Article

Reflex Inhibition of Electrically Induced Muscle Cramps in Hypohydrated Humans

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Abstract

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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... Ingesting pickle juice (PJ), a solution that contains acetic acid and high concentrations of salt, has become popular [10,14]. Miller et al. [17] reported that ingesting 1 mL·kg −1 body-mass (BM) of PJ during an electrically induced muscle cramp (EIMC) reduced cramp time by up to 45%. Given that EIMCs are strongly correlated with EAMC [16], the authors concluded that the inhibitory effects of PJ on EAMC may be caused by acetic acid [17]. ...
... Miller et al. [17] reported that ingesting 1 mL·kg −1 body-mass (BM) of PJ during an electrically induced muscle cramp (EIMC) reduced cramp time by up to 45%. Given that EIMCs are strongly correlated with EAMC [16], the authors concluded that the inhibitory effects of PJ on EAMC may be caused by acetic acid [17]. The sour taste of acetic acid is thought to stimulate the oropharyngeal receptors to trigger a supraspinal reflex that increases inhibitory neurotransmitter activity, potentially activating interneurons to postsynaptically inhibit the "α"-motor neuron pool of the cramping muscle [17]. ...
... Given that EIMCs are strongly correlated with EAMC [16], the authors concluded that the inhibitory effects of PJ on EAMC may be caused by acetic acid [17]. The sour taste of acetic acid is thought to stimulate the oropharyngeal receptors to trigger a supraspinal reflex that increases inhibitory neurotransmitter activity, potentially activating interneurons to postsynaptically inhibit the "α"-motor neuron pool of the cramping muscle [17]. This notion would support the "altered neuromuscular control theory"; however, evidence for this is lacking. ...
Article
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(1) Background: Stimulating oropharyngeal transient receptor potential (TRP) channels inhibits muscle cramping by triggering a supraspinal reflex to reduce α-motor neuron hyperexcitability. This study investigated whether the longer stimulation of the TRP channels via mouth rinsing with PJ is more effective than drinking PJ at inhibiting an electrically induced muscle cramp (EIMC). Both conditions were compared to the control (water). (2) Methods: The tibial nerves in 11 cramp-prone adults were percutaneously stimulated to elicit an EIMC of the flexor hallucis brevis in three trials that took place one week apart from each other. At cramp onset, the participants received mouth rinsing and expelling PJ (25 mL), ingesting PJ (1 mL∙kg−1 body-mass (BM)), or ingesting water (1 mL∙kg−1 BM). Cramp onset and offset were induced by electromyography, and the severity of discomfort was recorded using a visual analogue scale (VAS). (3) Results: The median time to cramp cessation as a percentage of water was 82.8 ± 14.63% and 68.6 ± 47.78% for PJ ingestion and PJ mouth rinsing, respectively. These results had large variability, and no statistically significant differences were observed. There were also no differences in perceived cramp discomfort between conditions, despite the hazard ratios for the time taken to reach VAS = 0, which was higher than water (control) for PJ ingestion (22%) and mouth rinsing (35%) (p = 0.66 and 0.51, respectively). (4) Conclusions: The data suggest no difference in cramp duration and perceived discomfort between PJ and water.
... As this study failed to find a significant relationship between TF and compartmental fluid (ECW/ICW), our findings do not support the fluid/electrolyte imbalance etiology. These results are in line with previous studies that have found that changes in TBW (representing changes in body mass from exercise) or serum and plasma electrolyte concentrations are not related to changes in TF or cramp occurrence during exercise (3,15,22,23). ...
... Although previous work has failed to find a relationship between indirect measures of body water and cramp sensitivity (3,15,22,23), these studies tracked body water changes during prolonged exercise (22,23) or during a deliberate period of dehydration (3,15). Therefore, previous designs provided information as to how changes in body water can influence cramp sensitivity. ...
... Although previous work has failed to find a relationship between indirect measures of body water and cramp sensitivity (3,15,22,23), these studies tracked body water changes during prolonged exercise (22,23) or during a deliberate period of dehydration (3,15). Therefore, previous designs provided information as to how changes in body water can influence cramp sensitivity. ...
Article
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.
... Based on the widespread assumption that muscle cramps are caused by an electrolyte depletion, it was proposed that ingesting fluids with high electrolyte concentrations, such as pickle juice, would be an efficient strategy to prevent EAMC (Miller et al. 2010a;Williams and Conway 2000). Although some studies found beneficial effects of pickle juice on skeletal muscle cramps (Miller et al. 2010a;Williams and Conway 2000), Miller et al. (2010b) pointed out that these effects set in too fast (i.e. within a few minutes) to be explainable by an intestinal uptake of pickle-juice ingredients. ...
... within a few minutes) to be explainable by an intestinal uptake of pickle-juice ingredients. Miller et al. (2010b) suggested that the acetic acid (vinegar) in pickle juice triggered a reflex in the oropharyngeal region that reduced the activity of the alpha motor neuron pool. ...
... This outcome supports the general concept that TRPactivation in the oropharyngeal mucosa inhibits skeletal muscle cramps, possibly by reducing the excitability of the involved alpha motor neuron pool Craighead et al. 2017). As acetic acid in pickle juice (Dale et al. 2003) activates TRPA1 channels (Wang et al. 2011), the rapid inhibition of muscle cramps after pickle juice ingestion, reported by Miller et al. (2010b), may be mediated by the same receptors. It is known that strong sensory stimuli can inhibit the motor cortex (Sailer et al. 2002) and depress the efferent neural output (Okun and Lampl 2008). ...
