Ultramarathon runners are a relatively small and unique group of distance runners with somewhat different medical issues than other distance runners. This article outlines some of those differences so that clinicians caring for these runners in the clinic or at competitions might be better prepared.
Key points
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Participation in ultramarathons has grown exponentially in recent years, but those running ultramarathons represent a small subset of runners. Ultramarathon runners can range widely in age but most are between 30 and 49 years, most are men, and as a group, ultramarathon runners tend to be well-educated.
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Injury rates appear similar for ultramarathon runners compared with other distance runners, and the types of injuries are also similar across groups. However, ultramarathon runners are observed to have fewer stress fractures and, when they occur, are more common in the foot as opposed to the lower leg, thigh, or pelvis.
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Because ultramarathons often take place in remote locations, preparticipation screening for these events is particularly important.
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Compared with shorter distance races, medical issues more unique to ultramarathon races include blisters, gastrointestinal distress, exercise-associated hyponatremia, dehydration, and transient vision impairment.
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The long-term health implications from ultramarathon running and training are not clear.
Introduction
Ultramarathons are foot races longer than the 42.195-km marathon distance, and may be continuous or staged (discontinuous) over several days. These events may take place on tracks or roads, but most are on trails, often in wilderness environments. As a result, the physiologic stress of running extended distances may be compounded by challenging terrain and environmental factors. These geographic barriers reduce the level of aid and medical support compared with urban events.
The most typical distances for ultramarathons are 50 km, 80 km (50 miles), 100 km, and 161 km (100 miles). More than half of ultramarathons in North America are 50 km in distance, and the second most common distance is 80 km. Additionally, events longer than 161 km exist, including fixed time events and events of nonstandard distances.
Although marathon participation has shown continued steady growth for the past 3 decades, participation in ultramarathons has grown exponentially in recent years. There were more than 76,000 ultramarathon finishes in North America in 2014, which is approximately twice the number of finishes 5 years ago. Despite the growth in ultramarathon participation, the number of ultramarathon finishes is currently less than 13% of the number of marathon finishes, so ultramarathon runners continue to represent a relatively small subset of runners. The present work focuses on the unique characteristics and medical issues in this running population.
Introduction
Ultramarathons are foot races longer than the 42.195-km marathon distance, and may be continuous or staged (discontinuous) over several days. These events may take place on tracks or roads, but most are on trails, often in wilderness environments. As a result, the physiologic stress of running extended distances may be compounded by challenging terrain and environmental factors. These geographic barriers reduce the level of aid and medical support compared with urban events.
The most typical distances for ultramarathons are 50 km, 80 km (50 miles), 100 km, and 161 km (100 miles). More than half of ultramarathons in North America are 50 km in distance, and the second most common distance is 80 km. Additionally, events longer than 161 km exist, including fixed time events and events of nonstandard distances.
Although marathon participation has shown continued steady growth for the past 3 decades, participation in ultramarathons has grown exponentially in recent years. There were more than 76,000 ultramarathon finishes in North America in 2014, which is approximately twice the number of finishes 5 years ago. Despite the growth in ultramarathon participation, the number of ultramarathon finishes is currently less than 13% of the number of marathon finishes, so ultramarathon runners continue to represent a relatively small subset of runners. The present work focuses on the unique characteristics and medical issues in this running population.
Characteristics of ultramarathon runners
Ultramarathon runners vary widely in characteristics. This may be especially true with regard to their reasons for running ultramarathons. Many run and train for these events largely for health and social reasons, as well as for personal discovery and growth. Although most may have personal goals driving them to run their best during a race, many are not focused on winning or age group placing. Because prize money in these events is rare, only a very few make a profession of ultramarathon running, and even those runners must rely on sponsorship support.
Because competition is not the focus for many ultramarathon participants, the age of participants crosses a wide spectrum. For instance, in analyzing 161-km ultramarathon participation from 1997 through 2008, we found finishers ranged in age from 15 to 75 years. The largest proportion of ultramarathon participants are in the 30 to 39-year and 40 to 49-year age groups, with each group accounting for approximately one-third of total participants, and median age has been at 41 to 42 years for the past couple of years. In general, shorter distance runners tend to be younger than ultramarathon runners. For perspective, the median age of recent American marathon participants has been 36 to 37 years.
