Muscle cramps: A comparison of the two-leading hypothesis

The effects of a sugar-free amino acid-containing electrolyte beverage on 5-kilometer performance, blood electrolytes, and post-exercise cramping versus a conventional carbohydrate-electrolyte sports beverage and water

OBJECTIVE

The purpose of this study was to examine the acute effects of a multi-ingredient, low calorie dietary supplement (MIDS, XTEND® Healthy Hydration) on 5-kilometer (5-km) time trial performance and blood electrolyte concentrations compared to a carbohydrate-electrolyte beverage (CE, GATORADE® Thirst Quencher) and distilled water (W).

METHODS

During visit 1 (V1), participants (10 men and 10 women, 20-35 years old, BMI ≤ 29 kg/m2, recreationally active) reported to the laboratory whereby the following tests were performed: i) height and weight measurements, ii) body composition analysis, iii) treadmill testing to measure maximal aerobic capacity, and iv) 5-km time trial familiarization. The second visit (V2) was one week after V1 in the morning (0600 - 0900) and participants arrived 12-14 h fasted (no food or drink). The first battery of assessments (V2-T1) included nude body mass, urine specific gravity (USG), a profile of mood states (POMS) questionnaire, and the completion of a visual analogue scale (VAS) questionnaire to quantify cramping. Then heart rate (HR), blood pressure (BP), total body hydration (via bioelectrical impedance spectroscopy [BIS]) were examined. Finally, a measurement of blood markers via finger stick was performed. Participants consumed a randomized beverage (16 fl. oz. of MIDS, 16 fl. oz. of W, or 16 fl. oz. of CE) within 3 min followed by a 45-min rest. Following the rest period, a second battery (V2-T2) was performed whereby participants' USG was assessed and they completed the POMS and VAS questionnaires, and HR, BP, and blood markers were measured. The participants then performed a 5-km treadmill time trial. Immediately following the 5-km time trial, participants completed a third testing battery (V2-T3) that began with blood markers, HR and BP assessments, followed by nude body weight assessment, and the POMS and VAS questionnaires. After 60 min, a fourth battery (V2-T4) was performed that included HR, BP, and blood markers. After sitting quietly for another 60 min a fifth battery assessment was performed (V2-T5) that included participants' USG, POMS and VAS questionnaires, HR, BP, blood markers, and total body hydration. Visits 3 (V3) and 4 (V4) followed the same protocol except a different randomized drink (16 oz. of CE, MIDS, or W) was consumed; all of which were separated by approximately one week.

RESULTS

No differences occurred between conditions for 5-km time trial completion, indirect calorimetry outcomes during 5-km time trials, USG, or nude mass measurements (p > 0.05 for all relevant statistical tests). However, blood potassium and the sodium/potassium ratio displayed significant interactions (p < 0.05), and post hoc testing indicated these values were better maintained in the MIDS versus other conditions. Post-exercise cramp prevalence was greater in the CE (p < 0.05) and trended higher with W (p = 0.083) compared to the MIDS condition. Post-exercise cramp severity was also elevated with the W and CE beverages (p < 0.05) but not the MIDS (p = 0.211).

CONCLUSIONS

The MIDS did not affect 5-km time trial performance but exhibited favorable effects on blood electrolyte and post-exercise self-reporting cramp outcomes compared to the CE and W drinks.

Muscle cramps and contractures: causes and treatment

Muscle cramps are painful, sudden, involuntary muscle contractions that are generally self-limiting. They are often part of the spectrum of normal human physiology and can be associated with a wide range of acquired and inherited causes. Cramps are only infrequently due to progressive systemic or neuromuscular diseases. Contractures can mimic cramps and are defined as shortenings of the muscle resulting in an inability of the muscle to relax normally, and are generally myogenic. General practitioners and neurologists frequently encounter patients with muscle cramps but more rarely those with contractures. The main questions for clinicians are: (1) Is this a muscle cramp, a contracture or a mimic? (2) Are the cramps exercise induced, idiopathic or symptomatic? (3) What is/are the presumed cause(s) of symptomatic muscle cramps or contractures? (4) What should be the diagnostic approach? and (5) How should we advise and treat patients with muscle cramps or contractures? We consider these questions and present a practical approach to muscle cramps and contractures, including their causes, pathophysiology and treatment options.

