If I had a krone for each time someone has stated to me that «ultramarathons cannot possibly be good for your health», well, I might have had enough to cover the starting fee for my next ultramarathon. On the other hand, there are also plenty of people who argue that we are born to run (as the book claims), and historical evidence shows that it has been relatively normal to run what today is considered ultra distances. For professional runners in ancient Greece, and other old civilisations, running 100-200km to deliver messages was just a normal working day (Gotaas, 2008). As usual in such situations, I asked myself WDSS (What Does Science Say?), and headed to PubMed to find out.
That was a couple of years ago. A lack of deadlines and feline sabotage are some of the factors why I never got round to writing anything, but as I am taking part in a 100 miles grand slam this year my interest in this subject has been renewed. As a personal trainer I would also like to give my ultrarunner clients evidence based advice, as I was drilled to do in my previous career as a physiotherapist.
There is actually quite a lot of research on ultramarathon running, but few studies with any long term follow up. More is therefore known about the acute effects of running a 100 mile or 24 hour race than how long it takes before bodily functions returns to normal, or whether there are any detrimental long term effects.
Not surprisingly extreme ultramarathons put a lot of strain on the musculoskeletal system, and injuries are common. During a 6 day track race the injury rate was 60 %, with the ankles and feet being the most injury-prone body parts, followed by knees and hips (Hutson, 1984). One might argue that a 6 day race puts the body under a much greater strain than a 100 mile race, but the incidence and types of injuries reported in the Ultrarunners Longitudinal Tracking Study (Hoffman & Krishnan, 2014) are quite similar. This study looked at self reported injuries and health issues in 1212 ultrarunners, 95 % of which had completed an ultramarathon of at least 50km in the last 12 months. In this population 77 % reported exercise related injuries in the same period; again lower leg and feet were the most injury prone body part (44 %) followed by knee and iliotibial band issues (40 %) with back pain and hamstring strains making up the bulk of the remaining injuries (12 % each). On average these injuries caused the runners 14 missed training days per year, but only 0,3 missed work or school days.
Even in the absence of an outright injury the musculoskeletal system sustains a high level of microtrauma. In one study of participants in a 24 hour race there was a marked elevation of white blood cells (WBC), and in particular the subtypes involved in inflammation, post race compared to baseline values. There was also a 70 fold increase in blood levels of creatine kinase (CK) post race compared to prerace. Minute damage to muscle fibres or contractile fibres will result in the release of CK, a marker of muscle damage. The authors of this study therefore concluded that prolonged submaximal exercise is associated with significant skeletal muscle damage (Waskiewicz et al, 2012). A study of paticipants in a 100 km run found that CK levels and other markers of stress and inflammation rose markedly after the 50th kilometer, and stayed elevated or continued to rise in the first 24 hours after, leading the authors to conclude that running longer that 50 km can lead to «toxic damage» to the body (Jastrzebski et al, 2015). However, it should be noted that this study seemed to have a negative bias throughout, stating in the introduction that there is evidence that running marathons can lead to death.
What we do learn from these two studies is that immediatly after an ultramarathon there is significant levels of muscle damage. A study of participants in the Ultra Trail Mont Blanc (UTMB) 2009 provides more insight into the recovery process as well as the acute effects, as they followed the athletes for several weeks after the event (Millet et al, 2011). This study found even greater levels of muscle damage, maybe not surprising considering the amount of altitude gain and time taken to complete this course, with CK and myoglobin levels respectively more than 100 and 600 times greater post race than pre. This study also looked at how such a race affect neuromuscular function, and found significant loss of strength in both knee extensors and calf muscles (other muscle groups were not measured). Strength loss was less and recovered faster in the knee extensors, but was restored in both muscle groups by 9 days post race, as was CK and myoglobin levels, indicating no long term muscle damage. Despite the extremely high levels of myoglobin measured, similar to levels in patients receiving treatment for rhabdomyolosis, none of the study participants required hospitalisation or treatment for this. The authors of the study noted that the year before there had been one incident of this condition, but this was found to have been linked to use of NSAIDs and dehydration in the week before the race.
Two studies from the 100 miles long Western States Endurance Race (WSER), seems to back up the anecdotal evidence from the UTMB regarding the use of NSAIDs. One study found that athletes using NSAIDs during the race had higher post race plasma levels of inflammatory proteins compared to non-users (Nieman et al, 2005), the other that Ibuprofen use leading up to and during this 160 km race was associated with significantly increased oxidative stress (McAnulty et al, 2007).
