Version May 2024
INTRODUCTION — Running is one of the world's most popular forms of exercise with millions of regular participants. In the United States alone, up to 40 million people run regularly, with more than 10 million running at least 100 days per year [1]. Although running is an effective way to achieve many health benefits, it is associated with a high risk of injury; yearly, up to one-half of runners report an injury [2]. Although some injuries are traumatic, most are due to overuse.
Given the popularity of running and the high rate of associated overuse injuries amenable to nonsurgical management, the primary care clinician is likely to manage many injured runners and should be familiar with the diagnosis and treatment of common problems. The epidemiology, risk factors, and methods for preventing running-related injuries are discussed here. Evaluation of the injured runner and descriptions of common injuries and conditions sustained by runners are reviewed separately. (See "Running injuries of the lower extremities: Patient evaluation and common conditions".)
Standalone topics devoted to particular injuries may also be found separately, including those listed here. (See "Ankle sprain in adults: Evaluation and diagnosis" and "Patellofemoral pain" and "Iliotibial band syndrome" and "Hamstring muscle and tendon injuries" and "Stress fractures of the metatarsal shaft" and "Stress fractures of the tarsal (foot) navicular" and "Plantar fasciitis".)
GENERAL EPIDEMIOLOGY — The incidence of lower extremity injuries in runners ranges from 19.4 to 79.3 percent [3]. The knee is the most injured body part. The most common diagnoses include patellofemoral pain (PFP), medial tibial stress syndrome (MTSS; ie, "shin splints"), Achilles tendinopathy, iliotibial band syndrome (ITBS), plantar fasciitis, and stress fractures of the metatarsals and tibia [3-6]. According to a 2009 survey of more than 11,000 year-round runners, many of them recreational runners, more than 10 percent experienced hip and/or low back pain in the previous 12 months [7]. Among marathon runners, males report more hamstring and calf problems, whereas females report more hip complaints [8]. Running is a common cause of injury among military personnel [9].
One retrospective survey of 2886 runners reported an overall injury rate of 46 percent but found a higher incidence of soft tissue injuries to the calf, Achilles tendon, and hamstring among masters runners (>40 years), who comprised 34 percent of the participants [10]. Injured runners were more likely to be male, run six days per week, and run more than 30 miles per week.
Available evidence does not reveal important differences in overall injury rates between female and male adult runners. In a 2021 systematic review of 38 studies, the average overall injury rate per 100 female runners was 20.8 (95% CI 19.9-21.7) injuries compared with 20.4 (95% CI 19.7-21.1) injuries per 100 male runners [11]. A prospective cohort study of 300 runners followed for two years showed that 73 percent of females and 62 percent of males sustained an injury, with 56 percent of the injured runners sustaining more than one injury during the study period [12]. Female runners appear to be more susceptible to hip, knee, and bone stress (eg, stress fracture) injuries, while male runners appear to have higher rates of ankle and foot injuries, including Achilles tendinopathy [11,13].
RISK FACTORS — Despite the popularity of running and the prevalence of related injuries, few studies have successfully identified the individual factors most responsible, suggesting that many running injuries are multifactorial. A history of prior injury is one of the few variables that has consistently been shown to increase the risk of incurring a subsequent running injury [2,4,14,15]. Therefore, every injured runner seeking medical attention should be questioned about prior injuries, including treatments. Incomplete rehabilitation and failure to address potential risk factors associated with a prior injury increase the likelihood of recurrence. Greater mileage is another factor that is consistently associated with increased injury risk [16]. Obesity is also associated with an increased risk [17,18].
Multiple risk factors are likely to contribute to running injuries. These can be stratified into intrinsic risk factors (eg, anatomic and other individual variables, including sex and body mass index [BMI]) and extrinsic risk factors (eg, training variables and equipment).
Intrinsic risk factors
Anatomy — Running injuries have been attributed to several anatomic variables, but the literature does not support many of these commonly held beliefs. A prime example is patellofemoral pain (PFP), a common cause of knee pain in runners. Lower extremity alignment that results in a greater Q angle at the knee (common in females) has often been cited as a cause of PFP, but most studies refute this assertion.
