Physiology and Pathophysiology in Ultra-Marathon Running

Themes and trends in marathon performance research: a comprehensive bibliometric analysis from 2009 to 2023

Background: When marathon runners break the 2-h barrier at the finishing line, it attracts global attention. This study is aimed to conduct a bibliometric analysis of publications in the field of marathon running, analyze relevant research contributors, and visualize the historical trends of marathon performance research over the past 15 years. Methods: On 8 December 2023, we extracted high-quality publication data from the Web of Science Core Collection spanning from 1 January 2009 to 30 November 2023. We conducted bibliometric analysis and research history visualization using the R language packages biblioshiny, VOSviewer, and CiteSpace. Results: A total of 1,057 studies were published by 3,947 authors from 1,566 institutions across 63 countries/regions. USA has the highest publication and citation volume, while, the University of Zurich being the most prolific research institution. Keywords analysis revealed several hotspots in marathon research over the past 3 years: (1) physiology of the elite marathon runners, (2) elite marathon training intensity and pacing strategies, (3) nutritional strategies for elite marathon runners, (4) age and sex differences in marathon performance, (5) recovery of inflammatory response and muscle damage. Conclusion: This study presents the first comprehensive bibliometric analysis of marathon performance research over the past 15 years. It unveils the key contributors to marathon performance research, visually represents the historical developments in the field, and highlights the recent topical frontiers. The findings of this study will guide future research by identifying potential hotspots and frontiers.

Personality of marathon runners: a narrative review of recent findings

Participation in marathons has dramatically increased over the last few years. Marathon running has many proven beneficial effects, especially on cardiovascular health and fitness. Most research has focused on physiologic and pathophysiologic adaptations in connection with endurance exercise. Nevertheless, marathon running also has a major impact on psychological aspects and positively influences mental health, which has only recently attracted research interest. The present narrative review aimed to review the personality traits of marathon runners with an emphasis on recent literature. Marathon runners show a distinct personality and highly characteristic personality traits needed to successfully finish such a demanding race, i.e., a strong sense of vigor, self-sufficiency, and intelligence as well as low scores in anger, fatigue, tension, and depression. Furthermore, personality differences are detectable between runners of different sexes, ages, and performance level groups. This has significant clinical implications for athletes, coaches and competition organizers, as these groups show different patterns of personality traits. Future studies should focus on changes in cognition and mood states pre-, during, and post-endurance events, as well as during training periods. Large-scale studies comparing personality differences by sex, age, and performance are also important for better clinical guidance. See also the graphical abstract(Fig. 1).

Impact of Running Exercise on Intervertebral Disc: A Systematic Review

CONTEXT

Running is one of the most popular sports worldwide. However, controversies exist regarding how running affects runner's intervertebral discs (IVD).

OBJECTIVE

The purpose of this study was to systematically review studies that evaluated IVD morphology or composition changes in response to running exercise, to determine the impact of running exercise on IVD.

DATA SOURCES

A systematic literature search was performed for 4 major databases: PubMed, Cochrane, Embase, and Web of Science.

STUDY SELECTION

Inclusion criteria were as follows: (1) healthy people without known IVD disease or major complications such as tuberculosis (IVD degeneration or low back pain are considered as minor complications); (2) subjects performed 1-time or regular running exercises; (3) pre and post comparison of runners or comparison between runners and healthy control subjects; (4) direct or indirect IVD morphology or composition measured; (5) IVD assessed before and after either acute or chronic running exercise, or compared cross-sectionally between runners and controls. Exclusion criteria were as follows: (1) reviews, editorials, letters or abstracts only; (2) animal studies; (3) subjects performed exercise other than running.

STUDY DESIGN

Systematic review.

LEVEL OF EVIDENCE

Level 3.

DATA EXTRACTION

The extracted data included study design and primary outcomes of the included studies. The Newcastle-Ottawa scale (NOS) was used to evaluate study quality and risk of bias.

RESULTS

A total of 13 studies with 632 participants were included in the final analysis; 4 studies measured IVD changes using stature or spinal height, and the other 9 measured IVD changes using magnetic resonance imaging; 6 studies found that running acutely and negatively impacts IVD; 3 out of 5 cross-sectional studies found that IVD parameters are better for runners than controls; 1 longitudinal study found no significant difference in IVD before and after training for marathon in runners; 1 longitudinal study found no significant difference in changes of IVD between runners and controls after 15 years of follow-up.

CONCLUSION

Negative changes in IVD exist for a short period of time after running, which may be due to the temporary compression pushing water content out of the disc. Cross-sectional studies suggest that long-term running exerts a mild positive effect on IVD; however, this inference has not been confirmed by high-quality longitudinal studies.

Differences in training characteristics of recreational endurance runners by race distance - results from the NURMI Study (Step 2)

Background

Although runner's profiles were previously investigated, information on the training frequency and training distance for short (5 km, 10 km) and long-distance (>21 km) running is absent. The present study aimed to investigate the associations between training routines and exercise habits of recreational endurance runners considering self-reported preferred race distance [10 km, half-marathon (HM), and marathon/ultra-marathon (M/UM)] subgroups.

Methods

This is a cross-sectional study, sampling 154 recreational runners of both sexes. A web survey was used for data collection regarding age, sex, preferred distance (10-km, HM, M/UM), training routines, exercise habits, and periodized training routines. The Chi-square test (Cramer's V) and Kruskal-Wallis test (Eta-Squared η2) with effect sizes were used for comparisons between race distances.

Results

Significant differences were shown for anthropometric, training, and periodization characteristics. Highly significant differences were found between subgroups for the number of sessions, running kilometers, and training hours at all periods and within all four preparation conditions. M/UM runners were training more frequently, for longer durations, and ran greater distances each week.

Conclusion

This finding supports the notion that training habits and periodization characteristics are different for different race distances (10-km, half marathon, marathon, and ultramarathon).

Limits of Ultra: Towards an Interdisciplinary Understanding of Ultra-Endurance Running Performance

Ultra-endurance running (UER) poses extreme mental and physical challenges that present many barriers to completion, let alone performance. Despite these challenges, participation in UER events continues to increase. With the relative paucity of research into UER training and racing compared with traditional endurance running distance (e.g., marathon), it follows that there are sizable improvements still to be made in UER if the limitations of the sport are sufficiently understood. The purpose of this review is to summarise our current understanding of the major limitations in UER. We begin with an evolutionary perspective that provides the critical background for understanding how our capacities, abilities and limitations have come to be. Although we show that humans display evolutionary adaptations that may bestow an advantage for covering large distances on a daily basis, these often far exceed the levels of our ancestors, which exposes relative limitations. From that framework, we explore the physiological and psychological systems required for running UER events. In each system, the factors that limit performance are highlighted and some guidance for practitioners and future research are shared. Examined systems include thermoregulation, oxygen delivery and utilisation, running economy and biomechanics, fatigue, the digestive system, nutritional and psychological strategies. We show that minimising the cost of running, damage to lower limb tissue and muscle fatigability may become crucial in UER events. Maintaining a sustainable core body temperature is critical to performance, and an even pacing strategy, strategic heat acclimation and individually calculated hydration all contribute to sustained performance. Gastrointestinal issues affect almost every UER participant and can be due to a variety of factors. We present nutritional strategies for different event lengths and types, such as personalised and evidence-based approaches for varying types of carbohydrate, protein and fat intake in fluid or solid form, and how to avoid flavour fatigue. Psychology plays a vital role in UER performance, and we highlight the need to be able to cope with complex situations, and that specific long and short-term goal setting improves performance. Fatigue in UER is multi-factorial, both physical and mental, and the perceived effort or level of fatigue have a major impact on the ability to continue at a given pace. Understanding the complex interplay of these limitations will help prepare UER competitors for the different scenarios they are likely to face. Therefore, this review takes an interdisciplinary approach to synthesising and illuminating limitations in UER performance to assist practitioners and scientists in making informed decisions in practice and applicable research.

Thalamic Neuron Resilience during Osmotic Demyelination Syndrome (ODS) Is Revealed by Primary Cilium Outgrowth and ADP-ribosylation factor-like protein 13B Labeling in Axon Initial Segment

A murine osmotic demyelinating syndrome (ODS) model was developed through chronic hyponatremia, induced by desmopressin subcutaneous implants, followed by precipitous sodium restoration. The thalamic ventral posterolateral (VPL) and ventral posteromedial (VPM) relay nuclei were the most demyelinated regions where neuroglial damage could be evidenced without immune response. This report showed that following chronic hyponatremia, 12 h and 48 h time lapses after rebalancing osmolarity, amid the ODS-degraded outskirts, some resilient neuronal cell bodies built up primary cilium and axon hillock regions that extended into axon initial segments (AIS) where ADP-ribosylation factor-like protein 13B (ARL13B)-immunolabeled rod-like shape content was revealed. These AIS-labeled shaft lengths appeared proportional with the distance of neuronal cell bodies away from the ODS damaged epicenter and time lapses after correction of hyponatremia. Fine structure examination verified these neuron abundant transcriptions and translation regions marked by the ARL13B labeling associated with cell neurotubules and their complex cytoskeletal macromolecular architecture. This necessitated energetic transport to organize and restore those AIS away from the damaged ODS core demyelinated zone in the murine model. These labeled structures could substantiate how thalamic neuron resilience occurred as possible steps of a healing course out of ODS.