In several of the above studies the researchers also found large increases in blood levels of the enzymes aspartate aminotransferase (AST) and alanine aminotransferase (ALT) (Millet et al, 2011, Wu et al, 2004, Waskiewicz et al, 2012, Jastrzebski et al, 2015). Both these enzymes are seen as reliable tests for liver damage, i.e. it is not just the muscles that sustain damage during prolonged exercise. The amount of liver damage increases with distance, and continues to rise during the first 24 hours of recovery (Jastrzebski et al, 2015) Luckily, the effect seems to be transient. The study from UTMB showed that liver enzymes were back to baseline values by day 9 post race (Millet et al, 2011). A study of participants in the Asian 24h Championship also found that liver values had recovered back to baseline values after 9 days (Wu et al 2004). However, it was noted in this study that the mean pre-race ALT and AST exceeded the normal range, leading the authors to raise concerns that ultrarunning may lead to chronic liver damage. The study done in connection with the UTMB did not note such findings or concerns, and the baseline values of ALT and AST were lower in than in the Asian study. The sample size was also bigger; 60 vs 11 athletes. It is also worth noting that the study by Waskiewicz et al (2012) interpreted their results as to indicate only minor liver damage following a 24 hour race.
Ultramarathons also induce transient sports anemia due to accumulate destruction of red blood cells (RBC) due to mechanical and oxidative stress. The study by Wu et al (2004) demonstrated a decrease in RBC and haemoglobin (Hb) levels in blood, and an increase in serum ferritin due to iron being released from damaged cells. The values for RBC and Hb were lowest 2 days after the 24 hour race, but had recovered within 9 days, whereas serum ferritin remained high. Since this study only had a 9 day follow up it is unknown how long it takes for iron levels in blood to normalise.
It has long been known that high training loads can leave endurance athletes more susceptible to upper respiratory tract infections (URTIs). Several studies have found that WBC count rise markedly during ultramarathons (Waskiewicz et al, 2012, Wu et al, 2004, Nieman et al, 2003) as the body deals with inflammatory reactions from mechanical and oxidative stress. Whether or not this increases risk of URTIs is not clear, as results differ. No URTIs were reported by any of the participants in a study of participants in the Comrades ultramarathon in South Africa or the Asian 24h Championships (McKune et al 2005, Wu et al, 2004), however two studies of participants in the WSER found a 24 % and 26 % incidence of URTIs in the two weeks after the race (Nieman et al, 2006, Nieman et al, 2003).
The evidence presented thus far seems to indicate that ultramarathons can be bad for you, as it has a negative effect on the musculoskeletal system, liver, oxygen delivery system and (maybe) the immune system. However, studies with a longer follow up has found these negative effects to be transient. Ultrarunners also have better health compared to the general population, with very low incidence of serious illnesses such as cancer and cerebrovascular disease (4,5 and 0,7 % respectively), and have less than half the number of sick days than average American (1,5 vs 3,7 days per year) (Hoffman & Krishnan, 2014). Some changes that occur in the body during ultramarathons are even favourable, such as changes in blood lipid levels. Total serum cholesterol and fatty acids decreases, whereas LDL cholesterol decreases and HDL cholesterol leading to a more favourable ratio between «good» and «bad» cholesterol (Waskiewicz et al, 2012, Wu et al, 2004). This could mean that ultrarunning lowers risk of cardiovascular disease (Waskiewicz et al 2012), however lipid levels returned to baseline values within two weeks in the study by Wu et al (2004).
In conclusion, although there are several negative acute effects of running an ultramarathon our bodies seem to cope with these well, and repair damage to muscles, blood cells, and the liver within two weeks. The Ultrarunners Longitudinal Tracking Study found that ultrarunners have better health than the general population, suggesting that there are few, if any, negative long term effects. However, this could be due to a survival of the fittest process as those that develop health problems withdraw from the sport and therefore are not included in such studies. No studies with a longer follow up than 9 days – 2 weeks were found. More studies with long term follow up and studies targeting ultrarunners who are no longer active in the sport are therefore needed to shed light on this issue.
Based on the findings in this literature review the following advice for post ultramarathon recovery seems prudent:
- Avoid strenuous endurance exercise for the first two weeks after a 100 mile/24 hour race. Endurance training should be kept below anaerobic threshold, approximately 80 % of HRmax or lower. Although ultramarathons result in significant muscle damage shorter exercise duration at low intensity is known to primarily lead to adaptations in the cardiorespiratory system, putting less stress on the musculoskeletal system. High intensity short duration aerobic exercise (interval training, speedwork etc) is known to generate microtrauma in the muscles, leading to high levels of local adaptations in the muscles exercising (Docherty & Sporer, 2000). The latter type of exercise would be at best ineffective following an ultramarathon, and could at worst lead to rhabdomyolosis or other serious health issues by overloading systems that are already stressed.
