Muscle damage and endurance events

Physiology and Pathophysiology of Marathon Running: A narrative Review

BACKGROUND

Marathon training and running have many beneficial effects on human health and physical fitness; however, they also pose risks. To date, no comprehensive review regarding both the benefits and risks of marathon running on different organ systems has been published.

MAIN BODY

The aim of this review was to provide a comprehensive review of the benefits and risks of marathon training and racing on different organ systems. A predefined search strategy including keywords (e.g., marathon, cardiovascular system, etc.) and free text search was used. Articles covering running regardless of sex, age, performance level, and event type (e.g., road races, mountain marathons) were considered, whereas articles examining only cycling, triathlon, stress-tests or other sports were excluded. In total, we found 1021 articles in PubMed, Scopus, and Google Scholar, of which 329 studies were included in this review. Overall, marathon training offers several benefits for different organ systems and reduces all-cause mortality. As such, it improves cardiovascular risk factors, leads to favorable cardiac adaptations, enhances lung function, and improves quality of life in chronic kidney disease patients. It also enhances gastrointestinal mobility and reduces the risk of specific tumors such as colorectal cancer and hepatocellular carcinoma. Marathon training enhances bone health and skeletal muscle metabolism. It further positively affects hematopoiesis and cytotoxic abilities of natural killer cells, and may act neuroprotective on a long-term basis. After a marathon, changes in biomarkers suggesting pathological events in certain organ systems such as cardiovascular, renal, gastrointestinal, liver, hematological, immune, musculoskeletal, central nervous, and endocrine systems can often be observed. Mostly, these changes are limited to 1-3 days post-race and usually normalize within a week. Moreover, marathon running poses the risk of serious adverse events such as sudden cardiac death or acute liver failure. Concerning lung function, a decrease after a marathon race was observed. Acute kidney injury, as well as electrolyte imbalances, are relatively common amongst marathon finishers. Many runners complain of gastrointestinal symptoms during or after long-distance running. Many runners suffer from running-related musculoskeletal injuries often impairing performance. A marathon is often accompanied by an acute inflammatory response with transient immunosuppression, making runners susceptible to infections. Also, hormonal alterations such as increased cortisol levels or decreased testosterone levels immediately after a race are observed. Disturbances in sleep patterns are commonly found in marathon runners leading up to or directly after the race.

CONCLUSION

All in all, marathon training is generally safe for human health and individual organ systems. Considering the high popularity of marathon running, these findings supply athletes, coaches, sports scientists, and sports medicine practitioners with practical applications. Further large-scale studies examining long-term effects on the cardiovascular, renal, and other system are needed.

Recovery Strategies in Endurance Sports: A Survey in Coaches and Athletes

PURPOSE

This study explored endurance athletes' and coaches' views on recovery strategies, focusing on their use across competition levels, perceived importance and effectiveness, and common barriers.

METHODS

Endurance athletes (26.6% international, 35.7% national, 28.7% regional, and 9.1% other levels; mean experience 10.04 [7.84] y, n = 143) and coaches (mean experience 17.45 [12.44] y, n = 20) completed an online survey on frequency of usage, perceived importance, effectiveness, and common barriers of 25 recovery strategies. Data were coded and analyzed thematically. A Fisher exact test (P < .05) was conducted on 5-point Likert-scale responses.

RESULTS

Predominant strategies among athletes were hydration, hot showers, and carbohydrate (mean scores 4.62 [0.60], 4.32 [0.82], and 4.17 [0.87]). Only antioxidants showed significant variation in use across levels (P = .033). Coaches favored warm-down/cooling (4.56 [0.62]), hydration (4.41 [0.80]), and extra protein (4.12 [0.70]). Both groups ranked hydration as most important and effective. Athletes ranked extra protein and warm-down/cooling second and third, while coaches considered extra sleep/naps, warm-down/cooling, and extra protein equally important. Barriers of both populations included insufficient time (14.41%), limited knowledge (13.72%), lack of resources (12.63%), and skepticism regarding benefits and effectiveness (12.63%).

CONCLUSIONS

Athletes show no significant differences in recovery choices based on competitive level, except for antioxidants. Coaches and athletes have partially different views on effective recovery. Furthermore, a lack of time, as well as a lack of (shared) knowledge and education, hinders the effective implementation of recovery strategies for athletes.

A new histopathology scoring protocol reveals myopathy features in PSE-like pork

Pale, Soft, and Exudative (PSE)-like pork defects are associated with fiber destruction and pale discoloration and have become a severe economic burden for the European meat sector. However, robust detection of PSE-like pork and its diverse features is challenging and makes studies into defect causation difficult. Implementation of histological examination may improve our knowledge about less-known features linked to PSE-like defects. Here we evaluate if a new histological protocol can reveal how myopathy in ham may be associated with visual and traditional physicochemical anomalies of PSE-like pork. We first created a list of pathological features, quantified them, and integrated them into a myodegeneration scoring scheme (MYO) for semimembranosus muscle sections. We then explored potential associations between overall MYO scoring and individual histology features with visual PSE-like defect scoring (DES) and with individual meat quality variables [pHu, color: L*, a*, b* (CIELAB), bioimpedance, and near-infrared spectroscopy (NIR)]. As the primary finding of this study, we show a significant association between overall myopathy (MYO) scoring and PSE-like defect (DES) scores. We also found associations of specific myopathy features with DES scores, and of overall MYO scoring with specific quality variables. In all, our data suggest links between signs of acute myodegeneration and PSE-like defects. Our data, hence, supports the implementation of semi-quantitative histopathological approaches for diagnosing PSE-like pork features and may help identify the underlying mechanisms behind these defects.

Vortex formation time in female athletes

Regular, vigorous physical activity can have a significant impact on cardiac function, leading to cardiac morphological alterations that may be challenging to distinguish from pathological changes. Therefore, new screening methods are needed to accurately differentiate between adaptive changes and pathological alterations in athletes. Vortex formation time (VFT) is an emerging method that shows potential in this regard, as it involves the formation of a rotating vortex ring in the left ventricle during the early filling phase of diastole. In this study, we investigated the difference in VFT between two groups of women: professional handball players and healthy middle-aged female athletes, along with their corresponding control groups. By using echocardiography-Doppler analysis of the heart, VFT was calculated based on the left ventricular ejection fraction, the ratio between the end-diastolic volume and the diameter of the mitral annulus, and the ratio of the atrial contraction volume to the total inflow via the mitral valve. The study reveals a significant increase in VFT in both professional handball players and middle-aged female athletes compared to their respective control groups. Moreover, statistically significant differences between handball players and middle-aged female athletes were observed, indicating that the level of physical activity may affect the VFT. These results suggest that VFT could be a promising screening tool for identifying cardiac adaptations due to long-term vigorous training, potentially enabling more accurate diagnoses of cardiac morphological alterations in athletes.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Altered Circulating MicroRNA Profiles After Endurance Training: A Cohort Study of Ultramarathon Runners

BACKGROUND

Despite the positive effects of endurance training on the cardiovascular (CV) system, excessive exercise induces not only physiological adaptations but also adverse changes in CV system, including the heart. We aimed to evaluate the selected miRNAs expression based on bioinformatic analysis and their changes before and after an ultramarathon run.

MATERIALS AND METHODS

Cardiac tissue-specific targets were identified with the Tissue 2.0 database. Gene-gene interaction data were retrieved from the STRING app for Cytoscape. Twenty-three endurance athletes were recruited to the study. Athletes ran to completion (100 km) or exhaustion (52-91 km, median 74 km). All participants completed pre- and post-run testing. miRNAs expressions were measured both before and after the race.

