Exercise-associated Muscle Cramping Research Articles

Sex, training variables, history of chronic disease, and chronic injury are risk factors associated with a history of exercise-associated muscle cramping in 10,973 ultramarathon race entrants: a safer XXXVIII study.

The prevalence of a history of exercise-associated muscle cramping (hEAMC) among ultramarathon runners is high. While the Comrades is one of the most popular mass community-based participation ultramarathons (90 km) globally, research on the epidemiology, clinical characteristics, and risk factors of entrants' lifetime hEAMC are scarce. This research aimed to describe the epidemiology, clinical characteristics, and risk factors of hEAMC among Comrades Marathon entrants. This was a retrospective, cross-sectional study in which 10973 race entrants of the 2022 Comrades Marathon participated. Entrants completed a prerace medical screening questionnaire that included questions related to the lifetime prevalence (%; 95% CI), severity, treatment and risk factors (demographics, training/racing variables, chronic disease/allergies, injury) for EAMC. One thousand five hundred eighty-two entrants reported hEAMC in their lifetime (14.4%; 95% CI: 13.77-15.09). There was a significantly (P<0.01) higher prevalence of male (16.10%; 95% CI:15.34-16.90) than female (8.31%; 95% CI: 7.27-9.50) entrants with hEAMC (PR=1.94; 95% CI:1.68-2.23). The prevalence of hEAMC was highest in entrants with a: 1) 1 disease increase in composite disease score (PR=1.31; 95% CI:1.25-1.39); 2) history of collapse (PR=1.87; 95% CI 1.47-2.38); 3) past chronic musculoskeletal (MSK) injury (PR=1.71; 95% CI 1.50-1.94); and 4) MSK injury in the previous 12 months (PR=2.38;95% CI: 2.05-2.77). Training-related risk factors included an increase of 10 km weekly running distance (PR=0.97; 95% CI:0.95-0.99) and a training pace increase of 1min/ km (slower) (PR=1.07; 95% CI:1.03-1.12). Future research should investigate the causal relationship between risk factors identified and hEAMC in ultramarathon runners. Findings from this study could assist in effective anticipation and adequate planning for treating EAMC encounters during community-based mass participation events.

Does Prophylactic Stretching Reduce the Occurrence of Exercise-Associated Muscle Cramping? A Critically Appraised Topic.

Exercise-associated muscle cramps (EAMC) are sudden, painful, and involuntary contractions of skeletal muscles during or after physical activity. The best treatment for EAMC is gentle static stretching until abatement. Stretching is theorized to relieve EAMC by normalizing alpha motor neuron control, specifically by increasing Golgi tendon organ activity, and physically separating contractile proteins. However, it is unclear if stretching or flexibility training prevents EAMC via the same mechanisms. Despite this, many clinicians believe prophylactic stretching prevents EAMC occurrence. Do athletes who experience EAMC during athletic activities perform less prophylactic stretching or flexibility training than athletes who do not develop EAMC during competitions? In 3 cohort studies and 1 case-control study, greater preevent muscle flexibility, stretching, or flexibility training (ie,duration, frequency) was not predictive of who developed EAMC during competition. In one study, athletes who developed EAMC actually stretched more often and 9 times longer (9.8 [23.8]min/wk) than noncrampers (1.1 [2.5]min/wk). There is minimal evidence that the frequency or duration of prophylactic stretching or flexibility training predicts which athletes developed EAMC during competition. To more effectively prevent EAMC, clinicians should identify athletes' unique intrinsic and extrinsic risk factors and target those risk factors with interventions. Minimal evidence from 3 prospective cohort studies and 1 case-control study (mostly level 3 studies) that suggests prophylactic stretching or flexibility training can predict which athletes develop EAMC during athletic competitions.

Males, Older Age, Increased Training, Chronic Diseases, Allergies, and History of Injury Are Independent Risk Factors Associated With a History of Exercise-Associated Muscle Cramping in Distance Runners in 76 654 Race Entrants - SAFER XXIX.