- Since it has been demonstrated that muscle strength and neuromuscular function is diminished for up to nine days after an extreme ultramarathon (Millet et al, 2012) it is probably also wise to avoid strength training for the same period. Strength training works by overloading the muscles, inducing microtrauma and small tears in the muscle fibres and contractile tissues. The body responds by repairing the damage and making muscle fibres and tendons stronger and thicker so they can withstand this level of load in the future. As with strenuous aerobic exercise, starting strength training to soon after an ultramarathon could overload the systems, disrupt recovery, and lead to injury.
- Upper body conditioning work is also included in the recommendation concerning strength training above. Although these muscles are not stressed directly by running, heavy upper body resistance work would contribute to increase the total circulating levels of CK, myoglobin, oxidants, and inflammatory proteins, and could therefore stress the body further and hamper recovery.
- Do not use NSAIDs/Ibuprofen: Studies from the WSER found that NSAID use had the opposite of the desired effects: it did not lead to less muscle damage or soreness, but significantly increased oxidative stress and inflammation (McAnulty et al, 2007, Nieman et al, 2005).
- As several of the studies discussed have demonstrated liver damage during and after extreme ultramarathons it would probably also be wise to abstain from or at least limit alcohol consumption during the time it takes for the AST and ALT to return to baseline values.
Docherty. D, Sporer, B. (2000). A proposed model for examining the interference phenomenon between concurrent aerobic and strength training. Sport Med 2000 Dec; 30(6); 385-94
Gotaas, T. Løping. En verdenshistorie. Gyldendal (Oslo), 2008.
Hoffman, MD, Krishnan, E (2014). Health and exercise-related medical issues among 2012 ultramarathon runners: Baseline findings from the Uktrarunners Longitudinal TRAcking (ULTRA) study. PLoS ONE 9(1):e83867. doi:10.1371/journal.pone.0083867
Hutson, MA (1984). Medical implications of ultra marathon running: observations on a six day track race. Br J Sports Med. 1984 mar;18(1):44-5
Jastrzebski, Z, Zychowska, M, Radziminski, L, Konieczna, A, Kortas, J (2015). Damage to liver and skeletal muscles in marathon runners during a 100km run with regard to age and running speed. Journal of Human Kinetics vol 45/2015, 93-102.
McAnulty, SR, Owens, JT, McAnulty, LS, Nieman, DC, Morrow, JD, Dumke, CL, Milne, GL (2007). Ibuprofen use during extrene exercise: effects on oxidative stress and PGE2. Med Sci Sports Exerc. 2007 Jul; 39(7): 1075-9
McKune, AJ, Smith, LL, Semple, SJ, Wadee, AA (2005). Ibfluence og ultra-endurance exercise on immunoglobin isotypes and subclasses. Br J Sports Med. 2005 Sep; 39(9):665-70
Millet, GY, Tomazin, K, Verges, S, Vincent, C, Bonnefoy, R, Boisson, RC, Gergelé, L, Féasson, L. (2011). Neuromuscular consequences of an extreme mountain ultra-marathon. PLoS One. 2011 Feb 22;6(2):e17059. doi 10.1371/journal.pone.0017059
Nieman, DC, Dumke, CL, henson, DA, McAnulty, SR, McAnulty, LS; Lind, RH, Morrow, JD: Immune and oxidative changes during and following the Western States Endurance Run. Int J Sport Med. 2003 Oct; 24(7):541-7
Nieman, DC, Dumke, CL, Henson, DA, McAnulty, SR, Gross, SJ, Lind, RH: Muscle damage is linked to cytokine changes following a 160-km race. Brain Behav Immon. 2005 Sep;19(5): 398-403
Nieman, DC, Henson, DA, Duke, CL, Lind, RH, Shooter, LR, Gross, SJ: Relationship between salivary IgA secretion and upper respiratory tract infection follwoing a 160 km race. J Sports Med Psyh Fitness. 2006 Mar; 46(1): 158-62
Waskiewicz, Z, Klapcinska, B, Sadowska_krepa, E. Czuba, M, kempa, K, Kimsa, E, Gerasimuk, D (2012). Acute metabolic responses to a 24-h ultra-marathon race in male amateur runners. Eur J Appl Psyiol. 2012 May;112(5):1679-88.
Wu, HJ, Chen, KT, Shee, BW, Chang, HC, Huang, YJ, Yang, RS (2004). Effects of 24 h ultra-marathon on biochemical and hematological parameter. World J Gastreoenterol. 2004 Sept 15;10(18):2711-4.