Pain perception after running a 100-mile ultramarathon

Athletes and Experimental Pain: A Systematic Review and Meta-Analysis

The evidence that athletes respond to and report indices of experimental pain differently to non-athlete populations was analysed. Databases screened were SPORTDiscus, PubMED, PsycArticles, the Cochrane Library (Cochrane Database of Systematic Reviews), Web of Science, Scopus, and CINAHL. Studies that compared experimentally induced pain responses (threshold, tolerance, intensity, unpleasantness, bothersomeness, and effect on performance) in athletes and controls were included. Meta-analyses were performed where appropriate and effects were described as standardised mean differences, pooled using random effects models. Thirty-six studies (2,492 participants) met the inclusion criteria comprising 19 pain tolerance, 17 pain threshold, 21 pain intensity, 5 pain unpleasantness, 2 performance in pain and 1 bothersomeness study. Athletes demonstrated greater pain tolerance (g = .88 [95% confidence interval [CI] .65, .13]) and reported less pain intensity (g = -.80, [95% CI -1.13, -.47]) compared to controls; they also had higher pain threshold but with smaller effects (g = .41, [95% CI .08, .75]). Differences for unpleasantness did not reach statistical significance but the effects were large (g = -1.23 [95% CI -2.29, .18]). Two studies reported that performance in pain was better in contact athletes than non-athletes, and one concluded that athletes find pain less bothersome than controls. There were considerable inconsistencies in the methods employed that were reflected in the meta-analyses' findings. Sub-group analyses of tolerance and intensity were conducted between endurance, contact, and other athlete groups, but were not significant. The data suggest that athletic participation is associated with altered pain responses, but mechanisms remain unclear and more transparent methods are recommended.This study was registered on the PROSPERO site in January 2019 (ref ID: CRD42019119611). PERSPECTIVE: This review examined differences in pain outcomes (threshold, tolerance, intensity, unpleasantness, bothersomeness) and the effect of pain on performance, in athletes versus controls. Meta-analyses revealed athletes had higher threshold and tolerance and found pain less intense than controls; there was some evidence of differences in bothersomeness and performance.

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.

24 Hours on the Run-Does Boredom Matter for Ultra-Endurance Athletes' Crises?

Sport and exercise can be boring. In the general population, thinking of sports as boring has been linked to exercising less. However, less is known about the role of boredom in people who participate in ultra-endurance competitions: Do these athletes also associate their sports with boredom, and does boredom pose a self-regulatory challenge that predicts if they encounter a crisis during an ultra-endurance competition? Here, we investigate these questions with a sample of N = 113 (n = 34 female) competitors of a 24 h hour running competition, aged M = 37.6 ± 13.8 years. In this study, n = 23 very extreme athletes competed as single starters or in a relay team of 2, and n = 84 less extreme athletes competed in relay teams of 4 or 6. Before the run, athletes completed self-report measures on sport-specific trait boredom, as well as the degree to which they expected boredom, pain, effort, and willpower to constitute self-regulatory challenges they would have to cope with. After the run, athletes reported the degree to which they actually had to deal with these self-regulatory challenges and if they had faced an action crisis during the competition. Analyses revealed that very extreme athletes displayed a significantly lower sport-specific trait boredom than less extreme athletes (p = 0.024, d=-0.48). With respect to self-regulatory challenges, willpower, pain, and effort were expected and reported at a much higher rate than boredom. However, only boredom was as a significant predictor of experiencing a crisis during the competition (odds ratio = 12.5, p = 0.02). Our results show that boredom also matters for highly active athletes. The fact that the experience of boredom-and not more prototypical competition-induced challenges, such as pain or effort-were linked to having an action crisis highlights the relevance of incorporating boredom into the preparation for a race and to the performance management during competition.