To determine independent risk factors associated with a history of exercise-associated muscle cramps (hEAMCs) in distance runner race entrants in a community-based mass participation event. Cross-sectional study. 2012 to 2015, Two Oceans marathon races (21.1 and 56 km), South Africa. Seventy six thousand six hundred fifty-four consenting race entrants. Entrants completed an online prerace medical screening questionnaire as part of the entry process. In a multiple model, sex, age, training variables, history of chronic disease, allergies, and running injuries were included as potential factors associated with hEAMC in 21.1 and 56 km entrants. Prevalence (%) and prevalence ratios (PRs, 95% confidence intervals) are reported. Men ( P < 0.0001) and older age (>40 years, P < 0.0001) were significantly associated with hEAMC. Therefore, the model was adjusted for sex and age group and run separately for 21.1- and 56-km entrants. Specific independent risk factors associated with hEAMC in 21.1- and 56-km entrants were: a history of chronic diseases (21.1 km: PR = 1.9; 56 km: PR = 1.6; P < 0.0001), running injury in the last 12 months (21.1 km: PR = 1.7; 56 km: PR = 1.4; P < 0.0001), history of allergies (21.1 km: PR = 1.4; 56 km: PR = 1.2; P < 0.0001), and various training variables (PR = 1.0-1.1). In 21.1- and 56-km race entrants, independent risk factors associated with hEAMC were men, older age, longer race distances, training variables, chronic diseases, history of allergies, and history of a running injury in the past 12 months.

Prevalence, Clinical Characteristics, and Self-Reported Treatment of Exercise-Associated Muscle Cramping Differ Between 21.1- and 56-Km Running Race Entrants-SAFER XXII.

To determine whether the lifetime prevalence and clinical characteristics of exercise-associated muscle cramping (EAMC) differ between runners entering a 21.1- versus 56-km road race. Cross-sectional study. The 2012 to 2015 Two Oceans Marathon races (21.1 and 56 km), South Africa. Participants were consenting race entrants (21.1 km = 44 458; 56 km = 26 962) who completed an online prerace medical screening questionnaire. A history of EAMC. The main outcome variables were lifetime prevalence (%) and clinical characteristics (muscle groups affected, timing of occurrence, severity, frequency of serious EAMC, and self-reported treatment) of a history of EAMC. Differences between 56- and 21.1-km race entrants were explored (relative risk [RR]). The lifetime prevalence of EAMC was 12.8%, which was higher in 56- (20.0%; 95% CI 19.5-20.6) versus 21.1-km race entrants (8.5%; 8.2-8.8) ( P = 0.0001). In all entrants, the fourth quarter was the most common onset (46.4%), calf muscles were the most commonly affected (53.1%), and most EAMCs were of mild-to-moderate severity (95%). In 56- versus 21.1-km entrants, hamstring (RR = 1.7; 1.5-1.9) and quadriceps muscle groups (RR = 1.5; 1.3-1.7) were more frequently affected ( P = 0.0001), the onset of EAMC during racing was less common in the first quarter (RR = 0.3; 0.2-0.4) ( P = 0.0001), and serious EAMC was more frequent (RR = 1.6; 1.4-1.9) ( P = 0.0001). In 56- versus 21.1-km runners, a history of EAMC is 2 times more frequent and muscle groups affected, onset in a race, and severity of EAMC differed. The lifetime prevalence was lower than previously reported in other events. Risk factors associated with EAMC may differ between entrants for different race distances.

Medical Encounters in a 90-km Ultramarathon Running Event: A 6-year Study in 103 131 Race Starters-SAFER XVII.