RESULTS

Enrichment analysis of the signaling pathways associated with the genes targeted by miRNAs selected for qRT-PCR validation (miR-1-3p, miR-126, miR-223, miR-125a-5p, miR-106a-5p, and miR-15a/b). All selected miRNAs showed overlap in regulation in pathways associated with cancer, IL-2 signaling, TGF-β signaling as well as BDNF signaling pathway. Analysis of metabolites revealed significant regulation of magnesium and guanosine triphosphate across analyzed miRNA targets. MiR-1-3p, miR-125a-5p, miR-126, and miR-223 expressions were measured in 23 experienced endurance athletes, before and after an ultramarathon wherein athletes ran to completion (100 km) or exhaustion (52-91 km, median 74 km). The expressions of miR-125a-5p, miR-126, and miR-223 were significantly increased after the race (p = 0.007, p = 0.001, p = 0.014, respectively). MiR-1-3p expression post-run showed a negative correlation with the post-run levels of high-sensitivity C-reactive protein (hs-CRP) (r = -0.632, p = 0.003). Higher miR-1-3p expression was found in runners, who finished the race under 10 h compared to runners who finished over 10 h (p = 0.001). Post-run miR-125a-5p expression showed a negative correlation with the peak lactate during the run (r = -0.576, p = 0.019).

CONCLUSION

Extreme physical activity, as exemplified by an ultramarathon, is associated with changes in circulating miRNAs' expression related to inflammation, fibrosis, and cardiac muscle function. In particular, the negative correlations between miR-125a-5p and lactate concentrations, and miR-1-3p and hs-CRP, support their role in specific exercise-induced adaptation. Further studies are essential to validate the long-term effect of these observations.

Pathophysiology of exercise-induced muscle damage and its structural, functional, metabolic, and clinical consequences

Extreme or unaccustomed eccentric exercise can cause exercise-induced muscle damage, characterized by structural changes involving sarcomere, cytoskeletal, and membrane damage, with an increased permeability of sarcolemma for proteins. From a functional point of view, disrupted force transmission, altered calcium homeostasis, disruption of excitation-contraction coupling, as well as metabolic changes bring about loss of strength. Importantly, the trauma also invokes an inflammatory response and clinically presents itself by swelling, decreased range of motion, increased passive tension, soreness, and a transient decrease in insulin sensitivity. While being damaging and influencing heavily the ability to perform repeated bouts of exercise, changes produced by exercise-induced muscle damage seem to play a crucial role in myofibrillar adaptation. Additionally, eccentric exercise yields greater hypertrophy than isometric or concentric contractions and requires less in terms of metabolic energy and cardiovascular stress, making it especially suitable for the elderly and people with chronic diseases. This review focuses on our current knowledge of the mechanisms underlying exercise-induced muscle damage, their dependence on genetic background, as well as their consequences at the structural, functional, metabolic, and clinical level. A comprehensive understanding of these is a prerequisite for proper inclusion of eccentric training in health promotion, rehabilitation, and performance enhancement.

The efficacy of protein supplementation during recovery from muscle-damaging concurrent exercise

This study investigated the effect of protein supplementation on recovery following muscle-damaging exercise, which was induced with a concurrent exercise design. Twenty-four well-trained male cyclists were randomised to 3 independent groups receiving 20 g protein hydrolysate, iso-caloric carbohydrate, or low-calorific placebo supplementation, per serve. Supplement serves were provided twice daily, from the onset of the muscle-damaging exercise, for a total of 4 days and in addition to a controlled diet (6 g·kg−1·day−1 carbohydrate, 1.2 g·kg−1·day−1 protein, remainder from fat). Following the concurrent exercise session at time-point 0 h, comprising a simulated high-intensity road cycling trial and 100 drop-jumps, recovery of outcome measures was assessed at 24, 48, and 72 h. The concurrent exercise protocol was deemed to have caused exercise-induced muscle damage (EIMD), owing to time effects (p < 0.001), confirming decrements in maximal voluntary contraction (peaking at 15% ± 10%) and countermovement jump performance (peaking at 8% ± 7%), along with increased muscle soreness, creatine kinase, and C-reactive protein concentrations. No group or interaction effects (p > 0.05) were observed for any of the outcome measures. The present results indicate that protein supplementation does not attenuate any of the indirect indices of EIMD imposed by concurrent exercise, when employing great rigour around the provision of a quality habitual diet and the provision of appropriate supplemental controls.

Acute kidney injury associated with endurance events-is it a cause for concern? A systematic review

INTRODUCTION

A growing body of evidence suggests even small rises in serum creatinine (SCr) are of considerable clinical relevance. Given that participants in endurance events are exposed to potential (repeated) renal insults, a systematic review was undertaken to collate current evidence for acute kidney injury (AKI), complicating such events.

METHODS

A systematic review of studies and case reports meeting inclusion criteria on Medline and EMBASE (inception to October 2015). Included: studies with markers of renal function before and after endurance or ultraendurance events; case reports of severe AKI. Two reviewers assessed risk of bias using the Newcastle-Ottawa scale.

RESULTS

Eleven case report publications (n=27 individuals) of severe AKI, were retrieved, with risk factors including systemic illness or nephrotoxic medications usually identified. From 30 studies of endurance and ultraendurance events, mean rise in SCr was 29 (±12.3) µmol/L after marathon or ultramarathon (17 studies, n=568 participants) events. Where follow-up tests were conducted, SCr returned to baseline within 48 hours. Rises in biomarkers suggest potential parenchymal insult, rather than simply muscle breakdown. However, evidence of long-term deleterious effects is lacking.

CONCLUSIONS

Raised levels of SCr are reported immediately after endurance events. It is not clear whether this is either clinically significant, or if repeated participation predisposes to long-term sequelae. The aetiology of severe exercise-associated AKI is usually multifactorial, with risk factors generally identified in the rare cases reported. On-site biochemistry, urine analysis and biomarkers of AKI may help identify collapsed runners who are at significant short-term risk and allow suitable follow-up.

Biochemical, physiological, and performance response of a functional watermelon juice enriched in L-citrulline during a half-marathon race

Background: Watermelon is a rich natural source of l-citrulline. This non-essential amino acid increases exercise performance.

Objective: Evaluate the effect of Fashion watermelon juice enriched in l-citrulline (CWJ) (3.45 g per 500 mL) in physical performance and biochemical markers after a half-marathon race.

Design: A randomised, double blind, crossover design where 2 h after drinking 500 mL of CWJ or placebo (PLA, beverage without l-citrulline) amateur male runners performed two half-marathon races. Jump height, heart rate and rating of perceived exertion were evaluated before and after the races. Moreover, muscle soreness and plasma markers of muscle damage and metabolism were evaluated for 72 h after the races.

Results: Muscle soreness perception was significantly lower from 24 to 72 h after the race with CWJ beverage. Immediately after the races, runners under CWJ condition showed plasma lactate and glucose concentrations significantly lower and higher lactate dehydrogenase and l-arginine concentration than runners under PLA. A maintenance of jump heights after the races under CWJ supplementation was found, decreasing significantly with PLA.

Conclusion: A single Fashion watermelon juice enriched in l-citrulline dose diminished muscle soreness perception from 24 to 72 h after the race and maintained lower concentrations of plasma lactate after an exhausting exercise.

Exercise-Induced Vasculitis: A Review with Illustrated Cases

Although exercise-induced vasculitis (EIV) is usually misdiagnosed, it is not uncommon. Occurring mostly after prolonged exercise, especially in hot weather, EIV is an isolated cutaneous vasculitis with stereotypical presentation. This article reviews the clinical characteristics, treatments, and outcomes of EIV based on the published literature. We report 99 patients who developed EIV after walking, dancing, swimming, or hiking especially during hot weather, including the records of 16 patients with EIV treated at our hospital from 2007 to 2015. Erythematous or purpuric plaques arise on the lower legs, without the involvement of compression socks or stockings. Symptoms include itch, pain, and a burning sensation. EIV is an isolated cutaneous vasculitis. Lesions resolve spontaneously after 10 days. When triggering conditions persist, relapses are frequent (77.5 %). Histopathology demonstrates leukocytoclastic vasculitis in 95 % of cases with C3 or immunoglobulin M deposits in 88 and 46 % of cases, respectively. Blood investigations are negative. EIV appears to be a consequence of venous stasis induced by an acute failure of the muscle pump of the calf and thermoregulation decompensation. Both appear after prolonged and unusual exercise in hot weather. Treatment is not codified; topical corticosteroids may reduce symptoms and wearing light clothes might limit lesion occurrence.