The fastest ultramarathon runners also tend to be slightly older than the fastest runners at shorter distances. The fastest marathon performances have typically been achieved by runners who are 25 to 35 years of age. In contrast, previous cross-sectional and longitudinal analyses have shown that top ultramarathon performances can be achieved at age 40 years and beyond.
Ultramarathon participation among women has been increasing, although women account for only roughly 30% of ultramarathon participants in North America. This compares with women accounting for more than 40% of American marathon finishers and approximately 60% of half-marathon finishers.
Ultramarathon runners are more likely to be in a stable relationship and to have a higher education level than the general American population. With regard to education level, we have found that more than 80% have at least a bachelor’s degree, and 38% to 46% have a graduate degree. Ultramarathon runners also tend to have professional occupations. To some, it might be surprising that people so well-educated would voluntarily choose to run such long distances. But, the predictable findings that ultramarathon runners tend to be goal oriented and internally motivated, are characteristics that likely impact both professional and personal life.
An interesting trend we have observed is that a subset of ultramarathon runners are exploring the limits of human potential by running multiple 161-km ultramarathons in a given year. This is partly because the opportunity to attempt such feats has increased with a constantly increasing number of available races of this distance. For instance, there are 140,161-km ultramarathons in North America in 2015, up more than threefold from the 45 races of this distance in 2007. A number of individuals have accomplished what is inconceivable for most people by completing more than ten 161-km ultramarathons in a year. Reportedly, a man finished 40,161-km ultramarathons in 2014 ( https://www.strava.com/athletes/309028 ).
Another trend of interest observed is a decrease in the number of years of regular running before the first ultramarathon is completed. In other words, those individuals running their first ultramarathon tend to have less running experience now than in the past. This may have important implications on the risk of injuries and medical issues during events.
Injuries in ultramarathon runners
Runners preparing to run both short and long distances are at risk for various overuse musculoskeletal injuries. A number of factors affect the injury patterns and injury incidence in runners. Potential factors of particular importance to consider for ultramarathon runners include regular training distance, age and experience level, typical running surface and exercise intensity, and use of alternate activities in training. Not a lot is known about how these factors might affect injuries in this group of athletes.
The annual incidence of injuries in ultramarathon runners appears similar to that of shorter distance runners. For instance, we found that 52% of a large cohort of 161-km ultramarathon entrants had suffered an injury severe enough to interfere with training in the previous year, and 65% of active ultramarathon runners participating in a longitudinal health study (the Ultrarunners Longitudinal TRAcking or ULTRA Study) reported an exercise-related injury resulting in lost training of at least 1 day in the previous year. This is comparable to the annual injury incidence rate reported among long-distance runners of 50% to 60%.
The finding that injury rate is not higher among ultramarathon runners compared with shorter distance runners is interesting given that running distance has been found to be a risk factor for injury, and the ultramarathon runners we had examined were generally running greater distances than the runners in the studies of other runners. The ultramarathon runners we examined in one study reported running an average of 3347 km in the previous year, and those who did and did not sustain an injury during the study year had similar average annual running distances. In other studies of runners preparing for 161-km ultramarathons, we found that the highest running distance in 1 week during the 3 months before the events averaged between 123 and approximately 160 km, although the distance varied considerably. We also know that it is not uncommon for these runners to have training runs of 80 km or longer in preparation for long ultramarathons. In general, those running longer races put in greater training distances, and presumably those with limited running distances in training for ultramarathons incorporate alternate forms of exercise besides running into their training program.