Differences in race history by distance of recreational endurance runners from The NURMI Study (Step 2)

Few studies were developed to understand the relationship between running characteristics and motivation. The purpose of this study was to assess the relationship between running event history, running experience, and best race performances in recreational distance runners. We used a web survey to obtain information regarding running experience, racing history, and periodization training routines/exercise habits, including weekly volumes and daily mileage and duration across periods and conditions. Associations between variables were conducted with the Chi-square test (χ2; nominal scale) and Wilcoxon test. Multiple linear regression analysis and multivariate linear regression were performed. Concerning the participants' motive for exercising, a significant difference was identified between the race distance subgroups (p < 0.001), where 58% of M/UM runners exercised for performance (n = 38) and 64% of HM runners (n = 57) and 57% of 10 km runners (n = 52) exercised for recreational purposes. A significant difference was found in the number of years of running completed without taking a break (p = 0.004), with marathoners/ultramarathoners reporting the most years. Runners competing in different race distances such as 10 km, half-marathon, marathon, and ultra-marathon presented differences in training background and habits according to the distance of preference.

The Effects of Omega-3 Fatty Acid Supplementation on the Lipid Profile and Cardiovascular Markers Following Downhill Running in Long-Distance Runners

Exercise-induced injury may intensify inflammatory response and reduce the cardiovascular protection mechanisms of omega 3 polyunsaturated fatty acids (ω 3 PUFA). Therefore, this study aimed to determine the erythrocyte content of fatty acids (ω 3 and ω 6), the levels of cardiac damage markers (CKMB, hsTnT, H - FABP), the concentration of inflammation mediators (IL-6, TNF α) in long distance runners supplemented with ω 3 PUFA. Twenty-four male long distance runners, who were randomly assigned to a placebo group (GrP) or a group supplemented (GrSuppl) with a daily dose of 3,000 mg of ω 3 PUFA for three weeks, participated in the study. Participants performed a downhill running exercise test. Blood samples were collected at rest and after the exercise protocol to analyse the levels of cardiac markers and inflammatory cytokines. The erythrocyte membrane content of EPA and DHA in the GrSuppl at the 3rd week of supplementation was significantly higher than at the baseline (p < 0.001). The erythrocyte membrane content of ω 3 PUFA in the GrSuppl was significantly higher at the completion of supplementation (p < 0.001). Supplementation with ω 3 PUFA improved blood lipid profiles and reduced the concentration of inflammation mediators measured after the eccentric exercise tests. The increased ω 3 PUFA content in the erythrocyte membrane and lower blood concentrations of cardiac damage markers and inflammation mediators in distance runners supplemented for three weeks with ω 3 PUFA suggest that the cardiovascular function has been improved.

Changes in Running Kinematics and Kinetics Following a 10 km Run

Background

Little is known about changes in kinetics or kinematics following a 10 km training run. This information has implications on risk of running-related injury.

Purpose

The purpose of this study was to examine the effect of a 10 km run on running kinematics and kinetics in a sample of experienced runners.

Study Design

Cross-Sectional Study.

Subjects

Nineteen runners ages 18-48 (7 female, 12 male) consented to participate including eight (3 female, 5 male) ultra-runners, and 11 (4 female, 7 male) recreational runners.

Methods

Following collection of demographic data and completion of a short running survey, participants did a 6-minute run at their self-selected running speed to acclimate to the instrumented treadmill. Reflective markers were placed over designated anatomical landmarks on both sides of the pelvis as well as the left lower extremity and marked with a skin pen. Subjects then ran on the treadmill and 30 seconds of video data were recorded at 240 frames/sec using a high-speed camera for the sagittal plane and the frontal plane. Simultaneously, ground reaction forces (GRFs) were recorded at 1200 Hz through the treadmill's embedded force plates. Each runner then ran 10 km on a paved trail at their self-selected pace. Immediately following the run, reflective markers were reattached, guided by markings placed before the run, and a 30-second post-run trial of the video and GRF data were recorded. Video data were analyzed using Kinovea software to measure the kinematic variables of interest. Paired t-tests with Bonferroni corrections were used to find if significant differences existed between pre- and post-run data for all kinematic and kinetic variables.

Results

No significant or clinically relevant differences existed between the pre- and post-run measurements for the kinematic or kinetic variables. The only significant difference noted between the ultra-runners and recreational runners was that the ultra-runners had significantly higher cadence (p=0.045).

Conclusions

A 10 km run at a self-selected pace did not result in change in the mean kinematic or kinetic variables in this group of experienced runners. Ultra-runners employ higher cadence than recreational runners, but their kinematics and kinetics are similar.

Level of Evidence

Level 3.

Sleep in marathon and ultramarathon runners: a brief narrative review

Introduction

Sleep is considered a fundamental biological function in humans necessary for recovery from daily physical activities. Considering the increasing popularity of long-distance running and participation in races such as marathons and ultramarathons, the aim of the present study was to review the relationship of such strenuous physical activities with sleep.

Methods

A search of Scopus was performed on 24/6/2023 using the syntax [ABS (sleep) AND ABS (marathon)] to identify relevant papers, the references of which were hand-searched to find additional sources.

Results

Optimal sleep has been shown to affect injury prevention and susceptibility to infection positively. In turn, participation in a marathon race may influence nocturnal autonomic modulation and disturb homeostasis. Ultramarathon races may have such a long duration that results in sleep deprivation even for several days, where sleep duration is quite below the physiological range. It seems that for ultramarathons of short duration, continuous running and sleep deprivation are beneficial for performance. In contrast, for races longer than 200 miles, it is necessary to develop sleep strategies to sustain performance.

Conclusion

In summary, the longer the distance of a running race, the greater the importance of an optimal sleep for race performance as well as the impact of a race on sleep.

An echocardiographic study of acute, progressive cardiac changes following a 246 km running race

We describe the case of an ultra-marathon runner who finished first the "Spartathlon", a 246 km running race. The finishing time was the second fastest time ever in "Spartathlon". After finishing the race, the athlete suffered non-cardiac syncope and was administered intravenously 3 L of fluids for 5 hours. He underwent two echocardiographic assessments, one immediately after the finish of the race and the second 5 h later. Post-exercise fluid administration led to an increase in dimensions of all cardiac cavities, accompanied by a decrease in left ventricular (LV) end-diastolic interventricular septum thickness and posterior wall thickness of 0.1 cm. Dimensions and the respiratory profile of inferior vena cava improved after the race, reflecting alleviation of exercise-related hypovolaemia. Additionaly, LV global longitudinal strain improved, but right ventricular (RV) systolic function continued to deteriorate, mainly due to impairment of basal and medial RV free wall longitudinal strain. Study of this case offers a unique model for understanding the successive changes of cardiac structure and function following an ultra-marathon running race.

Eating habits and nutritional knowledge among amateur ultrarunners

Introduction

Many studies concerning the diet of physically active people refer to individuals who run; however, the importance of nutrition in professional and amateur sports plays a different role. This study aimed to evaluate the nutritional behavior and knowledge of amateur ultrarunners. This study involved a group of 308 respondents (89 women and 219 men) aged 18 -65. It investigated the influence of the level of knowledge about nutrition, gender, education, and smoking on dietary food habits and eating frequency.

Methods

The KomPAN questionnaire was used to determine the dietary habits, diet quality, lifestyle, and nutrition knowledge of ultramarathon runners. The nutrition knowledge influenced the eating habits and frequency of specific meals expressed as the Healthy Diet Index-10 (HDI-10) and Unhealthy Diet Index-14 (UDI-14).

Results

In women with sufficient knowledge about nutrition, lower HDI-10 scores were observed compared to those with a good level of knowledge, while men did not show a similar relationship. However, the effect of smoking on the frequency of food intake in men was noted. Interestingly, male smokers had a lower UDI-14 score than non-smokers. Depending on the level of knowledge, female and male ultrarunners more often or less frequently used selected food products. In turn, no effect of education on the frequency of consumption of specific foods was observed.

Discussion

Such different results are most likely caused by the specificity of the study group, which consisted of amateur runners. Additionally, the study looked at general eating habits, not those employed when preparing for marathons. In the future, more respondents should be surveyed, also taking into account nutrition during training.

Flat versus Simulated Mountain Trail Running: A Multidisciplinary Comparison in Well-Trained Runners

This paper compares cardiopulmonary and neuromuscular parameters across three running aerobic speeds in two conditions that differed from a treadmill's movement: flat condition (FC) and unpredictable roll variations similar to mountain trail running (URV). Twenty well-trained male runners (age 33 ± 8 years, body mass 70.3 ± 6.4 kg, height 1.77 ± 0.06 m, V˙O₂max 63.8 ± 7.2 mL·kg^-1·min^-1) voluntarily participated in the study. Laboratory sessions consisted of a cardiopulmonary incremental ramp test (IRT) and two experimental protocols. Cardiopulmonary parameters, plasma lactate (BLa^-), cadence, ground contact time (GT) and RPE values were assessed. We also recorded surface electromyographic (sEMG) signals from eight lower limb muscles, and we calculated, from the sEMG envelope, the amplitude and width of peak muscle activation for each step. Cardiopulmonary parameters were not significantly different between conditions (V˙O₂: p = 0.104; BLa^-: p = 0.214; HR: p = 0.788). The amplitude (p = 0.271) and width (p = 0.057) of sEMG activation peaks did not change between conditions. The variability of sEMG was significantly affected by conditions; indeed, the coefficient of variation in peak amplitude (p = 0.003) and peak width (p < 0.001) was higher in URV than in FC. Since the specific physical demands of running can differ between surfaces, coaches should resort to the use of non-traditional surfaces, emphasizing specific surface-related motor tasks that are normally observed in natural running environments. Seeing that the variability of muscle activations was affected, further studies are required to better understand the physiological effects induced by systematic surface-specific training and to define how variable-surface activities help injury prevention.