Comparison of Changes in Biochemical Markers for Skeletal Muscles, Hepatic Metabolism, and Renal Function after Three Types of Long-distance Running: Observational Study

The purpose of this study is to compare changes in biochemical markers for the skeletal muscles, hepatic metabolism, and renal function based on extreme long-distance running.Among healthy amateur endurance athletes who participated in a marathon, 100 km-, or 308 km ultramarathon, 15 athletes with similar physical and demographic characteristics were chosen to be the subjects in this study, upon completion of each course. The subjects' blood was collected before and after the course to identify biochemical markers for the skeletal muscles, hepatic metabolism, and renal function.After all of the courses, creatinine kinase (CK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), alanine transaminase (ALT), blood urea nitrogen (BUN), and creatinine were found to be significantly increased compared with values obtained before the race (P <0.05 for each marker). CK, LDH, AST, and LDH were significantly higher after completion of the 100 km race than the marathon (P <0.05) and were significantly higher after the 308 km race than the marathon or 100 km race (P <0.05). Total protein was significantly lower after the 308 km race than the marathon or 100 km race (P <0.05). Albumin significantly increased after the marathon but significantly decreased after the 308 km course (P <0.05). Total and direct bilirubin were significantly increased after the 100 km and 308 km races (P <0.05), and were significantly higher after the 308 km than the marathon or 100 km course (P <0.05). BUN was significantly higher after the 100 km race than the marathon (P <0.05) and was significantly lower after the 308 km than the 100 km race (P <0.05). Creatinine was significantly higher after the marathon and 100 km than the 308 km race (P <0.05). Uric acid significantly increased after the marathon and 100 km race (P <0.05); it was significantly higher after completing the marathon and 100 km than the 308 km race (P <0.05).Muscular damage, decline in hepatic function, and hemolysis in the blood were higher after running a 308 km race, which is low-intensity running compared with a marathon, and a temporary decline in renal function was higher after completing a 100 km race, which is medium-to-high intensity.

Influence of compression garments on recovery after marathon running

Strenuous physical activity can result in exercise-induced muscle damage. The purpose of this study was to investigate the efficacy of a lower limb compression garment in accelerating recovery from a marathon run. Twenty four subjects (female, n = 7; male, n = 17) completed a marathon run before being assigned to a treatment group or a sham treatment group. The treatment group wore lower limb compression tights for 72 hours after the marathon run, the sham treatment group received a single treatment of 15 minutes of sham ultrasound after the marathon run. Perceived muscle soreness, maximal voluntary isometric contraction (MVIC), and serum markers of creatine kinase (CK) and C-reactive protein (C-RP) were assessed before, immediately after, and 24, 48, and 72 hours after the marathon run. Perceived muscle soreness was significantly lower (p ≤ 0.05) in the compression group at 24 hours after marathon when compared with the sham group. There were no significant group effects for MVIC, CK, and C-RP (p > 0.05). The use of a lower limb compression garment improved subjective perceptions of recovery; however, there was neither a significant improvement in muscular strength nor a significant attenuation in markers of exercise-induced muscle damage and inflammation.

A Neuromuscular Approach to Statin-Related Myotoxicity

Approximately 95% of statin-treated patients tolerate this form of cholesterol management without any adverse effects. However, given their efficacy in reducing low density lipoproteins and cardiovascular events large numbers of patients are selected for statin therapy. Therefore muscle complications are, in fact, quite common. Limited understanding of the underlying pathophysiology has hampered physicians' ability to identify patients at risk for developing statin myotoxicity. A growing number of published case reports/series have implicated statins in the exacerbation of both acquired and genetic myopathies. A clinical management algorithm is presented which outlines a variety of co-morbidities which can potentiate the adverse effects of statins on muscle. In addition, a rational approach to the selection of those patients most likely to benefit from skeletal muscle biopsy is discussed. Ongoing work will define the extent to which statin-intolerant patients represent carriers of recessive metabolic myopathies or pre-symptomatic acquired myopathies. The expanding importance of pharmacogenomics will undoubtedly be realized in the field of statin myopathy research within the next few years. Such critical information is needed to establish more definitive management and diagnostic strategies.

Respostas bioquímicas e físicas ao treinamento realizado dentro e fora da água em atletas de futsal

O objetivo deste estudo foi analisar os efeitos do treinamento físico em quadra e do treinamento físico em piscina (hidroginástica) sobre os índices bioquímicos relativos ao dano muscular e a aptidão física de atletas de futsal. Doze jogadores de futsal foram divididos em dois grupos: 1) grupo de treinamento em quadra (GTQ, n = 6) e 2) grupo de treinamento em piscina (GTP, n =6). Foram verificados os índices de capacidades aeróbicas e aneróbicas pelos testes de RAST e Yo-yo intermitent, o dano muscular pela creatina quinase (CK) e lactato desidrogenase (LDH) e os níveis de stress oxidativo pelos níveis de ácido tiobarbitúrico (TBARS) e atividade da catalase (CAT) antes e após 10 sessões de trainamento (p<0,05). Os resultados mostraram que ambos os grupos melhoraram a condição aeróbica após as 10 sessões de treinamento. Mas o GTP apresentou maior atividade da CAT em repouso e menores níveis de CK ao ser comparado com o GTQ na 10ª sessão de treino. Concluiu-se que o treino com hidroginástica parece ser uma alternativa interessante para a melhoria das capacidades físicas e para a proteção muscular durante a preparação física inicial de atletas de futsal.

Monocyte/macrophage interactions with myogenic precursor cells during skeletal muscle regeneration

Adult skeletal muscle has the remarkable property of regenerating after damage, owing to satellite cells and myogenic precursor cells becoming committed to adult myogenesis to rebuild the muscle. This process is accompanied by the continuing presence of macrophages, from the phagocytosis of damaged myofibres to the full re-formation of new myofibres. In recent years, there has been huge progress in our understanding of the roles of macrophages during skeletal muscle regeneration, notably concerning their effects on myogenic precursor cells. Here, we review the most recent knowledge acquired on monocyte entry into damaged muscle, the various macrophage subpopulations, and their respective roles during the sequential phases of muscle repair. We also discuss the role of macrophages after exercise-induced muscle damage, notably in humans.

Hypoxia preconditioning by cobalt chloride enhances endurance performance and protects skeletal muscles from exercise-induced oxidative damage in rats

AIM

Training under hypoxia has several advantages over normoxic training in terms of enhancing the physical performance. Therefore, we tested the protective effect of hypoxia preconditioning by hypoxia mimetic cobalt chloride against exercise-induced oxidative damage in the skeletal muscles and improvement of physical performance.

METHOD

Male Sprague-Dawley rats were randomly divided into four groups (n=8), namely control, cobalt-supplemented, training and cobalt with training. The red gastrocnemius muscle was examined for all measurements, viz. free radical generation, lipid peroxidation, muscle damage and antioxidative capacity.

RESULTS

Hypoxic preconditioning with cobalt along with training significantly increased physical performance (33%, P<0.01) in rats compared with training-only rats. Cobalt supplementation activated cellular oxygen sensing system in rat skeletal muscle. It also protected against training-induced oxidative damage as observed by an increase in the GSH/GSSG ratio (36%, P<0.001; 28%, P<0.01 respectively) and reduced lipid peroxidation (15%, P<0.01; 31%, P<0.01 respectively) in both trained and untrained rats compared with their respective controls. Cobalt supplementation along with training enhanced the expression of antioxidant proteins haem oxygenase-1 (HO-1; 1.2-fold, P<0.05) and metallothionein (MT; 4.8-fold, P<0.001) compared with training only. A marked reduction was observed in exercise-induced muscle fibre damage as indicated by decreased necrotic muscle fibre, decreased lipofuscin content of muscle and plasma creatine kinase level (16%, P<0.01) in rats preconditioned with cobalt.

