Intensity and physiological strain of competitive ultra-endurance exercise in humans

Ultra-Cycling- Past, Present, Future: A Narrative Review

BACKGROUND

Ultra-endurance events are gaining popularity in multiple exercise disciplines, including cycling. With increasing numbers of ultra-cycling events, aspects influencing participation and performance are of interest to the cycling community.

MAIN BODY

The aim of this narrative review was, therefore, to assess the types of races offered, the characteristics of the cyclists, the fluid and energy balance during the race, the body mass changes after the race, and the parameters that may enhance performance based on existing literature. A literature search was conducted in PubMed, Scopus, and Google Scholar using the search terms 'ultracycling', 'ultra cycling', 'ultra-cycling', 'ultra-endurance biking', 'ultra-bikers' and 'prolonged cycling'. The search yielded 948 results, of which 111 were relevant for this review. The studies were classified according to their research focus and the results were summarized. The results demonstrated changes in physiological parameters, immunological and oxidative processes, as well as in fluid and energy balance. While the individual race with the most published studies was the Race Across America, most races were conducted in Europe, and a trend for an increase in European participants in international races was observed. Performance seems to be affected by characteristics such as age and sex but not by anthropometric parameters such as skin fold thickness. The optimum age for the top performance was around 40 years. Most participants in ultra-cycling events were male, but the number of female athletes has been increasing over the past years. Female athletes are understudied due to their later entry and less prominent participation in ultra-cycling races. A post-race energy deficit after ultra-cycling events was observed.

CONCLUSION

Future studies need to investigate the causes for the observed optimum race age around 40 years of age as well as the optimum nutritional supply to close the observed energy gap under consideration of the individual race lengths and conditions. Another research gap to be filled by future studies is the development of strategies to tackle inflammatory processes during the race that may persist in the post-race period.

Exploring the Nutrition Strategies Employed by Ultra-Endurance Athletes to Alleviate Exercise-Induced Gastrointestinal Symptoms-A Systematic Review

(1) Background: Participation in ultra-endurance sports, particularly ultra-running, has increased over the previous three decades. These are accompanied by high energetic demands, which may be further exacerbated by extreme environmental conditions. Preparation is long-term, comprising of sufficient exercise management, supportive dietary habits, and nutritional intakes for optimal adaptations. Gastrointestinal symptoms are often cited as causing underperformance and incompletion of events. Though the majority do not pose serious long-term health risks, they may still arise. It has been suggested that the nutritional interventions employed by such athletes prior to, during, and after exercise have the potential to alter symptom incidence, severity, and duration. A summary of such interventions does not yet exist, making it difficult for relevant personnel to develop recommendations that simultaneously improve athletic performance by attenuating gastrointestinal symptoms. The aim of this research is to systematically review the literature investigating the effects of a nutrition intervention on ultra-endurance athletes exercise-induced gastrointestinal symptom incidence, severity, or duration. (2) Methods: A systematic review of the literature was conducted (PubMed, CINAHL, Web of Science, and Sports Discus) in January 2023 to investigate the effects of various nutrition interventions on ultra-endurance athletes' (regardless of irritable bowel syndrome diagnosis) exercise-induced gastrointestinal symptoms. Variations of key words such as "ultra-endurance", "gastrointestinal", and "nutrition" were searched. The risk of bias in each paper was assessed using the ADA quality criteria checklist. (3) Results: Of the seven eligible studies, one was a single field-based case study, while the majority employed a crossover intervention design. A total of n = 105 participants (n = 50 male; n = 55 female) were included in this review. Practicing a diet low in short-chain, poorly absorbed carbohydrates, known as fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs), as well as employing repetitive gut challenges of carbohydrates, remain the most promising of strategies for exercise-induced gastrointestinal symptom management. (4) Conclusion: Avoiding high-FODMAP foods and practicing repetitive gut challenges are promising methods to manage gastrointestinal symptoms. However, sample sizes are often small and lack supportive power calculations.

A Single Dose of Ibuprofen Impacts IL-10 Response to 164-km Road Cycling in the Heat

Purpose: The purpose was to determine the effect of a single-dose prophylactic ibuprofen use before a 164-km road cycling event in high ambient temperature on the circulating cytokine and leukocyte responses. Methods: Twenty-three men (53 ± 8 y, 172.0 ± 22.0 cm, 85.1 ± 12.8 kg, 19.6 ± 4.4% body fat) completed a 164-km self-paced recreational road cycling event in a hot, humid, sunny environment (WBGT = 29.0 ± 2.9°C) after consuming 600 mg of ibuprofen (n = 13) or a placebo (n = 10). Blood samples were obtained one to two hours before (PRE) and immediately after (POST) the event, and analyzed for concentrations of circulating cytokines interleukins (IL)-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, GM-CSF, IFN-γ, and TNF-α and leukocytes (total leukocytes, granulocytes, monocytes, and lymphocytes). Results: Event completion time was 400.2 ± 74.8 min. Concentrations of all cytokines (except IL-1β, IL-2, IL-5, IL-12, GM-CSF, and IFN-γ) and of all leukocyte subsets increased from PRE to POST. Ibuprofen ingestion attenuated the increase in IL-10 (86% increase with Ibuprofen; 270% increase with placebo). Conclusions: Consuming 600 mg of Ibuprofen prior to a 164-km road cycling event in a hot-humid environment attenuates exercise-induced increases in the concentration of the anti-inflammatory cytokine IL-10, but does not alter the effect of the exercise event on concentrations of other circulating cytokines or leukocyte subset concentrations.

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.