A macro to micro analysis to understand performance in 100-mile ultra-marathons worldwide

The purposes of this study were (i) to describe differences in participation in 100-mile ultra-marathons by continent; (ii) to investigate differences in performance between continents; and (iii) to identify the fastest runners by continent and country. Data from 148,169 athletes (119,408 men), aged 18-81 years, and finishers in a 100-miles ultra-marathon during 1870-2020 were investigated. Information about age, gender, origin, performance level (top three, top 10, top 100) was obtained. Kruskal-Wallis tests and linear regressions were performed. Athletes were mostly from America and Europe. A macro-analysis showed that the fastest men runners were from Africa, while the fastest women runners were from Europe and Africa. Women from Sweden, Hungary and Russia presented the best performances in the top three, top 10 and top 100. Men from Brazil, Russia and Lithuania were the fastest. The lowest performance and participation were observed for runners from Asia. In summary, in 100-miles ultra-marathon running, the majority of athletes were from America, but for both sexes and performance levels, the fastest runners were from Africa. On a country level, the fastest women were from Sweden, Hungary and Russia, while the fastest men were from Brazil, Russia and Lithuania.

Is There Evidence for the Development of Sex-Specific Guidelines for Ultramarathon Coaches and Athletes? A Systematic Review

BACKGROUND

There is evidence of sex differences in the physiology of endurance exercise, yet most of the advice and guidelines on training, racing, nutrition, and recovery for ultramarathons are based on research that has largely excluded female athletes. The objective was therefore to review the current knowledge of sex differences in ultramarathon runners and determine if sufficient evidence exists for providing separate guidelines for males and females.

METHODS

This systematic review was carried out in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Three databases were searched for studies investigating differences in elite and recreational male and female ultramarathon runners. Studies were included if they compared males and females and looked at outcomes relating to the performance or health of ultramarathon runners. The quality of the included studies was determined using the Grading of Recommendations Assessment Development and Evaluation (GRADE) approach.

RESULTS

The search strategy identified 45 studies that met the inclusion criteria. Most studies were observational in design, with only three papers based on randomised controlled trials. The overall quality of the evidence was low. Sex differences in the predictors of ultramarathon performance; physiological responses to training, racing, and recovery; chronic and acute health issues; and pacing strategies were found. There were areas with contradictory findings, and very few studies examined specific interventions.

CONCLUSION

The results from this review suggest that the development of sex-specific guidelines for ultramarathon coaches and athletes could have a significant effect on the performance and health of female runners. At present, there is insufficient high-quality evidence on which to formulate these guidelines, and further research is required.

Personality Traits Associated with the Risk of Exercise Dependence in Ultraendurance Athletes: A Cross-Sectional Study

Exercise dependence (ED) is common in endurance athletes and can lead to physical and psychological distress with various health effects. We designed a prospective cross-sectional study to investigate the personality traits associated with ED among ultraendurance athletes. A total of 507 participants (41.6 (9.8) years, men: 73.7%) completed (1) a screening questionnaire about sociodemographic data, sporting habits, and healthcare data, (2) the Exercise Dependence Scale-Revised (EDS-R, 21 items scored from 1 (never) to 6 (always), 7 subscales), (3) the Big Five Inventory (BFI), and (4) 2 items of the SCOFF (Sick-Control-One Stone-Fat-Food) questionnaire regarding possible eating disorders. Based on the EDS-R scores, 37 (7.3%) participants were at risk for ED (scores ≥ 5/6 on ≥3 subscales), 366 (72.2%) were nondependent but symptomatic (scores ≥ 3/6 on ≥3 subscales), and 104 (20.5%) were asymptomatic. Participants with ED had a greater training volume and a higher prevalence of possible eating disorders. A higher level of neuroticism was associated with increased EDS-R scores (r = 0.294; p < 0.001), with significantly higher scores in the ED group (F = 14.50, p < 0.001). The association between neuroticism and ED was not moderated by the presence of eating disorders. These findings will help to screen ultraendurance athletes at risk for ED and optimize their care.

Are the Consumption Patterns of Sports Supplements Similar among Spanish Mountain Runners?

BACKGROUND

The use of sports supplements (SS) to improve sports performance is widespread in all types of athletes, however, the specific characteristics of mountain races may require the use of certain SS. Despite being a sport where the consumption of SS seems widespread, few studies have been conducted in this regard. The objective of this study is to analyze the pattern of SS consumption of mountain runners in relation to the degree of scientific evidence, sex, and level of competition.

METHODS

Descriptive and cross-sectional study on the consumption and habitual use of SS of 357 federated mountain runners in Spain. Data were collected through a validated questionnaire.

RESULTS

From the total sample, 93.84% of the athletes stated that they consumed SS, with no differences observed based on the competitive level or in terms of sex; however, there were significant differences according to the competitive level in terms of the number of SS consumed, with consumption being greater at a higher competitive level (p = 0.009). The most consumed SS were sports bars (66.1%), sports drinks (60.5%), sports gels (52.9%), and caffeine (46.2%).

CONCLUSIONS

The consumption of SS in mountain races is high, and the number of SS consumed is higher as the competition level increases. The four SS most consumed by the participants in this study were all included in category A in the classification of the Australian Institute of Sport (AIS), this category is the one with the greatest scientific evidence.

Exercise-related hemoconcentration and hemodilution in hydrated and dehydrated athletes: An observational study of the Hungarian canoeists

Hemoconcentration during exercise is a well-known phenomenon, however, the extent to which dehydration is involved is unclear. In our study, the effect of dehydration on exercise-induced hemoconcentration was examined in 12 elite Hungarian kayak-canoe athletes. The changes of blood markers were examined during acute maximal workload in hydrated and dehydrated states. Dehydration was achieved by exercise, during a 120-minute extensive-aerobic preload. Our research is one of the first studies in which the changes in blood components were examined with a higher time resolution and a wider range of the measured parameters. Hydration status had no effect on the dynamics of hemoconcentration during both the hydrated (HS) and dehydrated (DHS) load, although lower maximal power output were measured after the 120-minute preload [HS Hemoglobin(Hgb)Max median 17.4 (q1 17.03; q3 17.9) g/dl vs. DHS HgbMax median 16.9 (q1 16.43; q3 17.6) g/dl (n.s); HS Hematocrit(Hct)Max 53.50 (q1 52.28; q3 54.8) % vs. DHS HctMax 51.90 (q1 50.35; q3 53.93) % (n.s)]. Thirty minutes after the maximal loading, complete hemodilution was confirmed in both exercises. Dehydration had no effect on hemoconcentration or hemodilution in the recovery period [HS HgbR30' 15.7 (q1 15.15; q3 16.05) g/dl (n.s.) vs. DHS HgbR30' 15.75 (q1 15.48; q3 16.13) g/dl (n.s.), HS HctR30' 48.15 (q1 46.5; q3 49.2) % vs. DHS HctR30' 48.25 (q1 47.48; q3 49.45) % (n.s.)], however, plasma osmolality did not follow a corresponding decrease in hemoglobin and hematocrit in the dehydrated group. Based on our data, metabolic products (glucose, lactate, sodium, potassium, chloride, bicarbonate ion, blood urea nitrogen) induced osmolality may not play a major role in the regulation of hemoconcentration and post-exercise hemodilution. From our results, we can conclude that hemoconcentration depends mainly on the intensity of the exercise.

Ultra-Endurance Participation and Acute Kidney Injury: A Narrative Review

Increasingly popular, ultra-endurance participation exposes athletes to extremely high levels of functional and structural damage. Ultra-endurance athletes commonly develop acute kidney injury (AKI) and other pathologies harmful to kidney health. There is strong evidence that non-steroidal anti-inflammatory drugs, common amongst ultra-athletes, is linked to increased risk and severity of AKI and potentially ischaemic renal injury, i.e., acute tubular necrosis. Ultra-endurance participation also increases the risk of exertional rhabdomyolysis, exercise-associated hyponatremia, and gastrointestinal symptoms, interlinked pathologies all with potential to increase the risk of AKI. Hydration and fuelling both also play a role with the development of multiple pathologies and ultimately AKI, highlighting the need for individualised nutritional and hydration plans to promote athlete health. Faster athletes, supplementing nitrates, and being female also increase the risk of developing AKI in this setting. Serum creatinine criteria do not provide the best indicator for AKI for ultra-athletes therefore further investigations are needed to assess the practicality and accuracy of new renal biomarkers such as neutrophil gelatinase-associated lipocalin (NGAL). The potential of recurring episodes of AKI provide need for further research to assess the longitudinal renal health impact of ultra-participation to provide appropriate advice to athletes, coaches, medical staff, and event organisers.