CONCLUSION

Our study provides strong evidence that hypoxic preconditioning with cobalt chloride enhances physical performance and protects muscle from exercise-induced oxidative damage via GSH, HO-1 and MT-mediated antioxidative capacity.

Effect of postexercise recovery procedures following strenuous stair-climb running

This study compared the effects of hot/cold water immersion, static stretching, and no recovery (control) interventions on leg strength, rowing performance, and indicators of muscle soreness/damage in the 72 hours following strenuous stair-climb running. Club (n = 14) and elite (Sports Institute) (n = 6) rowers performed the training run on three separate occasions. After each run, participants completed a randomly assigned 15-minute recovery treatment, either hot/cold, static stretching, or control, which were repeated at 24 and 48 hours postrun. No significant strength or performance differences existed between the three recovery treatments for either group. Muscle soreness for both groups remained significantly elevated (p < 0.05) above baseline at 72 hours postrun. At 48-hours postrun serum creatine kinase levels had returned to baseline and at 72 hours postrun were below baseline in both groups. In conclusion, neither hot/cold nor static stretching accelerated recovery at 72 hours beyond that achieved by the control condition.

Alterations in muscular enzymes of horses competing long-distance endurance rides under tropical climate

This study tried to monitor the alterations of muscle enzymes activity - creatinokinase (CK), lactate dehydrogenase (LDH), and aspartate aminotransferase (AST) - in a group of horses that participated of 70 and 100km distance rides in five competitions of an annual endurance championship under tropical climate. Pre ride levels (U/l) were 245.13±9.84 for CK, 496.61±14.76 for LDH, and 328.95±8.65 for AST. When compared to these levels, the results revealed a significant decrease in all enzymes activities in the first moment of the rides. Peak levels, significantly different, were reached, immediately after rides by CK (413.591±50.75); 24 hours post rides by LDH (628.61±33.30); and 48 hours after rides by AST (389.89±16.96). Monitoring of recovery period revealed different behavior among enzymes activities with CK values returning to pre ride values (279.61±23.05) 24 hours post rides, while LDH and AST values returned to pre ride values (505.25±33.78 and 359.35±24.90, respectively) 72 hours post rides. These data revealed different alterations in concentration of muscular enzymes in endurance horses directly related to the duration of the effort.

Gene expression profiling in blood cells of endurance horses completing competition or disqualified due to metabolic disorder

REASONS FOR PERFORMING STUDY

Genomics using cDNA microarrays could provide useful information about physiological adaptations and metabolic disorders in endurance horses.

OBJECTIVES

In order to show that genes are modulated in leucocytes in relationship with performance and clinical status of the horses, gene expression in leucocytes, haematological and biochemical parameters were compared between successful and disqualified endurance horses.

METHODS

Blood samples were collected at rest (TO) and just after a 140-160 km endurance race (T1) in 2 groups of horses: 10 continuing successful (S) and 10 disqualified horses stopped at a vet-gate for metabolic disorders (D). Total RNA was extracted from the blood cells (leucocytes), checked for purity, amplified and hybridised using mouse cDNA microarrays including 15,264 unique genes. Differential gene expressions were studied by hybridisation of each sample T1 vs. a control sample collected at TO (pool of 20 sound horses).

RESULTS

Some significant differences were observed in the haematology and biochemistry of the 2 groups (S vs. D). In Group D, rhadomyolysis was confirmed with CK 13,124 u/l and AST 1242 u/l. The list of 726 (including 603 annotated genes) significant genes was filtered according to a high P-value cut-off (P<0.00001). Among them, 130 were upregulated (expression ratio>1.5) and 288 were down-regulated (<1/1.5). Analysis of variance revealed 62 genes differentially expressed (P<0.05) in Groups D and S. The expression levels of 28 and 50 genes were significantly correlated (r>0.75) with CK and AST level in Group D, respectively. The gene ontology classification showed that more genes were up-regulated in S than in the D. More genes were down-regulated in the disqualified horses.

CONCLUSIONS

Long exercise induced many significant gene modulations in leucocytes. Some genes were expressed in relationship with the clinical phenotype observed in Group D: rhabdomyolysis and haemolysis.

POTENTIAL RELEVANCE

Some of these genes could be candidates to explain poor performance or pathologies. Further association studies with a greater number of genes should be conducted.

Effect of exercise-induced muscle damage on endurance running performance in humans

Exercise-induced muscle damage (EIMD) is known to decrease muscle strength and power but its effect on endurance performance is unclear. Thirty moderately trained adult runners (24 men and six women) were randomly assigned to EIMD or control. The EIMD group jumped 100 times from a 35 cm bench, while controls did not perform any muscle-damaging exercise. Before and 48 h after treatment, subjects were tested on markers of EIMD, steady-state cardiorespiratory, metabolic and perceptual responses during a constant speed submaximal run; distance ran in 30 min on a treadmill. There were significant changes in muscle soreness, creatine kinase, and knee extensors strength (P<0.01). This EIMD significantly reduced self-paced time trial performance by 4% (P<0.01) because subjects reduced running speed (P=0.02), with no change in perceived exertion (P=0.31). No significant alterations in running economy and other physiological responses to submaximal running were found. However, there was a trend (P=0.08) for increased perceived exertion, which was correlated with decreased time trial performance (P<0.01). In conclusion, EIMD has a significant impact on endurance running performance in humans, and this effect seems to be mediated by alterations in the sense of effort.

Exertional Rhabdomyolysis during a 246-km Continuous Running Race

BACKGROUND

To evaluate the effect of continuous, moderate-intensity ultra-endurance running exercise on skeletal muscle and hepatic damage, as indicated by serum enzyme activity measured immediately following the race.

METHODS

Thirty-nine runners of the Spartathlon race (a 246-km continuous race from Athens to Sparta, Greece) who managed to complete the race within the 36-h limit participated in this study. Mean finishing time of the study participants was 33.3+/-0.5 h and their average age, height, and body mass were 41+/-1 yr, 174+/-1 cm, and 67.5+/-1.1 kg, respectively. Blood samples, taken a day before and immediately after completion of the race, were assayed for the following variables: creatine kinase (CK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma-glutamyltransferase (gamma-GT).

RESULTS

A dramatic increase in most of muscle and liver damage indicators was observed. The mean values for CK, LDH, AST, and ALT after the race were 43,763+/-6,764, 2,300+/-285, 1,182+/-165, and 264+/-37 IU.L, respectively. These values were 29,384+/-4,327, 585+/-89, 5,615+/-902, and 1,606+/-331% higher than the corresponding values before the race (P<0.001) for CK, LDH, AST, and ALT, respectively. However, there was not a significant increase in gamma-GT levels.

CONCLUSION

Muscle and liver damage indicators were elevated at the highest level ever reported as a result of prolonged exercise, although no severe symptoms that required hospitalization were observed in any of the participants. The data suggest that even moderate-intensity exercise of prolonged duration can induce asymptomatic exertional rhabdomyolysis.

Effects of number of eccentric muscle actions on first and second bouts of eccentric exercise of the elbow flexors

This study compared changes in indirect markers of muscle damage following eccentric exercise of the elbow flexors among the exercises consisting of different number of eccentric actions. Sixty male athletes were placed into one of the six groups (n=10 per group) based on the number of eccentric actions for the first (ECC1) and second exercise bouts (ECC2). Single bout groups (30, 50, and 70) performed ECC1 only, and repeated bout groups (30-30, 50-50, and 70-70) performed ECC2 3 days after ECC1. Another 10 male athletes performed different number of eccentric actions for ECC1 (30) and ECC2 (70) separated by 3 days (30-70). Changes in maximal isometric strength (MVC), range of motion (ROM), upper arm circumference (CIR), serum creatine kinase activity, myoglobin, and nitric oxide concentrations and muscle soreness for 10 days following ECC1 were compared among groups by two-way repeated measures ANOVA. Changes in MVC, ROM, and CIR following ECC1 were significantly (P<0.05) smaller for the groups that performed 30 eccentric actions compared with other groups. No significant differences between 30 and 30-30, 50 and 50-50, and 70 and 70-70 were evident for the changes in the measures for 10 days following ECC1 except for the acute decreases in MVC and ROM immediately after ECC2 for the repeated bout groups. The 30-30 and 30-70 groups showed similar changes in all criterion measures. It is concluded that recovery from eccentric exercise is not retarded by the second bout of eccentric exercise regardless of the number of eccentric actions.