To determine the incidence and nature of illness-related medical encounters (MEs) at a 90-km, ultramarathon, mass, community-based, endurance running event. Retrospective, descriptive epidemiological study. Comrades Marathon (90 km), South Africa. One lakh three thousand one hundred thirty-one race starters over 6 years (2014-2019). Incidence of moderate and serious/life-threatening MEs. All MEs were recorded by race medical doctors on race day each year. Medical encounters were recorded by severity, organ system, and final specific diagnosis (2019 consensus statement definition on mass community-based events). Incidences (I: per 1000 starters; 95% confidence intervals) were calculated for MEs. There were 1971 illness-related MEs, with an overall incidence of 19.1 (range, 18.3-20.0). The incidence for serious/life-threatening MEs was 1.8 (range, 1.6-2.1). Incidences of MEs by organ systems affected were as follows: fluid/electrolyte (8.8; 8.3-9.4), central nervous system (4.0; 3.7-4.5), and gastrointestinal system (2.9; 2.6-3.2). Dehydration (I = 7.5: 7.0-8.1) and exercise-associated muscle cramping (I = 3.2: 2.9-3.6) were the 2 most common specific diagnoses. The incidence of MEs in the 90-km Comrades Marathon was one of the highest incidences of MEs reported in an endurance running event (1 in 52 starters and 1 in 556 starters for serious/life-threatening MEs). Preventative measures to reduce MEs are needed, and further investigations into the risk factors associated with MEs could assist in managing the risk and better prepare athletes, race organizers, and medical directors.

Potential nutrition contributions to exercise-associated muscle cramping in four recreational half-marathoners: A case series

Objectives: Nutrition-related practices and outcomes vary dramatically between athletes, and traditional beliefs regarding the role of electrolytes and hydration in exercise-associated muscle cramping (EAMC) may be hindering meaningful prevention strategies. The aim of this study was to characterize the role of carbohydrate (CHO), energy, and exertion level, in conjunction with electrolyte and hydration status to assess the role of these possible predictors of EAMC.&#x0D; Methods: A case study series approach was used to capture pre-race and on-course food and beverage intake, pre and post-race body weight, relative perceived exertion (RPE), and history of EAMC for four recreational runners prior to and during a half-marathon race.&#x0D; Results: CHO intake, energy intake, and hydration status varied among the runners with one occurrence of EAMC. Reported pre-race CHO intake for all but one runner fell below 5 g/kg/day. Weight loss during the race was between 1.23-3.03%. Two of the four runners reported a prior history of EAMC, one of which experienced EAMC during the race. The two runners with a prior history of EAMC, also reported the lowest 3-day energy and CHO intakes. The one runner who encountered an EAMC did not experience the greatest net race sodium loss. However, this runner did have the greatest race weight loss, the greatest race sweat loss, the longest duration of activity, the lowest RPE, and suboptimal energy and CHO intakes.&#x0D; Conclusions: The observed case of EAMC does not appear to be entirely inconsistent with the traditional dehydration/ electrolyte loss theory. However, the in-depth characterization of each runner illustrates the complex interaction of potential predictors and also generates questions regarding the potential contribution of suboptimal energy and CHO intakes.

Exercise Associated Muscle Cramping in Recreational Half-marathoners: A Case Series

Exercise Associated Muscle Cramping in Recreational Half-marathoners: A Case Series

Exercise-Associated Muscle Cramps in the Tennis Player

Better define the proposed etiologies, risk factors, and treatment plans for exercise-associated muscle cramps in the tennis player. 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.

Sweat Characteristics in Individuals With Varying Susceptibilities of Exercise-Associated Muscle Cramps.