Article
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Purpose: Previous data indicate that a strong sensory input from orally administered TRPV1 and TRPA1 activators alleviates muscle cramps in foot muscles by reducing the α-motor neuron hyperexcitability. We investigated if TRP activators increase the cramp threshold frequency of the medial gastrocnemius. Methods: We randomly assigned 22 healthy male participants to an intervention (IG) and a control group (CG). While participants of the IG ingested a mixture of TRPV1 and TRPA1 activators, the CG received a placebo. We tested the cramp threshold frequency (CTF), the cramp intensity (EMG activity), and the perceived pain of electrically induced muscle cramps before (pre), and 15 min, 4, 8, and 24 h after either treatment. We further measured the maximal isometric force of knee extensors at pre, 4, and 24 h to assess potential side-effects on the force output. Results: When we included all measurement time points, no group-by-time interaction was observed for the CTF. However, when only pre and 15 min values were incorporated, a significant interaction, with a slightly greater CTF increase in IG (3.1 ± 1.5) compared to the CG (2.0 ± 1.5), was observed. No significant group by time interaction was found for the cramp intensity, the perceived pain, and the maximal isometric force. Conclusion: Our data indicate that orally administered TRPV1 and TRPA1 activators exert a small short-term effect on the CTF, but not on the other parameters tested. Future studies need to investigate whether such small CTF increments are sufficient to prevent exercise-associated muscle cramps.
... Auf der Suche nach einer wirksamen Behandlung von Muskelkrämpfen stießen Miller et al. [16] auf eine Veröffentlichung von 2003 [17] über "Pickle Juice", die Verbreitung in Trainerkreisen fand. Miller et al. [16] schreiben in einem Artikel über ein US-Football-Spiel bei großer Hitze, bei dem mehrere Spieler wegen Krämpfen abbrechen musstenaber nur die Spieler eines Teams, das andere konnten weiterspielen; diese Spieler hatten Gurkenwasser (der Sud, in dem Gewürzgurken eingelegt sind) zu sich genommen. ...
... Auf der Suche nach einer wirksamen Behandlung von Muskelkrämpfen stießen Miller et al. [16] auf eine Veröffentlichung von 2003 [17] über "Pickle Juice", die Verbreitung in Trainerkreisen fand. Miller et al. [16] schreiben in einem Artikel über ein US-Football-Spiel bei großer Hitze, bei dem mehrere Spieler wegen Krämpfen abbrechen musstenaber nur die Spieler eines Teams, das andere konnten weiterspielen; diese Spieler hatten Gurkenwasser (der Sud, in dem Gewürzgurken eingelegt sind) zu sich genommen. Daraufhin untersuchten Miller et al. ...
... Es müssen also Rezeptoren im Mund-Rachen-Raum dafür verantwortlich sein, die durch Nervensignale eine dämpfende Wirkung auf die α-Motoneuronen-Aktivität haben. Belegt werden konnte dies durch Millers Untersuchung [16] bis heute nur therapeutisch, nicht präventiv, allerdings zeigen Eigenversuche in Sportlerkreisen, angeregt durch die Gurkenwasser-These, dass sich die Häufigkeit ihrer Muskelkrämpfe reduzieren ließ durch regelmäßigen Genuss von Gurkenwasser bzw. Gewürzgurken. ...
Article
Zusammenfassung Hintergrund Muskelkrämpfe sind weit verbreitet in der Bevölkerung, gerade auch bei Sportlern. Viele haben ihre Vorstellungen, was dagegen helfen könnte. Ziel Abgleich zwischen den therapeutischen Vorstellungen der Menschen, vornehmlich Sportlern, was sie gemeinhin bei Muskelkrämpfen als hilfreich erachten und der durch Studien belegten Wirksamkeit. Methode Literaturrecherche. Ergebnisse Die Studienlage unterscheidet sich deutlich vom „Halbwissen“ der Teilnehmer. Schlussfolgerung Mit Halbwissen sollte aufgeräumt werden, und aktuelles, wissenschaftlich belegtes Wissen muss sich, gerade auch über Multiplikatoren wie Trainer, Ärzte etc., in der Bevölkerung verbreiten.
... 16 Another possible concern is that ingesting PJ may increase [Na þ ] p and plasma osmolality (OSM p ), thereby rapidly expanding plasma volume, decreasing thirst, and impairing rehydration. 14 However, others have observed no changes in plasma electrolyte concentrations, OSM p , or plasma volume when euhydrated 17 or mildly hypohydrated [18][19][20] individuals ingested small volumes (approximately 80 mL) of PJ. Furthermore, ingesting PJ did not alter perceived thirst or the volume of water ingested ad libitum postexercise. ...
... 19 Previous examinations of the effect of PJ on the extracellular fluid space had 3 limitations. [17][18][19][20][21] First, the authors only provided 1 bolus of PJ at 1 time, either preexercise 17,21 or postexercise. [18][19][20] Anecdotally, some athletic trainers give athletes PJ multiple times over the course of an exercise session to treat or prevent EAMC (eg, before a game or at halftime). ...
... [17][18][19][20][21] First, the authors only provided 1 bolus of PJ at 1 time, either preexercise 17,21 or postexercise. [18][19][20] Anecdotally, some athletic trainers give athletes PJ multiple times over the course of an exercise session to treat or prevent EAMC (eg, before a game or at halftime). Second, participants did not exercise postingestion of PJ. [17][18][19]21 No researchers have examined the extracellular fluid space after individuals ingested PJ and then resumed exercise. ...