Physiological Responses and Nutritional Intake during a 7-Day Treadmill Running World Record

Ultra-running comprises running events longer than a marathon (>42.2 km). The prolonged duration of ultra-running leads to decrements in most or all physiological parameters and considerable energy expenditure (EE) and energy deficits. SG, 47 years, 162.5 cm, 49 kg, VO_2max 4 mL/kg/min⁻¹/2.37 L/min⁻¹, ran continuously for 7 days on a treadmill in 3 h blocks followed by 30 min breaks and slept from 1–5 a.m. Heart rate (HR) oxygen uptake (VO₂), rating of perceived exertion, weight, blood lactate (mmol·L⁻¹), haemoglobin (g·dL), haematocrit (%) and glucose (mmol·L⁻¹), and nutrition and hydration were recorded. SG ran for 17.5 h/day, covering ~120 km/day at ~7 km/h. Energy expenditure for each 24 h period was 6878 kcal/day and energy intake (EI) was 2701 kcal/day. EE was 382 kcal/h, with 66.6% from fat and 33.4% from carbohydrate oxidation. 7 day EI was 26,989 kcal and EE was 48,147 kcal, with a total energy deficit (ED) of 21,158 kcal. Average VO₂ was 1.2 L·min⁻¹/24.7 mL·kg·min⁻¹, Respriatory echange ratio (RER) 0.80 ± 0.03, HR 120–125 b·min⁻¹. Weight increased from 48.6 to 49.5 kg. Haemoglobin decreased from 13.7 to 11 g·dL and haematocrit decreased from 40% to 33%. SG ran 833.05 km. SG exhibits an enhanced fat metabolism through which she had a large daily ED. Her success can be attributed to a combination of physiological and psychological factors.

Physiological responses to a five-day adventure race: Continuous blood glucose, hemodynamics and metabolites the 2012 GODZone field-study

Background/Objective

Adventure racing is an ultra-endurance activity that imposes a unique multifaceted stress on the human body. The purpose of this field study was to examine the physiological responses to a 5-day adventure race.

Methods

Eight competitors, two teams (1 female each) in the 2012 GODZone adventure race volunteered. Competitors trekked, cycled and paddled ∼326 km in ∼116 hours. Continuous glucose was measured the day before and throughout. Body mass, urinary solutes, and blood pressure and heart rate during resting, standing, and repeated squat-stand conditions, were assessed pre and post.

Results

Despite no changes in mean blood glucose levels, there was increased glycemic variability (Standard deviation glucose; Pre: 0.5 ± 0.1 vs Race: 1.0 ± 0.2 mmol/L, p = 0.02) and periods of hypoglycemia (i.e., Min glucose Pre: 4.1 ± 0.3 vs Race: 3.6 ± 0.5 mmol/L, p = 0.05) during the race. After the race, the blood pressure during resting, standing and squat-stand conditions was significantly lower, by 14 ± 14 mmHg, 16 ± 15 mmHg and 18 ± 15 mmHg (all p < 0.05), respectively, with no change in heart rate. During five-days of adventure racing there is increased glycemic variability and more frequent periods of low blood glucose levels. Additionally, following the race pronounced hypotension is observed in competitors.

Conclusion

We observed more frequent glucose fluctuations, lower glucose levels and significant perturbations in blood pressure control. Further research is warranted to examine the long-term impact of adventure racing on metabolic and cardiovascular function.

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Five-days of adventure racing can cause blood pressure pertubations.

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Adventure racing results in fluctuations of blood glucose.

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There are periods of hypoglycemia during an adventure race which maynot be captured by pre-post- measures.

Short-term resource allocation during extensive athletic competition

OBJECTIVES

Following predictions from life history theory, we sought to identify acute trade-offs between reproductive effort (as measured by psychological arousal) and somatic maintenance (via functional measures of innate immunity) during conditions of severe energetic imbalance.

METHODS

Sixty-six male ultramarathon runners (ages 20 to 37 years) were sampled before and after a lengthy race. Saliva and sera were collected for testosterone and immunological analyses (hemolytic complement activity and bacterial killing ability). Lean body mass was assessed by bioelectrical impedance, and libido was measured using a slideshow of arousing and neutral images.

RESULTS

Following predictions, there was a significant decrease in salivary testosterone levels (109.59 pg/mL versus 97.61 pg/mL, P < .001) and arousal scores in response to provocative images (5.40 versus 4.89, P = .001) between prerace and postrace time points. Additionally, participant bacterial killing ability (P = .035) and hemolytic complement activity (P = .021) increased between prerace and postrace.

CONCLUSIONS

Decreased libido and testosterone with concomitant heightened innate immune responses suggest a shift in energetic priorities away from reproduction and toward maintenance/defense during a period of energetic stress.

Effects of load carriage on physiological determinants in adventure racers

Adventure racing athletes need run carrying loads during the race. A better understanding of how different loads influence physiological determinants in adventure racers could provide useful insights to gauge training interventions to improve running performance. We compare the maximum oxygen uptake (VO2max), the cost of transport (C) and ventilatory thresholds of twelve adventure running athletes at three load conditions: unloaded, 7 and 15% of body mass. Twelve healthy men experienced athletes of Adventure Racing (age 31.3 ± 7.7 years, height 1.81 ± 0.05 m, body mass 75.5 ± 9.1 kg) carried out three maximal progressive (VO2max protocol) and three submaximal constant-load (running cost protocol) tests, defined in the following quasi-randomized conditions: unloaded, 7% and, 15% of body mass. The VO2max (unload: 59.7 ± 5.9; 7%: 61.7 ± 6.6 and 15%: 64.6 ± 5.4 ml kg^-1 min^-1) did not change among the conditions. While the 7% condition does neither modify the C nor the ventilatory thresholds, the 15% condition resulted in a higher C (5.2 ± 0.9 J kg^-1 m^-1; P = 0.001; d = 1.48) than the unloaded condition (4.0 ± 0.7 J kg^-1 m^-1). First ventilatory threshold was greater at 15% than control condition (+15.5%; P = 0.003; d = 1.44). Interestingly, the velocities on the severe-intensity domain (between second ventilatory threshold and VO2max) were reduced 1% equivalently to 1% increasing load (relative to body mass). The loading until 15% of body mass seems to affect partially the crucial metabolic and ventilatory parameters, specifically the C but not the VO2max. These findings are compatible with the concept that interventions that enhance running economy with loads may improve the running performance of adventure racing’s athletes.