Changes in novel anti-infalmmatory cytokine concetration in the bood of endurance and race horses at different levels of training

Several anti-inflammatory cytokines have been proposed as markers for exercise monitoring in humans such as the interleukin 1 receptor agonist (IL-ra), or interleukin 13 (IL-13). Equine athletes may be considered a model for human exercise physiology research, however there is a lack of such studies of this species. Thus, we decided to examine the changes of IL-1ra and IL-13 in serum concentration during aerobic (endurance) and anaerobic (race) exercise in horses of different fitness levels in comparison with the well-known anti-inflammatory cytokine interleukin 10 (IL-10). The group of endurance horses (n = 13) consisted of animals competing over 100 (n = 7) and 120 km (n = 6) rides. The group of racehorses (n = 18) consisted of trained (n = 9) and untrained (n = 9) animals. The blood samples were obtained before and after the exercise. The ELISA test was performed to evaluate the changes of IL-1ra, IL-13 and IL-10 during different types of exercise. In endurance horses there was an increase in IL-13 (p = 0.0012) after the 100 km ride and in IL-1ra (p = 0.0411) after the 120 km ride. In race horses there was a higher IL-13 basal serum concentration in the untrained group, as well as a decrease of IL-13 after exercise (p = 0.0188). In trained racehorses there was an increase in IL-1ra (p < 0.0001) and IL-13 after exercise (p = 0.0028). In conclusion, the reaction of IL-1ra and IL-13 to different types of exercise differ from each other. Thus, in future, they may be helpful in monitoring the fitness of horses, however more research is needed.

Adiponectin, leptin, cortisol, neuropeptide Y and profile of mood states in athletes participating in an ultramarathon during winter: An observational study

Background: The Montane^® Yukon Arctic Ultra (YAU) is one of the longest (690 km) and coldest (+10.6°C-43.9°C) ultramarathons worldwide. Taking part in an ultramarathon is associated with great physiological and psychological stress, which can affect one's mood, level of hormones, and peptides. The current study aimed to identify relationships between peptides, hormones, and mood states in participants during this ultramarathon. Methods: The study cohort consisted of 36 participants (19 men, 17 women, 38.64 ± 9.12 years) split into a finisher (n = 10), non-finisher (n = 19), and control group (n = 7). Data were collected at four time points: baseline (PRE), during (D1 after 277 km, D2 after 383 km), and after the race (POST). Questionnaires were used to assess ratings of perceived exertion (RPE), total quality of recovery (TQR), and profile of mood states (POMS-SF). Serum NPY, leptin, adiponectin, and cortisol were measured. Results: Among non-finishers, scores for confusion, anger, depression, and tension-anxiety (PRE vs. D2, p < 0.05) increased, while vigor decreased (PRE vs. D1, p < 0.05). In contrast, finishers' tension-anxiety scores decreased (PRE vs. D1, p < 0.05). Fatigue increased in finishers (PRE vs. POST, p < 0.05) and non-finishers (PRE vs. D1, p < 0.05). In non-finishers, depressive mood correlated positively with leptin, anger, and confusion at several time points (p < 0.001). In finishers, NPY correlated with TQR at PRE (p < 0.05), while leptin correlated negatively with TQR at POST (p < 0.05). Tension-anxiety correlated highly with perceived exertion in non-finishers (p < 0.001) and with cortisol in finishers (p < 0.05) and non-finishers (p < 0.001). In finishers, confusion correlated negatively with NPY (p < 0.01). Conclusion: The study reveals an essential interplay between hormones and mood states affecting performance: Leptin was associated with anger and a depressive mood state in non-finishers and worse recovery in finishers. In contrast, NPY appeared linked to a lower confusion score and heightened recovery in finishers. A simultaneous increase in depressed mood, anger, tension-anxiety, and confusion might harm performance and lead to race failure.

The Effects of Sex, Age and Performance Level on Pacing in Ultra-Marathon Runners in the ‘Spartathlon’

Background

Pacing has been investigated in different kinds of ultra-marathon races, but not in one of the toughest ultra-marathons in the world, the ‘Spartathlon’.

Objective

The aim of the present study was to analyse the pacing of female and male finishers competing in the ‘Spartathlon’ in regards to their age and performance groups.

Methods

A total of 2598 runners (2255 men and 343 women) finishing ‘Spartathlon’ between 2011 and 2019 were analysed. We selected 10 checkpoints with split times corresponding to important race sections. Average running speed was calculated for each participant and the average checkpoint running speed for each of the 10 race checkpoints. Furthermore, to assess the pacing strategy of each runner, the percentage of change in checkpoint speed (CCS) in relation to the average race speed was calculated (for each of 10 checkpoints). Finally, the average change in checkpoint speed (ACCS) was calculated for each participant as a mean of the 10 CCSs.

Results

Both women and men slowed down through the first 7 checkpoints but increased running speed towards the end of the race (reverse J-shaped pacing). Men showed a significantly greater CCS in the first and second checkpoint (p < 0.01 and p < 0.05, respectively), whereas women showed a more significant change in CCS in the last checkpoint (p < 0.05). Furthermore, age and sex showed no effect on ACCS, whereas ACCS differed between the performance groups. In particular, the slowest and the fastest runners showed a more minor change in ACCS than the two medium groups of both men and women (p < 0.01).

Conclusions

In summary, successful finishers in ‘Spartathlon’ showed a reverse J-shaped pacing curve with a decrease in running speed from the start to the 7th checkpoint and an increase in running speed thereafter. This strategy was most probably due to the profile of the race course. Men showed a more significant change in checkpoint speed in the first two checkpoints, whereas women showed a more substantial change in the last checkpoint. Age and sex did not affect average checkpoint speed, whereas this speed was different between the different performance groups. The slowest and the fastest runners showed fewer changes in average checkpoint speed than the two medium groups in men and women.

Running for Your Life: Metabolic Effects of a 160.9/230 km Non-Stop Ultramarathon Race on Body Composition, Inflammation, Heart Function, and Nutritional Parameters

Moderate endurance exercise leads to an improvement in cardiovascular performance, stress resilience, and blood function. However, the influence of chronic endurance exercise over several hours or days is still largely unclear. We examined the influence of a non-stop 160.9/230 km ultramarathon on body composition, stress/cardiac response, and nutrition parameters. Blood samples were drawn before (pre) and after the race (post) and analyzed for ghrelin, insulin, irisin, glucagon, cortisol, kynurenine, neopterin, and total antioxidant capacity. Additional measurements included heart function by echocardiography, nutrition questionnaires, and body impedance analyses. Of the 28 included ultra-runners (7f/21m), 16 participants dropped out during the race. The remaining 12 finishers (2f/10m) showed depletion of antioxidative capacities and increased inflammation/stress (neopterin/cortisol), while energy metabolism (insulin/glucagon/ghrelin) remained unchanged despite a high negative energy balance. Free fat mass, protein, and mineral content decreased and echocardiography revealed a lower stroke volume, left end diastolic volume, and ejection fraction post race. Optimizing nutrition (high-density protein-rich diet) during the race may attenuate the observed catabolic and inflammatory effects induced by ultramarathon running. As a rapidly growing discipline, new strategies for health prevention and extensive monitoring are needed to optimize the athletes’ performance.

Exercise-Associated Hyponatremia in Marathon Runners

Exercise-associated hyponatremia (EAH) was first described as water intoxication by Noakes et al. in 1985 and has become an important topic linked to several pathological conditions. However, despite progressive research, neurological disorders and even deaths due to hyponatremic encephalopathy continue to occur. Therefore, and due to the growing popularity of exercise-associated hyponatremia, this topic is of great importance for marathon runners and all professionals involved in runners' training (e.g., coaches, medical staff, nutritionists, and trainers). The present narrative review sought to evaluate the prevalence of EAH among marathon runners and to identify associated etiological and risk factors. Furthermore, the aim was to derive preventive and therapeutic action plans for marathon runners based on current evidence. The search was conducted on PubMed, Scopus and Google Scholar using a predefined search algorithm by aggregating multiple terms (marathon run; exercise; sport; EAH; electrolyte disorder; fluid balance; dehydration; sodium concentration; hyponatremia). By this criterion, 135 articles were considered for the present study. Our results revealed that a complex interaction of different factors could cause EAH, which can be differentiated into event-related (high temperatures) and person-related (female sex) risk factors. There is variation in the reported prevalence of EAH, and two major studies indicated an incidence ranging from 7 to 15% for symptomatic and asymptomatic EAH. Athletes and coaches must be aware of EAH and its related problems and take appropriate measures for both training and competition. Coaches need to educate their athletes about the early symptoms of EAH to intervene at the earliest possible stage. In addition, individual hydration strategies need to be developed for the daily training routine, ideally in regard to sweat rate and salt losses via sweat. Future studies need to investigate the correlation between the risk factors of EAH and specific subgroups of marathon runners.

Sex-Specific Physiological Responses to Ultramarathon

PURPOSE

Despite a growing body of literature on the physiological responses to ultramarathon, there is a paucity of data in females. This study assessed the female physiological response to ultramarathon and compared the frequency of perturbations to a group of race- and time-matched males.

METHODS

Data were collected from 53 contestants of an ultramarathon trail race at the Ultra-Trail du Mont-Blanc (UTMB®) in 2018/19. Before and within 2 h of the finish, participants underwent physiological assessments, including blood sampling for biomarkers (creatine kinase-MB isoenzyme [CK-MB], cardiac troponin I [cTnI], brain natriuretic peptide [BNP], and creatinine [Cr]), pulmonary function testing (spirometry, exhaled NO, diffusing capacities, and mouth pressures), and transthoracic ultrasound (lung comet tails, cardiac function). Data from eight female finishers (age = 36.6 ± 6.9 yr; finish time = 30:57 ± 11:36 h:min) were compared with a group of eight time-matched males (age = 40.3 ± 8.3 yr; finish time = 30:46 ± 10:32 h:min).

