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620 CRAMPING STUDIES IN 2600 ENDURANCE ATHLETES

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... Previous studies have hypothesized that increased exertion level during competition, history of cramping, higher body mass index (BMI), older age, and irregular stretching habits to be associated with EAMC. 5,9 In ultraendurance triathletes, EAMC was initially reported in 1990 by Kantorowski et al 11 and later analyzed with electrolyte data by Sulzer et al. 2 Despite these studies, EAMC experienced during triathlon competition and training is minimally represented in the scientific literature. ...
... A number of studies have previously demonstrated that muscle cramping is common among ultraendurance sports. 1,2,10,11,16 In ultramarathons, the incidence ranges from 23% to 41% 9,17 and in triathlons, EAMC ranges from 23% to 63%. 11,12,17,18 Our overall finding of 6.0% is much lower than these past reports, which is likely underestimated by the fact that we report on athletes who sought evaluation for EAMC, while previous studies rely on self-reported surveys. ...
... 1,2,10,11,16 In ultramarathons, the incidence ranges from 23% to 41% 9,17 and in triathlons, EAMC ranges from 23% to 63%. 11,12,17,18 Our overall finding of 6.0% is much lower than these past reports, which is likely underestimated by the fact that we report on athletes who sought evaluation for EAMC, while previous studies rely on self-reported surveys. Many athletes likely experience muscle cramping, but do not seek medical attention. ...
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Objective This study aimed to explore associations and trends for athletes experiencing exercise-associated muscle cramps (EAMC) in ultraendurance competitions. Design Retrospective analysis of prospectively collected data. Setting Medical tent data were collected from annual IRONMAN World Championship events. Participants In total, 10 533 medical records were reviewed among 49 530 race participants from 1989 to 2019. Assessment of Risk Factors Athlete demographics data, performance data, and additional medical conditions were examined. Main Outcome Measures Primary outcome of interest was to compare triathletes with and without EAMC. Secondary outcome was to analyze triathletes with subsequent EAMC. Results EAMC (N = 2863) occurred in 57.8 per 1000 participants (95% confidence interval = 55.7 to 60.0). The incidence of EAMC did not differ between athlete sex. Athletes with EAMC had greater weight loss but did not differ in serum sodium and serum potassium compared with those without EAMC. Further analysis with a logistic regression analysis revealed that dehydration, exhaustion, hypotension, abdominal pain, headaches, and a previous evaluation for cramping were strongly associated with muscle cramping. The most common treatment for EAMC was intravenous fluids. Conclusions Findings from the current study support previous reports that electrolyte abnormalities are not associated with cramping. However, our finding that dehydration is associated with muscle cramping contradicts current literature.
... For example, cramps have affected 14.3% of the participants during an ultramarathon 6 . Also, 67% of triathletes experienced cramp during or after training or racing 7 .Furthermore, the lifetime prevalence of skeletal muscle cramping in marathon runners has been reported to be as high as body mass. Cramps in the m. ...
... The dehydration theory has also been discussed in studies with triathletes. 7,24,26 The body weight in these studies was measured before and after the race. The crampers did not experience a greater body mass loss than the control athletes suggesting that there is no correlation between dehydration and the probability of cramping. ...
... Just the fluid and salt loss does not cause EAMC and therefore it is important to notice that muscle fatigue needs to be present for heat-related EAMC to occur. This is evidenced by the fact that cramps occur most of the time not at the beginning of exercise but more towards the end 7,8,22 . Moreover, the prevention method of being well hydrated and ingesting enough electrolytes only has effect up to a certain level of muscle fatigue. ...
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The occurrence of exercise associated muscle cramps can be detrimental for exercise performance and there is controversy about its relation to exercise in the heat. The purpose of this study is therefore to review the influence of exercising in the heat on the occurrence of cramps. There are three main theories for the development of cramps during exercise: dehydration, electrolyte depletion and altered neuromuscular control. Muscle cramps can be divided into two categories: fatigue-induced and heat-related. Fatigue-induced cramps can be explained by solely muscle fatigue which causes reduced neuromuscular control. Heat-related cramps are a result of muscle fatigue combined with fluid and electrolyte loss due to sweating. Heat results in more muscle fatigue and therefore an altered neuromuscular control. Moreover, heat will result in a higher sweat rate and sweat sodium concentration. Taken together, these heat-associated adaptations are likely to influence the occurrence of both fatigue-induced and heat-related muscle cramps.
... Exercise-associated muscle cramps often last from 1 to 3 minutes and generally occur in multijoint muscle groups when contracting in a shortened position (e.g., quadriceps, hamstrings, triceps surae). [4][5][6] The severity of EAMC can range from mild discomfort, with limited effects on physical performance, to extreme pain and debilitation. 7 EAMC are among the most common conditions that require medical intervention, either during or immediately upon completion of athletic events, representing up to two-thirds of complaints reported during endurance-related competitions. ...
... 7 EAMC are among the most common conditions that require medical intervention, either during or immediately upon completion of athletic events, representing up to two-thirds of complaints reported during endurance-related competitions. 5,8 In a 12-year summary report of marathon medical issues, cramping accounted for 6.1% of medical encounters, with 1.2 cases of EAMC per 1,000 participants. 9 Most recently, a prospective study of 26,354 ultramarathon runners revealed that 1 in every 526 race starters developed EAMC. 1 The 2 main theories behind EAMC, the dehydration and electrolyte imbalance theory and the altered neuromuscular control theory, have been reviewed elsewhere, and the strongest evidence supports a neuromuscular etiology. ...
... 6,20,26 The literature has consistently shown that shortened muscles that span 2 joints are more prone to cramping. [4][5][6] In view of this, stretching seems to be a plausible treatment. Although the precise mechanism is unclear, it has been suggested that passive stretching may increase tension in the GTO, resulting in increased afferent reflex inhibition to the alpha motor neuron. ...
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Although exercise-associated muscle cramps (EAMC) are highly prevalent among athletic populations, the etiology and most effective management strategies are still unclear. The aims of this narrative review are 3-fold: 1) Briefly summarize the evidence regarding EAMC etiology; 2) report the risk factors and possible physiological mechanisms associated with neuromuscular fatigue and EAMC; and 3) report the current evidence regarding prevention of, and treatment for, EAMC. Based upon the findings of several large prospective and experimental investigations, the available evidence indicates that EAMC is multifactorial in nature and stems from an imbalance between excitatory drive from muscle spindles and inhibitory drive from Golgi tendon organs (GTOs) to the alpha motor neurons rather than dehydration or electrolyte deficits. This imbalance is believed to stem from neuromuscular overload and fatigue. In concert with these findings, the most successful treatment of an acute bout of EAMC is stretching, while auspicious methods of prevention include efforts that delay exercise induced fatigue. This article is protected by copyright. All rights reserved.