Cardiovascular and thermal strain during 3-4 days of a metabolically demanding cold-weather military operation

BACKGROUND

Cardiovascular (CV) and thermal responses to metabolically demanding multi-day military operations in extreme cold-weather environments are not well described. Characterization of these operations will provide greater insights into possible performance capabilities and cold injury risk.

METHODS

Soldiers from two cold-weather field training exercises (FTX) were studied during 3-day (study 1, n = 18, age: 20 ± 1 year, height: 182 ± 7 cm, mass: 82 ± 9 kg) and 4-day (study 2, n = 10, age: 20 ± 1 year, height: 182 ± 6 cm, mass: 80.7 ± 8.3 kg) ski marches in the Arctic. Ambient temperature ranged from -18 to -4 °C during both studies. Total daily energy expenditure (TDEE, from doubly labeled water), heart rate (HR), deep body (T_pill), and torso (T_torso) skin temperature (obtained in studies 1 and 2) as well as finger (T_fing), toe (T_toe), wrist, and calf temperatures (study 2) were measured.

RESULTS

TDEE was 6821 ± 578 kcal day^-1 and 6394 ± 544 for study 1 and study 2, respectively. Mean HR ranged from 120 to 140 bpm and mean T_pill ranged between 37.5 and 38.0 °C during skiing in both studies. At rest, mean T_pill ranged from 36.0 to 36.5 °C, (lowest value recorded was 35.5 °C). Mean T_fing ranged from 32 to 35 °C during exercise and dropped to 15 °C during rest, with some T_fing values as low as 6-10 °C. T_toe was above 30 °C during skiing but dropped to 15-20 °C during rest.

CONCLUSIONS

Daily energy expenditures were among the highest observed for a military training exercise, with moderate exercise intensity levels (~65% age-predicted maximal HR) observed. The short-term cold-weather training did not elicit high CV and T_pill strain. T_fing and T_toe were also well maintained while skiing, but decreased to values associated with thermal discomfort at rest.

Physiological intensity profile, exercise load and performance predictors of a 65-km mountain ultra-marathon

The aims of the study were to describe the physiological profile of a 65-km (4000-m cumulative elevation gain) running mountain ultra-marathon (MUM) and to identify predictors of MUM performance. Twenty-three amateur trail-runners performed anthropometric evaluations and an uphill graded exercise test (GXT) for VO_2max, ventilatory thresholds (VTs), power outputs (PMax, PVTs) and heart rate response (HRmax, HR@VTs). Heart rate (HR) was monitored during the race and intensity was expressed as: Zone I (<VT1), Zone II (VT1-VT2), Zone III (>VT2) for exercise load calculation (training impulse, TRIMP). Mean race intensity was 77.1%±4.4% of HRmax distributed as: 85.7%±19.4% Zone I, 13.9%±18.6% Zone II, 0.4%±0.9% Zone III. Exercise load was 766±110 TRIMP units. Race time (11.8±1.6h) was negatively correlated with VO_2max (r = -0.66, P <0.001) and PMax (r = -0.73, P <0.001), resulting these variables determinant in predicting MUM performance, whereas exercise thresholds did not improve performance prediction. Laboratory variables explained only 59% of race time variance, underlining the multi-factorial character of MUM performance. Our results support the idea that VT1 represents a boundary of tolerable intensity in this kind of events, where exercise load is extremely high. This information can be helpful in identifying optimal pacing strategies to complete such extremely demanding MUMs.

Myocardial dimensions and hemodynamics during 24-h ultraendurance ergometry

PURPOSE

This study aimed to evaluate cardiorespiratory and hemodynamic responses during 24 h of continuous cycle ergometry in ultraendurance athletes.

METHODS

Eight males (mean ± SD; age = 39 ± 8 yr, height = 179 ± 7 cm, body weight [Wt] = 77.1 ± 6.0 kg) were monitored during 24 h at a constant workload,∼25% below the first lactate turn point at 162 ± 23 W. Measurements included Wt, HR, oxygen consumption (V˙O2), cardiac output (Q), and stroke volume (SV) determined by a noninvasive rebreathing technique (Innocor; Innovision, Odense, Denmark). Myocardial dimensions were evaluated using a two-dimensional echocardiogram. [M-mode measurement]-left atrial (LAD), ventricular end-diastolic (LVEDD), and end-systolic diameters (LVESD) were obtained over the left parasternal area. Venous blood samples were analyzed for hematocrit (Hct%), albumin (g·L(-1)), aldosterone (pg·mL(-1)), CK, CK-MB (U·L(-1)), and N-terminal pro-brain natriuretic peptide (NT-proBNP) (pg·mL(-1)).

RESULTS

HR (bpm) significantly increased (P < 0.01) from 1 h (132 ± 11) to 6 h (143 ± 10) and significantly decreased (P < 0.001) from 6 to 24 h (116 ± 10). V˙O2 and (Q were unchanged during the 24 h. Wt (76.6 ± 5.6 vs 78.7 ± 5.4), SV (117 ± 13 vs 148 ± 19), LVEDD (4.9 ± 0.3 vs 5.6 ± 0.2), and LAD (3.6 ± 0.5 vs 4.3 ± 0.7) significantly increased between 6 and 24 h (P < 0.001). No significant changes were observed for LVESD. Hct (45.1 ± 1.3 vs 41.3 ± 1.2) significantly decreased (P < 0.05) and CK (181 ± 60/877 ± 515), aldosterone (48 ± 17 vs 661 ± 172), and NT-proBNP (23 ± 13 vs 583 ± 449) significantly increased (P < 0.05). The increase in SV (ΔSV) was significantly related to changes in Wt (ΔWt), and HR (ΔHR) and ΔWt were significantly related to ΔLAD and ΔLVEDD.

CONCLUSION

Our findings suggest that the decrease in HR during 24 h of ultraendurance exercise was due to hypervolemia and the associated ventricular loading, increasing left ventricular diastolic dimensions because of increased SV and LVEDD, resulting in an increase in NT-proBNP.