The Consequences of Training and Competition to the Musculoskeletal System in Ultramarathon Runners: A Narrative Review

Ultramarathons are becoming increasingly popular every year, leading to more and more publications focusing on athletes of these endurance events. This paper summarizes the current state of knowledge on the effects of ultramarathons on the motor system. Various studies have attempted to answer questions about negative and positive effects on the musculoskeletal system, common injuries, optimal strategies, and regeneration. Considering the increasing number of ultramarathon athletes, the discoveries may have practical applications for a multitude of experts in the field of sports medicine, as well as for the athletes themselves. Acute locomotor system changes in runners as assessed by locomotor biomarkers are reversible and may be asymptomatic or painful. Injuries suffered by runners largely allow them to finish the competition and are usually overlooked. Regeneration, including regular massage and the use of supporting techniques, allows for faster convalescence. This publication is meant to be a source of knowledge for people associated with this discipline.

Pain During a Marathon Run: Prevalence and Correlates in a Cross-Sectional Study of 1,251 Recreational Runners in 251 Marathons

This cross-sectional study aimed to obtain fundamental knowledge about pain during a marathon run. During the first seven months of 2007, announcements on websites of interest to marathon runners were used to recruit participants. A total of 1,251 runners (550 female runners) completed a 41-question online survey about the location and intensity of their primary pain during their last marathon and potentially related variables [perception of effort during the marathon, number of prior marathons run, typical pain intensity during training runs, percentage of training days with run-induced pain, highest intensity pain ever experienced]. Pain location was selected from a list of 27 specified body sites covering the entire body. Kilometer at which pain first occurred indexed pain threshold. Pain intensity at the primary location of pain was measured with a standardized, well-validated 0–10 pain intensity scale. Pearson correlations and multiple regression quantified the associations between average pain intensity and other variables. Sex-related differences in pain were tested using independent t-tests. Effort ratings (6–20) were added as a covariate in an ANCOVA to test if perceived effort accounted for possible sex-related differences in pain. Based on the available research, it was hypothesized that: (i) most runners would report moderate intensity pain, (ii) pain would be associated with both exercise intensity during the marathon and pain during training, and (iii) after adjusting for expected sex-related differences in perceived effort, females would experience pain earlier and rate the pain intensity as higher. All but two runners (99.8%) reported pain during a marathon, and most frequently in the anterior/medial thigh (17.1%), hamstring (10%), and calf (9.3%) locations. Pain threshold occurred at 25.3 ± 9.8 km (15.7 ± 6.1 miles) and the overall pain intensity of the run was 5.26 ± 2.45. No sex-related pain differences were found. Overall pain intensity during a marathon was significantly associated with: pain intensity during training runs (r = 0.39), percentage of training days with run-induced pain (r = 0.23), highest intensity pain ever experienced (r = 0.23), number of prior marathons (r = −0.18), and intensity of effort (r = 0.11) (all P < 0.001). Most runners experience moderate to very strong intensity pain during a marathon; the pain was independent of biological sex, and the pain is weakly associated with marathon race experience, pain during training, race effort, and the highest intensity of pain ever experienced.

To Be a Champion of the 24-h Ultramarathon Race. If Not the Heart ... Mosaic Theory?

This comprehensive case analysis aimed to identify the features enabling a runner to achieve championship in 24-h ultramarathon (UM) races. A 36-year-old, multiple medalist of the World Championships in 24-h running, was assessed before, one and 10 days after a 24-h run. Results of his extensive laboratory and cardiological diagnostics with transthoracic echocardiography (TTE) and a one-time cardiopulmonary exercise test (CPET) were analyzed. After 12 h of running (approximately 130 km), the athlete experienced an increasing pain in the right knee. His baseline clinical data were within the normal range. High physical efficiency in CPET (VO₂max 63 mL/kg/min) was similar to the average achieved by other ultramarathoners who had significantly worse results. Thus, we also performed genetic tests and assessed his psychological profile, body composition, and markers of physical and mental stress (serotonin, cortisol, epinephrine, prolactin, testosterone, and luteinizing hormone). The athlete had a mtDNA haplogroup H (HV0a1 subgroup, belonging to the HV cluster), characteristic of athletes with the highest endurance. Psychological studies have shown high and very high intensity of the properties of individual scales of the tools used mental resilience (62–100% depending on the scale), openness to experience (10th sten), coherence (10th sten), positive perfectionism (100%) and overall hope for success score (10th sten). The athlete himself considers the commitment and mental support of his team to be a significant factor of his success. Body composition assessment (%fat 13.9) and the level of stress markers were unremarkable. The tested athlete showed a number of features of the champions of ultramarathon runs, such as: inborn predispositions, mental traits, level of training, and resistance to pain. However, none of these features are reserved exclusively for “champions”. Team support’s participation cannot be underestimated. The factors that guarantee the success of this elite 24-h UM runner go far beyond physiological and psychological explanations. Further studies are needed to identify individual elements of the putative “mosaic theory of being a champion”.