... Indeed, in a study following 12 years of the Twin Cities Marathon, Roberts [3] reported an incidence of EAMC of 1.2 cases per 1000 racers, and EAMC represented 6.1% of medical encounters. It represents 6% to 67% of complaints in endurance exercises (triathlon or marathon) [3][4][5][6], and 30 to 50% in team sports [7][8][9]. EAMC leads to pain and musculo-skeletal dysfunction that could induce a decrease in performance [10] and could also lead to muscle damage. ...
... This has been hypothesised from case reports/series (LoE: 4) [48,49], case-control study in football players (LoE: 3) [37], and an expert opinion narrative review including data without clear explanation of their measurements (LoE: 5) [29]. Given the fact that EAMC often occurs during endurance or prolonged exercise [3][4][5][6], it has been suggested that EAMC could be due to the change/decrease in hydration and serum electrolyte status induced by exercise [22,24,28]. Moreover, exercise-induced electrolyte losses were reported in subjects who benefited rehydration with intravenous saline solution for severe muscle cramps, but without comparison to control group (LoE: 4) [8]. ...
... Moreover, it seems that larger exercise-induced sweat losses are adequately and physiologically tolerated by concomitant fluid and electrolyte compartments adjustments [55]. In addition, 4 well-design prospective studies [4][5][6]32] (LoE: 2) and a case-control study [38] (LoE: 3) in long-duration exercises (marathon and triathlon), and two humans laboratory-based studies [39,46] (LoE: 4), reported no relationships between EAMC occurrence and loss of serum electrolyte and/or dehydration status, and/or no clinically significant alterations in serum electrolyte concentrations and/or hydration status in subjects with EAMC. Braulick et al. [10], in a well-designed case-controlled study (LoE: 3), reported no changes in EAMC susceptibility when significant and serious hypohydration with moderate electrolyte losses were induced in subjects. ...
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Objective: To discuss the causes, prevention and treatment of exercise associated muscle cramps (EAMC) according to the level of evidence of the available literature, in order to present some evidence-based guidelines for athletes, coaches and health professionals. News: Since it appears fundamental for sports medicine physicians and sports health professionals to be able to manage and prevent EAMC, although pathophysiology and causes of EAMC are discussed, clear understanding of EAMC causes seems important in order to treat and prevent EAMC. Perspectives and projects: The present review evaluated the available literature on EAMC based on their level of evidence to present some evidence-based guidelines for sports professionals. Fifty articles were selected: 24 after full-text reading and 26 articles after screening selected articles references. Level of evidence was from 1 (n= 3), 2 (n= 8), 3 (n= 10), 4 (n= 13), and 5 (n= 16). Conclusions: The "Altered neuromuscular control theory" seems to be the most scientifically acceptable theory, and suggests that EAMC are caused by an imbalance between increased afferent activity (e.g. muscle spindle, Ia) and decreased inhibitory afferent activity (e.g. Golgi tendon organs, Ib) which leads to increased α-motor neuron activity and muscle cramping, especially with muscle contraction in a shortened position. EAMC prevention measures should take into account the preparation of muscle to exercise (adapted training) and the respect of muscle fatigue during exercise (warm-up before exercise, well-controlled effort and rest during exercise). EAMC treatments should be non-pharmacological and should play a role on neuromuscular control (rest and/or stretching).
... T he ironman triathlon is an ultraendurance event, which includes a 3.9-km swim, 180.2-km bicycle ride, and 42.2-km run. Among the more common medical problems experienced by athletes participating in such races are skeletal muscle cramps (4), accounting for between 6% and 20% of the medical diagnoses encountered at ironman triathlon events (3,5). Exercise-associated muscle cramping (EAMC) can be defined as a "painful spasmodic involuntary contraction of skeletal muscle that occurs during or immediately after exercise" (13). ...
... Exercise-associated muscle cramping (EAMC) can be defined as a "painful spasmodic involuntary contraction of skeletal muscle that occurs during or immediately after exercise" (13). Despite the high incidence of EAMC at these events, there has only been one published study of muscle cramping in triathletes (4), and no published studies have yet identified the cause of EAMC in triathletes. ...
... Thus, these results do not support the widely publicized hypothesis that EAMC is related to dehydration (2,8). Rather, the findings confirm the results of others showing that EAMC is not associated with dehydration in marathon runners (6,14) or in ironman triathletes (4). The results of the present study therefore add to the growing body of literature, which shows dissociation between dehydration and EAMC in athletes, irrespective of the type or duration of the activity. ...
Article
To compare serum electrolyte concentrations of cramping and control Ironman triathletes. Triathletes suffering from acute exercise-associated muscle cramping (EAMC) after the 2000 South African Ironman Triathlon formed the cramping group (CR, N = 11). Non-cramping triathletes matched for race finishing time and body mass formed the control group (CON, N = 9). All subjects were weighed at race start and immediately post-race. Blood samples were drawn from both groups during recovery for the analysis of serum magnesium, glucose, sodium, potassium and chloride concentrations. Hemoglobin concentration and hematocrit were also measured. Surface electromyography (EMG) (mV) was recorded from a non-cramping control muscle (triceps) and the most severely cramping lower limb muscle of the CR group. EMG was recorded at the beginning of every minute for a 10-min period during recovery. There were no significant differences between the groups for body mass or percent body mass loss during the race. Post-race sodium concentration was significantly lower (P = 0.01) in the CR group than the CON group (140 +/- 2 vs 143 +/- 3 mmol.L) but was within the normal clinical range of post-race serum sodium concentrations. There were no significant differences between the two groups for post-race serum electrolytes, glucose, hemoglobin concentrations or hematocrit. Surface EMG (mV) was significantly higher (P < 0.05) in the cramping muscles than the control muscle of the CR group at 0, 3, 4, and 5 min of the 10-min recording period. Acute EAMC in ironman triathletes is not associated with a greater percent body mass loss or clinically significant differences in serum electrolyte concentrations. The increased EMG activity of cramping muscles may reflect increased neuromuscular activity.
... While EAMC has been noted to frequently occur in competitive tennis players, its prevalence among this cohort has not been specifically defined in the available literature. Lifetime prevalence of EAMC has been better defined in several endurance sports including triathlons (67%) [8], marathon runners (30-50%) [2], and cyclists (60%) [2], as well as several team sports like American football (30-53%) [9,10] and rugby (52%) [2]. There is no clear evidence regarding the prevalence of cramping in tennis players; however, it is suspected to be fairly high given the propensity of an individual athlete exposed to repetitive bouts of competition on the same day. ...