Raised troponin T and echocardiographic abnormalities after prolonged strenuous exercise--the Australian Ironman Triathlon

BACKGROUND

There is concern about whether cardiac damage occurs as a result of prolonged strenuous exercise.

OBJECTIVE

To investigate whether competing in a triathlon is associated with cardiac damage based on a sustained increase in cardiac troponin T (cTnT), and whether such an increase correlates with echocardiographic changes

METHODS

cTnT and echocardiographic measurements were made in 38 participants in the 2001 Australian ironman triathlon. cTnT was measured the day before, immediately after, and the day following the race. Echocardiography was done the day before, immediately after, and two to six weeks later for measurement of ejection fraction, stroke volume, cardiac output, wall motion analysis, and global left ventricular function (LVF).

RESULTS

No subject had detectable cTnT in the pre-race sample. Following the race, 32 subjects (86.5%) had detectable levels of cTnT (>0.01 ng/ml), with six (16.2%) having >0.10 ng/ml. The day after the race, nine subjects (23.7%) still had detectable cTnT, with two recording a level >0.10 ng/ml. Previously described echocardiographic changes of "cardiac fatigue" were observed in the whole cohort. There was a modest but significant correlation between change in ejection fraction and peak cTnT level (p = 0.02, r = 0.39). Athletes with a post-race cTnT >0.10 ng/ml had a greater decrease in global LVF (p = 0.02) and a trend toward a greater fall in ejection fraction and stroke volume than athletes with cTnT levels <0.10 ng/ml. Cardiac output fell in the group with cTnT >0.10 ng/ml (p>0.05).

CONCLUSIONS

Participation in ironman triathlon often resulted in persistently raised cTnT levels, and the troponin rise was associated with echocardiographic evidence of abnormal left ventricular function. The clinical significance and long term sequelae of such damage remains to be determined.

Exercise-induced vasculitis

BACKGROUND

Usually misdiagnosed and ignored in the literature, exercise-induced vasculitis (EIV) is not uncommon, occurring mostly in long-distance runners and in females after long walks, especially in hot weather.

OBSERVATIONS

I report 23 otherwise healthy patients (22 females, 1 male) who developed EIV after walking or hiking in hot weather. Erythematous, urticarial or purpuric plaques arose on the lower legs, not involving skin compressed by socks. Symptoms included itch, pain, and burning sensation. Lesions resolved after some days. Relapses were frequent at further muscular exercise, and could be prevented in some cases by compression hosiery, manual lymphatic drainage, intake of oedema protective agents, or steroids (local or systemic).

INVESTIGATIONS

Histopathology demonstrated leucocytoclastic vasculitis in five biopsies, and urticarial vasculitis in one. Extensive blood investigations have been performed in six patients and were negative. No clear relation with chronic venous disease (duplex or Doppler) had been established in 12 patients.

CONCLUSIONS

I suggest denominating this condition exercise-induced vasculitis. This clinical entity is well defined, but poorly recognized. The presentation of 23 original cases demonstrates its reality.

Antioxidants did not prevent muscle damage in response to an ultramarathon run

PURPOSE

This study was conducted to determine if 6 wk of supplementation with vitamins E and C could alleviate exercise-induced muscle damage. We studied 22 runners during a 50-km ultramarathon.

METHODS

Subjects were randomly assigned to one of two groups: (a) placebos (PL) or (b) antioxidants (AO) (1000 mg vitamin C and 300 mg RRR-alpha-tocopheryl acetate). Blood samples were obtained before supplementation (baseline), 24 h pre-, 12 h pre-, and 1 h prerace; midrace, postrace, 2 h postrace, and for 6 d postrace. Plasma alpha-tocopherol (alpha-TOH), ascorbic acid (AA), and muscle damage markers (creatine kinase (CK) and lactate dehydrogenase (LDH)), as well as maximal voluntary contraction (MVC) of the hamstring and quadriceps were assessed.

RESULTS

With supplementation, plasma alpha-TOH and AA increased in the AO but not the PL group. LDH and CK increased in response to the race; LDH peaked at postrace and CK reached maximal values 2 h and 1 d postrace; neither was affected by treatment. Adjusting for between-subject differences in baseline CK values revealed that men had higher levels of CK than did women throughout the study. Correcting CK values for lean body mass (kg) eliminated sex differences, but not changes over time. CK was significantly correlated (R = 0.52, P < 0.0001) with C-reactive protein, an acute phase response marker. MVC decreased 14-26% in all groups in response to the run. Eccentric hamstring (EH) torque and concentric quadriceps (CQ) power exhibited the largest deficits, 26 and 24%, respectively, with no effect of treatment. CQ recovered at a faster rate in women than in men.

CONCLUSION

Antioxidants appeared to have no effect on exercise-induced increases in muscle damage or recovery, but important sex differences were observed.

Epidemiological analysis of factors influencing an episode of exertional rhabdomyolysis in high school students

BACKGROUND

An episode of rhabdomyolysis occurred after an endurance test in high school students in Taipei County in November 2003.

PURPOSE

To determine the incidence, outcome, and risk factors in an episode of exertional rhabdomyolysis in high school students.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

We enrolled all 225 high school students who had performed an endurance test. Using data from retrospective questionnaires, we estimated the incidence and assessed risk factors of exertional rhabdomyolysis among these students. Multiple logistic regression was used to determine risk factors associated with exertional rhabdomyolysis.

RESULTS

The completed questionnaire was returned by 70% (157 of 225) of the students. Of these, 43.3% (68 of 157) were identified as having exertional rhabdomyolysis, and the incidence was not statistically different between male and female students (P = .49). Dark urine was noted in only 25% of the students. None of the students developed acute renal failure. The risk of exertional rhabdomyolysis was significantly higher in those students who had not exercised 1 day before the endurance test (odds ratio [OR], 6.10; 95% confidence interval [CI], 2.00-18.00) and those who had performed postexercise stretching of the legs (OR, 3.13; 95% CI, 1.28-7.69) or performed complete squats during the test (OR, 3.21; 95% CI, 1.12-10.00). There were no statistically significant differences in gender, body mass index, presence of flulike symptoms, previous exercise routine, and medication history between students with or without exertional rhabdomyolysis.

CONCLUSION

Our findings suggest that exertional rhabdomyolysis is not uncommon in strenuous eccentric exercise in both men and women, but the risk of developing acute renal failure is very low. Exercise 1 day before eccentric exercise was significantly associated with a reduced risk of exertional rhabdomyolysis, whereas postexercise stretching of the involved extremities might increase the risk.

Effect of weightlifting upon left ventricular function and markers of cardiomyocyte damage

The purpose of this study was to assess left ventricular (LV) function and biochemical markers of myocyte after prolonged weightlifting activity. Seventeen male subjects (age range 20-34 years) performed a 90-min bout of weightlifting exercise consisting of three sets of 8-10 repetitions at 70% one-repetition maximum. Body mass, heart rate, systolic blood pressure (SBP) and echocardiographically determined indices of LV loading (LV internal diameter during diastole, LV meridonial wall stress), systolic function (stroke volume (SV), ejection fraction (EF), end-systolic pressure volume relationship; SBP/ESV) and diastolic filling (ratio of early to late; E:A) were obtained pre-exercise, immediately after and 24 h post-exercise. A 5-ml venous blood sample was obtained for the assessment of cardiac troponin T (cTnT) via third generation electrochemiluminescence assay. Data were assessed via one-way ANOVA and Pearson's correlation. Although SV declined (80.9 +/- 18.3 vs. 66.9 +/- 17.2, p < 0.05) there was no alteration in LV contractility (EF 62 +/- 6 vs. 59 +/- 7; SBP/ESV 3.51 +/- 1.4 vs. 3.51 +/- 1.4, p > 0.05). The E:A ratio was significantly decreased following exercise (1.78 +/- 0.41 vs. 1.33 +/- 0.37, p < 0.05). This decrease was not fully explained by loading conditions (r2 = 0.05 to 0.24). All values returned to baseline 24 h post-exercise. No cTnT was reported in any of the blood samples. In conclusion, there was no significant evidence of any LV contractile depression and no cTnT was observed post exercise. The small reduction in diastolic filling could not be explained by changes in haemodynamic loading or the post-exercise elevation in heart rate.