RESULTS

Females exhibited significant pre- to postrace increases in BNP (25.8 ± 14.6 vs 140.9 ± 102.7 pg·mL -1 ; P = 0.007) and CK-MB (3.3 ± 2.4 vs 74.6 ± 49.6 IU·L -1 ; P = 0.005), whereas males exhibited significant pre- to postrace increases in BNP (26.6 ± 17.5 vs 96.4 ± 51.9 pg·mL -1 ; P = 0.002), CK-MB (7.2 ± 3.9 vs 108.8 ± 37.4 IU·L -1 ; P = 0.002), and Cr (1.06 ± 0.19 vs 1.23 ± 0.24 mg·dL -1 ; P = 0.028). Lung function declined in both groups, but males exhibited additional reductions in lung diffusing capacities (DL CO = 34.4 ± 5.7 vs 29.2 ± 6.9 mL⋅min -1 ⋅mm Hg -1 , P = 0.004; DL NO = 179.1 ± 26.2 vs 152.8 ± 33.4 mL⋅min -1 ⋅mm Hg -1 , P = 0.002) and pulmonary capillary blood volumes (77.4 ± 16.7 vs 57.3 ± 16.1 mL; P = 0.002). Males, but not females, exhibited evidence of mild postrace pulmonary edema. Pooled effect sizes for within-group pre- to postrace changes, for all variables, were generally larger in males versus females ( d = 0.86 vs 0.63).

CONCLUSIONS

Ultramarathon negatively affects a range of physiological functions but generally evokes more frequent perturbations, with larger effect sizes, in males compared to females with similar race performances.

Continuous Thermoregulatory Responses to a Mass-Participation 89-km Ultramarathon Road Race

PURPOSE

To continuously measure body core temperature (Tc) throughout a mass-participation ultramarathon in subelite recreational runners to quantify Tc magnitude and the influence of aerobic fitness and body fat.

METHODS

Twenty-three participants (19 men and 4 women; age 45 [9] y; body mass 72.0 [9.3] kg; body fat 26% [6%]; peak oxygen uptake 50 [6] mL·kg-1·min-1) had gastrointestinal temperature measured during an 89-km ultramarathon. Prerace-to-postrace changes in body mass, plasma sodium, and fluid and food recall quantified body water balance.

RESULTS

In maximal environmental conditions of 26.3 °C and 53% humidity, 21 of the 23 participants finished in 10:28 (01:10) h:min while replacing 49% (27%) of sweat losses, maintaining plasma sodium (140 [3] mmol·L-1), and dehydrating by 4.1% (1.3%). Mean maximum Tc was 39.0 (0.5) (range 38.2-40.1 °C) with 90% of race duration ≤39.0 °C. Mean maximum ΔTc was 1.9 (0.9) (0.9-2.7 °C) with 95% of race duration ≤2.0 °C. Over 0 to 45 km, associations between ΔTc and peak oxygen uptake (positive) and body fat (negative) were observed. Over 58 to 89 km, associations between Tc and peak oxygen uptake (negative) and body fat (positive) were observed.

CONCLUSIONS

Modest Tc responses were observed in recreational ultramarathon runners. Runners with higher levels of aerobic fitness and lower levels of body fat demonstrated the greatest changes in Tc during the first half of the race. Conversely, runners with lower levels of aerobic fitness and higher levels of body fat demonstrated the greatest absolute Tc in the final third of the race.

Effects of nutritional and hydration strategies during ultramarathon events between finishers and non-finishers: A systematic review protocol

Ultramarathon running is a sport that is growing in popularity. Competing in an ultramarathon event is physiologically taxing on the human body, and it should not be surprising that not all individuals who enroll for an event ultimately finish. While many factors can contribute to this phenomenon, it is likely that nutritional and hydration strategies play a large role between finishing and not finishing an ultramarathon. No published paper has systematically reviewed the effects of nutritional and hydration strategies during ultramarathon events between finishers and non-finishers. This paper details our intended protocol with the following steps that create the flow of the systematic review: 1) Determine the review question and Participant, Intervention, Comparator, Outcome, Study Design (PICOS) criteria; 2) Create inclusion and exclusion criteria; 3) Create and follow a search strategy; 4) Document sources that are included and excluded according to the pre-determined eligibility criteria; 5) Assess final sources for risk of bias; 6) Extract pertinent data from final full-text articles and synthesize the information; and 7) Disseminate findings of the systematic review.

Could Repeated Cardio-Renal Injury Trigger Late Cardiovascular Sequelae in Extreme Endurance Athletes?

Regular exercise confers multifaceted and well-established health benefits. Yet, transient and asymptomatic increases in markers of cardio-renal injury are commonly observed in ultra-endurance athletes during and after competition. This has raised concerns that chronic recurring insults could cause long-term cardiac and/or renal damage. Indeed, extreme endurance exercise (EEE) over decades has sometimes been linked with untoward cardiac effects, but a causal relation with acute injury markers has not yet been established. Here, we summarize the current knowledge on markers of cardiac and/or renal injury in EEE athletes, outline the possible interplay between cardiac and kidney damage, and explore the roles of various factors in the development of potential exercise-related cardiac damage, including underlying diseases, medication, sex, training, competition, regeneration, mitochondrial dysfunction, oxidative stress, and inflammation. In conclusion, despite the undisputed health benefits of regular exercise, we speculate, based on the intimate link between heart and kidney diseases, that in rare cases excessive endurance sport may induce adverse cardio-renal interactions that under specific, hitherto undefined conditions could result in persistent cardiac damage. We highlight future research priorities and provide decision support for athletes and clinical consultants who are seeking safe strategies for participation in EEE training and competition.

Health status of recreational runners over 10-km up to ultra-marathon distance based on data of the NURMI Study Step 2

Endurance running is well-documented to affect health beneficially. However, data are still conflicting in terms of which race distance is associated with the maximum health effects to be obtained. Therefore, the aim of this study was to compare the health status of endurance runners over different race distances. A total of 245 recreational runners (141 females, 104 males) completed an online survey. Health status was assessed by measuring eight dimensions in two clusters of health-related indicators (e.g., body weight, mental health, chronic diseases and hypersensitivity reactions, medication intake) and health-related behaviors (e.g., smoking habits, supplement intake, food choice, healthcare utilization). Each dimension consisted of analytical parameters derived to a general domain score between 0 and 1. Data analysis was performed by using non-parametric ANOVA and MANOVA. There were 89 half-marathon (HM), 65 marathon/ultra-marathon (M/UM), and 91 10-km runners. 10-km runners were leaner than both the HM and M/UM runners (p ≤ 0.05). HM runners had higher health scores for six dimensions (body weight, mental health, chronic diseases and hypersensitivity reactions, medication intake, smoking habits, and health care utilization), which contributed to an average score of 77.1% (score range 62–88%) for their overall state of health. Whereas 10-km and M/UM runners had lesser but similar average scores in the overall state of health (71.7% and 72%, respectively). Race distance had a significant association with the dimension “chronic diseases and hypersensitivity reactions” (p ≤ 0.05). Despite the null significant associations between race distance and seven (out of eight) multi-item health dimensions, a tendency towards better health status (assessed by domain scores of health) among HM runners was found compared to other distance runners. However, the optimal state of health across all race distances supported the notion that endurance running contributed to overall health and well-being.

Trial registration number: ISRCTN73074080. Retrospectively registered 12th June 2015.

Guinness World Record: Personal Experience and Physiological Responses of a Non-Professional Athlete Successfully Covering 620 Km in 7-Days by Foot Across the United Arab Emirates

Ultra-endurance record-breaking attempts place significant metabolic, cardiovascular, and mechanical stress on the athlete. This research explores the personal experience and physiological responses of a non-professional athlete attempting the Guinness World Record of covering 620 km on foot across the United Arab Emirates in 7-days or less. The participant wore a smartwatch throughout the challenge to collect heart rate, activity, and environmental temperature data. Anthropometric, body composition, and inflammatory, haematological, and endocrine biomarkers measurements were completed pre- and post-event. A pre- and post-event interview was conducted to collect data on training and preparation, and self-reported experiences during the challenge. Despite episodes of diarrhoea, vomiting, and muscle cramps due to hypohydration during the first days of the challenge, the participant successfully completed 619.01 km in six days, 21 hours, and 47 minutes (average pace 10.11 min/km) achieving a new Guinness World Record. Body mass remained unchanged, fat mass decreased, and fat-free mass especially in the legs increased over the seven days, most likely due to water retention. Biomarkers of stress, cell damage, and inflammation increased. Haematological markers related to red blood cells decreased probably due to exercise-induced increases in plasma volume with the participant classified with mild anaemia post-event. This case study reinforces the importance of amateur athletes attempting similar ultra-endurance events adhering to a pre-planned hydration and nutrition strategy to maximise performance and minimise the risk of injury.

Fractal Correlation Properties of Heart Rate Variability as a Biomarker for Intensity Distribution and Training Prescription in Endurance Exercise: An Update

While established methods for determining physiologic exercise thresholds and intensity distribution such as gas exchange or lactate testing are appropriate for the laboratory setting, they are not easily obtainable for most participants. Data over the past two years has indicated that the short-term scaling exponent alpha1 of Detrended Fluctuation Analysis (DFA a1), a heart rate variability (HRV) index representing the degree of fractal correlation properties of the cardiac beat sequence, shows promise as an alternative for exercise load assessment. Unlike conventional HRV indexes, it possesses a dynamic range throughout all intensity zones and does not require prior calibration with an incremental exercise test. A DFA a1 value of 0.75, reflecting values midway between well correlated fractal patterns and uncorrelated behavior, has been shown to be associated with the aerobic threshold in elite, recreational and cardiac disease populations and termed the heart rate variability threshold (HRVT). Further loss of fractal correlation properties indicative of random beat patterns, signifying an autonomic state of unsustainability (DFA a1 of 0.5), may be associated with that of the anaerobic threshold. There is minimal bias in DFA a1 induced by common artifact correction methods at levels below 3% and negligible change in HRVT even at levels of 6%. DFA a1 has also shown value for exercise load management in situations where standard intensity targets can be skewed such as eccentric cycling. Currently, several web sites and smartphone apps have been developed to track DFA a1 in retrospect or in real-time, making field assessment of physiologic exercise thresholds and internal load assessment practical. Although of value when viewed in isolation, DFA a1 tracking in combination with non-autonomic markers such as power/pace, open intriguing possibilities regarding athlete durability, identification of endurance exercise fatigue and optimization of daily training guidance.