Greater muscle damage in athletes with ACTN3 R577X (RS1815739) gene polymorphism after an ultra-endurance race: a pilot study

In this study, we aimed to investigate the influence of ACTN3 R577X gene polymorphism on muscle damage responses in athletes competing in an ultra-endurance race. Twenty moderate to well-trained ultra-runners who had entered in an official 37.1 km adventure race (22.1 km mountain biking, 10.9 km trekking, 4.1 km water trekking, 30 m rope course, and orienteering) volunteered for the study. Blood samples were collected for genotyping and analysis of muscle protein levels before and after the race. Percentage changes (pre- to post-race) of serum myoglobin [XX = 5,377% vs. RX/RR = 1,666%; P = 0.005, effect size (ES) = 1.73], creatine kinase (XX = 836.5% vs. RX/RR = 455%; P = 0.04, ES = 1.29), lactate dehydrogenase (XX = 82% vs. RX/RR = 65%; P = 0.002, ES = 1.61), and aspartate aminotransferase (XX = 148% vs. RX/RR = 75%; P = 0.02, ES = 1.77) were significantly greater for XX than RX/RR genotypes. ES analysis confirmed a large magnitude of muscle damage in XX genotype ultra-runners. Therefore, athletes with the ACTN3 577XX genotype experienced more muscle damage after an adventure race. This suggests that ultra-runners with alpha-actinin-3 deficiency may be more susceptible to rhabdomyolysis and associated health complications during ultra-endurance competitions.

An Extreme Mountain Ultra-Marathon Decreases the Cost of Uphill Walking and Running

Purpose: To examine the effects of the world's most challenging mountain ultramarathon (MUM, 330 km, cumulative elevation gain of +24,000 m) on the energy cost and kinematics of different uphill gaits.

Methods: Before (PRE) and immediately after (POST) the competition, 19 male athletes performed three submaximal 5-min treadmill exercise trials in a randomized order: walking at 5 km·h⁻¹, +20%; running at 6 km·h⁻¹, +15%; and running at 8 km·h⁻¹, +10%. During the three trials, energy cost was assessed using an indirect calorimetry system and spatiotemporal gait parameters were acquired with a floor-level high-density photoelectric cells system.

Results: The average time of the study participants to complete the MUM was 129 h 43 min 48 s (range: 107 h 29 min 24 s to 144 h 21 min 0 s). Energy costs in walking (−11.5 ± 5.5%, P < 0.001), as well as in the first (−7.2 ± 3.1%, P = 0.01) and second (−7.0 ± 3.9%, P = 0.02) running condition decreased between PRE and POST, with a reduction both in the heart rate (−11.3, −10.0, and −9.3%, respectively) and oxygen uptake only for the walking condition (−6.5%). No consistent and significant changes in the kinematics variables were detected (P-values from 0.10 to 0.96).

Conclusion: Though fatigued after completing the MUM, the subjects were still able to maintain their uphill locomotion patterns noted at PRE. The decrease (improvement) in the energy costs was likely due to the prolonged and repetitive walking/running, reflecting a generic improvement in the mechanical efficiency of locomotion after ~130 h of uphill locomotion rather than constraints imposed by the activity on the musculoskeletal structure and function.

Moving in extreme environments: extreme loading; carriage versus distance

This review addresses human capacity for movement in the context of extreme loading and with it the combined effects of metabolic, biomechanical and gravitational stress on the human body. This topic encompasses extreme duration, as occurs in ultra-endurance competitions (e.g. adventure racing and transcontinental races) and expeditions (e.g. polar crossings), to the more gravitationally limited load carriage (e.g. in the military context). Juxtaposed to these circumstances is the extreme metabolic and mechanical unloading associated with space travel, prolonged bedrest and sedentary lifestyle, which may be at least as problematic, and are therefore included as a reference, e.g. when considering exposure, dangers and (mal)adaptations. As per the other reviews in this series, we describe the nature of the stress and the associated consequences; illustrate relevant regulations, including why and how they are set; present the pros and cons for self versus prescribed acute and chronic exposure; describe humans' (mal)adaptations; and finally suggest future directions for practice and research. In summary, we describe adaptation patterns that are often U or J shaped and that over time minimal or no load carriage decreases the global load carrying capacity and eventually leads to severe adverse effects and manifest disease under minimal absolute but high relative loads. We advocate that further understanding of load carrying capacity and the inherent mechanisms leading to adverse effects may advantageously be studied in this perspective. With improved access to insightful and portable technologies, there are some exciting possibilities to explore these questions in this context.

Progressive and biphasic cardiac responses during extreme mountain ultramarathon

Investigations on the cardiac function consequences of mountain ultramarathon (MUM) >100 h are lacking. The present study assessed the progressive cardiac responses during the world's most challenging MUM (Tor des Géants; Italy; 330 km; 24,000 m of cumulative elevation gain). Resting echocardiographic evaluation of morphology, function, and mechanics of left and right ventricle (LV and RV) including speckle tracking echocardiography was conducted in 15 male participants (46 ± 13 yr) before (pre), during (mid; 148 km), and after (post) the race. Runners completed the race in 126 ± 15 h. From pre to post, the increase in stroke volume (SV) (103 ± 19 vs. 110 ± 23 vs. 116 ± 21 ml; P < 0.001 at pre, mid, and post) was concomitant to the increase in LV early filling (peak E; 72.9 ± 15.7 vs. 74.6 ± 13.1 vs. 82.1 ± 11.5 cm/s; P < 0.05). Left and right atrial end-diastolic areas, RV end-diastolic area, and LV end-diastolic volume were 12-19% higher at post compared with pre (P < 0.05). Resting heart rate and LV systolic strain rates demonstrated a biphasic adaptation with an increase from pre to mid (55 ± 8 vs. 72 ± 11 beats/min, P < 0.001) and a return to baseline values from mid to post (59 ± 8 beats/min). Significant correlations were found between pre-to-post percent changes in peak E and LV end-diastolic volume (r = 0.63, P < 0.05) or RV (r = 0.82, P < 0.001) or atrial end-diastolic areas (r = 0.83, P < 0.001). An extreme MUM induced a biphasic pattern of heart rate in parallel with specific cardiac responses characterized by a progressive increase in diastolic filling, biventricular volumes, and SV. The underlying mechanisms and their clinical implications remain challenging for the future.