It is evident there are determinants of injury besides running distance. Likely those individuals who have withstood the stress associated with ultramarathon running have better adapted for such demands and/or have favorable intrinsic characteristics that reduce their injury risk relative to the distances they run. However, ultramarathon runners also tend to have a high use of running surfaces other than concrete or asphalt. Use of running surfaces softer and with greater variation than concrete or asphalt may offer some protection from certain injuries. Differences in relative intensity and running speed, along with the associated effects this might have on stride frequency, foot strike pattern, and impact forces, could also be of importance in limiting injuries among ultramarathon runners.
Although running distance does not seem to be a distinguishing factor for whether ultramarathon runners sustain injuries, we have found several other important characteristics. Those sustaining an injury were younger and less experienced at running, had relatively less focus on running compared with other activities, spent a greater proportion of their exercise time at high intensities, and were more likely to have performed regular resistance training. In examining the characteristics of those with exercise-related stress fractures, the results were similar except that runners sustaining stress fractures were more likely to be women, were running greater distances, and were less likely to have performed regular resistance exercise. A previous history of exercise-related stress fracture was also found to be another risk factor for a stress fracture in this group.
The types of injuries sustained by ultramarathon runners are similar to injuries occurring in shorter distance runners ( Table 1 ), but the distribution of injuries varies between groups. The knee is the most common site of injury for both ultramarathon runners and other distance runners. However, stress fractures are a relatively less common issue in ultramarathon runners compared with shorter distance runners. We found that stress fractures accounted for 3.7% of exercise-related injuries, and 5.5% of the ultramarathon runners reported having suffered a stress fracture in the previous year. Previous work has reported that stress fractures account for 5% to 16% of all injuries in runners, and annual incidence has been reported to be as high as 25.9% among a group of elite middle and long-distance runners.
| Injury Type and/or Location | n | Distribution, % | Incidence, % |
|---|---|---|---|
| Knee issues | 291 | 15.3 | 24.0 |
| Iliotibial band issue | 191 | 10.1 | 15.8 |
| Calf strain | 159 | 8.4 | 13.1 |
| Back injuries | 150 | 7.9 | 12.4 |
| Hamstring strain | 143 | 7.5 | 11.8 |
| Achilles tendinitis or tear | 131 | 6.9 | 10.8 |
| Ankle sprain | 131 | 6.9 | 10.8 |
| Plantar fasciitis | 129 | 6.8 | 10.6 |
| Lower leg or ankle tendinitis not involving Achilles | 111 | 5.8 | 9.2 |
| Hip flexor strain | 106 | 5.6 | 8.7 |
| Other foot and ankle injuries | 54 | 2.8 | 4.5 |
| Other leg, pelvis, or hip issues | 45 | 2.4 | 3.7 |
| Stress fracture involving foot | 41 | 2.2 | 3.4 |
| Morton neuroma | 38 | 2.0 | 3.1 |
| Metatarsalgia | 38 | 2.0 | 3.1 |
| Great toe metatarsal phalangeal joint pain (bunion) | 30 | 1.6 | 2.5 |
| Stress fracture involving tibia or fibula | 23 | 1.2 | 1.9 |
| Other lower leg injuries | 18 | 0.9 | 1.5 |
| Skin wounds, blisters, and infections | 18 | 0.9 | 1.5 |
| Other not previously specified | 18 | 0.9 | 1.5 |
| Upper extremity injuries including fractures | 17 | 0.9 | 1.4 |
| Fractures not involving the extremities | 12 | 0.6 | 1.0 |
| Stress fracture involving femur/hip | 6 | 0.3 | 0.5 |
In addition to stress fractures appearing to be less common in ultramarathon runners than shorter distance runners, the anatomic site for stress fractures appears to differ among running groups. Although the lower leg is typically reported as the site of most stress fractures in runners, we have found that ultramarathon runners sustain most of their stress fractures in the foot. We have suggested that the lower incidence of stress fractures in ultramarathon runners relates to the fact that, in general, only approximately half of their running is on concrete or asphalt. The higher distribution of stress fractures involving the foot may be due to greater demands sustained by the foot from running on irregular terrain.