Effect of an Ultra-Endurance Event on Cardiovascular Function and Cognitive Performance in Marathon Runners

Background

Ultra-marathon running participation has become increasingly more popular in recent years; however, there is inconclusive evidence concerning the effects of participation on cognition and cardiovascular function. The purpose of this study was to examine alterations in cardiovascular function and cognitive performance and their association in ultra-marathon runners prior to and following an ultra-endurance event.

Methods

In total, 24 runners (19 males and 5 females) participated in an ultra-marathon race (FatDog120) held in British Columbia, Canada. Participants competed in varying races distances [48 km (n = 2), 80 km (n = 7), 113 km (n = 3), and 193 km (n = 12)]. Cognition was assessed prior to and upon race completion using simple reaction time, choice reaction time, discrimination reaction time, and recognition memory (% correct). Cardiovascular function was assessed prior to and upon race completion using radial applanation tonometry for diastolic pulse contour examination.

Results

Cognitive performance displayed significantly (p < 0.001) slower reaction times post-race for simple (30.2%), discrimination (22.7%), and choice reaction time (30.5%), as well as a significant (p < 0.05) reduction in memory test performance (−8.2%). A significant association between systemic vascular resistance and choice reaction time was observed post-race (r = 0.41, p < 0.05). Significant changes in post-race cardiovascular function were observed in resting heart rate (31.5%), cardiac output (27.5%), mean arterial blood pressure (−5.6%), total systemic resistance (−17.6%), systolic blood pressure (−7.0%), pulse pressure (−11.2%), and rate pressure product (22.4%). There was evidence of enhanced cardiovascular function being associated with improved cognitive performance before and after the ultra-endurance event.

Conclusion

Ultra endurance running is associated with marked impairments in cognitive performance that are associated (at least in part) with changes in cardiovascular function in healthy adults.

One hundred marathons in 100 days: Unique biomechanical signature and the evolution of force characteristics and bone density

BACKGROUND

An extraordinary long-term running performance may benefit from low dynamic loads and a high load-bearing tolerance. An extraordinary runner (age = 55 years, height = 1.81 m, mass = 92 kg) scheduled a marathon a day for 100 consecutive days. His running biomechanics and bone density were investigated to better understand successful long-term running in the master athlete.

METHODS

Overground running gait analysis and bone densitometry were conducted before the marathon-a-day challenge and near its completion. The case's running biomechanics were compared pre-challenge to 31 runners who were matched by a similar foot strike pattern.

RESULTS

The case's peak vertical loading rate (Δx̄ = -61.9 body weight (BW)/s or -57%), peak vertical ground reaction force (Δx̄ = -0.38 BW or -15%), and peak braking force (Δx̄ = -0.118 BW or -31%) were remarkably lower (p < 0.05) than the control group at ∼3.3 m/s. The relatively low loading-related magnitudes were attributed to a remarkably high duty factor (0.41) at the evaluated speed. The foot strike angle of the marathoner (29.5°) was greater than that of the control group, affecting the peak vertical loading rate. Muscle powers in the lower extremity were also remarkably low in the case vs. controls: peak power of knee absorption (Δx̄ = -9.16 watt/kg or -48%) and ankle generation (Δx̄ = -3.17 watt/kg or -30%). The bone mineral density increased to 1.245 g/cm² (+2.98%) near completion of the challenge, whereas the force characteristics showed no statistically significant change.

CONCLUSION

The remarkable pattern of the high-mileage runner may be useful in developing or evaluating load-shifting strategies in distance running.

Bone Turnover Alterations after Completing a Multistage Ultra-Trail: A Case Study

A series of case studies aimed to assess bone and stress fractures in a 768-km ultra-trail race for 11 days. Four nonprofessional male athletes completed the event without diagnosing any stress fracture. Bone turnover markers (osteocalcin (OC), serum C-terminal cross-linking telopeptide of type I collagen (CTX), bone-specific alkaline phosphatase (BALP), and serum turnover calcium (Ca²⁺)) were assessed before (pre) and after the race (post) and on days two and nine during the recovery period (rec2 and rec9), respectively. Results showed: post-pre-OC = −45.78%, BALP = −61.74%, CTX = +37.28% and Ca²⁺ = −3.60%. At rec2 and rec9, the four parameters did not return to their pre-run levels: OC, −48.31%; BALP, −61.66%; CTX, +11.93% and Ca²⁺, −3.38%; and OC = −25.12%, BALP = −54.65%, CTX = +93.41% and Ca²⁺ = +3.15%), respectively. Our results indicated that the ultra-trail race induced several changes in bone turnover markers, uncoupling of bone metabolism, increased bone resorption: OC and BALP and suppressed bone formation: CTX and Ca²⁺. Bone turnover markers can help determine the response of bone to extreme effort and might also help predict the risk of stress fractures.

Mountain Ultra-Marathon (UTMB) Impact on Usual and Emerging Cardiac Biomarkers

The number of participants in ultra-marathons is increasing. However, the data regarding the impact of this type of exercise on the cardiovascular system are contradictory. In our study, 28 ultra-trail runners were enrolled. Blood samples were collected at three time points: immediately before, immediately after, and 7 days after the ultra-marathon. Different biomarkers were measured. Immediately after the race, the blood concentrations of the different cardiac and inflammatory biomarkers increased significantly. Interestingly, some biomarkers remained high even after 7 days of recovery.

Serum and Urinary Neutrophil Gelatinase-Associated Lipocalin Are Not Associated With Serum Redox Parameters in Amateur Athletes After an Ultramarathon

Objective

To evaluate the relationship between oxidative stress and NGAL levels in blood and urine of amateur athletes after participating in a 100 km ultramarathon.

Methodology

The sample was composed of seven athletes, submitted to anthropometric assessment, cardiopulmonary exercise test, collection of urine and blood, measurement of body weight. The rate of perceived exertion (RPE), competition duration, heart rate (HR), energy expenditure and oxygen consumption (V'O2") were also measured during the event. The energy consumption during the race was verified at its end. The analyses were based on the means (M) and respective standard deviations (SD), with statistical significance set at 5% (p < 0.05). Paired t-test was used for comparison between the periods before and after the competition, and Pearson's correlation coefficient was used to measure the linear correlation between quantitative variables.

Results

Body mass index (BMI) of the sample was 25.75 kg/m2 ± 3.20, body fat percentage 18.54% ± 4.35% and V'O2"max 48.87% ± 4.78. Glucose, cortisol, and neutrophil gelatinase-associated lipocalin (NGAL) (p < 0.01) as well as glutathione peroxidase (GPx) active were higher after the race when compared to basal values. Moreover, lactate, creatinine, microalbuminuria, and glomerular filtration rate (GFR) (p < 0.001) were also higher after the race. After the competition, there was a significant correlation only between serum NGAL and creatinine, which was classified as strong and positive (r: 0.77; p < 0.05). There was a significant reduction (p < 0.05) of body weight after the event (72.40 kg ± 9.78) compared to before it (73.98 kg ± 10.25). In addition, we found an increase of RPE (p < 0.001) after the race. The competition lasted 820.60 min (±117.00), with a 127.85 bpm (±12.02) HR, a 2209.72 kcal ± 951.97 energy consumption, 7837.16 kcal ± 195.71 energy expenditure, and 28.78 ml/kg/min-1 (±4.66) relative V'O2"max.

Conclusion

The lack of correlation between oxidative stress biomarkers and serum and urine NGAL suggests that NGAL is more sensitive to inflammatory processes than to ROS levels.

Study of the kinetics of the determinants of performance during a mountain ultra marathon: Multidisciplinary protocol of the first Trail Scientifique de Clécy 2021 (Preprint)

Background

The growing interest of the scientific community in trail running has highlighted the acute effects of practice at the time of these races on isolated aspects of physiological and structural systems; biological, physiological, cognitive, and muscular functions; and the psychological state of athletes. However, no integrative study has been conducted under these conditions with so many participants and monitoring of pre-, per-, and postrace variables for up to 10 days over a distance close to 100 miles.

Objective

The aim of this study was to evaluate the kinetics of the performance parameters during a 156 km trail run and 6000 m of elevation gain in pre-, per-, and postrace conditions. The general hypothesis is based on significant alterations in the psychological, physiological, mechanical, biological, and cognitive parameters.

Methods

The Trail Scientifique de Clécy took place on November 11, 2021. This prospective experimental study provides a comprehensive exploration of the constraints and adaptations of psychophysiological and sociological variables assessed in real race conditions during a trail running of 156 km on hilly ground and 6000 m of elevation gain (D+). The study protocol allowed for repeatability of study measurements under the same experimental conditions during the race, with the race being divided into 6 identical loops of 26 km and 1000 m D+. Measurements were conducted the day before and the morning of the race, at the end of each lap, after a pit stop, and up to 10 days after the race. A total of 55 participants were included, 43 (78%) men and 12 (22%) women, who were experienced in ultra–trail-running events and with no contraindications to the practice of this sport.

