if simple interventions are not sufficient to allow for safe healing. An herbicide pump sprayer available from most hardware stores and mentholated gel shave cream can be used to clean these wounds in the field. (See "Friction blisters".)

Documentation — For each event, it is useful to record the weather conditions. These include ambient temperature, relative humidity, sky cover (percent sun), wind speed and direction, wet-bulb temperature, black-globe temperature, and WBGT if measured (or calculated from race data). Measurements are taken at the start of the race and hourly thereafter. This allows the medical team to determine how conditions affect casualty rates and how this varies from year to year and event to event.

Documenting each individual medical encounter is essential, as this becomes the medical and legal record. These records too can be used to study the types and rates of injury associated with a race and assist with future planning.

POST-EVENT REVIEW — Following any mass-participation endurance sporting event, we suggest performing a careful review of the medical management provided and outcomes with the goal of improving future performance. At the Twin Cities Marathon, we ask for an after-action report from each area leader. Essentially, the report is intended to elicit information about what went right, what went wrong, and what potential solutions or changes in practice might be useful for the next event.

Important elements of management to consider include:

●Efficiency and effectiveness of medical management

●Unanticipated medical problems

●Communications plan

●Supply and equipment needs

●Access for emergency transport

Possible solutions for the problems identified should be discussed and developed by the medical team for the next race. Related budget items should be addressed and prioritized for the coming year. If possible, permanent race staff personnel can be assigned to address and institutionalize the solutions so important items are implemented.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Exertional heat illness".)

SUMMARY AND RECOMMENDATIONS

●Terminology – A mass-participation endurance sporting event can be loosely defined as any endurance competition that has the potential to generate a significant number of casualties due to the large number of participants or the potential injury risk. The "classic" mass-participation event is a running road race of 5 to 42 km (3 to 26 miles). (See 'Terminology' above.)

●Factors affecting casualty rates – Factors that influence the number of medical encounters at a mass-participation endurance sporting event include (table 1):

•Weather (abnormal heat and humidity or cold increase encounters)

•Participant acclimatization (eg, heat and humidity; altitude)

•Event type (more strenuous races increase encounters)

•Distance of race

•Participant health and fitness

•Safety preparations (eg, hydration strategies, medical triage, course evacuation)

●Epidemiology – Event-related deaths are relatively uncommon. Sudden cardiac arrest (SCA), exertional heat stroke (EHS), and exercise-associated hyponatremia (EAH) are the most common causes. Most deaths during triathlons occur during the swim portion but are due to SCA rather than drowning; the overall mortality rate is similar to marathons. SCA occurs in races of all types and distances, and outcomes are better if an emergency action plan (EAP) is in place. Exercise-associated postural hypotension (EAPH, ie, exercise-associated collapse [EAC]) is relatively common but generally self-limited and benign. (See 'Epidemiology' above.)

●Key tasks for medical planning – Medical coverage can be approached as a "planned disaster" [36]. The number and type of medical conditions and injuries likely to be encountered during the "disaster" can estimated based on the type of event, (running, bicycling, swimming, multi-activity (triathlon), obstacles course), number of participants, location, and expected weather conditions. Organizations like World Athletics Endurance Medicine have developed race management training materials and a race medicine handbook that can assist planners (table 2 and table 3). Key concepts and core tasks in the medical preparation for such events include:

•Be aware of and plan for the potentially catastrophic risks to participants, including SCA, EHS, and EAH.

•Be aware of and plan for the common medical problems likely to require care at medical aid stations. Ensure that adequate personnel and resources are available to manage these conditions.

•Coordinate with community emergency medicine leaders and organizations.

•Develop or adopt standardized medical management protocols for common and important medical conditions likely to occur, and train medical staff in the application of these protocols.

Details pertaining to medical protocols, race safety, placement of aid stations, and integration with community medical services, are provided in the text. (See 'Key concepts and tasks' above and 'Medical management protocols' above and 'Race safety and injury reduction strategies' above and 'Course survey and emergency action plan' above and 'Placement of aid stations and AEDs' above and 'Integrating area emergency medical services and hospitals' above.)

●Medical team – The background, skills, and responsibilities of the medical director and other staff needed to provide medical care during a mass-participation endurance sporting event, and methods for determining medical personnel needs, are discussed in the text. (See 'Medical team' above.)

●Equipment – Necessary medical equipment and supplies are determined based upon the number and type of casualties typical for a given event. Weather conditions are an important factor in determining supply needs. Equipment needs are discussed in the text, while the following tables provide a comprehensive list of supplies that may be needed (table 7 and table 8). (See 'Determining medical equipment and medication needs based on environment and event' above and 'Shelter for the primary medical station' above.)

●Communications – An effective communications system that encompasses the entire event course is essential for medical management on race day. A backup system is crucial should the primary system fail. Some combination of cell phones, handheld radios, and ham radios allows for rapid communication. Radio communications may not be confidential. (See 'Communications center' above and 'What communications systems work best in a race environment?' above.)

●Fluid for race participants – Particularly during hot weather and longer races, it is important to provide appropriate fluids to participants along the race course to help them maintain hydration. For events that last 60 to 80 minutes for the slowest runners (10-km race), one water stop at the midpoint or two water stops one-third and two-thirds of the course are typically adequate. Most long races have water stops every 3 to 5 km. Educating runners to avoid overhydration is critical, particularly for longer races. Overhydration may lead to life-threatening hyponatremia. (See 'Determining an individual’s fluid needs and fluid recommendations for participants' above and 'Determining how much and where fluid should be available' above.)

●Hazardous conditions and race cancellation – Depending upon the time of year, location, and nature of the event, hazardous conditions may arise that require cancellation. Extreme temperatures, lightning in the event vicinity, icy surfaces, strong winds, and poor air quality are examples of factors that put participants at risk and are reason for cancellation. The safety of event volunteers and staff must also be considered. Additional guidance about cancellation decisions is provided in the text. (See 'Hazardous conditions and indications to cancel an event' above.)

●Collapsed athlete – Most athletes who collapse or appear ill during a mass-participation endurance sporting event are experiencing EAPH, a self-limited and benign condition that resolves with leg elevation (picture 3), rest, and oral fluids. However, distinguishing between EAPH and a life-threatening medical condition such as exertional heat illness can be difficult even for seasoned clinicians. The initial evaluation and management of the collapsed athlete are reviewed in detail separately and summarized in the following table (table 13). (See "Evaluation of the collapsed adult athlete".)