Preparticipation screening for ultramarathons
Ultramarathons commonly take place in remote locations that may become harsh in terms of weather conditions and terrain. Such environments necessitate considerations to greater attention to preparticipation screening. For instance, certain medical issues may not cause inordinate risk for running in urban settings, but once in a remote location, that condition may create risks that could preclude safe participation. An example might be a runner with history of epilepsy, which might be considered relatively safe for an urban marathon because a swift emergency medical response could be enacted. In contrast, a seizure experienced during an ultramarathon in a remote location would preclude a swift emergency medical response. Thus, preparticipation medical screening for clinical and medical-legal risk reduction at ultramarathons is particularly important.
When event logistics allow, the medical screening process is best performed in advance of the race. Ideally, this means performing the screening with enough time in advance to avoid a situation in which a runner has spent considerable time and money traveling to an event and is subsequently excluded from participation, yet not too far in advance that new medical issues develop in the interim between the screening and the event.
The screening is best performed when considering the relative risk of participation, and whether the event and athlete can both reasonably accept those risks. The athlete and the event organizers must recognize that it may not be only the athlete with the medical issue who is at risk, as other athletes may inadvertently be exposed to greater risk as well. Certainly, the relative risk should be considered in the context of previous training and competition, such that uneventful training and competition may lower the perceived risk. Considerations might also include whether the athlete can participate with reduced expectations (eg, participating but not competing with full effort) or using accommodations (eg, pacers).
An approach to the preparticipation screening process for remote endurance events has been provided elsewhere. The reader is referred to that work, which also details considerations relative to various medical issues, including anaphylaxis and severe allergy, seizure disorder, diabetes, previous exertional heat stroke, kidney injury, coronary artery disease, arrhythmias, following ablation therapy for conduction abnormalities, use of antiplatelet agents, pregnancy, gastrointestinal bleeding, exercise-associated hyponatremia (EAH), mental illness, and altitude illness.
Medical issues during ultramarathons
The common medical issues that present during ultramarathons and their management have been detailed elsewhere. Although the medical issues that present during an ultramarathon also can present during shorter races, certain medical issues tend to be more pertinent to ultramarathons because of the longer exercise durations and remote environments typical of these events. Issues most unique to ultramarathons are the focus of this review and include blisters, gastrointestinal distress, EAH, severe dehydration, and transient vision impairment.
Blisters
Blisters are the most commonly encountered medical problem in ultramarathons. Although blisters rarely lead to a more severe illness, such as cellulitis, they can have serious adverse effects on race performance, as evident from Table 2 . For instance, blisters and “hot spots” on the feet were reported the most (40.1%) as a factor adversely affecting race performance among finishers of a 161-km ultramarathon. However, skin issues were reported as the main reason for dropping out by only 5.8% of nonfinishers. In general, painful nonbloody blisters that present during a competition are best drained, while taking care to preserve the overlying skin, taped, and then lubricated. In the case of blood blisters, draining should be with caution because of the theoretic risk of infection to the exposed dermal vasculature. Prevention is best achieved by proper training, regular filing of calloused areas, avoiding changes in footwear for races, and use of lubricants.
| Finishers | Nonfinishers | P | |
|---|---|---|---|
| Blisters or “hot spots” on feet | 40.1 | 17.3 | <.0001 |
| Nausea and/or vomiting | 36.8 | 39.6 | .60 |
| Muscle pain | 36.5 | 20.1 | .0005 |
| Exhaustion | 23.1 | 13.7 | .024 |
| Inadequately heat acclimatized | 21.0 | 28.1 | .12 |
| Inadequately trained | 13.5 | 15.1 | .66 |
| Muscle cramping | 11.4 | 15.8 | .22 |
| Injury during the race | 9.0 | 10.1 | .73 |
| Ongoing injury | 7.5 | 15.8 | .010 |
| Illness before the race | 6.0 | 5.0 | .83 |
| Started out too fast | 5.1 | 6.5 | .52 |
| Vision problems | 2.1 | 3.6 | .35 |
| Difficulty making cutoff times | 1.8 | 27.3 | <.0001 |
| Other, not categorized | 11.7 | 26.6 | .0001 |
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