Results

The launch of the study was authorized on October 26, 2021, under the trial number 21-0166 after a favorable opinion from the Comité de Protection des Personnes Ouest III (21.09.61/SIRIPH 2G 21.01586.000009). Of the 55 runners enrolled, 41 (75%) completed the race and 14 (25%) dropped out for various reasons, including gastric problems, hypothermia, fatigue, and musculoskeletal injuries. All the measurements for each team were completed in full. The race times (ie, excluding the measurements) ranged from 17.8206 hours for the first runner to 35.9225 hours for the last runner. The average time to complete all measurements for each lap was 64 (SD 3) minutes.

Conclusions

The Trail Scientifique de Clécy, by its protocol, allowed for a multidisciplinary approach to the discipline. This approach will allow for the explanation of the studied parameters in relation to each other and observation of the systems of dependence and independence. The initial results are expected in June 2022.

International Registered Report Identifier (IRRID)

RR1-10.2196/38027

Renal Function Recovery Strategies Following Marathon in Amateur Runners

Long distance races have a physiological impact on runners. Up to now, studies analyzing these physiological repercussions have been mainly focused on muscle and cardiac damage, as well as on its recovery. Therefore, a limited number of studies have been done to explore acute kidney failure and recovery after performing extreme exercises. Here, we monitored renal function in 76 marathon finishers (14 females) from the day before participating in a marathon until 192 h after crossing the finish line (FL). Renal function was evaluated by measuring serum creatinine (sCr) and the glomerular filtration rate (GFR). We randomly grouped our cohort into three intervention groups to compare three different strategies for marathon recovery: total rest (REST), continuous running at their ventilatory threshold 1 (VT1) intensity (RUN), and elliptical workout at their VT1 intensity (ELLIPTICAL). Interventions in the RUN and ELLIPTICAL groups were performed at 48, 96, and 144 h after marathon running. Seven blood samples (at the day before the marathon, at the FL, and at 24, 48, 96, 144, and 192 h post-marathon) and three urine samples (at the day before the marathon, at the finish line, and at 48 h post-marathon) were collected per participant. Both heart rate monitors and triaxial accelerometers were used to control the intensity effort during both the marathon race and the recovery period. Contrary to our expectations, the use of elliptical machines for marathon recovery delays renal function recovery. Specifically, the ELLIPTICAL group showed a significantly lower ∆GFR compared to both the RUN group (p = 4.5 × 10−4) and the REST group (p = 0.003). Hence, we encourage runners to carry out an active recovery based on light-intensity continuous running from 48 h after finishing the marathon. In addition, full resting seems to be a better strategy than performing elliptical workouts.

Changes in Cytokines Concentration Following Long-Distance Running: A Systematic Review and Meta-Analysis

Long-distance running is an exhausting effort for the whole organism. Prolonged aerobic exercise induces changes in inflammatory markers. However, predicting muscle damage in response has limitations in terms of selecting biomarkers used to measure inflammatory status. The present study conducts a systematic review and meta-analysis of articles focusing in ultra-marathon, marathon, and half-marathon and levels of cytokines. The search was conducted in PubMed, Web of Science, and Scopus databases, resulting in the inclusion of 76 articles. IL-6 was highlighted, evaluated in 62 studies and show increase in the standard mean difference (SMD): half-marathon (SMD −1.36; IC 95%: −1.82, −0.89, Ch²:0.58; tau²:0.00; p < 0.0001), marathon (SMD −6.81; IC 95%: −9.26, −4.37; Ch²:481.37 tau²:11.88; p < 0.0001) and ultra-marathon (SMD −8.00 IC 95%: −10.47, −5.53; Ch²:328.40; tau²:14.19; p < 0.0001). In contrast meta-regression analysis did not show relationship to the running distance (p = 0.864). The meta-analysis evidenced increase in the concentration of IL-1ra (p < 0.0001), IL-1B (p < 0.0001), IL-8 (p < 0.0001), IL-10 (p < 0.0001) and TNF-α (p < 0.0001). Reduction in IL-2 (p < 0.0001) and INF-y (p < 0.03) and no change in the IL-4 (p < 0.56). The number of studies evaluating the effect of adipokines was limited, however Leptin and Resistin were recurrent. The effects of an acute bout of prolonged aerobic exercise will protect against chronic systemic inflammation. The time to return to baseline values showed a substantial and dose-dependent relationship with run volume. The concentration of IL-6 was robustly studied and the marathon running was the most explored. Network of endocrine interactions in which circulating factors, released in extreme exercises, interplay through inter-organ crosstalk and physiologic changes were expressed. The running volume variability was able to modulate compounds that play a fundamental role in the maintenance of homeostasis and cell signaling.

Acute Kidney Injury Biomarkers and Hydration Outcomes at the Boston Marathon

The purpose of our field study was to investigate the effects of running the Boston Marathon on acute kidney injury (AKI) biomarkers. We hypothesized that biomarker values would be elevated immediately post-marathon but would resolve in the 24-h post-marathon. Secondarily, we sought to identify sex differences related to renal stress. Participants were 65 runners who completed the Boston Marathon (46 ± 9 years, 65.4 ± 10.8 kg). Urine samples were collected at three different time points (pre-marathon, post-marathon, and 24-h post-marathon). Blood samples were collected post-marathon and 24-h post-marathon. Urine specific gravity (USG) and AKI biomarkers were evaluated. Pre-marathon USG (1.012 ± 0.007) was significantly less than post-marathon (1.018 ± 0.008) and 24-h post-marathon (1.020 ± 0.009; P < 0.001). Male USG (1.024 ± 0.009) was significantly greater 24-h post-marathon than females (1.017 ± 0.008; P = 0.019). Urinary neutrophil gelatinase-associated lipocalin values were significantly greater over time (P < 0.001), and there was a main effect of sex with female urinary creatinine (_UCr) greater than males at all three time points (P = 0.040). Post-marathon_UCr (366.24 ± 295.16 mg/dl) was significantly greater than pre-marathon (206.65 ± 145.28.56 mg/dl; p < 0.001) and 24-h post-marathon was significantly lower than other time-points (93.90 ± 125.07 mg/dl; P < 0.001). Female_UCr values were significantly greater than males 24-h post-marathon (P < 0.001). There was no difference in serum cystatin C (_SCys) values post- or 24-h post-marathon (P = 0.178). Serum creatinine (_SCr) significantly decreased between post-marathon and 24-h post-marathon, (P < 0.001). We can infer that the characteristics unique to the Boston Marathon may have attributed to prolonged elevations in AKI biomarkers. Sex differences were observed during the Boston Marathon warranting further investigation.

768-km Multi-Stage Ultra-Trail Case Study-Muscle Damage, Biochemical Alterations and Strength Loss on Lower Limbs

A series of case studies aimed to evaluate muscular fatigue in running a 768-km ultra-trail race in 11 days. Four non-professional athletes (four males) were enrolled. Muscle damage blood biomarkers (creatine kinase (CK), lactodeshydrogenase (LDH), aspartate transaminase (AST) and alanine aminotransferase (ALT) and lower limb strength were evaluated by using Bosco jumps test; squat jump (SJ), countermovement jump (CMJ) and Abalakov jump (ABA) were assessed before (pre), after the race (post) and for two and nine days during the recovery period (rec2 and rec9), respectively. Results showed: pre-post SJ = −28%, CMJ = −36% and ABA = −21%. Values returned to basal during rec9: SJ = −1%, CMJ = −2% or even exceeded pre-values ABA = +3%. On the contrary, muscle damage blood biomarkers values increased at post; CK = +888%, LDH = +172%, AST = +167% and ALT = +159% and the values returned gradually to baseline at rec9 except for AST = +226% and ALT = +103% which remained higher. Nonparametric bivariate Spearman’s test showed strong correlations (Rs ≥ 0.8) between some jumps and muscle damage biomarkers at post (SJ-LDH Rs = 0.80, SJ-AST Rs = 0.8, ABA-LD H Rs = 0.80 and ABA-AST Rs = 0.80), at rec2 (SJ-CK Rs = 0.80 and SJ-ALT Rs = 0.80) and even during rec9 (ABA-CK). Similarly, some parameters such as accumulated elevation and training volume showed a strong correlation with LDH values after finishing the ultra-trail race. The alteration induced by completing an ultra-trail event in the muscle affects lower limb strength and may in some circumstances result in serious medical conditions including post- exertional rhabdomyolysis.

High-Resolution Dynamics of Hemodilution After Exercise-Related Hemoconcentration

Purpose: Hemoconcentration during acute intense exercise is intensively investigated, while the rearrangement of hematological parameters during the recovery period is less understood. The aim of our study was to understand the mechanisms of hemodilution after short-term dynamic exercise. Methods: Twelve euhydrated male kayak athletes and 6 untrained controls were examined on a spiroergometer. In addition to the continuous recording of circulatory parameters, blood samples were taken at rest, at maximum load, and during restitution with a dense sampling frequency. Hemoglobin, hematocrit, osmolality, blood components, and core temperature were measured. Results: The hemoconcentration, independently of training status, reached its maximum (athletes Δ9.59% [4.18%] vs controls Δ11.85% [2.71%]) in the first minute of the recovery period. There was a significant increase in core temperature, reducing the viscosity of blood and promoting tissue oxygenation. High cardiac output and the increased blood flow compensate for viscosity being elevated by hemoconcentration during exercise. Hemoconcentration was maintained for 7 to 10 minutes and then diluted back to baseline 30 minutes after exercise. Temporarily higher viscosity during reduced cardiac output may result in a critical hemoconcentration zone, elevating the risk of circulatory overload. Elite athletes have a faster cardiac output decrease compared with that of hemodilution, making the circulation more vulnerable. We supposed that hemodilution was guided independently by plasma- and erythrocyte-related effectors. Conclusions: After high-intensity dynamic acute exercise, hemodilution is driven by independent factors, and a critical hemoconcentration zone may be formed during the recovery period in trained elite athletes.