Epidemiology of Injury and Illness Among Trail Runners: A Systematic Review

BACKGROUND

Trail running is characterised by large elevation gains/losses and uneven varying running surfaces. Limited information is available on injury and illness among trail runners to help guide injury and illness prevention strategies.

OBJECTIVE

The primary aim of this review was to describe the epidemiology of injury and illness among trail runners.

METHODS

Eight electronic databases were systematically searched (MEDLINE Ovid, PubMed, Scopus, SportsDiscus, CINAHL, Health Source: Nursing/Academic, Health Source: Consumer Ed., and Cochrane) from inception to November 2020. The search was conducted according to the PRISMA statement and the study was registered on PROSPERO international prospective register of systematic reviews (CRD42019135933). Full-text English and French studies that investigated injury and/or illness among trail runners participating in training/racing were included. The main outcome measurements included: trail running injury (incidence, prevalence, anatomical site, tissue type, pathology-type/specific diagnosis, severity), and illness (incidence, prevalence, symptoms, specific diagnosis, organ system, severity). The methodological quality of the included studies was assessed using an adapted Downs and Black assessment tool.

RESULTS

Sixteen studies with 8644 participants were included. Thirteen studies investigated race-related injury and/or illness and three studies included training-related injuries. The overall incidence range was 1.6-4285.0 injuries per 1000 h of running and 65.0-6676.6 illnesses per 1000 h of running. The foot was the most common anatomical site of trail running injury followed by the knee, lower leg, thigh, and ankle. Skin lacerations/abrasions were the most common injury diagnoses followed by skin blisters, muscle strains, muscle cramping, and ligament sprains. The most common trail running illnesses reported related to the gastro-intestinal tract (GIT), followed by the metabolic, and cardiovascular systems. Symptoms of nausea and vomiting related to GIT distress and dehydration were commonly reported.

CONCLUSION

Current trail running literature consists mainly of injury and illness outcomes specifically in relation to single-day race participation events. Limited evidence is available on training-related injury and illness in trail running. Our review showed that injury and illness are common among trail runners, but certain studies included in this review only focused on dermatological injuries (e.g. large number of feet blisters) and GIT symptoms. Specific areas for future research were identified that could improve the management of trail running injury and illness.

Do Sex Differences in Physiology Confer a Female Advantage in Ultra-Endurance Sport?

Ultra-endurance has been defined as any exercise bout that exceeds 6 h. A number of exceptional, record-breaking performances by female athletes in ultra-endurance sport have roused speculation that they might be predisposed to success in such events. Indeed, while the male-to-female performance gap in traditional endurance sport (e.g., marathon) remains at ~ 10%, the disparity in ultra-endurance competition has been reported as low as 4% despite the markedly lower number of female participants. Moreover, females generally outperform males in extreme-distance swimming. The issue is complex, however, with many sports-specific considerations and caveats. This review summarizes the sex-based differences in physiological functions and draws attention to those which likely determine success in extreme exercise endeavors. The aim is to provide a balanced discussion of the female versus male predisposition to ultra-endurance sport. Herein, we discuss sex-based differences in muscle morphology and fatigability, respiratory-neuromechanical function, substrate utilization, oxygen utilization, gastrointestinal structure and function, and hormonal control. The literature indicates that while females exhibit numerous phenotypes that would be expected to confer an advantage in ultra-endurance competition (e.g., greater fatigue resistance, greater substrate efficiency, and lower energetic demands), they also exhibit several characteristics that unequivocally impinge on performance (e.g., lower O₂-carrying capacity, increased prevalence of GI distress, and sex-hormone effects on cellular function/injury risk). Crucially, the advantageous traits may only manifest as ergogenic in the extreme endurance events which, paradoxically, are those that females less often contest. The title question should be revisited in the coming years, when/if the number of female participants increases.