Acute effects of different degrees of ultra-endurance exercise on systemic inflammatory responses

BACKGROUND

Intense physical stress might promote inflammatory responses, whereas a regular physical exercise has positive influence. Little is known on the acute metabolic and inflammatory responses to different levels of strenuous exercise in trained athletes.

AIM

To compare the short-term effect of two different ultra-endurance competitions on the inflammatory profile in male triathletes.

METHODS

We studied 14 Ironman (IR) and 13 Half Ironman (HIR) before and after their own specific race. We assessed body composition and measured blood cells, lipids, iron metabolism and plasma levels of some acute-phase cytokines and inflammatory markers.

RESULTS

After the race, IR showed reduced total body water and fat-free mass, not related with the duration of exercise, and increased white cells and platelets; high-density lipoprotein levels also increased. IR, but not HIR, showed reduced iron levels, increased ferritin and transferrin, reduced % saturated transferrin. HIR showed higher basal interleukin (IL)-6, tumour necrosis factor (TNF)-α, IL-10, IL-1β than IR; however, the post-performance rise was greater in IR. Irisin increased only in HIR and osteocalcin decreased in IR. In the whole study group, delta of white blood cells was directly related with delta of monocyte chemoattractant protein 1, and Δ ferritin was inversely related with Δosteocalcin.

CONCLUSIONS

A single ultra-endurance competition induces an inflammatory response depending on the duration of physical effort, with increased acute-phase cytokines, and an altered iron metabolism. Irisin, whose biological meaning is still uncertain, seems to be associated with acute variations of some metabolic parameters.

The impact of sleep restriction while performing simulated physical firefighting work on cortisol and heart rate responses

PURPOSE

Physical work and sleep restriction are two stressors faced by firefighters, yet the combined impact these demands have on firefighters' acute stress responses is poorly understood. The purpose of the present study was to assess the effect firefighting work and sleep restriction have on firefighters' acute cortisol and heart rate (HR) responses during a simulated 3-day and 2-night fire-ground deployment.

METHODS

Firefighters completed multiple days of simulated physical work separated by either an 8-h (control condition; n = 18) or 4-h sleep opportunity (sleep restriction condition; n = 17). Salivary cortisol was sampled every 2 h, and HR was measured continuously each day.

RESULTS

On day 2 and day 3 of the deployment, the sleep restriction condition exhibited a significantly higher daily area under the curve cortisol level and an elevated cortisol profile in the afternoon and evening when compared with the control condition. Firefighters' HR decreased across the simulation, but there were no significant differences found between conditions.

CONCLUSION

Findings highlight the protective role an 8-h sleep opportunity between shifts of firefighting work has on preserving normal cortisol levels when compared to a 4-h sleep opportunity which resulted in elevated afternoon and evening cortisol. Given the adverse health outcomes associated with chronically high cortisol, especially later in the day, future research should examine how prolonged exposure to firefighting work (including restricted sleep) affects firefighters' cortisol levels long term. Furthermore, monitoring cortisol levels post-deployment will determine the minimum recovery time firefighters need to safely return to the fire-ground.

A case study evaluation of competitors undertaking an antarctic ultra-endurance event: nutrition, hydration and body composition variables

Background

The nutritional demands of ultra-endurance racing are well documented. However, the relationship between nutritional consumption and performance measures are less obvious for athletes competing in Polar conditions. Therefore, the aim of this study was to evaluate dietary intake, hydration status, body composition and performance times throughout an 800-km Antarctic race.

Methods

The event organisers declared that 17 competitors would participate in the South Pole race. Of the 17 competitors, pre-race data were collected from 13 participants (12 males and 1 female (M ± SD): age: 40.1 ± 8.9 years; weight: 83.9 ± 10.3 kg; and body fat percentage: 21.9 ± 3.8%). Dietary recall, body composition and urinary osmolarity were assessed pre-race, midway checkpoint and end race. Data were compared on the basis of fast finishers (the Norwegian team (n = 3) who won in a record of 14 days) and slower finishers (the remaining teams (n = 10) reaching the South Pole between 22 and 28 days).

Results

The percentage contribution of macronutrients to daily energy intake for all participants was as follows: carbohydrate (CHO) = 23.7% (221 ± 82 g.day⁻¹), fat = 60.6% (251 ± 127 g.day⁻¹) and protein = 15.7% (117 ± 52 g.day⁻¹). Energy demands were closer met by faster finishers compared to slower finishers (5,332 ± 469 vs. 3,048 ± 1,140 kcal.day⁻¹, p = 0.02). Average reduction in body mass throughout the race was 8.3 ± 5.5 kg, with an average loss of lean mass of 2.0 ± 4.1 kg. There was a significant negative correlation between changes in lean mass and protein intake (p = 0.03), and lean mass and energy intake (p = 0.03). End-race urinary osmolarity was significantly elevated for faster finishers compared to slower finishers and control volunteers (faster finishers: 933 ± 157 mOsmol.L⁻¹; slower finishers: 543 ± 92 mOsmol.L⁻¹; control: 515 ± 165 mOsmol.L⁻¹, p = 0.04).

Conclusions

Throughout the race, both groups were subjected to a negative change in energy balance which partly explained reduced body mass. Carbohydrate availability was limited inferring a greater reliance on fat and protein metabolism. Consequently, loss in fat-free mass was more prevalent with insufficient protein and caloric intake, which may relate to performance.

Are we being drowned in hydration advice? Thirsty for more?