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

OBJECTIVE

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.

DESIGN

Cross-sectional study.

SETTING

The 2012 to 2015 Two Oceans Marathon races (21.1 and 56 km), South Africa.

PARTICIPANTS

Participants were consenting race entrants (21.1 km = 44 458; 56 km = 26 962) who completed an online prerace medical screening questionnaire.

INDEPENDENT VARIABLE

A history of EAMC.

MAIN OUTCOME MEASURES

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]).

RESULTS

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).

CONCLUSIONS

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.

Cardiovascular Effects of Whole-Body Cryotherapy in Non-professional Athletes

Objectives:

The study aimed to investigate changes in heart rate, blood pressure, respiratory rate, oxygen saturation, and body temperature in non-professional trained runners during whole body cryotherapy (WBC).

Methods

Ten middle-distance runners received 3 once-a-day sessions of WBC. Subjects underwent BP measurements and ECG recorded before and immediately after the daily WBC session. During WBC we recorded a single lead trace (D1) for heart rhythm control. In addition, the 5 vital signs Blood pressure, heart rate, respiratory rate, oxygen saturation, and body temperature were monitored before, during, and after all WBC session.

Results

We did not report significant changes in ECG main intervals (PR, QT, and QTc). Mean heart rate changed from 50.98 ± 4.43 bpm (before) to 56.83 ± 4.26 bpm after WBC session (p < 0.05). The mean systolic blood pressure did not change significantly during and after WBC [b baseline: 118 ± 5 mmHg, changed to 120 ± 3 mmHg during WBC, and to 121 ± 2 mmHg after session (p < 0.05 vs. baseline)]. Mean respiratory rate did not change during WBC as well as oxygen saturations (98 vs. 99%). Body temperature was slightly increased after WBC, however it remains within physiological values

Conclusion

In non-professional athletes WBC did not affect cardiovascular response and can be safely used. However, further studies are required to confirm these promising results of safety in elderly non-athlete subjects.

Programmed vs. Thirst-Driven Drinking during Prolonged Cycling in a Warm Environment

We compared the effect of programmed (PFI) and thirst-driven (TDFI) fluid intake on prolonged cycling performance and exercise associated muscle cramps (EAMC). Eight male endurance athletes (26 ± 6 years) completed two trials consisting of 5 h of cycling at 61% V˙O2peak followed by a 20 km time-trial (TT) in a randomized crossover sequence at 30 °C, 35% relative humidity. EAMC was assessed after the TT with maximal voluntary isometric contractions of the shortened right plantar flexors. Water intake was either programmed to limit body mass loss to 1% (PFI) or consumed based on perceived thirst (TDFI). Body mass loss reached 1.5 ± 1.0% for PFI and 2.5 ± 0.9% for TDFI (p = 0.10). Power output during the 20 km TT was higher (p < 0.05) for PFI (278 ± 41 W) than TDFI (263 ± 39 W), but the total performance time, including the breaks to urinate, was similar (p = 0.48) between conditions. The prevalence of EAMC of the plantar flexors was similar between the drinking conditions. Cyclists competing in the heat for over 5 h may benefit from PFI aiming to limit body mass loss to <2% when a high intensity effort is required in the later phase of the race and when time lost for urination is not a consideration.

Autosomal Dominant ANO5-Related Disorder Associated With Myopathy and Gnathodiaphyseal Dysplasia

Objective

To investigate the molecular basis of muscle disease and gnathodiaphyseal dysplasia (GDD) in a large kindred with 11 (6 women and 5 men) affected family members.

Methods

We performed clinical assessment of 3 patients and collected detailed clinical and family history data on 8 additional patients. We conducted molecular genetic analyses on 5 patients using comprehensive neuromuscular disorder panels, exome sequencing (ES), and targeted testing for specific genetic variants. We analyzed the segregation of the muscle and bone phenotypes with the underlying molecular cause.