Article
Context: Twenty-five percent of athletic trainers administer pickle juice (PJ) to treat cramping. Anecdotally, some clinicians provide multiple boluses of PJ during exercise but warn that repeated ingestion of PJ may cause hyperkalemia. To our knowledge, no researchers have examined the effect of ingesting multiple boluses of PJ on the same day or the effect of ingestion during exercise. Objective: To determine the short-term effects of ingesting a single bolus or multiple boluses of PJ on plasma variables and to characterize changes in plasma variables when individuals ingest PJ and resume exercise. Design: Crossover study. Setting: Laboratory. Patients or other participants: Nine euhydrated men (age = 23 ± 4 years, height = 180.9 ± 5.8 cm, mass = 80.7 ± 13.8 kg, urine specific gravity = 1.009 ± 0.005). Intervention(s): On 3 days, participants rested for 30 minutes, and then a blood sample was collected. Participants ingested 0 or 1 bolus (1 mL · kg(-1) body weight) of PJ, donned sweat suits, biked vigorously for 30 minutes (approximate temperature = 37 °C, relative humidity = 18%), and had a blood sample collected. They either rested for 60 seconds (0- and 1-bolus conditions) or ingested a second 1 mL · kg(-1) body weight bolus of PJ (2-bolus condition). They resumed exercise for another 35 minutes. A third blood sample was collected, and they exited the environmental chamber and rested for 60 minutes (approximate temperature = 21 °C, relative humidity = 18%). Blood samples were collected at 30 and 60 minutes postexercise. Main outcome measure(s): Plasma sodium concentration, plasma potassium concentration, plasma osmolality, and changes in plasma volume. Results: The number of PJ boluses ingested did not affect plasma sodium concentration, plasma potassium concentration, plasma osmolality, or changes in plasma volume over time. The plasma sodium concentration, plasma potassium concentration, and plasma osmolality did not exceed 144.6 mEq · L(-1) (144.6 mmol · L(-1)), 4.98 mEq · L(-1) (4.98 mmol · L(-1)), and 289.5 mOsm · kg(-1)H2O, respectively, in any condition at any time. Conclusions: Ingesting up to 2 boluses of PJ and resuming exercise caused negligible changes in blood variables. Ingesting up to 2 boluses of PJ did not increase plasma sodium concentration or cause hyperkalemia.
... 11,12 When using the TF model, it was found that hypohydration did not significantly affect TF 13,14 ; however, it was also observed that TF increased on average 1.8 Hz after consumption of pickle juice compared with deionized water in hypohydrated participants, supporting consumption of an EB to increase cramp resiliency. 15 While EB are widely available and commonly consumed during exercise, there is still no well-controlled, randomized control trial that has determined if commercially available EB can decrease cramp susceptibility in euhydrated individuals. Thus, the purpose of the present study is to determine if EB consumption alters the frequency of nerve stimulation at which a cramp occurs (TF) compared with a placebo beverage (PB) with similar fluid volume and flavor profile. ...
... Additionally, as four of the nine euhydrated cramp prone participants experienced no difference in TF between conditions, it is possible that either the effect size of the EB was smaller than the resolution (Δ2 Hz) of the test or that in these participants there was no effect of beverage on TF. However, the observed difference between conditions of 1.56 Hz is comparable to differences observed when comparing pickle juice to deionized water (1.8 Hz) 15 and TRPV1 and TRPA1 activators (motor neuron inhibitors) to gelatin gel capsules (1.1 Hz). 20 Sports drinks, such as the EB used in the present study, have the potential to decrease cramp susceptibility by maintaining fluid and electrolyte homeostasis as a result of the water and electrolyte components, and may increase energy availability during intense exercise, both of which may prevent fatigue. ...
... After the observation that TF was greater after consumption of pickle juice compared with deionized water, it has been suggested that differences between conditions may have results from an oropharyngeal-region neurally mediated reflex. 15 Although pickle juice has a distinct and contrasting taste compared with deioniozed water, the present study used two beverages with similar flavor profiles to account for a placebo effect and the general effects of flavoring on TF. However, this does not fully account for oropharyngeal-region reflexes as it was impossible to identically match flavor between beverages, and in our exit survey, only four of nine participants incorrectly guessed which condition they received on which day. ...
Article
Introduction: Recent investigations have questioned the role of hydration and electrolytes in cramp susceptibility and thus the efficacy of consuming electrolyte-rich beverages (EB) to control/prevent cramping. Methods: Nine euhydrated, cramp-prone participants had their cramp susceptibility assessed by measuring the nerve stimulation threshold frequency at which cramping occurs (TF) before and after consumption of an EB (kCal: 120, Na: 840 mg, K: 320 mg, Mg: 5 mg) and placebo beverage (PB: kCal: 5, Na: 35 mg). Cramp intensity was assessed using a verbal pain scale and post-stimulation electromyography (EMG). Results: TF was greater in EB (14.86±7.47 hz) than PB (14.00±5.03 hz, p=0.038) and reported pain was lower in EB (2.0±0.6) than PB (2.7±0.8, p=0.025) while EMG was similar (p=0.646). Discussion: EB consumption decreased cramp susceptibility and pain but did not prevent cramping in any participants. These results suggest that electrolyte consumption independent of hydration can influence cramp susceptibility in young people. This article is protected by copyright. All rights reserved.