Hydration pertains simplistically to body water volume. Functionally, however, hydration is one aspect of fluid regulation that is far more complex, as it involves the homeostatic regulation of total body fluid volume, composition and distribution. Deliberate or pathological alteration of these regulated factors can be disabling or fatal, whereas they are impacted by exercise and by all environmental stressors (e.g. heat, immersion, gravity) both acutely and chronically. For example, dehydration during exercising and environmental heat stress reduces water volume more than electrolyte content, causing hyperosmotic hypohydration. If exercise continues for many hours with access to food and water, composition returns to normal but extracellular volume increases well above baseline (if exercising upright and at low altitude). Repeating bouts of exercise or heat stress does likewise. Dehydration due to physical activity or environmental heat is a routine fluid-regulatory stress. How to gauge such dehydration and - more importantly-what to do about it, are contested heavily within sports medicine and nutrition. Drinking to limit changes in body mass is commonly advocated (to maintain ≤2% reduction), rather than relying on behavioural cues (mainly thirst) because the latter has been deemed too insensitive. This review, as part of the series on moving in extreme environments, critiques the validity, problems and merits of externally versus autonomously controlled fluid-regulatory behaviours, both acutely and chronically. Our contention is that externally advocated hydration policies (especially based on change in body mass with exercise in healthy individuals) have limited merit and are extrapolated and imposed too widely upon society, at the expense of autonomy. More research is warranted to examine whether ad libitum versus avid drinking is beneficial, detrimental or neither in: acute settings; adapting for obligatory dehydration (e.g. elite endurance competition in the heat), and; development of chronic diseases that are associated with an extreme lack of environmental stress.

Leukocytosis, muscle damage and increased lymphocyte proliferative response after an adventure sprint race

The effect of an adventure sprint race (ASR) on T-cell proliferation, leukocyte count and muscle damage was evaluated. Seven young male runners completed an ASR in the region of Serra do Espinhaço, Brazil. The race induced a strong leukocytosis (6.22±2.04×10³ cells/mm³ before vs 14.81±3.53×10³ cells/mm³ after the race), marked by a significant increase of neutrophils and monocytes (P<0.05), but not total lymphocytes, CD3⁺CD4⁺ or CD3⁺CD8⁺ cells. However, the T-cell proliferative response to mitogenic stimulation was increased (P=0.025) after the race, which contradicted our hypothesis that ASR, as a high-demand competition, would inhibit T-cell proliferation. A positive correlation (P=0.03, r=0.79) was observed between the proliferative response of lymphocytes after the race and the time to complete the race, suggesting that the proliferative response was dependent on exercise intensity. Muscle damage was evident after the race by increased serum levels of aspartate amino transferase (24.99±8.30 vs 50.61±15.76 U/L, P=0.003). The results suggest that humoral factors and substances released by damaged muscle may be responsible for lymphocyte activation, which may be involved in muscle recovery and repair.

Endocrine response to an ultra-marathon in pre- and post-menopausal women

Ultra-endurance competitions are becoming increasingly popular but there is limited research on female participants. The purpose of this study was to examine changes in estrogen and the IGF-I system in women after an ultra-marathon. Six pairs of pre- and post- menopausal women were matched for race finish times;mean finish time was 20 hours. Blood samples were drawn 24 hours before the race, at the finish, and 24 hours into recovery. Samples were analysed for estradiol, total IGF-I, IGFBP-1, and intact IGFBP-3. There was a significant increase in estradiol following the race in both groups (P < 0.05). Total IGF-I decreased after the race (P < 0.01) and remained lower in recovery. IGFBP-1 increased after the race (P < 0.001) but returned to pre-race levels after 24 hours, while intact IGFBP-3 was significantly lower post-race and in recovery (P < 0.001). Postmenopausal women had significantly lower estradiol at baseline, but there were no other group differences. These results demonstrate that among recreational female runners, an ultra-marathon is associated with IGF system changes that are consistent with an energy-deficient, catabolic state. Further research is needed to confirm the effect of these endocrine changes on health and performance.

Alterations of Neuromuscular Function after the World's Most Challenging Mountain Ultra-Marathon

We investigated the physiological consequences of the most challenging mountain ultra-marathon (MUM) in the world: a 330-km trail run with 24000 m of positive and negative elevation change. Neuromuscular fatigue (NMF) was assessed before (Pre-), during (Mid-) and after (Post-) the MUM in experienced ultra-marathon runners (n = 15; finish time  = 122.43 hours ±17.21 hours) and in Pre- and Post- in a control group with a similar level of sleep deprivation (n = 8). Blood markers of muscle inflammation and damage were analyzed at Pre- and Post-. Mean ± SD maximal voluntary contraction force declined significantly at Mid- (−13±17% and −10±16%, P<0.05 for knee extensor, KE, and plantar flexor muscles, PF, respectively), and further decreased at Post- (−24±13% and −26±19%, P<0.01) with alteration of the central activation ratio (−24±24% and −28±34% between Pre- and Post-, P<0.05) in runners whereas these parameters did not change in the control group. Peripheral NMF markers such as 100 Hz doublet (KE: −18±18% and PF: −20±15%, P<0.01) and peak twitch (KE: −33±12%, P<0.001 and PF: −19±14%, P<0.01) were also altered in runners but not in controls. Post-MUM blood concentrations of creatine kinase (3719±3045 Ul·¹), lactate dehydrogenase (1145±511 UI·L⁻¹), C-Reactive Protein (13.1±7.5 mg·L⁻¹) and myoglobin (449.3±338.2 µg·L⁻¹) were higher (P<0.001) than at Pre- in runners but not in controls. Our findings revealed less neuromuscular fatigue, muscle damage and inflammation than in shorter MUMs. In conclusion, paradoxically, such extreme exercise seems to induce a relative muscle preservation process due likely to a protective anticipatory pacing strategy during the first half of MUM and sleep deprivation in the second half.