Results

The unique clinical presentation of recurrent episodes of rhabdomyolysis associated with muscle cramps, hyperCKemia, muscle hypertrophy, with absent or mild muscle weakness, as well as cemento-osseous lesions of the mandible, with or without bone fractures and other skeletal abnormalities, prompted us to look for the underlying molecular cause of the disorder in this kindred. Molecular testing revealed a missense variant in anoctamin 5 (ANO5) designated as c.1538C>T; p.Thr513Ile, which was previously described in a large kindred with GDD. In silico analysis, searching publicly available databases, segregation analysis, as well as functional studies performed by another group provide strong evidence for pathogenicity of the variant. ES data in the proband excluded the contribution of additional genetic factors.

Conclusions

This report described the coexistence of muscle and bone phenotypes in the same patients with ANO5-related disorder. Our data challenge recent results that suggested complete dichotomy of these phenotypes and the proposed loss-of-function and gain-of-function mechanisms for the skeletal and muscle phenotypes, respectively.

Correlates of night-time and exercise-associated lower limb cramps in healthy adults

INTRODUCTION/AIMS

We explored correlates of night-time and exercise-associated lower limb cramps in participants of the 1000 Norms Project.

METHODS

A volunteer community sample of healthy people aged ≥18 y underwent assessment of motor function and physical performance, and were questioned about muscle cramps in the previous 3 mo.

RESULTS

Of 491 (221 female) participants age 18-101 y (mean: 59.12; SD: 18.03), about 1 in 3 experienced night-time lower limb cramps, and about 1 in 4 experienced exercise-associated lower limb cramps. For night-cramps, a one unit increase in Beighton score (greater whole-body flexibility) was associated with a 31% reduced odds of cramps (odds ratio [OR] = 0.69, 95% confidence interval [CI]:0.45, 0.99) and passing all three lesser-toe strength tests was associated with 50% reduced odds of cramps (OR = 0.50, 95% CI: 0.32, 0.78). For exercise-associated cramps, participants in the fourth (lowest arch) quartile of Foot Posture Index were 2.1 times (95% CI: 1.11, 3.95) more likely to experience cramps than participants in the first (highest arch) quartile. Odds of experiencing both types of cramps versus no cramps were lower with passing all three lesser-toe strength tests (OR = 0.40, 95% CI: 0.19, 0.85) and better performance in the six-minute walk test (OR = 0.997, 95% CI: 0.996, 0.998).

DISCUSSION

People who experienced both exercise-associated and night-time cramps were less functional. The association between night-time cramps with less whole-body flexibility and reduced lesser-toe flexor strength should be explored to determine causation. Planovalgus (low-arched) foot type was independently associated with exercise-associated cramps. The effectiveness of foot orthoses for secondary prevention of exercise-associated cramps in people with low-arched feet should be explored.

Effect of oral rehydration solution versus spring water intake during exercise in the heat on muscle cramp susceptibility of young men

Background

Muscle cramp is a painful, involuntary muscle contraction, and that occurs during or following exercise is referred to as exercise-associated muscle cramp (EAMC). The causes of EAMC are likely to be multifactorial, but dehydration and electrolytes deficits are considered to be factors. This study tested the hypothesis that post-exercise muscle cramp susceptibility would be increased with spring water ingestion, but reduced with oral rehydration solution (ORS) ingestion during exercise.

Methods

Ten men performed downhill running (DHR) in the heat (35–36 °C) for 40–60 min to reduce 1.5–2% of their body mass in two conditions (spring water vs ORS) in a cross-over design. The body mass was measured at 20 min and every 10 min thereafter during DHR, and 30 min post-DHR. The participants ingested either spring water or ORS for the body mass loss in each period. The two conditions were counter-balanced among the participants and separated by a week. Calf muscle cramp susceptibility was assessed by a threshold frequency (TF) of an electrical train stimulation to induce cramp before, immediately after, 30 and 65 min post-DHR. Blood samples were taken before, immediately after and 65 min after DHR to measure serum sodium, potassium, magnesium and chroride concentrations, hematocrit (Hct), hemoglobin (Hb), and serum osmolarity. Changes in these varaibles over time were compared between conditions by two-way repeated measures of analysis of variance.