... However, in the human model of electrically-invoked cramp, pickle juice (which has a high salt content and a sharp taste imparted by the acetic acid content) was reported to be effective in reducing the duration of cramps. Miller et al. found that cramp duration was reduced by about 37% on average when 1 mL of pickle juice was ingested 2 s after induction of cramping, compared with a trial where water was ingested (85 ± 19 s vs. 134 ± 16 s, respectively; p < 0.05); the intensity of cramping was not affected [64]. The same authors had previously shown that ingestion of small volumes of pickle juice had no measurable effect on plasma concentrations of sodium, potassium, magnesium or calcium concentration, or on plasma osmolality and plasma volume [65]. ...
... However, this and the results of other similar studies, raise some interesting questions; crossover designs involve using the same subjects in treatment and placebo trials, usually in the case of a single treatment, with half receiving treatment before placebo and the order reversed in the other half. The statistical analysis applied in the study by Miller et al. [64] assumes that there was no treatment order effect, but we cannot be sure that this is true, with only 1 week for recovery between experimental trials [66]. The authors of this and other studies involving similar experimental designs should have reported whether the cramp intensity and cramp duration were different between the first and second exposures, and should perhaps also have habituated the subjects to the electrical stimulation process prior to the experimental trials. ...
... These authors induced EAMC in the gastrocnemius medialis of one leg twice a week, while the opposite leg served as the control leg; after four cramp training sessions, the cramp threshold frequency (CTF) increased in the intervention leg but not in the control leg. This same consideration of course applies to many other laboratory studies of electrically-evoked cramping, but becomes particularly acute when, as in the study of Miller et al. [64], a large difference between conditions occurs in the first trial, with possible consequences for the succeeding trial. ...
Article
Full-text available
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.
... 16 Another possible concern is that ingesting PJ may increase [Na þ ] p and plasma osmolality (OSM p ), thereby rapidly expanding plasma volume, decreasing thirst, and impairing rehydration. 14 However, others have observed no changes in plasma electrolyte concentrations, OSM p , or plasma volume when euhydrated 17 or mildly hypohydrated [18][19][20] individuals ingested small volumes (approximately 80 mL) of PJ. Furthermore, ingesting PJ did not alter perceived thirst or the volume of water ingested ad libitum postexercise. ...
... 19 Previous examinations of the effect of PJ on the extracellular fluid space had 3 limitations. [17][18][19][20][21] First, the authors only provided 1 bolus of PJ at 1 time, either preexercise 17,21 or postexercise. [18][19][20] Anecdotally, some athletic trainers give athletes PJ multiple times over the course of an exercise session to treat or prevent EAMC (eg, before a game or at halftime). ...
... [17][18][19][20][21] First, the authors only provided 1 bolus of PJ at 1 time, either preexercise 17,21 or postexercise. [18][19][20] Anecdotally, some athletic trainers give athletes PJ multiple times over the course of an exercise session to treat or prevent EAMC (eg, before a game or at halftime). Second, participants did not exercise postingestion of PJ. [17][18][19]21 No researchers have examined the extracellular fluid space after individuals ingested PJ and then resumed exercise. ...
Article
Context: Some athletes ingest pickle juice (PJ) or mustard to treat exercise-associated muscle cramps (EAMCs). Clinicians warn against this because they are concerned it will exacerbate exercise-induced hypertonicity or cause hyperkalemia. Few researchers have examined plasma responses after PJ or mustard ingestion in dehydrated, exercised individuals. Objective: To determine if ingesting PJ, mustard, or deionized water (DIW) while hypohydrated affects plasma sodium (Na(+)) concentration ([Na(+)]p), plasma potassium (K(+)) concentration ([K(+)]p), plasma osmolality (OSMp), or percentage changes in plasma volume or Na(+) content. Design: Crossover study. Setting: Laboratory. Patients or other participants: A total of 9 physically active, nonacclimated individuals (age = 25 ± 2 years, height = 175.5 ± 9.0 cm, mass = 78.6 ± 13.8 kg). Intervention(s): Participants exercised vigorously for 2 hours (temperature = 37°C ± 1°C, relative humidity = 24% ± 4%). After a 30-minute rest, a baseline blood sample was collected, and they ingested 1 mL/kg body mass of PJ or DIW. For the mustard trial, participants ingested a mass of mustard containing a similar amount of Na(+) as for the PJ trial. Postingestion blood samples were collected at 5, 15, 30, and 60 minutes. Main outcome measure(s): The dependent variables were [Na(+)]p, [K(+)]p, OSMp, and percentage change in plasma Na(+) content and plasma volume. Results: Participants became 2.9% ± 0.6% hypohydrated and lost 96.8 ± 27.1 mmol (conventional unit = 96.8 ± 27.1 mEq) of Na(+), 8.4 ± 2 mmol (conventional unit = 8.4 ± 2 mEq) of K(+), and 2.03 ± 0.44 L of fluid due to exercise-induced sweating. They ingested approximately 79 mL of PJ or DIW or 135.24 ± 22.8 g of mustard. Despite ingesting approximately 1.5 g of Na(+) in the PJ and mustard trials, no changes occurred within 60 minutes postingestion for [Na(+)]p, [K(+)]p, OSMp, or percentage changes in plasma volume or Na(+) content (P > .05). Conclusions: Ingesting a small bolus of PJ or large mass of mustard after dehydration did not exacerbate exercise-induced hypertonicity or cause hyperkalemia. Consuming small volumes of PJ or mustard did not fully replenish electrolytes and fluid losses. Additional research on plasma responses pre-ingestion and postingestion to these treatments in individuals experiencing acute EAMCs is needed.