Nutrition for adventure racing

Adventure racing requires competitors to perform various disciplines ranging from, but not limited to, mountain biking, running, kayaking, climbing, mountaineering, flat- and white-water boating and orienteering over a rugged, often remote and wilderness terrain. Races can vary from 6 hours to expedition-length events that can last up to 10-consecutive days or more. The purpose of this article is to provide evidence-based nutritional recommendations for adventure racing competitors. Energy expenditures of 365-750 kcal/hour have been reported with total energy expenditures of 18 000-80 000 kcal required to complete adventure races, and large negative energy balances during competitions have been reported. Nutrition, therefore, plays a major role in the successful completion of such ultra-endurance events. Conducting research in these events is challenging and the limited studies investigating dietary surveys and nutritional status of adventure racers indicate that competitors do not meet nutrition recommendations for ultra-endurance exercise. Carbohydrate intakes of 7-12 g/kg are needed during periods of prolonged training to meet requirements and replenish glycogen stores. Protein intakes of 1.4-1.7 g/kg are recommended to build and repair tissue. Adequate replacement of fluid and electrolytes are crucial, particularly during extreme temperatures; however, sweat rates can vary greatly between competitors. There is considerable evidence to support the use of sports drinks, gels and bars, as they are a convenient and portable source of carbohydrate that can be consumed during exercise, in training and in competition. Similarly, protein and amino acid supplements can be useful to help meet periods of increased protein requirements. Caffeine can be used as an ergogenic aid to help competitors stay awake during prolonged periods, enhance glycogen resynthesis and enhance endurance performance.

Nutrition for adventure racing

Adventure racing requires competitors to perform various disciplines ranging from, but not limited to, mountain biking, running, kayaking, climbing, mountaineering, flat- and white-water boating and orienteering over a rugged, often remote and wilderness terrain. Races can vary from 6 hours to expedition-length events that can last up to 10-consecutive days or more. The purpose of this article is to provide evidence-based nutritional recommendations for adventure racing competitors. Energy expenditures of 365-750 kcal/hour have been reported with total energy expenditures of 18 000-80 000 kcal required to complete adventure races, and large negative energy balances during competitions have been reported. Nutrition, therefore, plays a major role in the successful completion of such ultra-endurance events. Conducting research in these events is challenging and the limited studies investigating dietary surveys and nutritional status of adventure racers indicate that competitors do not meet nutrition recommendations for ultra-endurance exercise. Carbohydrate intakes of 7-12 g/kg are needed during periods of prolonged training to meet requirements and replenish glycogen stores. Protein intakes of 1.4-1.7 g/kg are recommended to build and repair tissue. Adequate replacement of fluid and electrolytes are crucial, particularly during extreme temperatures; however, sweat rates can vary greatly between competitors. There is considerable evidence to support the use of sports drinks, gels and bars, as they are a convenient and portable source of carbohydrate that can be consumed during exercise, in training and in competition. Similarly, protein and amino acid supplements can be useful to help meet periods of increased protein requirements. Caffeine can be used as an ergogenic aid to help competitors stay awake during prolonged periods, enhance glycogen resynthesis and enhance endurance performance.

Extensive inflammatory cell infiltration in human skeletal muscle in response to an ultraendurance exercise bout in experienced athletes

The impact of a 24-h ultraendurance exercise bout on systemic and local muscle inflammatory reactions was investigated in nine experienced athletes. Blood and muscle biopsies were collected before (Pre), immediately after the exercise bout (Post), and after 28 h of recovery (Post28). Circulating blood levels of leukocytes, creatine kinase (CK), C-reactive protein (CRP), and selected inflammatory cytokines were assessed together with the evaluation of the occurrence of inflammatory cells (CD3(+), CD8(+), CD68(+)) and the expression of major histocompatibility complex class I (MHC class I) in skeletal muscle. An extensive inflammatory cell infiltration occurred in all athletes, and the number of CD3(+), CD8(+), and CD68(+) cells were two- to threefold higher at Post28 compared with Pre (P < 0.05). The inflammatory cell infiltration was associated with a significant increase in the expression of MHC class I in muscle fibers. There was a significant increase in blood leukocyte count, IL-6, IL-8, CRP, and CK at Post. At Post28, total leukocytes, IL-6, and CK had declined, whereas IL-8 and CRP continued to increase. Increases in IL-1β and TNF-α were not significant. There were no significant associations between the magnitude of the systemic and local muscle inflammatory reactions. Signs of muscle degenerative and regenerative events were observed in all athletes with various degrees of severity and were not affected by the 24-h ultraendurance exercise bout. In conclusion, a low-intensity but very prolonged single-endurance exercise bout can generate a strong inflammatory cell infiltration in skeletal muscle of well-trained experienced ultraendurance athletes, and the amplitude of the local reaction is not proportional to the systemic inflammatory response.

Effect of a multistage ultraendurance triathlon on aldosterone, vasopressin, extracellular water and urine electrolytes

Prolonged endurance exercise over several days induces increase in extracellular water (ECW). We aimed to investigate an association between the increase in ECW and the change in aldosterone and vasopressin in a multistage ultraendurance triathlon, the 'World Challenge Deca Iron Triathlon' with 10 Ironman triathlons within 10 days. Before and after each Ironman, body mass, ECW, urinary [Na(+)], urinary [K(+)], urinary specific gravity, urinary osmolality and aldosterone and vasopressin in plasma were measured. The 11 finishers completed the total distance of 38 km swimming, 1800 km cycling and 422 km running within 145.5 (18.8) hours and 25 (22) minutes. ECW increased by 0.9 (1.1) L from 14.6 (1.5) L prerace to 15.5 (1.9) L postrace (P < 0.0001). Aldosterone increased from 70.8 (104.5) pg/mL to 102.6 (104.6) pg/mL (P = 0.033); vasopressin remained unchanged. The increase in ECW was related neither to postrace aldosterone nor to postrace vasopressin. In conclusion, ECW and aldosterone increased after this multistage ultraendurance triathlon, but vasopressin did not. The increase in ECW and the increase in aldosterone were not associated.