Changes in Factors Regulating Serum Sodium Homeostasis During Two Ultra-Endurance Mountain Races of Different Distances: 69km vs. 121km

Overdrinking and non-osmotic arginine vasopressin release are the main risk factors for exercise-associated hyponatremia (EAH) in ultra-marathon events. However, particularly during ultra-marathon running in mountainous regions, eccentric exercise and hypoxia, which have been shown to modulate inflammation, hormones regulating fluid homeostasis (hypoxia), and oxidative stress, could contribute to serum sodium changes in a dose-dependent manner. To the best of our knowledge, the contribution of these factors, the extent of which depends on the duration and geographical location of the race, has not been well studied. Twelve male participants (11 finishers) of the short (69km, 4,260m elevation-gain) and 15 male participants (seven finishers) of the long (121km, 7,554m elevation-gain) single-stage Südtirol Ultra Sky-Race took part in this observational field study. Venous blood was drawn immediately before and after the race. Analyses included serum sodium concentration, copeptin (a stable marker for vasopressin), markers of inflammation, muscle damage and oxidative stress. Heart rate was measured during the race and race time was obtained from the race office. During the short and the long competition two and one finishers, respectively showed serum sodium concentrations >145mmol/L. During the long competition, one athlete showed serum sodium concentrations <135mmol/L. Only during the short competition percent changes in serum sodium concentrations of the finishers were related to percent changes in body mass (r=-0.812, p=0.002), total time (r=-0.608, p=0.047) and training impulse (TRIMP) (r=-0.653, p=0.030). Data show a curvilinear (quadratic) relationship between percent changes in serum sodium concentration and body mass with race time when including all runners (short, long, finishers and non-finishers). The observed prevalence of hypo- and hypernatremia is comparable to literature reports, as is the relationship between serum sodium changes and race time, race intensity and body mass changes of the finishers of the short race. The curvilinear relationship indicates that there might be a turning point of changes in serum sodium and body mass changes after a race time of approximately 20h. Since the turning point is represented mainly by non-finishers, regardless of race duration slight decrease in body mass and a slight increase in serum sodium concentration should be targeted to complete the race. Drinking to the dictate of thirst seems an adequate approach to achieve this goal.

Edema-like symptoms are common in ultra-distance cyclists and driven by overdrinking, use of analgesics and female sex - a study of 919 athletes

Background

Ultra-endurance cyclists regularly report various extents of bodily decline during long-distance bicycle rides, including potential kidney function-related symptoms such as swelling of body parts and urine changes. This study aimed to assess the prevalence of these symptoms in a representative cohort of ultra-endurance cyclists and shed light on potential predictors related to the ride, the rider and the rider’s behavior.

Methods

Between November 26 and December 14, 2020, 1350 people participated in an online survey investigating potential kidney-related symptoms of ultra-distance cycling. Frequency and severity of edema-like (“swelling”) symptoms and perceived changes in urine output, concentration and quality were associated with ride-related factors, demographic parameters and rider behavior-related variables.

Results

A total of 919 participants met the predefined inclusion criteria. The majority (N = 603, 65.6%) stated that they suffered from at least one potential kidney function-related symptom, out of which 498 (54.2%) stated one or more edema-like (“swelling”) symptoms. In correlational and multiple regression analyses, female sex, intake of analgesics and drinking strategies correlated with swelling symptoms. Further analyses indicated that drinking due to thirst and/or drinking adapted to ambient sweating and temperature negatively correlated with swelling symptoms, whereas “drinking as much as possible” enhanced these. Intake of analgesics was moderately positively correlated with swelling symptoms.

Conclusions

According to our survey, edema-like symptoms occur in the majority of ultra-distance cyclists and female sex, drinking strategy and intake of analgesic drugs are major predictors thereof. Studies are needed to investigate the underlying pathophysiological processes of such symptoms.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12970-021-00470-0.

Beetroot juice - a suitable post-marathon metabolic recovery supplement?

BACKGROUND

Red beetroot (Beta vulgaris L.) is a multifunctional functional food that reportedly exhibits potent anti-inflammatory, antioxidant, vasodilation, and cellular regulatory properties. This vegetable has gained a fair amount of scientific attention as a possible cost-effective supplement to enhance performance and expedite recovery after physical exercise. To date, no study has investigated the effects of incremental beetroot juice ingestion on the metabolic recovery of athletes after an endurance race. Considering this, as well as the beneficial glucose and insulin regulatory roles of beetroot, this study investigated the effects of beetroot juice supplementation on the metabolic recovery trend of athletes within 48 h after completing a marathon.

METHODS

By employing an untargeted two-dimensional gas chromatography time-of-flight mass spectrometry approach, serum samples (collected pre-, post-, 24 h post-, and 48 h post-marathon) of 31 marathon athletes that ingested a series (n = 7; 250 ml) of either beetroot juice (n = 15 athletes) or isocaloric placebo (n = 16 athletes) supplements within 48 h post-marathon, were analysed and statistically compared.

RESULTS

The metabolic profiles of the beetroot-ingesting cohort recovered to a pre-marathon-related state within 48 h post-marathon, mimicking the metabolic recovery trend observed in the placebo cohort. Since random inter-individual variation was observed immediately post-marathon, only metabolites with large practical significance (p-value ≤0.05 and d-value ≥0.5) within 24 h and 48 h post-marathon were considered representative of the effects of beetroot juice on metabolic recovery. These (n = 4) mainly included carbohydrates (arabitol and xylose) and odd-chain fatty acids (nonanoate and undecanoate). The majority of these were attributed to beetroot content and possible microbial fermentation thereof.

CONCLUSION

Apart from the global metabolic recovery trends of the two opposing cohorts, it appears that beetroot ingestion did not expedite metabolic recovery in athletes within 48 h post-marathon.

Consistency Is Key When Setting a New World Record for Running 10 Marathons in 10 Days

Background: We describe the requirements and physiological changes when running 10 consecutive marathons in 10 days at the same consistent pace by a female ultra-endurance athlete. Methods: Sharon Gayter (SG) 54 yrs, 162.5 cm, 49.3 kg maximal oxygen uptake (VO₂ max) 53 mL/kg⁻¹/min⁻¹. SG completed 42.195 km on a treadmill every day for 10 days. We measured heart rate (HR), Rating of Perceived Exertion (RPE), oxygen uptake (VO₂), weight, body composition, blood parameters, nutrition, and hydration. Results: SG broke the previous record by ~2.5 h, with a cumulative completion time of 43 h 51 min 39 s. Over the 10 days, weight decreased from 51 kg to 48.4 kg, bodyfat mass from 9.1 kg to 7.2 kg (17.9% to 14.8%), and muscle mass from 23.2 kg to 22.8 kg. For all marathons combined, exercise intensity was ~60% VO₂ max; VO₂ 1.6 ± 0.1 L.min⁻¹/32.3 ± 1.1 mL.kg⁻¹.min⁻¹, RER 0.8 ± 0, HR 143 ± 4 b.min⁻¹. Energy expenditure (EE) was 2030 ± 82 kcal/marathon, total EE for 10 days (including BMR) was 33,056 kcal, daily energy intake (EI) 2036 ± 418 kcal (20,356 kcal total), resulting an energy deficit (ED) of 12,700 kcal. Discussion: Performance and pacing were highly consistent across all 10 marathons without any substantial physiological decrements. Although overall EI did not match EE, leading to a significant ED, resulting in a 2.6 kg weight loss and decreases in bodyfat and skeletal muscle mass, this did not affect performance.

Skeletal Muscle Mitochondrial Function after a 100-km Ultramarathon: A Case Study in Monozygotic Twins

PURPOSE

Very little research has investigated the effects of ultraendurance exercise on the bioenergetic status of muscle. The primary objective of this case study was to characterize the changes that occur in skeletal muscle mitochondria in response to a 100-km ultramarathon in monozygotic twins. A second objective was to determine whether mitochondrial function is altered by consuming a periodized low-carbohydrate, high-fat diet during training compared with a high-carbohydrate diet.

METHODS

One pair of male monozygotic twins ran 100 km on treadmills after 4 wk of training on either a high-carbohydrate or periodized low-carbohydrate, high-fat diet. Muscle biopsies were collected 4 wk before the run, as well as 4 and 52 h postrun. Blood draws were also performed immediately before as well as 4 and 52 h after the run.

RESULTS

Four hours postrun, respiratory capacity, citrate synthase activity, and mitochondrial complex protein content were decreased. Two days later, both twins showed signs of rapid recovery in several of these measures. Furthermore, blood levels of creatine phosphokinase, C-reactive protein, and aspartate transaminase were elevated 4 h after the run but partially recovered 2 d later.

CONCLUSION

Although there were some differences between the twins, the primary finding is that there is significant mitochondrial impairment induced by running 100 km, which rapidly recovers within 2 d. These results provide ample rationale for future investigations of the effects of ultraendurance activity on mitochondrial function.