Foot type is another purported risk factor, but most studies of runners have not found consistent relationships between foot structure and specific injuries. One group studying collegiate cross country runners failed to identify any association between structural variations and the likelihood of developing exercise-related leg pain [19,20]. One notable exception is cavus foot (high arch), which is associated with myriad injuries [2,21]. Specific injuries implicated in one or more studies include tibial stress fractures, PFP, plantar fasciitis, and Achilles tendinopathy. (See "Stress fractures of the tibia and fibula" and "Patellofemoral pain" and "Plantar fasciitis" and "Achilles tendinopathy and tendon rupture".)
Some researchers have proposed that limb asymmetry (ie, leg length discrepancy) may increase injury risk, including stress fracture [22,23], but not all studies support this conclusion. These conflicting results suggest that anatomy alone is not sufficient to explain the high risk of injury among runners. Many experienced sports medicine clinicians believe that the important issue is whether the difference in leg length affects gait, rather than whether some measurement threshold is reached.
Sex and age — Sex and age may play a role in some running injuries, but the literature is conflicting in this regard:
●A prospective study of 844 male and female runners following a training program in preparation for a 10-km race reported an increased risk of injury among females age 50 or older and a lower risk among those 30 or younger [24].
●A prospective study of 532 novice runners participating in a 13-week training program noted that higher BMI was a risk factor for male but not female runners (hazard ratio [HR] 1.15, 95% CI 1.05-1.26) [25]. Conversely, navicular drop was associated with injury in females but not males (HR 0.85, 95% CI 0.75-0.97).
●A longitudinal study of former high school cross country runners over a 15-year period reported that females had significantly higher injury rates than males (16.7 versus 10.9 injuries per 1000 athletic exposures) [26].
Studies consistently report an association between female sex and stress fracture risk, particularly among females with low bone mineral density, as seen in the so-called "female athlete triad." The risk factors for stress fracture are discussed in detail separately. (See "Overview of stress fractures", section on 'Risk factors'.)
While not consistently identified as a risk factor for running injury, age has been associated with a number of injuries in several observational studies. In contrast to the prospective study described above [24], a retrospective study of more than 2000 runners found that age under 34 was associated with an increased risk for PFP in both males and females and an increased risk for iliotibial band syndrome (ITBS), patellar tendinopathy, and tibial stress syndrome among males [5]. These findings may reflect that masters runners (>40 years) are primarily those with low injury rates, while runners who sustain multiple injuries are more likely to give up the sport.
It is not known whether weight, regardless of sex, is an independent risk factor for injury. One prospective cohort study of 300 runners followed for two years found that knee stiffness, associated with weight greater than 80 kg, was associated with higher risk of injury [12].
Extrinsic risk factors — Studies have not consistently supported many traditional beliefs about the association between anatomic variations and injury risk [27]. This has led many researchers to focus both on the effects of extrinsic factors on running injury and on the combination of intrinsic and extrinsic variables.
Training variables — Measures to reduce running injuries often include modifying training variables such as mileage and intensity. A systematic review concluded that reducing the distance, frequency, and duration of running may be effective in preventing soft tissue injuries in runners [28].
Excessive mileage is associated with higher injury rates. Multiple observational studies report that training volumes of 65 km (40 miles) or more per week increase the risk of injury [2,3,10,16], and one reports increased risk with running over 32 km (20 miles) per week [29]. Most of these studies involve male runners. While most sports medicine practitioners believe excessive mileage also affects female runners, well-designed clinical studies have not been performed. It is unclear if more experienced runners are less susceptible.
Abrupt increases in training volume or intensity can contribute to running injuries [30,31]. Studies of military recruits report that sudden increases in training volume or changes in the type of training (eg, adding hill running) lead to increased injury rates [30]. A prospective observational study of 735 runners preparing for the New York City Marathon found that an acute to chronic workload ratio ≥1.5 was associated with an increased risk of injury (odds ratio [OR] 1.06, 95% CI 1.02-1.10) [31]. Although many sports medicine clinicians advocate the 10 percent rule (ie, increase training volume by no more than 10 percent per week), a randomized trial of this approach in 532 novice runners reported no reduction in injuries (20.8 versus 20.3 percent with standard training) [32]. Nevertheless, common sense would suggest that gradual increases in training volume are less likely to cause injury than sudden increases.
Some types of training may be protective. As an example, one research group found that regular interval training is protective against knee injury [33]. Running surface probably affects injury rates. Running on concrete is associated with increased risk, while running on a treadmill reduces the stresses placed on the tibia and may thereby reduce the risk of tibial stress fractures [34].