Szymanski, M, Miller, KC, O'Connor, P, Hildebrandt, L, and Umberger, L. Sweat characteristics in individuals with varying susceptibilities of exercise-associated muscle cramps. J Strength Cond Res 36(5): 1171-1176, 2022-Many medical professionals believe dehydration and electrolyte losses cause exercise-associated muscle cramping (EAMC). Unlike prior field studies, we compared sweat characteristics in crampers and noncrampers but accounted for numerous factors that affect sweat characteristics including initial hydration status, diet and fluid intake, exercise conditions, and environmental conditions. Sixteen women and 14 men (mean ± SD; age = 21 ± 2 year, body mass = 69.1 ± 11.6 kg, height = 171.4 ± 9.9 cm) self-reported either no EAMC history (n = 8), low EAMC history (n = 10), or high EAMC history (n = 12). We measured V̇o2max, and subjects recorded their diet. At least 3 days later, subjects ran at 70% of their V̇o2max for 30 minutes in the heat (39.9 ± 0.6° C, 36 ± 2% relative humidity). Dorsal forearm sweat was collected and analyzed for sweat sodium concentration ([Na+]sw), sweat potassium concentration ([K+]sw), and sweat chloride concentration ([Cl-]sw). Sweat rate (SWR) was estimated from body mass and normalized using body surface area (BSA). Dietary fluid, Na+, and K+ ingestion was estimated from a 3-day diet log. We observed no differences for any variable among the original 3 groups (p = 0.05-p = 0.73). Thus, we combined the high and low cramp groups and reanalyzed the data against the noncramping group. Again, there were no differences for [Na+]sw (p = 0.68), [K+]sw (p = 0.86), [Cl-]sw, (p = 0.69), SWR/BSA (p = 0.11), dietary Na+ (p = 0.14), dietary K+ (p = 0.66), and fluid intake (p = 0.28). Fluid and electrolyte losses may play a more minor role in EAMC genesis than previously thought.

Conceptual Design of a Massaging Device to Mitigate Exercise Associated Calf Muscle Cramps

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 &amp; 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). Keywords: EAMC, spasm, athlete, sports, theories. DOI : 10.7176/ISDE/10-2-01

Novel Factors Associated With Analgesic and Anti-inflammatory Medication Use in Distance Runners: Pre-race Screening Among 76 654 Race Entrants-SAFER Study VI.

Analgesic/anti-inflammatory medication (AAIM) increases the risk of medical complications during endurance races. We determined how many runners use AAIM before or during races, AAIM types, and factors associated with AAIM use. Cross-sectional study. 21.1-km and 56-km races. Seventy-six thousand six hundred fifty-four race entrants. Participants completed pre-race medical screening questions on AAIM use, running injury or exercise-associated muscle cramping (EAMC) history, and general medical history. Analgesic/anti-inflammatory medication use, types of AAIM (% runners; 95% confidence interval), and factors associated with AAIM use (sex, age, race distance, history of running injury or EAMC, and history of chronic diseases) [prevalence ratio (PR)]. Overall, 12.2% (12.0-12.5) runners used AAIM 1 week before and/or during races (56 km = 18.6%; 18.0-19.1, 21.1 km = 8.3%; 8.1-8.6) (P < 0.0001). During races, nonsteroidal anti-inflammatory drugs (NSAIDs) (5.3%; 5.1-5.5) and paracetamol (2.6%; 2.4-2.7) were used mostly. Independent factors (adjusted PR for sex, age, and race distance; P < 0.0001) associated with AAIM use were running injury (2.7; 2.6-2.9), EAMC (2.0; 1.9-2.1), cardiovascular disease (CVD) symptoms (2.1; 1.8-2.4), known CVD (1.7; 1.5-1.9), CVD risk factors (1.6; 1.5-1.6), allergies (1.6; 1.5-1.7), cancer (1.3; 1.1-1.5), and respiratory (1.7; 1.6-1.8), gastrointestinal (2.0; 1.9-2.2), nervous system (1.9; 1.7-2.1), kidney/bladder (1.8; 1.6-2.0), endocrine (1.5; 1.4-1.7), and hematological/immune (1.5; 1.2-1.8) diseases. 12.2% runners use AAIM before and/or during races, mostly NSAIDs. Factors (independent of sex, age, and race distance) associated with AAIM use were history of injuries, EAMC, and numerous chronic diseases. We suggest a pre-race screening and educational program to reduce AAIM use in endurance athletes to promote safer races.