Changes of Mood and Cognitive Performance before and after a 100 km Nighttime Ultramarathon Run

Ultramarathons are becoming an increasingly popular endurance sport. Year after year, the demands on athletes’ skills and endurance increase. Ultramarathons are particularly taxing on athletes’ psychological functioning. This study assessed the relationships between taking part in a nighttime ultramarathon and changes in mood and cognitive functioning. The study included 20 experienced runners aged 26–57 (M = 37.29; SD = 7.94) who had M = 7.08, SD = 5.41 (range 3–44) years of experience running. There were 18 men and 2 women. The mood states were measured twice, just before the start of the run and shortly after crossing the finish line, using the Polish version of the UMACL UWIST Mood Adjective Checklist by Mathews, Chamberlain, and Jones. To assess cognitive functioning, the Stroop Color and Word Test and “Forward digit span” subtest from the Wechsler Adult Intelligence Scale were used. We observed statistically significant changes in the mood of the runners: tense arousal, associated with the experienced stress, was significantly higher before the run than immediately after the finish. Moreover, we observed an improvement in cognitive functioning after finishing the 100 km run on both of the trials on the Stroop color word test and on the forward digit span test.

Exercise-induced hypoalgesia after acute and regular exercise: experimental and clinical manifestations and possible mechanisms in individuals with and without pain

This review describes methodology used in the assessment of the manifestations of exercise-induced hypoalgesia in humans and previous findings in individuals with and without pain. Possible mechanisms and future directions are discussed.

Exercise and physical activity is recommended treatment for a wide range of chronic pain conditions. In addition to several well-documented effects on physical and mental health, 8 to 12 weeks of exercise therapy can induce clinically relevant reductions in pain. However, exercise can also induce hypoalgesia after as little as 1 session, which is commonly referred to as exercise-induced hypoalgesia (EIH). In this review, we give a brief introduction to the methodology used in the assessment of EIH in humans followed by an overview of the findings from previous experimental studies investigating the pain response after acute and regular exercise in pain-free individuals and in individuals with different chronic pain conditions. Finally, we discuss potential mechanisms underlying the change in pain after exercise in pain-free individuals and in individuals with different chronic pain conditions, and how this may have implications for clinical exercise prescription as well as for future studies on EIH.

Pain Is Inevitable But Suffering Is Optional: Relationship of Pain Coping Strategies to Performance in Multistage Ultramarathon Runners

INTRODUCTION

Ultramarathon runners commonly endure musculoskeletal pain during endurance events. However, the effect of pain coping skills on performance has not been examined.

METHODS

A prospective observational study during three 250 km (155 mi), 6 stage ultramarathons was conducted. Finish line surveys were completed after each of the four 40 km (25 mi) and one 80 km (50 mi) stages of racing. Variables gathered included pain intensity, pain coping strategy use, pain interference, finishing position (quintile), and successful race completion.

RESULTS

A total of 204 participants (age 41.4±10.3 y; 73% male) reported average pain intensity of 3.9 (±2.0 SD) and worst pain intensity of 5.3 (±2.3) on a 0 to 10 scale. They used greater adaptive pain coping strategies (3.0±1.3) relative to maladaptive strategies (1.3±1.1). Worst pain and pain interference increased over each stage of the race for all runners (P<0.001), with worst pain being significantly different by finishing status (P=0.02). Although all runners endured increased pain and interference, the nonfinishers (28 [14%]) had significantly greater differences in changes in pain intensity (P<0.01) and pain interference (P<0.001). Maladaptive pain coping strategies were more common in nonfinishers; with each 1-point increase (0-6 scale), there was a 3 times increase in odds of not finishing the race.