... There have been several studies that show passive stretching of the affected musculature effectively alleviated EAMC in both humans and laboratory studies in actively cramping muscles and is recognized as the initial treatment of choice [16][17][18]. Despite the evidence that shows stretching is the treatment of choice during cramping, stretching has not been shown to have a preventative effect to reduce future chances of cramping with activity [8,19]. ...
Article
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Purpose of review: Better define the proposed etiologies, risk factors, and treatment plans for exercise-associated muscle cramps in the tennis player. Recent findings: While no one theory has been able to fully explain the etiology behind exercise-associated muscle cramping, further classification of acute localized cramping and systemic or recurrent cramping may help guide future treatment and prevention strategies. Neuromuscular fatigue more than electrolyte deficit or dehydration is believed to play a large role in development of exercise-associated muscle cramps. Despite inconclusive evidence at this time, electrolyte deficit may play more of a role in the development of recurrent or systemic muscle cramping in the tennis athlete. More research is needed to better define its conclusive etiology.
... 2,22,54,57 Finally, a correlation between body weight losses and EAMC has not been established in several groups of athletes. 32,52,57 The treatment for EAMC also fails to support the dehydration-electrolyte imbalance theory. If EAMC were due to dehydration, the simple cure would be fluid replacement. ...
... In humans, EAMC occurs more frequently at the end of competitions and physical work 32,38,41 and when the muscle contracts while it is already shortened. 51 Stretching, the primary treatment for acute EAMC, 56 is thought to relieve EAMC via autogenic inhibition. ...
Article
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Exercise-associated muscle cramps (EAMC) are a common condition experienced by recreational and competitive athletes. Despite their commonality and prevalence, their cause remains unknown. Theories for the cause of EAMC are primarily based on anecdotal and observational studies rather than sound experimental evidence. Without a clear cause, treatments and prevention strategies for EAMC are often unsuccessful. A search of Medline (EBSCO), SPORTDiscus, and Silverplatter (CINHAL) was undertaken for journal articles written in English between the years 1955 and 2008. Additional references were collected by a careful analysis of the citations of others' research and textbooks. Dehydration/electrolyte and neuromuscular causes are the most widely discussed theories for the cause of EAMC; however, strong experimental evidence for either theory is lacking. EAMC are likely due to several factors coalescing to cause EAMC. The variety of treatments and prevention strategies for EAMC are evidence of the uncertainty in their cause. Acute EAMC treatment should focus on moderate static stretching of the affected muscle followed by a proper medical history to determine any predisposing conditions that may have triggered the onset of EAMC. Based on physical findings, prevention programs should be implemented to include fluid and electrolyte balance strategies and/or neuromuscular training.
... 2,22,54,57 Finally, a correlation between body weight losses and EAMC has not been established in several groups of athletes. 32,52,57 The treatment for EAMC also fails to support the dehydration-electrolyte imbalance theory. If EAMC were due to dehydration, the simple cure would be fluid replacement. ...
... In humans, EAMC occurs more frequently at the end of competitions and physical work 32,38,41 and when the muscle contracts while it is already shortened. 51 Stretching, the primary treatment for acute EAMC, 56 is thought to relieve EAMC via autogenic inhibition. ...
... warning or apparent cause [7,8,9,10]. EAMC has been reported to occur frequently among triathletes, marathon runners, rugby players, and cyclists among others [4,11]. ...
Article
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Exercise-associated muscle cramps (EAMC) is prevalent among athletes during training or competitions where they are subjected to strenuous activities for a prolonged period. To manage this painful condition, health practitioners have used numerous treatment modalities having massage done with adjunct application such as cold compress or liniment. Studies show that it is debatable which combination of treatment modalities is more effective on people affected by EAMC. Hence, this study aimed to present evidence-based data to show if there is a difference in the effectiviteness of the two modalities in treating EAMC. A total of thirty-two (32) athletic participants were enrolled in this study and a total of 40 treatment trials were included in the analysis of data. Each participant performed strenuous exercises meant to induce muscle cramps. The onset of muscle cramps was identified using a set criteria. After which, treatment was applied and the length of time that the cramp was resolved was recorded. Determining relief from muscle cramps was based on the characteristic of muscle hardness and the level of pain by using a numerical rating scale. Results showed that though majority of the participants verbalized preference for the ice treatment, analysis of data using one-way ANOVA revealed that there is no evidence to prove that there is a difference in the effectivity among the treatment modalities performed. In conclusion, though all modalities performed were able to relieve the EAMC, the use of adjunct treatment in addition to massage and stretching may have a placebo effect component, which improves the patient's perception of greater efficacy.
... Several surveys have attempted to identify the prevalence of EAMC in different sports populations, but comparing results across studies is hampered by different definitions and different measurement periods, and also by the use of different assessment tools. Nonetheless, EAMC has been reported to affect 67% of triathletes during or after training or racing [2], 18-70% of marathoners or endurance cyclists [3][4][5], and 30-53% of American football players [6,7]. Although seemingly suggesting that cramp is common, these data are a mixture of incidence rates in single events and lifetime incidence. ...
Article
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Muscle cramp is a temporary but intense and painful involuntary contraction of skeletal muscle that can occur in many different situations. The causes of, and cures for, the cramps that occur during or soon after exercise remain uncertain, although there is evidence that some cases may be associated with disturbances of water and salt balance, while others appear to involve sustained abnormal spinal reflex activity secondary to fatigue of the affected muscles. Evidence in favour of a role for dyshydration comes largely from medical records obtained in large industrial settings, although it is supported by one large-scale intervention trial and by field trials involving small numbers of athletes. Cramp is notoriously unpredictable, making laboratory studies difficult, but experimental models involving electrical stimulation or intense voluntary contractions of small muscles held in a shortened position can induce cramp in many, although not all, individuals. These studies show that dehydration has no effect on the stimulation frequency required to initiate cramping and confirm a role for spinal pathways, but their relevance to the spontaneous cramps that occur during exercise is questionable. There is a long history of folk remedies for treatment or prevention of cramps; some may reduce the likelihood of some forms of cramping and reduce its intensity and duration, but none are consistently effective. It seems likely that there are different types of cramp that are initiated by different mechanisms; if this is the case, the search for a single strategy for prevention or treatment is unlikely to succeed.
... Moreover, other studies reported high prevalence of muscle cramping in elderly and in endurance athletes (Naylor and Young, 1994). Additionally, during endurance sports the incidence of muscle cramps seems associated with high intensity and long-lasting duration (Kantorowski et al., 1990). The 40% of the participants of the studies on muscle cramps, had cramp episodes more than three times per week, with an average duration of 9 min (Naylor and Young, 1994). ...