A prospective study of 264 recreational runners showed an association between being active in sports other than running and a reduced incidence of running-related injuries, supporting the commonly held belief that cross-training is an effective technique for reducing sports injury risk [35].
Long-distance races — Long-distance races, such as 10 km, half-marathons, and full marathons, have gained in popularity in recent decades. Risk factors for injury among runners preparing for and participating in such races vary somewhat from recreational runners engaged in regular exercise. Notable risk factors include previous musculoskeletal injury from running, inexperience with such races, and undertraining.
In a retrospective study involving 1043 half-marathoners and 624 full marathoners (survey response rate 83 percent), 24 percent of half-marathoners and 30 percent of full marathoners sustained some musculoskeletal injury [36]. Lower total weekly mileage and lower peak weekly training mileage (ie, longest run) in preparation for the race were associated with increased injury rates, suggesting that less prepared runners were at higher risk.
Stretching and warm-ups — It is hard to draw firm conclusions about the effectiveness of stretching for reducing the risk of running injuries due to the large number of variables involved. These variables include a runner's baseline flexibility, the timing of stretching (pre-exercise, post-exercise, or not in conjunction with exercise), and the method of stretching (eg, dynamic, static, or proprioceptive neuromuscular facilitation). Despite a dearth of convincing evidence, many sports medicine clinicians, running coaches, and runners believe that stretching is beneficial. However, further research is needed to determine which runners benefit and what methods to use.
Multiple studies question the benefit of stretching, long a piece of injury prevention advice given to runners [37,38]. A systematic review of randomized trials that assessed multiple interventions designed to prevent running injuries included six studies, involving 5130 runners, that looked at stretching exercises and concluded that stretching regimens do not protect against soft tissue injury [38]. The stretching regimens included in these studies varied in the muscle groups targeted, the timing of the intervention (eg, before or after training), whether a warm-up was also performed, and other factors. Another review that included both randomized trials and cohort studies investigating the effect of stretching on injury reduction during sports also concluded that stretching was not associated with a reduction in total injuries (OR 0.93, CI 0.78-1.11) [37].
Stretching may have other benefits. As an example, in a study of 900 military recruits, those who stretched regularly experienced lower rates of low back and soft tissue pain [39]. Stretching may also play a useful role in the management of other injuries, such as plantar fasciitis and Achilles tendinopathy. (See "Plantar fasciitis" and "Achilles tendinopathy and tendon rupture".)
There is insufficient high-quality research in runners to determine whether warming up reduces injury rates. One randomized trial involving 421 runners found that an educational intervention regarding warm-up, cool-down, and stretching did not significantly reduce the risk of injury [40]. Nevertheless, many clinicians advocate a dynamic warm-up or light jogging before engaging in strenuous running, and we concur with this approach.
Running shoes
Suggested approach to selection — Debate continues about the role running shoes and orthotics may play in reducing the risk of injury. Based on limited evidence and our clinical experience, we suggest using the running shoe that feels most comfortable, fits properly, and is well suited to the shape of the runner's foot [27,41-43]. This is consistent with views held by many experts, who generally advise using a comfortable shoe with moderate cushion and mild pronation control (figure 1).
Running shoe design — The running shoe industry traditionally has produced three basic types of running shoes:
●Shoes for runners with a low foot arch or no arch (over-pronators) that are designed to minimize pronation (picture 1) and maintain the foot in a neutral position. Higher-density foam and a rigid plastic counter are incorporated into the medial side of the shoe to support the arch.
●Shoes for runners with a neutral foot shape.
●Shoes with extensive cushioning for runners with a cavus (high-arched (picture 2)) foot (over-supinators).
More recently, manufacturers have developed a range of other design features, such as heel-to-toe drop, toe box width, and level of cushioning (figure 1). These are discussed below.
Many clinicians and runners believe that selecting the shoe best suited to the runner's foot type prevents injury. However, this concept is not well supported by the literature. In a systematic review of 12 randomized and quasi-randomized trials involving over 11,000 participants, researchers emphasized the low quality of most studies but concluded that most evidence demonstrates no reduction in lower extremity running injuries associated with particular types of running shoes [43]. The results of several studies suggest that specific features, such as additional cushioning or increased rigidity to control pronation, do not reduce injury risk [44-46]. Randomized trials involving recruits in the United States Marine Corps and Air Force undergoing basic training found that assigning shoes to recruits based on foot type did not significantly reduce injury rates [47,48].