CONCLUSIONS

Although increased pain intensity and pain interference was found in all multistage ultramarathon runners, successful event completion was significantly associated with less maladaptive pain coping. Training in coping with pain may be a beneficial part of ultramarathon preparation.

Lower Pressure Pain Thresholds in Patellofemoral Pain Patients, Especially in Female Patients: A Cross-Sectional Case-Control Study

Objective

It has been suggested that repeated overload might sensitize nociceptors, causing local hyperalgesia in patients with patellofemoral pain (PFP). This might also lead to generalized hyperalgesia, indicative of altered central pain processing. This study aimed to investigate differences in pressure pain threshold (PPT) as a measure of pressure hyperalgesia between patients with PFP and healthy controls and in predefined subgroups and to study associations between PPT and patient characteristics.

Design

Case-control study.

Setting

Physiotherapy, general practices, and sports medicine practices.

Subjects

Sixty-four patients with PFP and 70 healthy controls.

Methods

Demographics, pain (numerical rating score), and function (anterior knee pain score) were obtained by questionnaire. The PPT was measured with a handheld dynamometer with algometry tip at the most painful spot of the affected knee (medial facet in controls), the same spot at the contralateral knee, and at the contralateral forearm. Differences between groups were tested using analysis of variance techniques including the variables age, gender, body mass index, and sports participation.

Results

Patients had significantly lower PPTs compared with controls at all locations (affected knee: mean difference = -12.2, 95% confidence interval [CI] = -17.3 to -7.1; contralateral knee: mean difference = -4.7, 95% CI = -10.1 to 0.52; contralateral arm: mean difference = -5.7, 95% CI = -10.5 to -0.8). Both male and female patients demonstrated lower PPTs, though a significant subgroup effect was found for female gender (effect size ranging from 0.73 to 0.98).

Conclusions

Local and generalized pressure hyperalgesia, suggesting alterations in both peripheral and central pain processing, were present in patients with PFP, though females with PFP were most likely to suffer from generalized hyperalgesia.

How variability in pain and pain coping relate to pain interference during multistage ultramarathons

An important and substantial body of literature has established that maladaptive and adaptive coping strategies significantly impact pain-related outcomes. This literature, however, is based primarily on populations with painful injuries and illnesses. Little is known about coping in individuals who experience pain in other contexts and whether coping impacts outcomes in the same way. In an effort to better understand pain coping in such contexts, this study evaluated pain coping in ultramarathon runners, a population known to experience moderate levels of pain with minimal perceived negative effects. This study reports on pain coping in 204 entrants in 2016 RacingThePlanet multistage ultramarathon events. Participants provided data over 5 consecutive days on pain severity, pain interference, exertion, and coping. Results demonstrated that the study participants were more likely to use adaptive than maladaptive coping responses. However, maladaptive coping, but not adaptive coping, was positively associated with percent time spent thinking about pain and pain-related interference. Taken together, the study supports the idea that this high functioning group of individuals experiencing pain emphasizes the use of adaptive coping strategies over maladaptive strategies, reinforcing the perspective that such a pattern may be the most effective way to cope with pain. Within the group, however, results supported traditional patterns, such that greater use of maladaptive strategies was associated with greater pain-related interference, suggesting that optimizing pain coping may be critical to reducing factors that may interfere with ultramarathon performance.

The Impact of Exercise in Rodent Models of Chronic Pain

PURPOSE OF REVIEW

Physical activity is increasingly recommended for chronic pain. In this review, we briefly survey recent, high-quality meta-analyses on the effects of exercise in human chronic pain populations, followed by a critical discussion of the rodent literature.