Reduction of plasma lactate elevation and proteinuria by a complex dietary supplement in swimmers during over-loading training

Endurance training aiming at eliciting further increase of physical performance of competitive athletes demands serious time and intensity constraints. In addition, very high intensity training could lead to "over-loading" frequently associated with increased concentration of plasma lactate after maximum intensity exercise and proteinuria. We hypothesized that a newly available complex dietary (CD) supplement by providing the necessary substances and cofactors for increased tissue metabolism would reduce the increase in plasma lactate concentration and proteinuria after maximum intensity exercise in swimmers undergoing high intensity training and exercise (70 km/week, for 6 weeks) period. Subjects involved in the investigation were junior swimmers (n = 10). Data were collected four times during the third macrocycle of training; 1st: before, 2nd: after 10 days and 3rd: 14 days after withdrawal of CD-supplement, whereas 4th: after 10 days of placebo treatment. The study was a double-blinded random controlled investigation. In the first period, plasma lactate concentration was 8.4 +/- 2.1 mmol/l, whereas protein level in the urine was 8.9 +/- 5.8 mg/l. After use of CD-supplement plasma lactate concentration significantly decreased to 5.5 +/- 1.9 mmol/l and proteinuria decreased to 1.3 +/- 2.1 mg/l (p<0.05). Importantly, the intensity and the volume of the training did not change during the observation period. Thus, use of CD-supplement significantly reduced the increase in plasma lactate and proteinuria after maximum intensity exercise in athletes (swimmers) undergoing high endurance training despite maintained training load. We propose that the special components of CD-supplement support the mechanisms responsible for lactate elimination and reduction of protein catabolism and/or increase of protein reabsorption. These adaptations are likely to allow the athletes to undergo higher intensity training resulting in greater performance.

Protection against muscle damage in competitive sports players: the effect of the immunomodulator AM3

Strenuous physical exercise of the limb muscles commonly results in damage, especially when that exercise is intense, prolonged and includes eccentric contractions. Many factors contribute to exercise-induced muscle injury and the mechanism is likely to differ with the type of exercise. Competitive sports players are highly susceptible to this type of injury. AM3 is an orally administered immunomodulator that reduces the synthesis of proinflammatory cytokines and normalizes defective cellular immune fractions. The ability of AM3 to prevent chronic muscle injury following strenuous exercise characterized by eccentric muscle contraction was evaluated in a double-blind and randomized pilot study. Fourteen professional male volleyball players from the First Division of the Spanish Volleyball League volunteered to take part. The participants were randomized to receive either placebo (n=7) or AM3 (n=7). The physical characteristics (mean+/-s) of the placebo group were as follows: age 25.7+/-2.1 years, body mass 87.2+/-4.1 kg, height 1.89+/-0.07 m, maximal oxygen uptake 65.3+/-4.2 ml.kg(-1).min(-1). Those of the AM3 group were as follows: age 26.1+/-1.9 years, body mass 85.8+/-6.1 kg, height 1.91+/-0.07 m, maximal oxygen uptake 64.6+/-4.5 ml.kg(-1).min(-1). All participants were evaluated for biochemical indices of muscle damage, including concentrations of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, creatine kinase (CK) and its MB fraction (CK-MB), myoglobin, lactate dehydrogenase, urea, creatinine and gamma-glutamyltranspeptidase, both before and 30 days after treatment (over the peak of the competitive season). In the placebo group, competitive exercise (i.e. volleyball) was accompanied by significant increases in creatine kinase (494+/-51 to 560+/-53 IU.l(-1), P < 0.05) and myoglobin (76.8+/-2.9 to 83.9+/-3.1 microg.l(-1), P < 0.05); aspartate aminotransferase (30.8+/-3.0 to 31.1+/-2.9 IU.l(-1)) and lactate dehydrogenase (380+/-31 to 376+/-29 IU.l(-1)) were relatively unchanged after the 30 days maximum effort. AM3 not only inhibited these changes, it led to a decrease from baseline serum concentrations of creatine kinase (503+/-49 to 316+/-37 IU.l(-1), P < 0.05) and myoglobin (80.1+/-3.2 to 44.1+/-2.6 IU.l(-1), P < 0.05), as well as aspartate aminotransferase (31.1+/-3.3 to 26.1+/-2.7 IU.l(-1), P < 0.05) and lactate dehydrogenase (368+/-34 to 310+/-3 IU.l(-1), P < 0.05). The concentration of CK-MB was also significantly decreased from baseline with AM3 treatment (11.6+/-1.2 to 5.0+/-0.7 IU.l(-1), P < 0.05), but not with placebo (11.4+/-1.1 to 10.8+/-1.4 IU.l(-1)). In conclusion, the use of immunomodulators, such as AM3, by elite sportspersons during competition significantly reduces serum concentrations of proteins associated with muscle damage.

Excitation-induced Ca2+ influx and muscle damage in the rat: loss of membrane integrity and impaired force recovery

Prolonged or unaccustomed exercise leads to loss of contractility and muscle cell damage. The possible role of an increased uptake of Ca(2+) in this was explored by examining how graded fatiguing stimulation, leading to a graded uptake of Ca(2+), results in progressive loss of force, impairment of force recovery, and loss of cellular integrity. The latter is indicated by increased [(14)C]sucrose space and lactic acid dehydrogenase (LDH) release. Isolated rat extensor digitorum longus (EDL) muscles were allowed to contract isometrically using a fatiguing protocol with intermittent stimulation at 40 Hz. Force declined rapidly, reaching 11% of the initial level after 10 min and stayed low for up to 60 min. During the initial phase (2 min) of stimulation (45)Ca uptake showed a 10-fold increase, followed by a 4- to 5-fold increase during the remaining period of stimulation. As the duration of stimulation increased, the muscles subsequently regained gradually less of their initial force. Following 30 or 60 min of stimulation, resting (45)Ca uptake, [(14)C]sucrose space, and LDH release were increased 4- to 7-fold, 1.4- to 1.7-fold and 3- to 9-fold, respectively (P < 0.001). The contents of Ca(2+) and Na(+) were also increased (P < 0.01), a further indication of loss of cellular integrity. When fatigued at low [Ca(2+)](o) (0.65 mm), force recovery was on average twofold higher than that of muscles fatigued at high [Ca(2+)](o) (2.54 mm). Muscles showing the best force recovery also had a 41% lower total cellular Ca(2+) content (P < 0.01). In conclusion, fatiguing stimulation leads to a progressive functional impairment and loss of plasma membrane integrity which seem to be related to an excitation-induced uptake of Ca(2+). Mechanical strain on the muscle fibres does not seem a likely mechanism since very little force was developed beyond 10 min of stimulation.

Effects of Running Distance and Training on Ca2+ Content and Damage in Human Muscle

PURPOSE

Muscle damage and soreness are well-known adverse effects of running, especially when covering distances in excess of habitual running activity. Loss of Ca homeostasis is hypothesized to initiate the development of exercise-induced muscle damage. We tested the hypothesis that the Ca content of vastus lateralis muscle increases after a 10- or 20-km run and studied the relations between Ca accumulation and running distance, endurance training, and fiber type distribution.

METHODS

Twenty-four healthy young men and women were divided into two groups who ran either 10 or 20 km. Muscle biopsies and blood samples were collected before, immediately after, and in the days after the run.