Softer soles in running shoes may reduce the risk of injury, at least in some runners. In a randomized trial of 848 healthy runners, those given shoes with harder soles had a higher rate of injury (subhazard ratio [SHR] 1.52, 95% CI 1.07-2.16) [49]. The risk was greatest in lighter runners (males <78 kg and females <63 kg). In this trial, injury was defined as any complaint that interrupted running for at least seven days. Nevertheless, the evidence around running shoe cushioning is inconsistent, as the results of an earlier randomized trial suggest that the level of cushioning may not affect injury rates [17]. In this trial, 247 recreational runners were randomly assigned to wear running shoes that differed only in midsole firmness for five months and to report their running volume and all running-related injuries. No significant difference was noted in injury rates between the two groups.
It remains possible that particular shoe types reduce the risk of injury in particular subpopulations of runners (eg, more rigid support for cavus feet or pronated feet). One crossover randomized trial found that some popular, neutral-cushioned running shoes reduced plantar pressures in the cavus foot, theoretically reducing injury risk [50]. A prospective observational study of 372 recreational runners reported a reduction in injury rates among runners with foot pronation who were given shoes that restricted foot motion; no comparable reduction was seen among runners with neutral or supinated feet [51]. Thus, control of pronation may reduce injury in this subpopulation of runners, but further study is needed.
Regardless of shoe type, several studies of the shock absorption properties of running shoes have shown that new shoes lose up to half their cushioning after 250 to 500 running miles [52]. Therefore, many sports medicine practitioners counsel runners to change their running shoes every 350 to 500 miles. The results of a prospective observational study involving 264 runners suggest that alternating between two pairs of running shoes may reduce the risk of lower extremity injury compared with using a single pair [35].
Orthotics — Orthotics appear to reduce the risk of some running-related lower extremity injuries, but it remains unclear which subpopulations benefit most. Some clinicians advise runners with recurrent overuse injuries involving the foot (eg, metatarsalgia), ankle (eg, sprain), or tibia (eg, medial tibial stress syndrome [MTSS]), especially those with excessive pronation or supination, to use orthotics, but there is no consensus about these indications.
In a systematic review and meta-analysis of 14 randomized trials involving over 5000 runners, those assigned to train with a custom or prefabricated foot orthotic sustained 238 lower extremity injuries compared with 721 among controls (RR 0.6, 95% CI 0.5-0.7) [53]. These results should be interpreted with some caution, as significant heterogeneity among studies was noted, many studies had methodological flaws, and the majority were performed in military recruits, which presents challenges when extrapolating results to the general population of recreational runners.
Individual studies have reported that orthotics reduce the pain associated with PFP and cavus foot, both common issues in runners [54-57]. (See "Patellofemoral pain".)
Studies performed primarily in military recruits have found that orthotics reduce the risk of lower extremity stress fractures. The role of orthotics in reducing the risk of stress fractures is reviewed separately. (See "Overview of stress fractures", section on 'Prevention'.)
We have made custom orthotics for thousands of runners in our clinics. The most common conditions among our runners who use orthotics long-term include cavus foot (high arch), dynamic genu valgus (knee bends inward during gait (picture 3)), chronic foot conditions, and leg length discrepancy causing Trendelenburg shift during running (picture 4).
Shoe drop — An important design feature of running shoes is the "drop" of the shoe, which is the change in height from heel to forefoot (figure 1). Depending upon a person's running gait mechanics and training volume, different drops may predispose or, conversely, help to prevent injury according to some researchers. In one trial, 553 recreational runners were randomly assigned to use identical running shoes that differed only in drop (0, 6, or 10 mm) and followed for six months [58]. Although the overall injury rate did not differ by group, regular runners using low-drop shoes (0 or 6 mm) sustained injuries at a significantly higher rate than regular runners using high-drop shoes (HR 1.67, 95% CI 1.07-2.62). This finding is consistent with our clinical experience and suggests that many recreational runners benefit from the reduced impact associated with a larger drop, although additional study is needed to confirm this finding.
Overall, we suggest caution when runners, particularly those who run regularly (eg, several times per week), are considering a change in running shoe design. If a particular shoe design fits well and there is no history of injury, it seems prudent to continue with a shoe of similar design.