... Hz) than in those with a negative (25.561.6 Hz). According to previously published literature, the CTF can be increased by muscle fatigue [20] or by ice bag applications [21] and the duration of electrically induced muscle cramps can be reduced by pickle juice ingestion [22]. However, these findings are limited to acute effects, measured immediately after the respective treatment. ...
... To the knowledge of the authors, these data are the first of its kind. As denoted introductorily, the few studies available to date reporting CTF increments were limited to acute effects, measured immediately after the respective interventions [20,21,22]. ...
Article
Full-text available
To investigate if the cramp threshold frequency (CTF) can be altered by electrical muscle stimulation in a shortened position. A total of 15 healthy male sport students were randomly allocated to an intervention (IG, n = 10) and a non-treatment control group (CG, n = 5). Calf muscles of both legs in the IG were stimulated equally twice a week over 6 weeks. The protocol was 3×5 s on, 10 s off, 150 µs impulse width, 30 Hz above the individual CTF, and was at 85% of the maximal tolerated stimulation energy. One leg was stimulated in a shortened position, inducing muscle cramps (CT), while the opposite leg was fixated in a neutral position at the ankle, hindering muscle cramps (nCT). CTF tests were performed prior to the first and 96 h after the 6th (3 w) and 12th (6 w) training session. After 3 w, the CTF had significantly (p<0.001) increased in CT calves from 23.3±5.7 Hz to 33.3±6.9 Hz, while it remained unchanged in nCT (pre: 23.6±5.7 Hz, mid: 22.3±3.5 Hz) and in both legs of the CG (pre: 21.8±3.2 Hz, mid: 22.0±2.7 Hz). Only CT saw further insignificant increases in the CTF. The applied stimulation energy (mA2 • µs) positively correlated with the effect on the CTF (r = 0.92; p<0.001). The present study may be useful for developing new non-pharmacological strategies to reduce cramp susceptibility. German Clinical Trials Register DRKS00005312.
... Among these 50 articles, 20 were literature review including 3 systematic review (with homogeneity) of randomized controlled trials ( [40][41][42][43][44][45][46][47], 7 deal with ''heat cramps'' [28][29][30][31]37,48,49], and 9 deal with muscle cramps without clear diagnosis [2,[11][12][13][14][17][18][19][20]. ...
... Other non-pharmacologic interventions have been suggested without high scientific support: ice, massage, heat, walking, leg elevation, leg jiggling, pickle juice. . . [22,24,41]. ...
Article
Full-text available
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).
... 49,58 Pickle juice contains high concentrations of salt along with acetic acid, which is thought to trigger a reflex that increases inhibitory neurotransmitter activity in cramping muscles. 58,59 One case report indicated that drinking 30-60 ml of pickle juice relieved EAMC within 30-35 seconds after consumption by restoring electrolyte balance. 58 Miller et al. 59 compared the effects of consumption of 1 ml/kg of body weight of pickle juice to a similar volume of de-ionized water immediately after cramp induction in the flexor hallucis brevis muscles of 12 hypohydrated (3%) men. ...
... 58,59 One case report indicated that drinking 30-60 ml of pickle juice relieved EAMC within 30-35 seconds after consumption by restoring electrolyte balance. 58 Miller et al. 59 compared the effects of consumption of 1 ml/kg of body weight of pickle juice to a similar volume of de-ionized water immediately after cramp induction in the flexor hallucis brevis muscles of 12 hypohydrated (3%) men. The researchers reported that cramp duration was 49.1 6 14.6 seconds shorter after pickle juice ingestion compared with the water condition (P < 0.05). ...
Article
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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.
... Studies carried out with electrical stimulation-induced cramps (different from exerciseassociated muscle cramps) suggest that the ingestion of pickle juice triggers a reflex in the oropharyngeal region, which reduces the alpha motor neuron pool activity. 60 Considering the evidence yet available, it is premature to recommend using pickle juice to prevent exerciseassociated muscle cramps. Notwithstanding, pickle juice can be considered for the acute relief of reports generated by exercise-associated muscle cramps if players demand it. ...
... Notwithstanding, pickle juice can be considered for the acute relief of reports generated by exercise-associated muscle cramps if players demand it. For this purpose, about 1 mL/kg of pickle juice can be used, 60 typically in the form of available flavoured prepacked 75 mL bottles, to increase players adherence. 61 Protein and amino acids Recently, a set of ready-to-drink products with added protein or amino acids (particularly branched-chain amino acids, BCAA) have emerged. ...
Article
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Nutrition is an undeniable part of promoting health and performance among football (soccer) players. Nevertheless, nutritional strategies adopted in elite football can vary significantly depending on culture, habit and practical constraints and might not always be supported by scientific evidence. Therefore, a group of 28 Portuguese experts on sports nutrition, sports science and sports medicine sought to discuss current practices in the elite football landscape and review the existing evidence on nutritional strategies to be applied when supporting football players. Starting from understanding football's physical and physiological demands, five different moments were identified: preparing to play, match-day, recovery after matches, between matches and during injury or rehabilitation periods. When applicable, specificities of nutritional support to young athletes and female players were also addressed. The result is a set of practical recommendations that gathered consensus among involved experts, highlighting carbohydrates periodisation, hydration and conscious use of dietary supplements.