Results

The average (±SD) baseline TF (25.6 ± 0.7 Hz) was the same between conditions. TF decreased 3.8 ± 2.7 to 4.5 ± 1.7 Hz from the baseline value immediately to 65 min post-DHR for the spring water condition, but increased 6.5 ± 4.9 to 13.6 ± 6.0 Hz in the same time period for the ORS condition (P < 0.05). Hct and Hb did not change significantly (P > 0.05) for both conditions, but osmolarity decreased (P < 0.05) only for the spring water condition. Serum sodium and chloride concentrations decreased (< 2%) at immediately post-DHR for the spring water condition only (P < 0.05).

Conclusions

These results suggest that ORS intake during exercise decreased muscle cramp susceptibility. It was concluded that ingesting ORS appeared to be effective for preventing EAMC.

Effectiveness of 4-Week Oral Taurine Treatment for Muscle Cramps in Patients with Liver Cirrhosis: A Single-Arm Pilot Study

PURPOSE

Painful muscle cramps are a common complication in liver cirrhosis patients, and no effective treatment is available. This pilot study aimed to evaluate whether taurine supplementation improves muscle cramps in Korean cirrhotic patients.

MATERIALS AND METHODS

Ten cirrhotic patients who experienced muscle cramps one or more times/week were enrolled in this prospective single-arm study and administered with an oral taurine solution (1 g/50 mL) thrice a day for 4 weeks. Taurine was discontinued for the subsequent 4 weeks. The frequency and intensity of muscle cramps were evaluated using a questionnaire at weeks 0, 2, 4, 6, and 8 after the start of treatment.

RESULTS

At baseline, the median frequency of muscle cramps was six times/week, and all patients had severe pain. Muscle cramp scores (frequency×intensity) decreased in seven patients by weeks 4 and 8 after treatment initiation. Compared to baseline muscle cramp scores [median 21, interquartile range (IQR): 8-84], median muscle cramp scores were lower at week 4 (6.5, IQR: 3-12, p=0.126) and week 8 (5, IQR: 1.5-56, p=0.066). All five patients whose baseline plasma taurine levels were below the normal limit showed increased taurine levels at week 4; 60% of them experienced improvements in their muscle cramps. Of the five patients with normal or higher taurine levels, 80% experienced an improvement in symptoms at week 4. The safety and tolerability of the 4-week taurine therapy were excellent.

CONCLUSION

Oral taurine therapy for 4 weeks improved muscle cramps safely in cirrhotic patients.

Total Body and Extracellular Water Measures Are Unrelated to Cramp Sensitivity in Euhydrated Cramp-Prone Individuals

Earp, JE, Stearns, RL, Agostinucci, J, Lepley, AS, and Ward-Ritacco, CL. Total body and extracellular water measures are unrelated to cramp sensitivity in euhydrated cramp-prone individuals. J Strength Cond Res XX(X): 000-000, 2020-Spectral bioelectrical impedance analysis (BIA) is a valid and noninvasive tool for measuring total body water (TBW), intracellular water (ICW), and extracellular water (ECW). As altered hydration and electrolyte imbalance have been proposed as one of 2 etiologies for exercise-associated muscle cramps (EAMC), the purpose of this study was to determine if distribution of body water is related to cramp sensitivity in similarly hydrated cramp-prone individuals. To this end, 11 euhydrated subjects who regularly experience EAMC had their relative TBW, ICW, and ECW assessed using 8-pole spectral BIA. Subjects' cramp sensitivity was then assessed by electrically stimulating the tibial nerve at increasing frequencies until a muscle cramp occurred, allowing for the determination of the threshold frequency (TF) at which the cramp occurred. It was observed that TF was not significantly related to TBW (r = 0.087, p = 0.368), ICW (r = 0.105, p = 0.338), ECW (r = 0.087, p = 0.368), or ECW:TBW (r = 0.147, p = 0.280). As cramp etiology is poorly understood, these results add to a growing body of literature questioning the role of hydration and electrolyte imbalance in EAMC. Although fluid distribution may be unrelated to TF in those who commonly experience EAMC, additional research is needed to compare those who commonly experience cramps (athletes as well as individuals with specific neuropathies or pharmacologically induced cramps) with those who do not experience cramps and to determine if acute shifts in body water compartmentalization are related to changes in cramp sensitivity.