Toe box — More running shoes are being manufactured with a wide toe box. The wider toe box allows sufficient space for splaying of the toes during the gait cycle and is intended to mimic a barefoot gait. Whether splaying of the toes reduces injury risk remains unproven.
Running barefoot or with minimalist shoes — Although running barefoot or with "minimalist" shoes (eg, Vibram FiveFingers) is gaining popularity, few controlled studies of these approaches to running have been performed, and it remains unclear whether such shoes have negative or positive effects upon performance or injury rates [43,59,60]. A review by a noted authority concludes that little is known about barefoot running, and there is much work to be done to determine whether a barefoot style can be used to treat or prevent injury [61]. The potential benefits of barefoot running or the use of minimalist shoes may be due to the changes in gait that are required when using such an approach. These include a shorter stride length and a midfoot or forefoot strike, which is thought to reduce impact compared with the rearfoot strike used by many runners wearing traditional, cushioned running shoes.
Given the limited studies available, the indications and guidelines for transitioning to a barefoot style or minimalist running shoes are largely anecdotal [62,63]. One of the few randomized trials of minimalist running shoes found that greater body mass and higher mileage appear to increase the risk of injury [64]. In this trial, 61 trained runners with a rearfoot strike were randomly assigned to minimalist or standard running shoes and then gradually increased the time spent running in the designated shoes over 26 weeks. Of the 27 injuries sustained, 16 occurred in runners using minimalist shoes and 11 in runners using conventional running shoes. Injury risk was increased among runners with increased body mass using minimalist shoes (HR 2.00, 95% CI 1.10-3.66 for runners with a body mass of 85.7 kg).
Based on available evidence and our clinical experience, we suggest that those making the transition to barefoot running or running in minimalist shoes do so gradually, starting with relatively low mileage and increasing their weekly training by no more than 1.7 km (1 mile) per week. In addition, available evidence supports running no more than 35 km (22 miles) total per week in minimalist shoes or barefoot, as additional mileage may increase the risk of injury. Furthermore, we suggest that runners over 85 kg (187 lbs) not use minimalist shoes, and even runners over 75 kg (165 lbs) may sustain fewer injuries by using conventional running shoes. Runners who develop lower extremity pain during or following the transition to minimalist shoes are likely better off training solely in conventional running shoes.
A few studies, mostly observational and involving small numbers of runners, suggest that some injuries (eg, stress fractures of the foot) occur more often in those using minimalist shoes, particularly if the transition to such footwear is not made gradually [65-69]. However, other observational studies report no increase in injuries overall among younger and fitter runners who use minimalist shoes [70]. (See "Stress fractures of the metatarsal shaft" and "Stress fractures of the tarsal (foot) navicular".)
Carbon-plated "supershoes" — Running shoes that incorporate a rigid carbon plate and highly responsive foam have gained notoriety. Several preliminary studies performed in high-level runners report significant improvements in running economy when using such shoes compared with other standard, high-end running shoes or track spikes [71-73]. Although intended for elite marathoners, such shoes are being used increasingly by recreational runners. Carbon-plated shoes alter foot and ankle biomechanics, and it remains unclear how these shoes will affect injury risk. A case series has been published reporting five navicular stress fractures in elite runners using carbon-plated shoes [74]. The authors advise those wishing to use such shoes to transition gradually and to avoid daily use in order to prevent losing intrinsic foot strength.
Gait, strength, and biomechanics — Many laboratory and observational studies have examined the role of running biomechanics, vertical load, and plantar pressures in the development of running injuries. However, it is difficult to draw firm conclusions because many studies involve small numbers, few prospective clinical trials have been performed, and multiple factors are likely to contribute to the risk of injury [75-78]. Higher ground reaction forces, overstriding, and hip abductor weakness are three possible contributors to lower extremity running injury risk.
Multiple studies included in two systematic reviews have tried to assess ground reaction forces and vertical load in runners with and without stress fractures [75,79]. These are the forces sustained primarily by the lower extremity, but also the body generally, during the foot strike phase of running. Studies suggest that higher ground reaction forces and vertical load may be risk factors for stress fractures, but such associations remain speculative.