... The present work further demonstrates that the use of sodium supplements and the rate of intake of sodium in supplements are not related to muscle cramping. Interestingly, it has been shown that pickle juice can inhibit electrically induced muscle cramps in mildly dehydrated humans; however, the effect was evident before absorption could have occurred [34]. It was speculated that some component (not necessarily the electrolyte content) of the pickle juice might trigger a reflex from the oropharyngeal region that inhibits alpha motor neurons [34]. ...
... Interestingly, it has been shown that pickle juice can inhibit electrically induced muscle cramps in mildly dehydrated humans; however, the effect was evident before absorption could have occurred [34]. It was speculated that some component (not necessarily the electrolyte content) of the pickle juice might trigger a reflex from the oropharyngeal region that inhibits alpha motor neurons [34]. ...
Article
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This work sought to identify characteristics differing between those with and without muscle cramping during a 161-km ultramarathon. In this observational study, race participants underwent body weight measurements before, during, and after the race; completed a post-race questionnaire about muscle cramping and “near” cramping (controllable, not reaching full-blown cramping), drinking strategies, and use of sodium supplementation during four race segments; and underwent a post-race blood draw for determination of serum sodium and blood creatine kinase (CK) concentrations. The post-race questionnaire was completed by 280 (74.5 %) of the 376 starters. A post-race blood sample was provided by 181 (61.1 %) of the 296 finishers, and 157 (53.0 %) of finishers completed the post-race survey and also provided a post-race blood sample. Among those who completed the survey, the prevalence of cramping and near cramping was 14.3 and 26.8 %, respectively, with greatest involvement being in the calf (54 %), quadriceps (44 %), and hamstring (33 %) muscles. Those with cramping or near cramping were more likely to have a prior history of muscle cramping during an ultramarathon (p < 0.0001) and had higher blood CK concentrations (p = 0.001) than those without cramping. Weight change during the race, use of sodium supplements, intake rate of sodium in supplements, and post-race serum sodium concentration did not differ between those with and without cramping. Muscle cramping is most common in those with a prior history of cramping and greater muscle damage during an ultramarathon, suggesting an association with relative muscular demand. Impaired fluid and sodium balance did not appear to be an etiology of muscle cramping during an ultramarathon.
... Pickle juice, a salty ([Na þ ] ranging from 415.2 to 978.5 mmolÁL À1 ), acidic brine [8][9][10] has been advocated as a treatment for exercise-associated muscle cramps (EAMCs). 7,11,12 In fact, 25% (92 of 370) of athletic trainers studied used or had used pickle juice as a treatment for EAMCs. ...
... 12 Although experimental data on pickle juice's effectiveness for treating EAMCs are limited, 7 pickle juice has been shown to reduce electrically induced musclecramp duration in 3% hypohydrated males without altering [Na þ ] p . 9 Some clinicians 13 have expressed concern about athletes ingesting pickle juice because of its high Na þ content. They 13 fear that drinking pickle juice will increase [Na þ ] p and cause a rapid plasma volume restoration, thereby decreasing thirst and delaying rehydration. ...
Article
Context: Adding sodium (Na(+)) to drinks improves rehydration and ad libitum fluid consumption. Clinicians (∼25%) use pickle juice (PJ) to treat cramping. Scientists warn against PJ ingestion, fearing it will cause rapid plasma volume restoration and thereby decrease thirst and delay rehydration. Advice about drinking PJ has been developed but never tested. Objective: To determine if drinking small volumes of PJ, hypertonic saline (HS), or deionized water (DIW) affects ad libitum DIW ingestion, plasma variables, or perceptual indicators. Design: Crossover study. Setting: Laboratory. Patients or other participants: Fifteen, euhydrated (urine specific gravity ≤ 1.01) men (age = 22 ± 2 years, height = 178 ± 6 cm, mass = 82.9 ± 8.4 kg). Intervention(s): Participants completed 3 testing days (≥ 72 hours between days). After a 30-minute rest, a blood sample was collected. Participants completed 60 minutes of hard exercise (temperature = 36 ± 2°C, relative humidity = 16 ± 1%). Postexercise, they rested for 30 minutes; had a blood sample collected; rated thirst, fullness, and nausea; and ingested 83 ± 8 mL of PJ, HS, or DIW. They rated drink palatability (100-mm visual analog scale) and were allowed to drink DIW ad libitum for 60 minutes. Blood samples and thirst, fullness, and nausea ratings (100-mm visual analog scales) were collected at 15, 30, 45, and 60 minutes posttreatment drink ingestion. Main outcome measure(s): Ad libitum DIW volume, percentage change in plasma volume, plasma osmolality (OSMp,) plasma sodium concentration ([Na(+)]p), and thirst, fullness, nausea, and palatability ratings. Results: Participants consumed more DIW ad libitum after HS (708.03 ± 371.03 mL) than after DIW (532.99 ± 337.14 mL, P < .05). Ad libitum DIW ingested after PJ (700.35 ± 366.15 mL) was similar to that after HS and DIW (P > .05). Plasma sodium concentration, OSMp, percentage change in plasma volume, thirst, fullness, and nausea did not differ among treatment drinks over time (P > .05). Deionized water (73 ± 14 mm) was more palatable than HS (17 ± 13 mm) or PJ (26 ± 16 mm, P < .05). Conclusions: The rationale behind advice about drinking PJ is questionable. Participants drank more, not less, after PJ ingestion, and plasma variables and perceptual indicators were similar after PJ and DIW ingestion. Pickle juice did not inhibit short-term rehydration.