Hemolysis induced by an extreme mountain ultra-marathon is not associated with a decrease in total red blood cell volume

Prolonged running is known to induce hemolysis. It has been suggested that hemolysis may lead to a significant loss of red blood cells; however, its actual impact on the erythrocyte pool is unknown. Here, we test the hypothesis that prolonged running with high hemolytic potential decreases total red blood cell volume (RCV). Hemolysis (n = 22) and RCV (n = 19) were quantified in ultra-marathon runners before and after a 166-km long mountain ultra-endurance marathon (RUN) with 9500 m of altitude gain/loss. Assessment of total hemoglobin mass (Hbmass) and RCV was performed using a carbon monoxide rebreathing technique. RUN induced a marked acute-phase response and promoted hemolysis, as shown by a decrease in serum haptoglobin (P < 0.05). Elevated serum erythropoietin concentration and reticulocyte count after RUN were indicative of erythropoietic stimulation. Following RUN, runners experienced hemodilution, mediated by a large plasma volume expansion and associated with a large increase in plasma aldosterone. However, neither Hbmass nor RCV were found to be altered after RUN. Our findings indicate that mechanical/physiological stress associated with RUN promotes hemolysis but this has no impact on total erythrocyte volume. We therefore suggest that exercise 'anemia' is entirely due to plasma volume expansion and not to a concomitant decrease in RCV.

100 Years Since Scott Reached the Pole: A Century of Learning About the Physiological Demands of Antarctica

The 1910–1913 Terra Nova Expedition to the Antarctic, led by Captain Robert Falcon Scott, was a venture of science and discovery. It is also a well-known story of heroism and tragedy since his quest to reach the South Pole and conduct research en route, while successful was also fateful. Although Scott and his four companions hauled their sledges to the Pole, they died on their return journey either directly or indirectly from the extreme physiological stresses they experienced. One hundred years on, our understanding of such stresses caused by Antarctic extremes and how the body reacts to severe exercise, malnutrition, hypothermia, high altitude, and sleep deprivation has greatly advanced. On the centenary of Scott's expedition to the bottom of the Earth, there is still controversy surrounding whether the deaths of those five men could have, or should have, been avoided. This paper reviews present-day knowledge related to the physiology of sustained man-hauling in Antarctica and contrasts this with the comparative ignorance about these issues around the turn of the 20th century. It closes by considering whether, with modern understanding about the effects of such a scenario on the human condition, Scott could have prepared and managed his team differently and so survived the epic 1,600-mile journey. The conclusion is that by carrying rations with a different composition of macromolecules, enabling greater calorific intake at similar overall weight, Scott might have secured the lives of some of the party, and it is also possible that enhanced levels of vitamin C in his rations, albeit difficult to achieve in 1911, could have significantly improved their survival chances. Nevertheless, even with today's knowledge, a repeat attempt at his expedition would by no means be bound to succeed.

Physiologic alterations and predictors of performance in a 160-km ultramarathon

OBJECTIVE

To describe physiologic alterations in runners competing in a 160-km endurance event and to evaluate the utility of weight and blood pressure measurements in the assessment of runner performance.

DESIGN

Prospective cohort study.

SETTING

One hundred sixty-km ultramarathon.

PARTICIPANTS

Ninety-one of the 101 participants in the 2010 Tahoe Rim 100 Mile Endurance Run.

ASSESSMENT OF RISK FACTORS

Brachial blood pressure, heart rate, and weight were assessed before competition, at 80 km, and at 160 km.

MAIN OUTCOME MEASURES

Alterations in brachial blood pressure, heart rate, and weight were assessed in finishers. Weight loss, brachial blood pressure, pulse pressure, and heart rate at 80 km were assessed in all participants for their ability to predict failure to finish the race.

RESULTS

Participants who finished 160 km (57%) experienced their fastest heart rates (P < 0.05), lowest systolic pressures (P < 0.05), highest diastolic pressures (P < 0.05), narrowest pulse pressures (P < 0.05), and lowest weights (P < 0.05) at 80 km. High rates of finishing were seen in those who lost >5% of their prerace weight (87%). Categorical weight loss (<3%, 3%-5%, and >5%) was not associated with the ability to finish (P > 0.05) or finishing time (P > 0.05), whereas the presence of a narrow pulse pressure was associated with a high likelihood (likelihood ratio = 9.84; P = 0.002) of failure to finish.

CONCLUSIONS

Greater intracompetition weight loss is not associated with impaired performance but rather may be an aspect of superior performance. Narrow pulse pressure was associated with a high likelihood of failure to finish.

Subjecting elite athletes to inspiratory breathing load reveals behavioral and neural signatures of optimal performers in extreme environments

Background

It is unclear whether and how elite athletes process physiological or psychological challenges differently than healthy comparison subjects. In general, individuals optimize exercise level as it relates to differences between expected and experienced exertion, which can be conceptualized as a body prediction error. The process of computing a body prediction error involves the insular cortex, which is important for interoception, i.e. the sense of the physiological condition of the body. Thus, optimal performance may be related to efficient minimization of the body prediction error. We examined the hypothesis that elite athletes, compared to control subjects, show attenuated insular cortex activation during an aversive interoceptive challenge.

Methodology/Principal Findings

Elite adventure racers (n = 10) and healthy volunteers (n = 11) performed a continuous performance task with varying degrees of a non-hypercapnic breathing load while undergoing functional magnetic resonance imaging. The results indicate that (1) non-hypercapnic inspiratory breathing load is an aversive experience associated with a profound activation of a distributed set of brain areas including bilateral insula, dorsolateral prefrontal cortex and anterior cingulated; (2) adventure racers relative to comparison subjects show greater accuracy on the continuous performance task during the aversive interoceptive condition; and (3) adventure racers show an attenuated right insula cortex response during and following the aversive interoceptive condition of non-hypercapnic inspiratory breathing load.

Conclusions/Significance

These findings support the hypothesis that elite athletes during an aversive interoceptive condition show better performance and an attenuated insular cortex activation during the aversive experience. Interestingly, differential modulation of the right insular cortex has been found previously in elite military personnel and appears to be emerging as an important brain system for optimal performance in extreme environments.