While keeping in mind its limitations, evidence suggests that overstriding and hip abductor weakness are likely to increase the overall risk of sustaining a lower extremity running injury. Overstriding (ie, low stride rate) means the runner's lead foot strikes the ground in front of the body's center of mass. Multiple studies show that overstriding produces increased ground reaction forces and loading rates and is associated with a greater risk of shin and knee injuries [80-83]. Similar associations have been noted for subjects with a longer stride length and tibial angle [84,85]. Overstriding is not equivalent to landing with a heel strike, and there is no clear evidence that foot strike pattern influences injury risk.
While there is no definitive evidence that hip abductor weakness contributes directly to running injuries, weak hip abductor muscles reduce the body's capacity to absorb ground reaction forces, and hip abductor strengthening reduces pain associated with PFP and ITBS [86,87]. Therefore, it seems reasonable to recommend hip abductor strengthening to patients with running-related knee pain, particularly if hip weakness is noted on strength testing or gait analysis (eg, hip drop). Strength can be increased through a sound resistance exercise program or by using some of the exercises described below. (See "Practical guidelines for implementing a strength training program for adults" and 'Training suggestions to reduce injury risk' below.)
Nutrition and supplementation — Little data exists to confirm or refute associations between nutritional factors and running injuries, with the important exception of stress fractures in female runners. Multiple studies report that inadequate vitamin D, calcium, and calorie intake increases the risk of stress fracture in female military recruits and runners. In addition, a prospective study of 86 female runners found that low fat intake increased the risk of sustaining a lower extremity injury [88]. (See "Overview of stress fractures", section on 'Risk factors'.)
While there is little high-quality evidence to support any particular diet to prevent running injuries, optimal nutrition does enhance performance and recovery; common sense suggests that runners should eat a balanced diet that includes adequate lean protein and all essential vitamins and minerals. A position paper on nutrition and performance authored jointly by Dietitians of Canada, the American College of Sports Medicine, and the American Dietetic Association makes the following recommendations for athletes [89]:
●Consume adequate calories. Insufficient calories can lead to reduced muscle mass and bone density, cessation of menses, and delayed recovery and can increase fatigue and the risk of injury and illness. In general, fewer than 1800 to 2000 kcals/day is inadequate for an exercising individual, although many female runners restrict calories to this level. Several tools are available to estimate calorie needs, including the Dietary Reference Intakes (available here) and the Dietary Guidelines from the United States Department of Agriculture (available here).
●Consume adequate carbohydrates. Runners need approximately 6 to 10 g/kg body weight of carbohydrates daily. Carbohydrates are important for maintaining blood glucose during exercise and replenishing muscle glycogen stores. Unhealthy, processed carbohydrates should be avoided.
●Consume adequate protein. Endurance athletes need 1.2 to 1.7 g/kg body weight of protein daily.
●Consume adequate healthy fats. Healthy fats are a source of energy, provide essential fatty acids and fat-soluble vitamins, and should comprise 20 to 35 percent of total calorie intake. (See "Dietary fat".)
●Stay hydrated. Water loss of as little as 2 percent body mass can decrease performance [89]. Runners should drink before, during, and after exercise. An easy rule of thumb is to weigh yourself before and after running and drink 16 to 24 ounces (450 to 675 mL) of fluid for every pound (0.5 kg) lost during exercise. For long or intense exercise (eg, marathon), it is also important to replace electrolytes. (See "Exercise-associated hyponatremia".)
The timing of nutrient intake is important [89-91]. A snack high in carbohydrates, moderate in protein, and low in fat and fiber is generally well tolerated prior to exercise, whereas a snack higher in fat and fiber may cause gastrointestinal cramping or other distress. During exercise that lasts more than one hour, the athlete needs fluids and small amounts of carbohydrate, such as that found in sports drinks. The runner should be encouraged to replenish glycogen stores by consuming carbohydrate, 1.0 to 1.5 g/kg of body weight, within 30 minutes of exercise and to continue "refueling" every two hours for four to six hours. These goals can be met with relatively small amounts of food.
Some researchers suggest adding protein to post-training snacks to aid muscle recovery; this is likely most beneficial to the runner who does not consume adequate carbohydrate following exercise [92]. Regardless of the specific approach, it is helpful for runners to become familiar with the concepts of "grams" and to learn how to apply this to their preferred foods.