... The altered neuromuscular control may be prevented by interventions that target muscle spindle and Golgi tendon organ receptors. This will delay the occurrence of neuromuscular fatigue and thus EAMC 45 . Static stretching pre-exercise was proposed as such an intervention. ...
... The other category of EAMC mentioned in literature is heat-related EAMC 17,35 . These cramps are a result of muscle fatigue combined with fluid and electrolyte loss due to sweating 16,36,45 . 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. ...
Article
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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.
... It has mainly been studied as a treatment to restore electrolyte balance as a result of dehydration and to treat muscle cramps. PJ has been shown to reduce muscle cramp duration significantly when compared to water (Miller, 2010). The underlying mechanism for this effect is not well understood. ...
... PJ is used by athletic trainers, primarily for muscle cramp and recovery (Miller et al., 2008;Miller et al., 2010). It is also believed to have positive effects on hydration and electrolyte replacement, but research has not confirmed these effects (Miller et al., 2009;Miller, 2014). ...
Article
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Pickle juice is widely used by athletes for muscle cramps and recovery. The purpose of this study was to evaluate the effects of pickle juice on core temperature (CT), heart rate (HR), movement economy, RPE, thermal sensation, and cognition during an exercise session simulating a soccer game in a hot and humid environment. 14 female soccer players (age=22.3+4.27y, body fat percentage= 25.2+6.38%, VO2 max=43.7+5.78 ml/kg/min) completed two counterbalanced sessions on a treadmill in a heat chamber (WBGT=31.2oC, & humidity=80-85%) during which they consumed water only versus pickle juice and water. HR and movement economy (oxygen consumption) were similar during sessions while core temperature was lower during the water-only trial. During the pickle juice trial, RPE was significantly lower and cognitive function was higher. Data indicates that pickle juice supplementation may reduce perception of exercise intensity and enhance cognitive function in hot environments but may cause a relatively small rise in core temperature.
... Minetto et al. 1 and Stone et al. 13 reported similar results for similar procedures. Recent studies have used electrical stimulation [15][16][17] or a combination of MVC and electrical stimulation 18 to study the possible causes of EAMC (e.g., dehydration, neuromuscular fatigue). The threshold electrical current frequency (Hz) at which a muscle will cramp has been shown to correspond to an individual's predisposition to cramping. ...
Article
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Context: Exercise-associated muscle cramping (EAMC) is difficult to induce experimentally. Purpose: To 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. Key Words: exercise-associated muscle cramping, maximum voluntary contraction, muscle spasm
... 8 Most of these clinicians instruct athletes to ingest 70 to 200 mL of PJ, provide it 30 to 60 minutes before exercise, and give unknown volumes of water concurrently to prevent cramping. 8 Ingesting small volumes (1 mL/kg body mass) of PJ reduces the duration of electrically induced muscle cramps 9 ; preventing muscle cramps may allow athletes to perform better. Some scientists have advised against drinking PJ because they are concerned that the high sodium content may negatively affect performance by accelerating dehydration, prolonging rehydration, or causing stomach upset and nausea. ...
Article
Context Ingesting high-sodium drinks pre-exercise can improve thermoregulation and performance. Athletic trainers (19%) give athletes pickle juice (PJ) prophylactically for cramping. No data exist on whether this practice affects aerobic performance or thermoregulation. Objective To determine if drinking 2 mL/kg body mass of PJ, hypertonic saline, or deionized water (DIW) pre-exercise affects aerobic performance or thermoregulation. Design Crossover study. Setting Controlled laboratory study. Patients or Other Participants Nine euhydrated men (age = 22 ± 3 years, height = 184.0 ± 8.2 cm, mass = 82.6 ± 16.0 kg) completed testing. Intervention(s) Participants rested for 65 minutes. During this period, they ingested 2 mL/kg of PJ, hypertonic saline, or DIW. Next, they drank 5 mL/kg of DIW. Blood was collected before and after ingestion of all fluids. Participants were weighed and ran in the heat (temperature = 38.3°C ± 1°C, relative humidity = 21.1% ± 4.7%) at increasing increments of maximal heart rate (50%, 60%, 70%, 80%, 90%, 95%) until exhaustion or until rectal temperature exceeded 39.5°C. Participants were weighed postexercise so we could calculate sweat volume. Main Outcome Measure(s) Time to exhaustion, rectal temperature, changes in plasma volume, and sweat volume. Results Time to exhaustion did not differ among drinks (PJ = 77.4 ± 5.9 minutes, hypertonic saline = 77.4 ± 4.0 minutes, DIW = 75.7 ± 3.2 minutes; F2,16 = 1.1, P = .40). Core temperature of participants was similar among drinks (PJ = 38.7°C ± 0.3°C, hypertonic saline = 38.7°C ± 0.4°C, DIW = 38.8°C ± 0.4°C; P = .74) but increased from pre-exercise (36.7°C ± 0.2°C) to postexercise (38.7°C ± 0.4°C) (P < .05). No differences were observed for changes in plasma volume or sweat volume among drinks (P > .05). Conclusions Ingesting small amounts of PJ or hypertonic saline with water did not affect performance or select thermoregulatory measures. Drinking larger volumes of PJ and water may be more effective at expanding the extracellular space.
... Miller a tenté de montrer qu'indépendamment des électrolytes, seule l'hydratation intervenait dans la genèse des crampes. Néamoins, il n'a pas observé de différence significative en comparant l'effet de l'absorption de jus de cornichon et d'eau non déminéralisée sur l'inhibition des crampes musculaires induites électriquement chez des humains déshydratés [11]. ...