RESULTS

: The Ca content in muscle biopsies increased from 0.70 +/- 0.02 to 0.93 +/- 0.04 micromol x g wet weight after the 20-km run (P < 0.001) and was still significantly elevated at 4 and 48 h after the run. In the 10-km runners, however, no significant increase in Ca was found (0.81 +/- 0.03 vs 0.91 +/- 0.06 micromol x g wet weight, P = 0.08). Plasma levels of lactate dehydrogenase and creatine kinase increased after both running distances, the increase being greatest after the 20-km run. Eight of the 10-km runners completed an endurance-training program and subsequently repeated the 10-km run. The response to a new 10-km run with regard to muscle Ca content and parameters of muscle damage was essentially unchanged by training.

CONCLUSIONS

The degree of muscle damage depends on running distance, and a significant Ca accumulation in muscle is seen after 20 km. Ten weeks of endurance training does not influence Ca homeostasis and muscle damage after 10-km running.

Overloaded training increases exercise-induced oxidative stress and damage

We hypothesized that overloaded training (OT) in triathlon would induce oxidative stress and damage on muscle and DNA. Nine male triathletes and 6 male sedentary subjects participated in this study. Before and after a 4-week OT, triathletes exercised for a duathlon. Blood ratio of reduced vs. oxidized glutathione (GSH/GSSG), plasma thiobarbituric acid reactive substances (TBARS), leukocyte DNA damage, creatine kinase (CK), and CK-MB mass in plasma, erythrocyte superoxide dismutase (SOD) activity, erythrocyte and plasma glutathione peroxidase (GSH-Px) activities, and plasma total antioxidant status (TAS) were measured before and after OT in pre- and postexercise situations. Triathletes were overloaded in response to OT. In rest conditions, OT induced plasma GSH-Px activity increase and plasma TAS decrease (both p < 0.05). In exercise conditions, OT resulted in higher exercise-induced variations of blood GSH/GSSG ratio, TBARS level (both p < 0.05), and CK-MB mass (p < 0.01) in plasma; and decreased TAS response (p < 0.05). OT could compromise the antioxidant defense mechanism with respect to exercise-induced response. The resulting increased exercise-induced oxidative stress and further cellular susceptibility to damage needs more study.

Muscle damage and soreness after endurance exercise of the elbow flexors

PURPOSE

This study investigated changes in indirect markers of muscle damage after endurance exercise of the elbow flexors and compared the changes with those after maximal eccentric actions (Max-ECC) of the elbow flexors.

METHODS

Eighteen male students rhythmically lifted (1 s) and lowered (1 s) a light dumbbell (1.1-1.8 kg: 9% of MIF) in 60-180 degrees of elbow joint angle for 2 h (2-h Ex). Maximal isometric force (MIF), relaxed (RANG) and flexed elbow joint angles (FANG), upper-arm circumference (CIR), muscle soreness (SOR), B-mode ultrasound (US), and plasma creatine kinase (CK) activity were assessed before and immediately after, and up to 96 h after exercise.

RESULTS

All measures were altered significantly (P < 0.05) after 2-h Ex in a similar time course to Max-ECC; however, changes in RANG, FANG, CIR, US, and CK (peak: 356 +/- 121 IU.L-1) were significantly (P < 0.05) smaller compared with those after Max-ECC. SOR developed immediately after 2-h Ex and peaked 24-48 h after exercise. MIF dropped to 44.1% of the preexercise level, which was significantly (P < 0.05) lower than that after Max-ECC (58.1%), immediately postexercise. MIF recovered to 79.8% at 24 h, and 97.8% at 96 h postexercise, which was a significantly (P < 0.05) faster recovery compared with that of Max-ECC (73.1% at 96 h).

CONCLUSION

These results showed low-intensity continuous muscle contractions (3600 times) resulted in muscle damage; however, the magnitude of the muscle damage was less severe, and the recovery was faster compared with 12 maximal eccentric muscle actions.

Membrane leakage and increased content of Na+ -K+ pumps and Ca2+ in human muscle after a 100-km run

During prolonged exercise, changes in the ionic milieu in and surrounding the muscle fibers may lead to fatigue or damage of the muscle and thereby impair performance. In 10 male subjects, we investigated the effects of 100 km running on muscle and plasma electrolyte contents, muscle Na+ -K+ pump content, and plasma concentrations of creatine kinase (CK) and lactate dehydrogenase (LDH). After completion of a 100-km run, significant increases were found in plasma K+ (from 4.0 +/- 0.1 to 5.5 +/- 0.2 mM, P < 0.001), muscle Na+ -K+ pump content (from 334 +/- 11 to 378 +/- 17 pmol/g, P < 0.05), and total muscle Ca2+ content (from 0.84 +/- 0.03 to 1.02 +/- 0.04 micromol/g, P < 0.001). There was also a large increase in the plasma levels of the muscle-specific enzymes CK and LDH, which reached peak values at the end of the run and lasted several days after the run, indicating that a significant degree of muscle membrane leakage was present. The simultaneous occurrence of raised cellular Ca2+ content and muscle membrane leakage supports the theory that Ca2+ plays a role in the initiation of degenerative processes in muscles after severe exercise.

Isolation and measurement of carbonic anhydrase isoenzyme III in plasma, sera, and tissues of dogs

OBJECTIVE

To purify canine carbonic anhydrase isoenzyme III (CA-III) and determine plasma, serum, and tissue concentrations of CA-III in healthy dogs and dogs with experimentally induced muscle damage.

ANIMALS

121 healthy Beagles.

PROCEDURE

Muscle was obtained from 2 Beagles after euthanasia, and CA-III was purified and characterized by use of column chromatography and electrophoresis, respectively. A CA-III-specific ELISA was developed to determine concentrations of CA-III in plasma of 116 dogs and tissues of 1 dog. Serum creatine kinase (CK) activity and CA-III concentration were also determined before and after induction of muscle damage by IM injection of 2 ml of 10% lidocaine to 2 dogs.

RESULTS

Canine CA-III had a molecular weight of 28 kd and an isoelectric point of 8.2. Mean (+/- SD) concentration of CA-III in plasma of healthy dogs was 16.91 +/- 9.55 ng/ml. The highest tissue concentration of CA-III was detected in skeletal muscle. Serum concentration of CA-III increased and peaked within the first 2 to 3 hours after induction of muscle damage. The increase in CA-III concentration was more rapid than that of CK activity, and concentration reached its maximum and returned to baseline sooner than did CK activity.

CONCLUSIONS AND CLINICAL RELEVANCE

The CA-III ELISA we developed was a sensitive method for determining CA-III concentrations in plasma, serum samples, and tissue specimens of dogs. Use of this ELISA requires only a small volume of serum and may enable the study of changes in CA isoenzyme concentrations associated with muscle disorders in dogs.

Factors affecting performance in an ultraendurance triathlon

In the recent past, researchers have found many key physiological variables that correlate highly with endurance performance. These include maximal oxygen uptake (VO2max), anaerobic threshold (AT), economy of motion and the fractional utilisation of oxygen uptake (VO2). However, beyond typical endurance events such as the marathon, termed 'ultraendurance' (i.e. >4 hours), performance becomes harder to predict. The ultraendurance triathlon (UET) is a 3-sport event consisting of a 3.8 km swim and a 180 km cycle, followed by a 42.2 km marathon run. It has been hypothesised that these triathletes ride at approximately their ventilatory threshold (Tvent) during the UET cycling phase. However, laboratory assessments of cycling time to exhaustion at a subject's AT peak at 255 minutes. This suggests that the AT is too great an intensity to be maintained during a UET, and that other factors cause detriments in prolonged performance. Potential defeating factors include the provision of fuels and fluids due to finite gastric emptying rates causing changes in substrate utilisation, as well as fluid and electrolyte imbalances. Thus, an optimum ultraendurance intensity that may be relative to the AT intensity is needed to establish ultraendurance intensity guidelines. This optimal UET intensity could be referred to as the ultraendurance threshold.