Underlying Chronic Disease, Medication Use, History of Running Injuries and Being a More Experienced Runner Are Independent Factors Associated With Exercise-Associated Muscle Cramping: A Cross-Sectional Study in 15778 Distance Runners.

Exercise-associated muscle cramping (EAMC) is a significant medical complication in distance runners, yet factors associated with EAMC are poorly documented. To document risk factors associated with EAMC in runners. Cross-sectional study. Two ocean races (21.1 km, and 56 km). Fifteen thousand seven hundred seventy-eight race entrants. Participants completed a prerace medical history screening tool including: training, cardiovascular disease (CVD), risk factors for, and symptoms of CVD, history of diseases affecting major organ systems, cancer, allergies, medication use, and running injury. Runners were grouped as having a history of EAMC (hEAMC group = 2997) and a control group (Control = 12 781). Independent factors associated with a higher prevalence ratio (PR) of hEAMC were any risk factor for CVD (PR = 1.16; P = 0.0002), symptoms of CVD (PR = 2.38; P < 0.0001), respiratory disease (PR = 1.33; P < 0.0001), gastrointestinal disease (PR = 1.86; P < 0.0001), nervous system or psychiatric disease (PR = 1.51; P < 0.0001), kidney or bladder disease, (PR = 1.60; P < 0.0001), haematological or immune disease (PR = 1.54; P = 0.0048), cancer (PR = 1.34; P = 0.0031), allergies (PR = 1.37; P < 0.0001), regular medication use (PR = 1.80; P < 0.0001), statin use (PR = 1.26; P = 0.0127), medication use during racing (PR = 1.88; P < 0.0001), running injury (PR = 1.66; P < 0.0001), muscle injury (PR = 1.82; P < 0.0001), tendon injury (PR = 1.62; P < 0.0001), and runners in the experienced category (PR = 1.22; P < 0.0001). Novel risk factors associated with EAMC in distance runners were underlying chronic disease, medication use, a history of running injuries, and experienced runners. These factors must be identified as possible associations, and therefore be considered in the diagnosis and treatment of EAMC.

Ingestion of transient receptor potential channel agonists attenuates exercise-induced muscle cramps.

Exercise-associated muscle cramping (EAMC) is a poorly understood problem that is neuromuscular in origin. Ingestion of transient receptor potential (TRP) channel agonists has been efficacious in attenuating electrically induced muscle cramps. This study examines the effect of TRP agonist ingestion on voluntarily induced EAMC and motor function. Study 1: Thirty-nine participants completed 2 trials after ingesting TRP agonist-containing active treatment (A), or vehicle (V) control. Cramping in the triceps surae muscle was induced via voluntary isometric contraction. Study 2: After ingesting A or V, 31 participants performed kinematic and psychomotor tests of manual dexterity. A increased precramp contraction duration (A, 36.9 ± 4.1 s; V, 27.8 ± 3.1 s), decreased cramp EMG area under the curve (A, 37.3 ± 7.7 %EMGmax ·s; V, 77.2 ± 17.7 %EMGmax ·s), increased contraction force to produce the cramp (A, 13.8 ± 1.8 kg; V, 9.9 ± 1.6 kg), and decreased postcramp soreness (A, 4.1 ± 0.3 arbitrary units (a.u.); V, 4.7 ± 0.3 a.u.). Kinematic and psychomotor tests were not affected. TRP agonist ingestion attenuated EAMC characteristics without affecting motor function. Muscle Nerve 56: 379-385, 2017.

NOVEL RISK FACTORS ASSOCIATED WITH MORE SEVERE EXERCISE ASSOCIATED MUSCLE CRAMPING (EAMC): A PROSPECTIVE COHORT STUDY OF 41 698 DISTANCE RUNNERS

BackgroundEAMC is a common clinical syndrome in endurance runners, and can range in severity. Risk factors for EAMC have been identified and include age, gender, racing distance, a history of...