Article
Exercise-Associated Muscle Cramps (EAMC) are a common painful condition of muscle spasms. Despite scientists tried to understand the physiological mechanism that underlies these common phenomena, the etiology is still unclear. From 1900 to nowadays, the scientific world retracted several times the original hypothesis of heat cramps. However, recent literature seems to focus on two potential mechanisms: the dehydration or electrolyte depletion mechanism, and the neuromuscular mechanism. The aim of this review is to examine the recent literature, in terms of physiological mechanisms of EAMC. A comprehensive search was conducted on PubMed and Google Scholar. The following terminology was applied: muscle cramps, neuromuscular hypothesis (or thesis), dehydration hypothesis, Exercise-Associated muscle cramps, nocturnal cramps, muscle spasm, muscle fatigue. From the initial literature of 424 manuscripts, sixty-nine manuscripts were included, analyzed, compared and summarized. Literature analysis indicates that neuromuscular hypothesis may prevails over the initial hypothesis of the dehydration as the trigger event of muscle cramps. New evidence suggests that the action potentials during a muscle cramp are generated in the motoneuron soma, likely accompanied by an imbalance between the rising excitatory drive from the muscle spindles (Ia) and the decreasing inhibitory drive from the Golgi tendon organs. In conclusion, from the latest investigations there seem to be a spinal involvement rather than a peripheral excitation of the motoneurons.
... 1 They can hinder athletic performance and have been reported to affect 67% of triathletes and between 30% and 50% of marathon runners. 2 Investigations of EAMCs are difficult because the spontaneous nature of the muscular phenomenon is unknown and difficult to test in the field. To date, the most frequent method used to provoke EAMCs is electrically induced muscle cramps (EIMCs). ...
Article
Full-text available
Context: Exercise-associated muscle cramps are a common clinical problem for athletes. Objective: To determine whether acute passive static stretching altered cramp threshold frequency (CTF) of electrically induced muscle cramps. Design: Crossover study. Setting: Laboratory. Patients or other participants: Seventeen healthy college-aged individuals. Intervention(s): Stretching or no stretching. Main outcome measures: The independent variable was the static stretch versus the no-stretch condition, and the dependent variable was the CTF. Results: The CTF increased in both the control (pretest: 18.12 ± 6.46 Hz, posttest: 19.65 ± 7.25 Hz; P = .033) and stretching (pretest: 18.94 ± 5.96 Hz, posttest: 20.47 ± 7.12 Hz; P = .049) groups. No difference between the groups was found (t15 = 0.035, P = .97). Conclusions: Acute passive static stretching did not seem to increase the CTF.
... 1 They can hinder athletic performance and have been reported to affect 67% of triathletes and between 30% and 50% of marathon runners. 2 Investigations of EAMCs are difficult because the spontaneous nature of the muscular phenomenon is unknown and difficult to test in the field. To date, the most frequent method used to provoke EAMCs is electrically induced muscle cramps (EIMCs). ...
... S keletal muscle cramps are common among physically active individuals. [1][2][3][4] Cramps that occur as a result of physical activity have been termed exercise-associated muscle cramps (EAMCs) and defined as a ''painful, spasmodic contraction of the skeletal muscle that occurs during or immediately after muscular exercise.'' 5 Muscle cramps have affected 67% of triathletes during or after training or racing 1 and 18% to 70% of marathoners or endurance cyclists, most often in the plantar-flexor muscle group. ...
... S keletal muscle cramps are common among physically active individuals. [1][2][3][4] Cramps that occur as a result of physical activity have been termed exercise-associated muscle cramps (EAMCs) and defined as a ''painful, spasmodic contraction of the skeletal muscle that occurs during or immediately after muscular exercise.'' 5 Muscle cramps have affected 67% of triathletes during or after training or racing 1 and 18% to 70% of marathoners or endurance cyclists, most often in the plantar-flexor muscle group. ...
Article
Full-text available
Exercise-associated muscle cramps (EAMCs) are common among physically active individuals and are temporarily disabling; therefore, prevention is of great interest. Objective: To determine the role of hydration and electrolyte supplementation in the prevention of EAMCs. Design: Each subject completed 2 counterbalanced trials in a repeated-measures design. Setting: University of Alabama. Patients or Other Participants: College-aged men (n 5 13) with a history of EAMCs. Intervention(s): In each trial, participants performed a calffatiguing protocol to induce EAMCs in the calf muscle group. Each trial was performed in a hot environment (dry bulb temperature of 378C, relative humidity of 60%). In the carbohydrateelectrolyte trial, subjects consumed, at a rate similar to sweat loss, a carbohydrate-electrolyte beverage with sodium chloride added. In the hypohydration trial, subjects were not allowed to consume any fluids. Main Outcome Measure(s): We measured the incidence and time to onset of EAMCs. Results: Nine participants experienced cramps in the carbohydrate-electrolyte trial, compared with 7 in the hypohydration trial. Of the 7 individuals who had EAMCs in both trials, exercise duration before onset was more than doubled in the carbohydrate-electrolyte trial (36.8 6 17.3 minutes) compared with the hypohydration trial (14.6 6 5.0 minutes, P , .01). Conclusions: Consumption of a carbohydrate-electrolyte beverage before and during exercise in a hot environment may delay the onset of EAMCs, thereby allowing participants to exercise longer. However, it appears that dehydration and electrolyte loss are not the sole causes of EAMCs, because 69% of the subjects experienced EAMCs when they were hydrated and supplemented with electrolytes. Key Words: hypohydration, heat stress, fatigue, environmental physiology, cramping protocol
... The change in the mechanical properties of collagen fibrils may also affect exercise-associated muscle cramping. In humans, exercise-associated muscle cramping occurs more frequently at the end of competitions and physical work [30][31][32] and when the muscle contracts while it is already shortened. The neuromuscular theory of exercise-associated muscle cramping proposes that muscle overload and neuromuscular fatigue cause an imbalance between excitatory impulses from muscle spindles and inhibitory impulses from Golgi tendon organs. ...