Although an adequate, well-rounded diet provides the majority of vitamins and minerals needed by athletes, special mention should be made of iron. Iron requirements are greater in endurance runners than in nonendurance athletes [93]. Iron is lost through sweat, the gastrointestinal tract, and menstruation. Thus, iron depletion is particularly common among premenopausal female runners. Any runner complaining of fatigue and decreased performance, especially females, should have a serum ferritin measured. If low, iron levels can be increased through diet and supplementation, but dietary replacement appears to be more effective [90].
Although muscle adapts to regular exercise, some exercise-induced muscle damage occurs, mediated in part by the production of reactive oxygen species. As antioxidants reduce reactive oxygen species, some athletes take high doses of the antioxidants (eg, vitamins C and E) hoping to attenuate muscle damage. However, there is little evidence to support this practice, and there is some evidence that interfering with reactive oxygen species signals may impair muscle performance [94]. Runners should be informed of the potential risks associated with taking high doses of antioxidants [95,96].
Psychology — There is little evidence that psychological factors play an important role in running injuries. One study of 30 runners found that those with type A personality traits did not have higher injury rates than others but did have a higher risk of multiple injuries [97]. General studies of athletes have found a weak association between injury risk and such psychological factors as aggressiveness, exhaustion, and stressful life events [98].
TRAINING SUGGESTIONS TO REDUCE INJURY RISK — Despite the dearth of high-quality evidence to determine best practice [38,99], we have found the training tips listed below to be helpful and to reduce the risk of injury for many runners, particularly recreational runners:
Beginning runners
●Inexperienced runners often progress best using a combination of running and walking for a set time and gradually increasing the percentage of time spent running.
●Beginning runners should start with no more than 20 minutes of total training time per day and increase training time no more than five minutes approximately every 14 days.
●Most beginners do best on an every-other-day training program, which enables gradual improvement of their aerobic and musculoskeletal fitness.
Mileage and rest guidelines
●With the exception of elite runners, most individuals develop fewer injuries by limiting their total mileage to 40 miles (65 km) per week. (See 'Training variables' above.)
●Runs longer than 13 miles (20 km) are best done no more frequently than once every 14 days.
●Most individuals do best running no more than four or five days per week, with at least one rest day and one to two days doing other activities, such as strength training, cycling, or swimming (ie, cross-training).
●Runners should limit themselves to two to three marathons per year.
Warm-up
●Ease into training with a dynamic warm-up or light jog.
●Stretching before runs does not appear to reduce injuries; runners may do better stretching after their run or improving their strength and flexibility using other techniques, such as yoga or Pilates. (See 'Stretching and warm-ups' above.)
Training variables
●Runners who experience frequent injuries are likely to benefit from running on a treadmill or a soft surface. Older athletes reduce their injury risk by running on softer surfaces. (See 'Training variables' above.)
Training techniques
●Runners need a solid base of aerobic fitness before adding speed work.
●Speed work is generally less risky if runners begin with the "Fartlek" (speed play) approach for 20 to 30 percent of their continuous runs for at least one month before progressing to interval training (alternating fixed activity and rest periods) or timed repeat speed distances (eg, 10 sets of 200-m runs). Fartlek training consists of running at a faster pace at random times of variable duration during an otherwise standard distance run.
●Most runners need to limit the total mileage for interval or repeat distance speed training to 3 miles (5 km) or less.
●Fast downhill runs increase impact and injury risk and should be avoided.
Footwear
●Athletes should select a running shoe that feels extremely comfortable and is well-suited to their foot structure (eg, high or low arch, wide or narrow forefoot) (figure 1). (See 'Running shoe design' above.)
●Barefoot running, while it may help to improve the biomechanics of some runners, probably only benefits those with sound running biomechanics at baseline and a foot structure that does not increase their injury risk, and it should be limited to softer surfaces. Many running clinics are seeing an increase in metatarsal stress fractures in individuals new to this approach. For those planning to adopt barefoot or minimalist running, we advocate a gradual transition over several months. Barefoot running and running in minimalist shoes is discussed in greater detail above. (See 'Running barefoot or with minimalist shoes' above.)
Nutrition and recovery
●Runners should maintain adequate hydration and increase their salt intake if they tend to sweat heavily.
●Carbohydrate and protein intake soon (within about 30 minutes) after an intense workout speeds recovery. (See 'Nutrition and supplementation' above.)