The effects of diuretic use and the presence of ascites on muscle cramps in patients with cirrhosis: a nationwide study

BACKGROUND

Administration of diuretics and the presence of ascites in patients with cirrhosis were reported to be associated with muscle cramps; however, the clinical evidence is limited. This study aimed to determine whether muscle cramps are a diuretic-induced complication and whether ascites was a factor related to muscle cramp.

METHODS

A total of 1064 adult patients with cirrhosis were enrolled from 10 hospitals in Japan between June 2017 and December 2018. A questionnaire regarding cramps was completed by all patients. The ratio of extracellular water (ECW) was analyzed using the bioelectrical impedance analysis. Logistic regression analysis was performed to analyze the effects of diuretic administration and the ECW ratio on cramps.

RESULTS

Patients using diuretics had a higher incidence rate, higher frequency, stronger pain, and longer duration of cramps than those who did not. In the multivariate analysis, diuretic administration and the ECW ratio values ≥ 0.4 were not significantly associated with the presence, frequency, intensity, or duration of cramps. However, in the case of patients limited to Child-Pugh B or C, diuretic use was significantly correlated with the cramp frequency.

CONCLUSIONS

These results demonstrated that muscle cramps were not a complication of diuretic use in patients with cirrhosis; however, in those limited to Child-Pugh B or C, diuretic use was a factor that affected the frequency of cramps. Moreover, no association was found between the presence of ascites and cramps.

Muscle Cramping in the Marathon: Dehydration and Electrolyte Depletion vs. Muscle Damage

Martínez-Navarro, I, Montoya-Vieco, A, Collado, E, Hernando, B, Panizo, N, and Hernando, C. Muscle Cramping in the marathon: Dehydration and electrolyte depletion vs. muscle damage. J Strength Cond Res XX(X): 000-000, 2020-Our aim was to compare dehydration variables, serum electrolytes, and muscle damage serum markers between runners who suffered exercise-associated muscle cramps (EAMC) and runners who did not suffer EAMC in a road marathon. We were also interested in analyzing race pacing and training background. Nighty-eight marathoners took part in the study. Subjects were subjected to a cardiopulmonary exercise test. Before and after the race, blood and urine samples were collected and body mass (BM) was measured. Immediately after the race EAMC were diagnosed. Eighty-eight runners finished the marathon, and 20 of them developed EAMC (24%) during or immediately after the race. Body mass change, post-race urine specific gravity, and serum sodium and potassium concentrations were not different between crampers and noncrampers. Conversely, runners who suffered EAMC exhibited significantly greater post-race creatine kinase (464.17 ± 220.47 vs. 383.04 ± 253.41 UI/L, p = 0.034) and lactate dehydrogenase (LDH) (362.27 ± 72.10 vs. 307.87 ± 52.42 UI/L, p = 0.002). Twenty-four hours post-race also values of both biomarkers were higher among crampers (CK: 2,438.59 ± 2,625.24 vs. 1,166.66 ± 910.71 UI/L, p = 0.014; LDH: 277.05 ± 89.74 vs. 227.07 ± 37.15 UI/L, p = 0.021). The difference in the percentage of runners who included strength conditioning in their race training approached statistical significance (EAMC: 25%, non-EAMC: 47.6%; p = 0.074). Eventually, relative speed between crampers and noncrampers only differed from the 25th km onward (p < 0.05). Therefore, runners who suffered EAMC did not exhibit a greater degree of dehydration and electrolyte depletion after the marathon but displayed significantly higher concentrations of muscle damage biomarkers.