Article
AIM: The aim of this study was to investigate whether COL5A1 rs12722 polymorphism is associated with musculoskeletal injuries in elite soccer players. METHODS: Fifty--four male professional soccer players of European origin (25.9±4.3 years) were recruited from a team participating at the Official Italian Professional Championship during four consecutive seasons (2009-2013). The incidence and severity of musculoskeletal injuries and its relationship to COL5A1 rs12722 polymorphism were analyzed. DNA was extracted from buccal swab. The cohort was genotyped for the COL5A1 rs12722 single nucleotide polymorphism (SNP) through PCR and enzyme digestion with BstUI, and musculoskeletal injuries data were collected during the four seasons. Injuries were categorized under 5 degrees of severity based on the number of days' absence, while musculoskeletal injuries incidence was calculated per 1,000 hours of exposure to training and matches ((Σ injuries/Σ exposure hours) x 1,000). RESULTS: No significant differences were found among genotypes for incidence of musculoskeletal injuries (P=0.683). Participants with TT genotype (3.71±0.5, n=4) showed a trend (P=0.193) versus an higher severity of injuries than individuals with TC (2.98±0.8, n=10) or CC (2.75±0.95, n=4) genotypes. The COL5A1 rs12722 accounted for 44% of severity of injuries (P=0.002). CONCLUSION: In conclusion, the COL5A1 rs12722 was found to be associated with severity of musculoskeletal injuries but not with incidence of musculoskeletal injuries in top--level soccer players.
... S keletal muscle cramps are common among physically active individuals. [1][2][3][4] Cramps that occur as a result of physical activity have been termed exercise-associated muscle cramps (EAMCs) and defined as a ''painful, spasmodic contraction of the skeletal muscle that occurs during or immediately after muscular exercise.'' 5 Muscle cramps have affected 67% of triathletes during or after training or racing 1 and 18% to 70% of marathoners or endurance cyclists, most often in the plantar-flexor muscle group. ...
... Exercise-associated muscle cramping (EAMC) is defined as "painful, spasmodic and involuntary contraction of skeletal muscle that occurs during or immediately after exercise." 1 It is a common medical condition among participants of endurance events such as ultra-marathons and triathlons. Exercise-associated muscle cramping has a reported lifetime prevalence of 26%, 30% to 50%, and 67% in physical education students, 2 marathon runners, 3 and triathletes, 4 respectively. Despite its high prevalence, the etiology of EAMC remains unknown. ...
Article
Full-text available
Objective: The authors hypothesized that variants within genes, such as COL5A1, COL3A1, COL6A1, and COL12A1, that code for connective tissue components of the musculoskeletal system may modulate susceptibility to exercise-associated muscle cramping (EAMC). Specifically, the aim of this study was to investigate if the COL5A1 rs12722 (C/T), COL3A1 rs1800255 (G/A), COL6A1 rs35796750 (T/C), and COL12A1 rs970547 (A/G) polymorphisms are associated with a history of EAMC. Design: Retrospective genetic case-control association study. Setting: Participants were recruited at triathlon and ultra-marathon events and were asked to report physical activity, medical history, and cramping history. Participants: One hundred sixteen participants with self-reported history of EAMC within the past 12 months before an ultra-endurance event were included as cases in this study (EAMC group). One hundred fifty participants with no self-reported history of previous (lifelong) EAMC were included as controls (NON group). Interventions: All participants were genotyped for the selected variants. Main outcome measures: Differences in genotype frequency distributions, for COL5A1 rs12722, COL3A1 rs1800255, COL6A1 rs35796750, and COL12A1 rs970547, among the cases and controls. Results: The COL5A1 CC genotype was significantly overrepresented (P = 0.031) among the NON group (21.8%) when compared with the EAMC group (11.1%). No significant genotype differences were found for the COL3A1 (P = 0.828), COL6A1 (P = 0.300), or COL12A1 (P = 0.120) genotypes between the EAMC and NON groups. Conclusions: This study identified, for the first time, the COL5A1 gene as a potential marker for a history of EAMC.
... A critical analysis of: (i) factors associated with EAMC that have been identified from epidemiologic studies, (ii) observations from animal experimentation on spinal reflex activity during muscle fatigue, and (iii) recent EMG data obtained during EAMC (Sulzer et al. 2005) have led to the development of a novel hypothesis for the etiology of EAMC . muscle cramping in marathon runners and triathletes has been reported to be as high as 30-50% and 67%, respectively (Kantorowski et al. 1990). The etiology, diagnosis, and management of this condition are not well understood. ...
Article
Skeletal muscle physiology with relevance to muscle damage and repairDelayed onset muscle sorenessExercise-associated muscle crampingEtiology of chronic exercise-associated fatigue and underperformanceMetabolic myopathiesExertional rhabdomyolysisClinical investigation of the athlete with muscle symptomatologyReferences
... In a study of sport academy students, researchers reported the prevalence of cramp to be 95% (Norris, Gasteiger, & Chatfield, 1957). In addition, it has been reported that 30-50% of marathon runners and 67% of triathletes report skeletal muscle cramp (Kantarowski, Hiller, & Garrett, 1990). Despite the prevalence of exercise-associated muscle cramp, relatively little is known about its aetiology. ...
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Though clinical observations and laboratory data provide some support for the neuromuscular imbalance theory of the genesis of exercise-associated muscle cramps, no direct evidence has been published. The purpose of this study was to determine the effect of local muscle fatigue on the threshold frequency of an electrically induced muscle cramp. To determine baseline threshold frequency, a cramp was electrically induced in the flexor hallucis brevis of 16 apparently healthy participants (7 males, 9 females; age 25.1 +/- 4.8 years). The testing order of control and fatigue conditions was counterbalanced. In the control condition, participants rested in a supine position for 30 min followed by another cramp induction to determine post-threshold frequency. In the fatigue condition, participants performed five bouts of great toe curls at 60% one-repetition maximum to failure with 1 min rest between bouts followed immediately by a post-threshold frequency measurement. Repeated-measures analysis of variance and simple main effects testing showed post-fatigue threshold frequency (32.9 +/- 11.7 Hz) was greater (P < 0.001) than pre-fatigue threshold frequency (20.0 +/- 7.7 Hz). An increase in threshold frequency seems to demonstrate a decrease in one's propensity to cramp following the fatigue exercise regimen used. These results contradict the proposed theory that suggests cramp propensity should increase following fatigue. However, differences in laboratory versus clinical fatiguing exercise and contributions from other sources, as well as the notion of a graded response to fatiguing exercise, on exercise-associated muscle cramp and electrically induced muscle cramp should be considered.
... [ case report ] E xercise-associated muscle cramping (EAMC) is a common problem amongst triathletes 10,33 and marathon runners. 18 Triathletes experience a lifetime prevalence of muscle cramping of 67%, 12 and marathon runners one of 30% to 50%. 18 The literature reports that muscles crossing 2 joints (ie, hamstrings) are more prone to EAMC than muscles that cross 1 joint. ...