Myths and Misconceptions About Exercise-Associated Muscle Cramping

Myths and Misconceptions About Exercise-Associated Muscle Cramping

Sodium Intake During an Ultramarathon Does Not Prevent Muscle Cramping, Dehydration, Hyponatremia, or Nausea.

BackgroundUltramarathon runners commonly believe that sodium replacement is important for prevention of muscle cramping, dehydration, hyponatremia, and nausea during prolonged continuous exercise. The purpose of this study was to measure total sodium intake to determine if these beliefs are supported.MethodsParticipants of a 161-km ultramarathon (air temperature reaching 39 °C) provided full dietary information during the race, underwent body weight measurements before and after the race, completed a post-race questionnaire about muscle cramping and nausea or vomiting during the race, and had post-race plasma sodium concentration measured.ResultsAmong 20 finishers providing dietary data, mean (±SD) total sodium intake was 13,651 ± 8444 mg (range 2541–38,338 mg), and sodium in food and drink accounted for 66 % of the sodium when averaged across subjects (range 34–100 %). Sodium intake rates were similar when comparing the 10 % of subjects who were hyponatremic with those who were not hyponatremic, the 39 % with muscle cramping or near cramping with those without cramping, and the 57 % who reported having symptoms of nausea or vomiting with those without these symptoms. Weight change between race start and finish was significantly related to rate of sodium intake (r = 0.49, p = 0.030) and total sodium intake (r = 0.53, p = 0.016), but the maximum weight loss among those taking the least total sodium (<4400 mg total sodium during the race) was 4–5 % below the weight measured immediately pre-race.ConclusionsExercise-associated muscle cramping, dehydration, hyponatremia, and nausea or vomiting during exercise up to 30 h in hot environments are unrelated to total sodium intake, despite a common belief among ultramarathon runners that sodium is important for the prevention of these problems.