RECENT FINDINGS

Most meta-analytical studies on the effects of exercise in human chronic pain populations describe moderate improvements in various types of chronic pain, despite substantial variability in the outcomes reported in the primary literature. The most consistent findings suggest that while greater adherence to exercise programs produces better outcomes, there is minimal support for the superiority of one type of exercise over another. The rodent literature similarly suggests that while regular exercise reduces hypersensitivity in rodent models of chronic pain, exercise benefits do not appear to relate to either the type of injury or any particular facet of the exercise paradigm. Potential factors underlying these results are discussed, including the putative involvement of stress-induced analgesic effects associated with certain types of exercise paradigms. Exercise research using rodent models of chronic pain would benefit from increased attention to the role of stress in exercise-induced analgesia, as well as the incorporation of more clinically relevant exercise paradigms.

Personality Traits and Vitamin D3 Supplementation Affect Mood State 12 h Before 100 km Ultramarathon Run

Background: Participation in extreme endurance sports is becoming an increasingly popular activity, and thus more and more people are getting involved in it. Taking part in a 100 km run is associated with great physiological and psychological stress, which can affect one’s mood state. Thus, the goal of this study was to determine if personality, experience, and motives for participation are related to a runner’s mood and its changes as well as to investigate whether vitamin D3 supplementation influences mood 12 h before and 12 h after the run.

Method: The study group consisted of 20 experienced marathon and ultramarathon runners taking part in a 100 km track run. All participants were males aged between 31 and 50 (M = 40.75, SD = 7.15). The group was divided in two equal subgroups: the placebo group and the group supplemented with vitamin D3. Personality traits were assessed using the Polish version of Eysenck’s EPQ-R 106 and mood states were measured twice (12 h before and after the run) using the Polish version of the UMACL by Mathews, Chamberlain, and Jones. Motives for participation in ultramarathons were measured with the IPAO by Lipowski and Zaleski.

Results: Levels of vitamin D3 correlated very strongly with energetic arousal (EA) (r_s = 0.80; p < 0.05) and strongly hedonic tone (HT) (r_s = 0.74; p < 0.05) 12 h before the run. There were no significant correlations between levels of vitamin D3 and mood states after the run. Moreover, extraversion correlated moderately with tense arousal (TA) (r_s = -0.48; p < 0.05) and EA (r_s = 0.47; p < 0.05) while neuroticism correlated moderately with TA (r_s = 0.53; p < 0.05) and HT (r_s = -0.57; p < 0.05).

Conclusion: Both personality and vitamin D3 supplementation are related to runners’ pre-run mood. These effects are nullified when it comes to post-run mood states.

Central and peripheral pain sensitization during an ultra-marathon competition

Background and aims

The participation in ultra-marathons and other ultra-endurance events has increased exponentially over the past decade. There is insufficient data on variation in pain mechanisms in exercise overall but especially in the ultra-endurance athlete population. To further understand peripheral and central pain sensitization we have investigated pressure pain threshold and conditioned pain modulation during three separate ultra-marathon competitions.

Methods

Each ultra-marathon investigated was held in the state of Florida, USA, over flat, sandy and paved surfaces under generally warm to hot, humid conditions. Pressure pain threshold was measured utilizing a Baseline © Dolorimeter. The blunt end of the dolorimeter stylus was placed onto the distal dominant arm, equidistant between the distal radius and ulna, three times in a blinded manner to insure that the testing technician did not influence the subject’s responses. Conditioned pain modulation was measured immediately after the PPT measures by placing the non-dominant hand in a cool water bath maintained at 15°C. The same dolorimeter measurement was repeated two more times on the dominant arm while the non-dominant hand remained in the water. Data was analyzed with a paired t-test.

Results

Pressure pain threshold was significantly decreased (p<0.05) at 25, 50 and 100 miles. Conditioned pain modulation was also significantly decreased (p<0.05) at 25, 50 and 100 miles of an ultra-marathon competition.