Article
Case report. To highlight the effects of an intervention program consisting of strengthening and neuromuscular reeducation of the gluteus maximus in an elite triathlete with exercise-associated muscle cramping (EAMC). Researchers have described 2 theories concerning the etiology of EAMC: (1) muscle fatigue and (2) electrolyte deficit. As such, interventions for EAMC typically consist of stretching/strengthening of the involved muscle and/or supplements to restore electrolyte imbalances. The patient was a 42-year-old male triathlete with a primary complaint of recurrent cramping of his right hamstring muscle, which prevented him from completing races at his desired pace. Strength testing revealed gluteus maximus muscle weakness bilaterally. Electromyographic (EMG) analysis (surface electrodes, 1560 Hz) revealed that the right hamstrings were being activated excessively during terminal swing and the first half of the stance phase (48.1% maximum voluntary isometric contraction [MVIC]). Following the intervention, the patient was able to complete 3 triathlons without hamstring cramping. Strength testing revealed that the right hip extension strength improved from 35.6 to 54.7 kg, and activation of the hamstrings during terminal swing and the first half of the stance phase decreased to 36.4% of MVIC. A program of gluteus maximus strengthening and neuromuscular training eliminated EAMC of the hamstrings in this patient. Given that the hamstrings and gluteus maximus work as agonists to decelerate the thigh during terminal swing phase and control hip flexion during loading response of running, we postulate that strengthening of the gluteus maximus decreased the relative effort required by the hamstrings, thus reducing EAMC. The results of the EMG evaluation that was performed as part of this case report provides support for this hypothesis. Therapy, level 4.
... S keletal muscle cramps are common among physically active individuals. [1][2][3][4] Cramps that occur as a result of physical activity have been termed exercise-associated muscle cramps (EAMCs) and defined as a ''painful, spasmodic contraction of the skeletal muscle that occurs during or immediately after muscular exercise.'' 5 Muscle cramps have affected 67% of triathletes during or after training or racing 1 and 18% to 70% of marathoners or endurance cyclists, most often in the plantar-flexor muscle group. ...
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Context: Exercise-associated muscle cramps (EAMCs) are common among physically active individuals and are temporarily disabling; therefore, prevention is of great interest.Objective: To determine the role of hydration and electrolyte supplementation in the prevention of EAMCs.Design: Each subject completed 2 counterbalanced trials in a repeated-measures design.Setting: University of Alabama.Patients or Other Participants: College-aged men (n = 13) with a history of EAMCs.Intervention(s): In each trial, participants performed a calf-fatiguing protocol to induce EAMCs in the calf muscle group. Each trial was performed in a hot environment (dry bulb temperature of 37 degrees C, relative humidity of 60%). In the carbohydrate-electrolyte trial, subjects consumed, at a rate similar to sweat loss, a carbohydrate-electrolyte beverage with sodium chloride added. In the hypohydration trial, subjects were not allowed to consume any fluids.Main Outcome Measure(s): We measured the incidence and time to onset of EAMCs.Results: Nine participants experienced cramps in the carbohydrate-electrolyte trial, compared with 7 in the hypohydration trial. Of the 7 individuals who had EAMCs in both trials, exercise duration before onset was more than doubled in the carbohydrate-electrolyte trial (36.8 +/- 17.3 minutes) compared with the hypohydration trial (14.6 +/- 5.0 minutes, P < .01).Conclusions: Consumption of a carbohydrate-electrolyte beverage before and during exercise in a hot environment may delay the onset of EAMCs, thereby allowing participants to exercise longer. However, it appears that dehydration and electrolyte loss are not the sole causes of EAMCs, because 69% of the subjects experienced EAMCs when they were hydrated and supplemented with electrolytes.
... Cycling 60% [12] Marathon (42.2 km) 39% [26] Triathlon 67%–68% [38] [39] Author's personal copy ...
Article
Exercise associated muscle cramping (EAMC) is defined as a painful, spasmodic, and involuntary contraction of skeletal muscle that occurs during or immediately after exercise. There is a high lifetime prevalence of EAMC in athletes, specifically in endurance athletes. The most important risk factors for EAMC in athletes are a previous history of EAMC, and performing exercise at a higher relative exercise intensity or duration, when compared with normal training and participating in hot and humid environmental conditions. The diagnosis of EAMC is made clinically, and the most effective immediate management of EAMC is rest and passive stretching. The key to the prevention of EAMC is to reduce the risk of developing premature muscle fatigue.
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Fasciculations and cramps originate in the motor unit, a functional unit that includes the lower motor neuron and their innervated muscle fibres. Both are common complaints in outpatient practice. These symptoms can be secondary to neurological or medical pathology, presenting a broad differential diagnosis and a complex approach. Recent neurophysiological studies have increased the knowledge of their origin mainly in amyotrophic lateral sclerosis. The symptomatic management of fasciculations and cramps depends on their etiology and includes pharmacological and non-pharmacological treatments. This article aims to present an updated review of the most relevant aspects of physiopathology, clinical approach, and differential diagnosis of both phenomena.
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Exercise-associated muscle-cramping (EAMC) is a-common-condition, experienced by recreational and competitive-athletes, which can potentially-endanger their-health, as-well-as professional-career. This paper reports the-synopsis of a-conceptual-design, simulation, and analysis of a-massaging-device to-mitigate paraphysiologic-EAMC, in-the-calf-area. Document-analysis was utilized as one of the-study-instruments (including published-research on the-concepts of cramps and their-treatments; selected-relevant International-patents; the-use of anthropometric-data in product-design; prior-art on massaging-devices, and selected-devices, currently available at the-market, with their-respective-limitations). The-study applied fundamental-Engineering-principles of product design, and was-carried-out in-compliance with ISO7250: 1996 (Basic-human-body-measurements for technological-design). The-best-ranked-design (out of the 3 design-alternatives, made) was chosen, via Engineering-Design Weighted-Decision-Matrix, and confirmed by the 'Drop and Re-vote' (D & R) method. 2D-drawings, of the-best-design-alternative, were created by computer-aided-design (CAD) AutoCAD-software, while 50 th percentile, adult-male was selected, as a design-target. Relevant-leg and hand-dimensions (one-dimensional measurements), were obtained from published-anthropometric-data-tables. Simulation of Stress-Analysis/Single-Point Static-Analysis (to-detect and eliminate rigid-body-modes; and separate stresses across contact-surfaces) was done by Autodesk Inventor-Version: 2016 (Build 200138000, 138). Conceptual-design of the-massaging-device was optimized according-to results of simulations, calculations, and fundamental engineering-product design principles. The-study also revealed that the-patho-physiology, causing EAMC, is most-likely multi factorial and complex. Overall, the-results of this-concise-study are rather-positive, providing a-good starting-point for advanced-exploration on the-same. Further-improvements and trials, however, are necessary. The-study, hence, recommended: (i) Further-studies, to-optimize the-dimensions of the-device, to-accommodate different-shapes of calf-muscles; (ii) More-advanced-methods, such-as PuCC; AHP, and TRIZ should be considered in-selection of the-best-design-alternative; (iii) Comprehensive-materials-selection should be detailed via Ashby-charts; (iv) To-carry-out a-detail-design; (v) To-fabricate a-prototype; (vi) To-conduct additional-tests (e.g., FEA/FEM) and explorative-use-ability-trials, in-collaboration-with the-department of Medical-Engineering, School of Medicine, MU; and (vii) To-analyze the-marketing-aspect of the-final-device. The-device is potentially-beneficial to sports-health-care-providers, coaches, and athletes; moreover, it could be included into-First-Aid Sport-kit (subject-to satisfactory-trails).