Weight Change and Hydration Status During a 161-km Ultramarathon

s From the Second Annual Medicine & Science in Ultra-Endurance Sports Conference, June 2015, Olympic Valley, CA The Influence of Hydration on Thermoregulation During a 161-km Ultramarathon Taylor R. Valentino, MS; Kristin J. Stuempfle, PhD; Marialice Kern, PhD; Martin D. Hoffman, MD San Francisco State University, Gettysburg College, Univeristy of California Davis Medical Center and Sacramento VA Medical Center Objective.—It is commonly advised that individuals should avoid losing 42% of their body weight during exercise because dehydration can ultimately lead to hyperthermia, which will impair performance. However, body weight losses of Z3% appear to be well tolerated in those participating in prolonged endurance exercise. This study sought to determine the relationship between hydration status and thermoregulation of runners participating in a hot ultramarathon and to assess whether a weight loss of42% body weight leads to elevations in core temperature. Methods.—Thirty runners of the 2014 161-km Western States Endurance Run agreed to take part in the study. Body weight and core temperature were measured at the start, at 3 locations during the race, and at the finish. Results.—Of the 30 starting participants, 20 finished the race. Ambient temperature at data collection sites ranged from 171C to 391C, and the highest core temperature recorded was 39.41C. Core temperature did not significantly differ during the race (P 1⁄4 .77) and was not correlated with body weight change (P 1⁄4 .19) or finish time (P 1⁄4 .11). However, body weight change was directly associated with finish time (r 1⁄4 .60, P 1⁄4 .006), such that the fastest runners had the greatest loss in body weight ( 3.5–4.0%). Neither core temperature nor percent body weight change differed between race finishers and non-finishers (P 1⁄4 .63 and .17, respectively). Conclusions.—While participating in endurance exercise up to 30 hours in hot conditions, runners can tolerate weight losses of 43% body weight without significant rises in core temperature. Therefore, since body weight losses of 43% were not associated with a rise in core temperature, an emphasis on fluid replacement for weight losses of this magnitude during prolonged exercise is not justified as a preventative measure for heat-related illnesses. Supported by the Western States Endurance Run Foundation. Weight Change and Hydration Status During a 161-km Ultramarathon Karin D. VanBaak, MD; Jack Spittler, MD; Bjorn Irion, MD; Martin D. Hoffman, MD; Morteza Khodaee, MD, MPH University of Colorado, Denver CO, Texas AM Theodore L. Bross, BS; Martin D. Hoffman, MD Palm Beach Atlantic University, Boonshoft School of Medicine, Wright State University, University of California Davis Medical Center and Sacramento VA Medical Center Objective.—To assess the quality of information currently available to the public about hydration needs during exercise. Methods.—Internet searches were conducted using the terms “hydration,” “hydration guidelines,” “drinking fluids,” and “drinking guidelines” with “and exercise.” From the first 50 websites for each search phrase, duplicates were removed, yielding 145 unique websites. Websites were then categorized and examined for specific information and recommendations. Results.—Overall correct endorsement of current knowledge was as follows (reported as percent endorsing the concept relative to the number of sites addressing the issue): some weight loss should be expected during exercise (67.6% of 102), fluid consumption during exercise should be based on thirst (9.4% of 106), electrolyte intake is not necessary during exercise (12.5% of 112), dehydration is not generally a cause of heat illness (6.9% of 58) or muscle cramping (2.3% of 43), exerciseassociated muscle cramping is not generally related to electrolyte loss (6.7% of 15), and overhydration is a risk for hyponatremia (98.5% of 65). There were 7.1% (of 70 websites addressing the issue) indicating that any weight loss during exercise should be avoided. Comparison of website information from those in the categories of medical or scientific organization (15.9%), academic institution (9.0%), peer-reviewed publication (8.3%), and medical professional individual or facility (8.3%) with those in the categories of media (19.3%), sports organization or coach (9.7%), sports drink or electrolyte replacement manufacturer (3.4%), and other (26.2%) revealed no differences (P 1⁄4 .38 to 1.0) in the frequency of endorsement of the criteria referred to above. Conclusions.—Misinformation about hydration needs during exercise continues to be widely spread on the Internet. In general, those websites that should be most trusted by the public appear to be no better than other websites at providing accurate information, and the potential risk of hyponatremia is not often raised.

Rethinking the Cause of Exercise-Associated Muscle Cramping

Rethinking the Cause of Exercise-Associated Muscle Cramping

Less experience and running pace are potential risk factors for medical complications during a 56 km road running race: a prospective study in 26 354 race starters—SAFER study II

BackgroundIt is important to identify risk factors associated with medical complications during ultra-marathons so that prevention programmes can be developed.ObjectiveTo determine risk factors for medical complications during ultra-marathons.DesignProspective study.SettingTwo Oceans...

Voluntary Inducement of Triceps Surae Muscle Cramping

Context:Exercise-associated muscle cramping (EAMC) is difficult to induce experimentally.Purpose:T o assess the reliability of a maximum voluntary contraction (MVC) procedure for inducement of a muscle cramp.Participants:Seventy-four healthy and physically active participants (23 ± 8 years of age; 49 males and 25 females); 63 who had previously experienced EAMC.Main Outcome Measure:Each participant’s triceps surae musculature was placed in a shortened and unloaded position. Participants were instructed to maximally contract the triceps surae musculature with the intent to induce a cramp within 60 seconds.Results:Cramping was induced in 31% of participants within 60 seconds, and 97% of participants who experienced cramping during the initial session and who returned for two subsequent testing sessions at one-week intervals reproduced cramping with the procedure.Conclusions:The MVC procedure consistently induced cramping in a subset of 18 cramp-prone participants during multiple testing sessions, which suggests that it may have value as a screening tool for identification of athletes with a predisposition for EAMC.