Conclusions

Together these data suggest an increased peripheral and/or central pain sensitization starting at 25 miles and continuing throughout an ultra-marathon competition run in these conditions. This is the first study that provides evidence of a decreased peripheral pain threshold and decreased central pain inhibition from ultra-marathon running. Decreases in both the peripheral pain threshold and central inhibition may result from nociceptor plasticity, central sensitization or a combination of both.

Implications

Based on previous research that has indicated a central sensitization resulting from inflammation and the well-documented inflammatory response to the rigors of ultra-marathon competition, we suggest the decreased peripheral pain threshold and decreased descending pain inhibition results from this inflammatory response of running an ultra-marathon.

Physiology and Pathophysiology in Ultra-Marathon Running

In this overview, we summarize the findings of the literature with regards to physiology and pathophysiology of ultra-marathon running. The number of ultra-marathon races and the number of official finishers considerably increased in the last decades especially due to the increased number of female and age-group runners. A typical ultra-marathoner is male, married, well-educated, and ~45 years old. Female ultra-marathoners account for ~20% of the total number of finishers. Ultra-marathoners are older and have a larger weekly training volume, but run more slowly during training compared to marathoners. Previous experience (e.g., number of finishes in ultra-marathon races and personal best marathon time) is the most important predictor variable for a successful ultra-marathon performance followed by specific anthropometric (e.g., low body mass index, BMI, and low body fat) and training (e.g., high volume and running speed during training) characteristics. Women are slower than men, but the sex difference in performance decreased in recent years to ~10–20% depending upon the length of the ultra-marathon. The fastest ultra-marathon race times are generally achieved at the age of 35–45 years or older for both women and men, and the age of peak performance increases with increasing race distance or duration. An ultra-marathon leads to an energy deficit resulting in a reduction of both body fat and skeletal muscle mass. An ultra-marathon in combination with other risk factors, such as extreme weather conditions (either heat or cold) or the country where the race is held, can lead to exercise-associated hyponatremia. An ultra-marathon can also lead to changes in biomarkers indicating a pathological process in specific organs or organ systems such as skeletal muscles, heart, liver, kidney, immune and endocrine system. These changes are usually temporary, depending on intensity and duration of the performance, and usually normalize after the race. In longer ultra-marathons, ~50–60% of the participants experience musculoskeletal problems. The most common injuries in ultra-marathoners involve the lower limb, such as the ankle and the knee. An ultra-marathon can lead to an increase in creatine-kinase to values of 100,000–200,000 U/l depending upon the fitness level of the athlete and the length of the race. Furthermore, an ultra-marathon can lead to changes in the heart as shown by changes in cardiac biomarkers, electro- and echocardiography. Ultra-marathoners often suffer from digestive problems and gastrointestinal bleeding after an ultra-marathon is not uncommon. Liver enzymes can also considerably increase during an ultra-marathon. An ultra-marathon often leads to a temporary reduction in renal function. Ultra-marathoners often suffer from upper respiratory infections after an ultra-marathon. Considering the increased number of participants in ultra-marathons, the findings of the present review would have practical applications for a large number of sports scientists and sports medicine practitioners working in this field.

Classical conditioning and pain: conditioned analgesia and hyperalgesia

This article reviews situations in which stimuli produce an increase or a decrease in nociceptive responses through basic associative processes and provides an associative account of such changes. Specifically, the literature suggests that cues associated with stress can produce conditioned analgesia or conditioned hyperalgesia, depending on the properties of the conditioned stimulus (e.g., contextual cues and audiovisual cues vs. gustatory and olfactory cues, respectively) and the proprieties of the unconditioned stimulus (e.g., appetitive, aversive, or analgesic, respectively). When such cues are associated with reducers of exogenous pain (e.g., opiates), they typically increase sensitivity to pain. Overall, the evidence concerning conditioned stress-induced analgesia, conditioned hyperalagesia, conditioned tolerance to morphine, and conditioned reduction of morphine analgesia suggests that selective associations between stimuli underlie changes in pain sensitivity.