ELECTROLYTE CHANGES RELATED TO MUSCLE PAIN AFTER RESISTANCE EXERCISES

ABSTRACT Introduction Resistance exercises (RE) performed at high intensity cause an inflammatory response and electrolyte abnormalities in blood plasma. Objectives To study the plasma electrolyte changes resulting from a high-intensity session of RE in untrained volunteers, and to correlate these with delayed onset muscle soreness (DOMS). Methods Twenty volunteers, aged 26.9 (±4.4) years, underwent an RE session. The workout (leg extension, squat and leg press) consisted of four sets of 10 maximum repetitions. Electrolytes (Na+, K+, Ca2+ e Mg2+) were evaluated before the training (baseline), immediately (0 min), and 30 minutes after the RE. The DOMS was assessed 24 hours after the sessions. Results The Na+ increased immediately after the RE and returned to normal after 30 min (p<0.001). After 30 min, K+ increased compared to baseline levels and immediately after the RE (p<0.001). Ca2+ and Mg2+ levels did not change throughout the study. Changes in Na+ and K+ levels were correlated immediately (r=-0.511; p=0.021) and 30 min (r=-0.455; p=0.049) after RE. Plasma concentrations of Na+ 0 min were correlated (r=-0.520; p=0.018) with the DOMS. Conclusion High-intensity RE in untrained volunteers leads to changes in plasma concentrations of Na+ and K+. Na+ concentrations immediately after RE were related to DOMS; individuals that presented smaller alterations in this electrolyte reported more muscular pain. Level of evidence II; Diagnostic Studies - Development of diagnostic criteria on consecutive patients (with universally applied reference “gold” standard).

Effect of Shakuyaku-kanzo-to in patients with muscle cramps: A systematic literature review

BACKGROUND

Previous clinical studies have reported that Shakuyaku-kanzo-to (SKT) has a therapeutic effect on muscle cramps, but few studies have clarified how SKT acts to treat muscle cramps. The aim of this study was to perform an updated systematic review of clinical trials for SKT in patients with muscle cramps.

METHODS

The literature was systematically reviewed to assess the effects of SKT in patients with muscle cramps. PubMed, Web of Science, Cochrane Library, Google Scholar, and Ichushi-Web were searched using the terms "Shakuyaku-kanzo-to" ("shakuyakukanzoto", etc), "clinical trials" and "muscle cramps". Two quality assessments were conducted independently by three authors. Data were extracted using a standardized extraction tool, and a qualitative synthesis of evidence was performed.

RESULTS

Three randomized controlled articles were identified and enrolled in this study. A systematic review, but not a meta-analysis, was performed because of the high heterogeneity and limited number of studies. In patients with liver cirrhosis, the odds ratio (OR) for improvement with SKT compared to placebo was 1.27 (95% confidence interval [CI], 0.445-2.086) and compared to Goshajinkigan was 0.81 (95%CI, -1.734-0.114). The OR for improvement with SKT compared with eperisone hydrochloride in patients with lumbar spinal stenosis was 2.86 (95%CI, 0.980-4.744).

CONCLUSIONS

Current evidence appears insufficient to allow a meta-analysis of the effects of SKT, but SKT might show efficacy in treating muscle cramps in patients with cirrhosis or lumbar spinal stenosis.

Muscle Cramping During Exercise: Causes, Solutions, and Questions Remaining

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.

Water intake after dehydration makes muscles more susceptible to cramp but electrolytes reverse that effect

Objective

No previous study has compared water and oral rehydration solution (ORS) intake after dehydration induced by exercise in the heat for the effect on muscle cramps. The present study tested the hypothesis that water ingestion after dehydration would increase muscle cramp susceptibility, but this would be prevented by ORS ingestion.

Methods

Ten men performed two bouts of downhill running (DHR; −5%) in the heat (35°C–36 °C) until their body mass was reduced by 2%. Ten minutes after DHR, either spring water or electrolyte water similar to ORS (OS-1^®) was ingested in a counter-balanced order on two different days separated by a week. Muscle cramp susceptibility was assessed by a threshold frequency (TF) of electrical train stimulation to induce cramp before, immediately after (0), and 30 and 60 min after the ingestion. Blood samples were taken before, immediately and 80 min after DHR to measure serum electrolyte concentrations.

Results

Muscle cramp susceptibility assessed by TF did not change from baseline to immediately after DHR for both conditions (water: 24.6 ± 2.1 Hz, OS-1^®: 24.7 ± 1.4 Hz). TF decreased after water intake by 4.3 Hz (30 min) and 5.1 Hz (60 min post-ingestion), but increased after OS-1^® intake by 3.7 and 5.4 Hz, respectively. Serum sodium and chloride concentrations decreased after water intake but maintained after OS-1^® intake.

Conclusion

These results suggest that water intake after dehydration makes muscles more susceptible to electrical simulation-induced muscle cramp, probably due to dilution of electrolytes, and when OS-1^® is consumed, the susceptibility to muscle cramp decreases.