Supplemental strength training
●Many runners have disproportionately strong hamstrings. Cross-training with a road or stationary bicycle or other equipment that develops quadriceps strength, or following a properly designed, supplemental weightlifting program, helps to balance the hamstring dominance of runners. (See "Practical guidelines for implementing a strength training program for adults".)
●Many runners have weak hip flexors and hip abductors. Performing supplemental strength exercises for these muscles may reduce the risk of injury.
Useful exercises may include:
•Step-ups – Step up onto a step or other raised platform (eg, bench) using bodyweight or while holding a weight
•Side stepping with resistance band (picture 5)
•Single-leg squats (movie 3 and picture 6)
●Exercises to improve ankle and foot strength and mobility may reduce the risk of running-related injury.
Useful exercises may include:
•"Toe yoga" – Alternate between pushing flexed big toe into the ground while other toes remain dorsiflexed, then pushing toes into the ground while big toe remains dorsiflexed
•Towel scrunches – Place a towel under your foot and scrunch it up using your toes (picture 7)
•Heel raises on a step (picture 8)
In a randomized trial involving 118 recreational runners, those assigned to an eight-week training course and subsequent online support involving a progressive series of exercises to improve mobility and strength primarily in the ankle and intrinsic muscles of the foot sustained significantly fewer injuries (20 versus 8) over 12 months than those in the control group, who were given a program of static stretching [100]. Further study is needed to confirm these findings.
●Achilles tendon flexibility wanes with age. Regular performance of eccentric strength exercises for the calf complex may help prevent injury. (See "Achilles tendinopathy and tendon rupture", section on 'Rehabilitation using resistance exercise'.)
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: General issues in muscle and tendon injury diagnosis and management" and "Society guideline links: Muscle and tendon injuries of the lower extremity (excluding Achilles)" and "Society guideline links: Plantar fasciitis" and "Society guideline links: Patellofemoral pain".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Achilles tendon injury (The Basics)" and "Patient education: Metatarsalgia (The Basics)" and "Patient education: Patellofemoral pain (The Basics)" and "Patient education: Iliotibial band syndrome (The Basics)" and "Patient education: Hamstring injury (The Basics)" and "Patient education: Shin splints (The Basics)")
SUMMARY AND RECOMMENDATIONS
●Epidemiology – Up to one-half of regular runners report an injury annually. Some injuries are traumatic, but most are due to overuse, and many of these involve the knee. The most common diagnoses include patellofemoral pain (PFP), medial tibial stress syndrome (MTSS; ie, "shin splints"), Achilles tendinopathy, iliotibial band syndrome (ITBS), plantar fasciitis, and stress fractures of the metatarsals and tibia. (See 'General epidemiology' above.)
●Risk factors – Multiple intrinsic and extrinsic risk factors are associated with running-related lower extremity injuries. The most easily modified are training variables such as mileage and intensity. The role of other factors, such as shoe type and biomechanics, is less clear. (See 'Risk factors' above.)
•Shoe selection – Based on limited evidence and our clinical experience, we suggest using the running shoe that feels most comfortable, fits properly, and is well suited to the shape of the runner's foot (figure 1). (See 'Running shoes' above.)
•Gait and strength – Evidence pertaining to gait and biomechanics is limited and difficult to interpret. Available evidence suggests that overstriding (runner's lead foot strikes the ground in front of the body's center of mass) and hip abductor weakness increase the risk of sustaining a lower extremity running injury. (See 'Gait, strength, and biomechanics' above.)
•Nutrition – Inadequate vitamin D and calcium increases the risk of stress fracture. Participants in a regular running program should eat a healthy diet that provides adequate calories, carbohydrates, protein, healthy fats, and hydration. (See 'Nutrition and supplementation' above.)
●Training suggestions – Guidance for beginning and experienced recreational runners is provided in the text. A few highlights include (see 'Training suggestions to reduce injury risk' above):
•Apart from elite runners, most individuals develop fewer injuries by limiting their total mileage to 40 miles (65 km) per week.
•Most individuals do best running no more than four or five days per week with at least one rest day and one to two days doing other activities, such as strength training, cycling, or swimming (ie, cross-training).
•Stretching before runs does not appear to reduce injuries; a dynamic warm-up or light jog is better preparation for a longer run.
•Many runners are susceptible to injury due to muscle weakness. Supplemental strength training, particularly for the hips, calves, and feet, helps to reduce such risk.
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