Can neuromuscular fatigue explain running strategies and performance in ultra-marathons?: the flush model

While the industrialized world adopts a largely sedentary lifestyle, ultra-marathon running races have become increasingly popular in the last few years in many countries. The ability to run long distances is also considered to have played a role in human evolution. This makes the issue of ultra-long distance physiology important. In the ability to run multiples of 10 km (up to 1000 km in one stage), fatigue resistance is critical. Fatigue is generally defined as strength loss (i.e. a decrease in maximal voluntary contraction [MVC]), which is known to be dependent on the type of exercise. Critical task variables include the intensity and duration of the activity, both of which are very specific to ultra-endurance sports. They also include the muscle groups involved and the type of muscle contraction, two variables that depend on the sport under consideration. The first part of this article focuses on the central and peripheral causes of the alterations to neuromuscular function that occur in ultra-marathon running. Neuromuscular function evaluation requires measurements of MVCs and maximal electrical/magnetic stimulations; these provide an insight into the factors in the CNS and the muscles implicated in fatigue. However, such measurements do not necessarily predict how muscle function may influence ultra-endurance running and whether this has an effect on speed regulation during a real competition (i.e. when pacing strategies are involved). In other words, the nature of the relationship between fatigue as measured using maximal contractions/stimulation and submaximal performance limitation/regulation is questionable. To investigate this issue, we are suggesting a holistic model in the second part of this article. This model can be applied to all endurance activities, but is specifically adapted to ultra-endurance running: the flush model. This model has the following four components: (i) the ball-cock (or buoy), which can be compared with the rate of perceived exertion, and can increase or decrease based on (ii) the filling rate and (iii) the water evacuated through the waste pipe, and (iv) a security reserve that allows the subject to prevent physiological damage. We are suggesting that central regulation is not only based on afferent signals arising from the muscles and peripheral organs, but is also dependent on peripheral fatigue and spinal/supraspinal inhibition (or disfacilitation) since these alterations imply a higher central drive for a given power output. This holistic model also explains how environmental conditions, sleep deprivation/mental fatigue, pain-killers or psychostimulants, cognitive or nutritional strategies may affect ultra-running performance.

Acute effects of high-intensity dumbbell exercise after isokinetic eccentric damage: interaction between altered pain perception and fatigue on static and dynamic muscle performance

This study aimed to determine whether high-intensity dumbbell exercise involving both concentric and eccentric contractions would provide a temporary alleviation of delayed-onset muscle soreness (DOMS). It also examined the effect of alleviated muscle soreness on dynamic muscle performance using a stretch-shortening cycle (SSC; peak angular acceleration and velocity of the elbow during both lowering and concentric phases) to provide indirect evidence that DOMS contributes to the dynamic performance decrement after eccentric injury. Thirteen untrained adults performed 30 maximal isokinetic eccentric contractions of the elbow flexors to induce eccentric damage. Five sets of arm curls using a dumbbell (equivalent to 70% of isometric maximal voluntary contraction) were then performed until failure on days 1, 2, 3, and 5 of recovery. Muscle soreness significantly decreased after each session of dumbbell exercise (p = 0.001). Isometric strength further decreased immediately after dumbbell exercise, indicating muscle fatigue (p < 0.001). Dynamic performance variables were less affected by fatigue, however, with performance being reduced only for peak lowering velocity (p < 0.001). Other measures of dynamic performance were relatively constant after dumbbell exercise, particularly on days 2 and 3 when soreness was greatest. It was concluded that high-intensity concentric/eccentric dumbbell exercise was able to temporarily alleviate DOMS and that this reduction in soreness served to counter the effect of peripheral muscle fatigue during dynamic activities. Practical applications of this study are that after eccentric damage, alleviation of muscle soreness through an optimal warm-up may be helpful to temporarily recover dynamic muscle performance. Free-weight loading is one suggested technique to temporarily manage DOMS.