Article
Exercise associated muscle cramp (EAMC) is common among athletes. However, no study has systematically investigated the effect of the amount of loss of fluid on EAMC. This study was designed to examine the relationship between the amount of decrease in body fluid through sweating and EAMC. A decrease in body fluid by 1%, 2%, and 3% of body mass were induced by sauna exposure on 3 different days, and the occurrence of EAMC was compared between the three conditions and a control (no sauna exposure) condition. Nine young men (age: 22.2 ± 1.4 yrs) who had experienced EAMC during and/or after exercise in the previous year volunteered for the study. A “cramp test”, in which the occurrence of EAMC during maximal voluntary muscle contraction of hamstrings at maximally shortened position for 15 s, was performed before and one hour after the body fluid reduction of 1%, 2%, and 3% of body mass. The cramp test was performed on 2 occasions separated by 3 hours without sauna exposure as the control condition. No EAMC occurred in the control and the 1% condition. Three subjects experienced EAMC in the 2%, and 6 in the 3% condition. These results suggest that body fluid loss of 2% body mass increases the likelihood of EAMC and loss of body fluid is a factor for EAMC.
Article
Objective: Many clinicians believe that exercise-associated muscle cramps (EAMC) occur because of dehydration. Experimental research supporting this theory is lacking. Mild hypohydration (3% body mass loss) does not alter threshold frequency (TF), a measure of cramp susceptibility, when fatigue and exercise intensity are controlled. No experimental research has examined TF following significant (3-5% body mass loss) or serious hypohydration (>5% body mass loss). Determine if significant or serious hypohydration, with moderate electrolyte losses, decreases TF. Design: A prepost experimental design was used. Dominant limb flexor hallucis brevis cramp TF, cramp electromyography (EMG) amplitude and cramp intensity were measured in 10 euhydrated, unacclimated men (age=24±4 years, height=184.2±4.8 cm, mass=84.8±11.4 kg). Subjects alternated exercising with their non-dominant limb or upper body on a cycle ergometer every 15 min at a moderate intensity until 5% body mass loss or volitional exhaustion (3.8±0.8 h; 39.1±1.5°C; humidity 18.4±3%). Cramp variables were reassessed posthypohydration. Results: Subjects were well hydrated at the study's onset (urine specific gravity=1.005±0.002). They lost 4.7±0.5% of their body mass (3.9±0.5 litres of fluid), 4.0±1.5 g of Na(+) and 0.6±0.1 g K(+) via exercise-induced sweating. Significant (n=5) or serious hypohydration (n=5) did not alter cramp TF (euhydrated=15±5 Hz, hypohydrated=13±6 Hz; F1,9=3.0, p=0.12), cramp intensity (euhydrated= 94.2±41%, hypohydrated=115.9±73%; F1,9=1.9, p=0.2) or cramp EMG amplitude (euhydrated=0.18±0.06 µV, hypohydrated= 0.18±0.09 µV; F1,9=0.1, p=0.79). Conclusions: Significant and serious hypohydration with moderate electrolyte losses does not alter cramp susceptibility when fatigue and exercise intensity are controlled. Neuromuscular control may be more important in the onset of muscle cramps than dehydration or electrolyte losses.
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Despite the high prevalence of exercise-associated muscle cramping (EAMC) in endurance athletes, the aetiology and risk factors for this condition are not fully understood. The aim of this prospective cohort study was to identify risk factors associated with EAMC in endurance triathletes. 210 triathletes competing in an Ironman triathlon were recruited. Prior to the race, subjects completed a detailed validated questionnaire and blood samples were taken for serum electrolytes. Immediately before the race, pre-race body weight was obtained. Body weight and blood samples for serum electrolyte concentrations were obtained immediately after the race. Clinical data on EAMC experienced during or immediately after the race were also collected. 43 triathletes reported EAMC (cramping group) and were compared with the 166 who did not report EAMC (non-cramping group). There were no significant differences between groups in any pre-race-post-race serum electrolyte concentrations and body weight changes. The development of EAMC was associated with faster predicted race times and faster actual race times, despite similarly matched preparation and performance histories in subjects from both groups. A regression analysis identified faster overall race time (and cycling time) and a history of cramping (in the last 10 races) as the only two independent risk factors for EAMC. The results from this study add to the evidence that dehydration and altered serum electrolyte balance are not causes for EAMC. Rather, endurance runners competing at a fast pace, which suggests that they exercise at a high intensity, are at risk for EAMC.
Article
Dehydration is hypothesized to cause exercise-associated muscle cramps. The theory states that dehydration contracts the interstitial space, thereby increasing the pressure on nerve terminals and cramps ensue. Research supporting this theory is often observational, and fatigue is rarely controlled. Inducing cramps with electrical stimulation minimizes many of the confounding factors associated with exercise-induced cramps (e.g., fatigue, metabolites). Thus, our goal was to minimize fatigue and determine whether hypohydration decreases the electrical stimuli required to elicit cramping (termed "threshold frequency"). Ten males cycled for 30-min bouts with their nondominant leg at 41°C and 15% relative humidity until they lost ~3% of their body mass (~2 h). Dominant leg flexor hallucis brevis muscle cramps were induced before and after hypohydration, and threshold frequency was recorded. Plasma osmolality (OSMp) characterized hydration status. Total sweat electrolytes (Na+, K+, Mg2+, and Ca2+) lost during exercise was calculated. Subjects repeated the protocol 1 wk later. Subjects were hypohydrated after exercise (preexercise OSMp = 282.5 T 1 mOsm·kg−¹ H2O, postexercise OSMp = 295.1 ± 1 mOsm·kg−¹ H2O, P < 0.001). Subjects lost 3.0% ± 0.1% of their body mass, 144.9 ± 9.8 mmol of Na+, 11.2 ± 0.4 mmol of K+, 3.3 ± 0.3 mmol of Mg2+, and 3.1 ± 0.1 mmol of Ca2+. Mild hypohydration with minimal neuromuscular fatigue did not affect threshold frequency (euhydrated = 23.7 ± 1.5 Hz, hypohydrated = 21.3 ± 1.4 Hz; F1,9 = 2.81, P = 0.12). Mild hypohydration with minimal neuromuscular fatigue does not seem to predispose individuals to cramping. Thus, cramps may be more associated with neuromuscular fatigue than dehydration/electrolyte losses. Health care professionals may have more success preventing exercise-associated muscle cramp by focusing on strategies that minimize neuromuscular fatigue rather than dehydration. However, the effect of greater fluid losses on cramp threshold frequency is unknown and merits further research.