Relationship between fat-to-fat-free mass ratio and decrements in leg strength after downhill running

The purpose of this study was to determine whether greater body fat mass (FM) relative to lean mass would result in more severe muscle damage and greater decrements in leg strength after downhill running. The relationship between the FM-to-fat-free mass ratio (FM/FFM) and the strength decline resulting from downhill running (-11% grade) was investigated in 24 male runners [age 23.4 +/- 0.7 (SE) yr]. The runners were divided into two groups on the basis of FM/FFM: low fat (FM/FFM = 0.100 +/- 0.008, body mass = 68.4 +/- 1.3 kg) and normal fat (FM/FFM = 0.233 +/- 0.020, body mass = 76.5 +/- 3.3 kg, P < 0.05). Leg strength was reduced less in the low-fat (-0.7 +/- 1.3%) than in the normal-fat individuals (-10.3 +/- 1.5%) 48 h after, compared with before, downhill running (P < 0.01). Multiple linear regression analysis revealed that the decline in strength could be predicted best by FM/FFM (r2 = 0.44, P < 0.05) and FM-to-thigh lean tissue cross-sectional area ratio (r2 = 0.53, P < 0.05), with no additional variables enhancing the prediction equation. There were no differences in muscle glycogen, creatine phosphate, ATP, or total creatine 48 h after, compared with before, downhill running; however, the change in muscle glycogen after downhill running was associated with a higher FM/FFM (r = -0.56, P < 0.05). These data suggest that FM/FFM is a major determinant of losses in muscle strength after downhill running.

Localized oxygen use of healthy and low back pain individuals during controlled trunk movements

Individuals who have low back pain (LBP) have significantly different motion characteristics than healthy individuals. However, the cause of these differences is unknown. Oxygen use of the erector spinae muscle was examined while simultaneously monitoring motion characteristics to determine whether oxygen use differed between healthy and LBP individuals. Thirty volunteers were classified as healthy, structural, or muscular-based LBP. A near-infrared spectrometer monitored oxygen use and blood volume in the lumbar region. Results showed significant differences in oxygen use but not blood volume between healthy and LBP subjects with muscular-based disorders. Inability of the muscular group to use oxygen in a manner similar to the healthy group indicates different processes at the tissue level, indicating that differences in oxygen use may provide insight into why motion patterns differ between healthy and LBP groups.

Exercise, oxidative stress and ageing

Skeletal muscle has the unique ability to increase the rate of oxygen usage during contraction. This has led several workers to suggest that by-products of this increased oxygen consumption, oxygen-derived free radicals, may be primarily responsible for exercise-induced damage to skeletal muscle. However, because of this rapidly changing redox state, skeletal muscle has developed a number of different endogenous mechanisms which adapt rapidly following a period of exercise. These include numerous structural and biochemical changes such as increased muscle activity of antioxidant enzymes and content of stress or heat shock proteins (HSPs). This adaptation is associated with protection against the potentially damaging effects of a second period of exercise. In addition, we have recently demonstrated a significant increase in free radical production during a period of nondamaging exercise, which is rapidly followed by a significant increase in the expression of antioxidant enzymes and HSPs, suggesting that a change in redox state of the muscle may act as signal for adaptation.

Effects of beta-hydroxy-beta-methylbutyrate on muscle damage after a prolonged run

This study examined the effects of supplemental beta-hydroxy-beta-methylbutyrate (HMB) on muscle damage as a result of intense endurance exercise. Subjects (n = 13) were paired according to their 2-mile run times and past running experience. Each pair was randomly assigned a treatment of either HMB (3 g/day) or a placebo. After 6 wk of daily training and supplementation, all subjects participated in a prolonged run (20-km course). Creatine phosphokinase and lactate dehydrogenase (LDH) activities were measured before and after a prolonged run to assess muscle damage. The placebo-supplemented group exhibited a significantly greater (treatment main effect, P = 0.05) increase in creatine phosphokinase activity after a prolonged run than did the HMB-supplemented group. In addition, LDH activity was significantly lower (treatment main effect, P = 0.003) with HMB supplementation compared with the placebo-supplemented group. In conclusion, supplementation with 3.0 g of HMB results in a decreased creatine phosphokinase and LDH response after a prolonged run. These findings support the hypothesis that HMB supplementation helps prevent exercise-induced muscle damage.

An investigation of perceived exertion via whole body exertion and direct muscle force indicators during the determination of the maximum acceptable weight of lift

The objective of this study was to identify the perceived exertion mechanisms (direct muscle force and whole body exertion) associated with the decision to change the weight of lift during the determination of the maximum acceptable weight of lift (MAWL). Fifteen males lifted a box of unknown weight at a rate of 4.3 lifts/min, and adjusted the weight until their MAWL was reached. Variables such as the predicted muscle forces and heart rate were measured during the lifting exertion, as well as the predicted spinal loading in three dimensions using an EMG-assisted biomechanical model. Multiple logistic regression techniques were used to identify variables that were associated with the decision to change the weights up and down prior to a subsequent lift. Results indicated that the force in the left erector spinae, right internal oblique, and left latissimus dorsi muscles as well as heart rate were associated with decreases in the weight prior to the next lift. It appears that a combination of local factors (muscle force) and whole body exertion factors (heart rate) provide the feedback for the perceived exertion when decreasing the weight. The up-change model indicated that the forces of the right erector spinae, left internal oblique, and the right latissimus dorsi muscles were associated with the decision to increase the weight prior to the next lift. Thus, local factors provide feedback during the decision to increase the weight when starting from light weights. Collectively, these findings indicate that psychophysically determined weight limits may be more sensitive to muscular strain rather than spinal loading.

Chronic eccentric exercise: improvements in muscle strength can occur with little demand for oxygen

Eccentric contractions, the lengthening of muscle while producing force, are a common part of our everyday movements. This study presents a challenge to the accepted notion that eccentric work causes obligatory muscle injury while demonstrating that an increase in muscle strength, via eccentric work, can occur with little demand for oxygen. Nine healthy subjects, ages 18-34, were randomly placed in either an eccentric or a concentric training group. Both groups trained for 6 wk while progressively increasing training frequency and duration. Significant gains in isometric leg strength were seen in the eccentrically trained subjects only. While training, the oxygen consumption required to do the eccentric work was equal to or less than that required to do the concentric work. The results demonstrate that by progressively increasing the eccentric work rate, significant isometric strength gains can be made without muscle injury and with minimal increase in metabolic demand for oxygen. The potential clinical implications of an eccentric training program that uncouples skeletal muscle strength improvements from the demand for oxygen are alluring.

Naproxen does not alter indices of muscle damage in resistance-exercise trained men

PURPOSE

Unaccustomed exercise is associated with an elevated plasma creatine kinase (CK), myofibrillar inflammation, and delayed onset muscle soreness (DOMS). Nonsteroidal antiinflammatory drugs (NSAID) may attenuate DOMS and indirect indices of inflammation in humans.

METHODS

We studied the effects of an NSAID (naproxen sodium (500 mg, 2 times a day for 48 h)) taken before and after resistance exercise in eight healthy, moderately trained men in a randomized, double-blind trial. The exercise consisted of unilateral knee concentric/eccentric weight lifting with 6 sets x 10 repetitions at 80-85% of the 1 repetition maximal contraction. Muscle biopsies of each vastus lateralis (EX = exercised/REST = control) were taken 24 h after exercise for immunohistochemical staining of inflammatory cells (leukocyte common antigen). At 24 and 48 h postexercise, we also determined DOMS, plasma CK activity, and knee extensor muscle torque.

RESULTS

Exercise resulted in an increased CK activity at +24 and +48 h (vs preexercise: P < 0.01), with no treatment effect. There were no treatment effects for any of the measured variables except for a return of voluntary knee extension torque to baseline by +48 h postexercise for NSAID treatment (P < 0.05).

CONCLUSIONS

NSAID administration did not alter CK rise, muscle force deficit at 24 h postexercise, nor perceived muscle pain. In addition, the increased CK at 24 h postexercise was not associated with an acute myofibrillar inflammatory cell infiltrate in moderately trained men after resistance exercise.