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Cramps are painful, involuntary contractions of skeletal muscle that occur during or immediately after exercise and are common in endurance athletes. Although cramps can occur in many rare medical conditions, most athletes who have exercise-associated muscle cramping do not have congenital or acquired medical disorders. The cause of cramping is not well understood but may have to do with abnormal spinal control of motor neuron activity, particularly when a muscle contracts in a shortened position. Important risk factors include muscle fatigue and poor stretching habits. Treatment consists mainly of passive stretching, with supportive measures as needed. Special diagnostic studies and conditioning programs may be necessary for recurrent episodes.
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Anecdotal evidence suggests that ingesting small volumes of pickle juice relieves muscle cramps within 35 s of ingestion. No experimental evidence exists supporting the ingestion of pickle juice as a treatment for skeletal muscle cramps. On two different days (1 wk apart), muscle cramps were induced in the flexor hallucis brevis (FHB) of hypohydrated male subjects (approximately 3% body weight loss and plasma osmolality approximately 295 mOsm x kg(-1) H2O) via percutaneous tibial nerve stimulation. Thirty minutes later, a second FHB muscle cramp was induced and was followed immediately by the ingestion of 1 mL x kg(-1) body weight of deionized water or pickle juice (73.9 +/- 2.8 mL). Cramp duration and FHB EMG activity during the cramp were quantified, as well as the change in plasma constituents. Cramp duration (water = 151.9 +/- 12.9 s and pickle juice = 153.2 +/- 23.7 s) and FHB EMG activity (water = 60% +/- 6% and pickle juice = 68% +/- 9% of maximum voluntary isometric contraction EMG activity) were similar during the initial cramp induction without fluid ingestion (P > 0.05). During FHB muscle cramp induction combined with fluid ingestion, FHB EMG activity was again similar (water = 55% +/- 9% and pickle juice = 66% +/- 9% of maximum voluntary isometric contraction EMG activity, P > 0.05). However, cramp duration was 49.1 +/- 14.6 s shorter after pickle juice ingestion than water (84.6 +/- 18.5 vs 133.7 +/- 15.9 s, respectively, P < 0.05). The ingestion of water or pickle juice had little impact on plasma composition 5 min after ingestion. Pickle juice, and not deionized water, inhibits electrically induced muscle cramps in hypohydrated humans. This effect could not be explained by rapid restoration of body fluids or electrolytes. We suspect that the rapid inhibition of the electrically induced cramps reflects a neurally mediated reflex that originates in the oropharyngeal region and acts to inhibit the firing of alpha motor neurons of the cramping muscle.
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The aetiology of exercise-associated muscle cramps (EAMC), defined as 'painful, spasmodic, involuntary contractions of skeletal muscle during or immediately after physical exercise', has not been well investigated and is therefore not well understood. This review focuses on the physiological basis for skeletal muscle relaxation, a historical perspective and analysis of the commonly postulated causes of EAMC, and known facts about EAMC from recent clinical studies. Historically, the causes of EAMC have been proposed as (1) inherited abnormalities of substrate metabolism ('metabolic theory') (2) abnormalities of fluid balance ('dehydration theory'), (3) abnormalities of serum electrolyte concentrations ('electrolyte theory') and (4) extreme environmental conditions of heat or cold ('environmental theory'). Detailed analyses of the available scientific literature including data from recent studies do not support these hypothesis for the causes of EAMC. In a recent study, electromyographic (EMG) data obtained from runners during EAMC revealed that baseline activity is increased (between spasms of cramping) and that a reduction in the baseline EMG activity correlates well with clinical recovery. Furthermore, during acute EAMC the EMG activity is high, and passive stretching is effective in reducing EMG activity. This relieves the cramp probably by invoking the inverse stretch reflex. In two animal studies, abnormal reflex activity of the muscle spindle (increased activity) and the Golgi tendon organ (decreased activity) has been observed in fatigued muscle. We hypothesize that EAMC is caused by sustained abnormal spinal reflex activity which appears to be secondary to muscle fatigue. Local muscle fatigue is therefore responsible for increased muscle spindle afferent and decreased Golgi tendon organ afferent activity. Muscles which cross two joints can more easily be placed in shortened positions during exercise and would therefore decrease the Golgi tendon organ afferent activity. In addition, sustained abnormal reflex activity would explain increased baseline EMG activity between acute bouts of cramping. Finally, passive stretching invokes afferent activity from the Golgi tendon organ, thereby relieving the cramp and decreasing EMG activity.
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To determine whether acute exercise associated muscle cramping (EAMC) in distance runners is related to changes in serum electrolyte concentrations and hydration status. A cohort of 72 runners participating in an ultra-distance road race was followed up for the development of EAMC. All subjects were weighed before and immediately after the race. Blood samples were taken before the race, immediately after the race, and 60 minutes after the race. Blood samples were analysed for glucose, protein, sodium, potassium, calcium, and magnesium concentrations, as well as serum osmolality, haemoglobin, and packed cell volume. Runners who suffered from acute EAMC during the race formed the cramp group (cramp, n = 21), while runners with no history of EAMC during the race formed the control group (control, n = 22). There were no significant differences between the two groups for pre-race or post-race body weight, per cent change in body weight, blood volume, plasma volume, or red cell volume. The immediate post-race serum sodium concentration was significantly lower (p = 0.004) in the cramp group (mean (SD), 139.8 (3.1) mmol/l) than in the control group (142.3 (2.1) mmol/l). The immediate post-race serum magnesium concentration was significantly higher (p = 0.03) in the cramp group (0.73 (0.06) mmol/l) than in the control group (0.67 (0.08) mmol/l). There are no clinically significant alterations in serum electrolyte concentrations and there is no alteration in hydration status in runners with EAMC participating in an ultra-distance race.
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