... 17,18 Further it could be shown that the ingestion of pickle juice reduces the duration of electrically induced muscle cramps. 19 However, all of these data are acute effects, assessed immediately after the respective treatment. By contrast, no other study to date investigated the time course of CTF changes following two bouts of EIMCs. ...
Article
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The cramp threshold frequency (CTF) is known to be positively correlated with the individual cramp susceptibility. Here we assessed CTF changes after two bouts of electrically induced muscle cramps (EIMCs). The EIMCs (6×5 sec) were unilaterally induced twice (separated by one week) in the gastrocnemius of an intervention group (n=8), while 5 participants served as control. The CTF increased from 25.1±4.6 Hz at baseline to 31.4±9.0 Hz and 31.7±8.5 Hz 24 h after bout 1 and 2 (P<0.05). Thereafter, the CTF declined following both bouts to reach values of 28.0±6.7 Hz and 29.1±7.7 Hz after 72 h after bout 1 and 2. Creatine kinase (CK) activity and perceived discomfort during cramps was lower after bout 2 (P<0.05). CTF, CK, and discomfort did not change in CG. That is, a single bout of EIMCs induces a 24 h CTF increment and a second bout sustains this effect, while perceived discomfort and muscle damage decreases. This short term effect may help athletes to reduce the cramp susceptibility for an important match.
... In an important study published in 2010, Miller et al, showed that the duration of muscle cramping was reduced by administration of oral pickle juice immediately following electrically induced muscle cramps in hypohydrated humans (1). The authors concluded that this effect could not be explained by rapid restoration of body fluids or electrolytes, and suggested it reflected a neutrally-mediated reflex originating in the oropharyngeal region and inhibiting the firing of alpha motor neurons of the cramping muscle. ...
... I doubt this model applies to heat (sweat) cramping in tennis or football, but one ''shocking'' finding in this model is that pickle juice ''works'' fast (in about 85 s) to alleviate the cramp. The hypothesis is that pickle juice sparks a neural reflex that originates from the oropharynx and inhibits the firing of the alpha motor neurons of the cramping muscle (5). ...
... There have been claims that a neutrally-mediated reflex originating with transient receptor potential channels in the oropharyngeal region can inhibit the firing of alpha motor neurons of cramping muscles. 69,70 This could yield a role for oral intake of sodium or other transient receptor potential channel agonists, but this effect has not been adequately examined. 71 Even so, it would not provide rationale for consuming excessive sodium during exercise. ...
Article
The health and performance of ultra-endurance athletes is dependent on avoidance of performance limiting hypohydration while also avoiding the potentially fatal consequences of exercise-associated hyponatremia due to overhydration. In this work, key factors related to maintaining proper hydration during ultra-endurance activities are discussed. In general, proper hydration need not be complicated and has been well demonstrated to be achieved by simply drinking to thirst and consuming a typical race diet during ultra-endurance events without need for supplemental sodium. As body mass is lost from oxidation of stored fuel, and water supporting the intravascular volume is generated from endogenous fuel oxidation and released with glycogen oxidation, the commonly promoted hydration guidelines of avoiding body mass losses of >2% can result in overhydration during ultra-endurance activities. Thus, some body mass loss should occur during prolonged exercise, and appropriate hydration can be maintained by drinking to the dictates of thirst.
... Apple cider vinegar, pickle juice, a bar of soap (Irish Spring is often mentioned) under the sheets, cream of tartar, a golden rod stems and flowers in tea, black strap molasses, mustard, a copper ring on the first digit of the cramping leg, each have their proponents. While one study indicated rapid relief of electrically-induced cramping in hypohydrated adults through the administration of pickle juice, the relief obtained could not have reflected any electrolyte effect, because its impact was much more rapid than can be explained by increased bioavailability of sodium or any other substance in the juice (18) . Another study which measured plasma electrolytes, osmolality and fluid volume showed no change during a 60 minute interval after ingestion of pickle juice. ...
... Subjects self-reported compliance with testing instructions between experimental days. Some data (e.g., urine data) have been previously reported (27). Data are presented as means T SE. ...
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.
... Quinine is therefore no longer recommended for use in cramp management. Pickle juice, which contains acetic acid, sipped during a limb cramp reduced cramp duration, probably by an inhibitory oropharyngeal reflex mechanism [76]. ...
Article
Muscular cramp is a common symptom in healthy people, especially among the elderly and in young people after vigorous or peak exercise. It is prominent in a number of benign neurological syndromes. It is a particular feature of chronic neurogenic disorders, especially amyotrophic lateral sclerosis. We undertook a literature review to understand the diverse clinical associations of cramp and its neurophysiological basis, taking into account recent developments in membrane physiology and modulation of motor neuronal excitability. Many aspects of cramping remain incompletely understood and require further study. Current treatment options are correspondingly limited. This article is protected by copyright. All rights reserved.
Chapter
Exercise-associated muscle cramps (EAMC) are painful, involuntary skeletal muscle contractions during and after exercise. Despite EAMC being the most prevalent heat-related illness in athletes, their cause remains unclear and controversial. Contrary to popular opinion, most recent observational and experimental evidence suggests EAMC are not solely due to dehydration or electrolyte imbalances. Rather, it is likely EAMC stem from a convergence of an individual’s intrinsic and extrinsic risk factors which act to alter central and peripheral nervous system excitability. Unfortunately, the lack of a clear etiology for EAMC has spawned numerous myths and anecdotes regarding the most effective treatment and prevention strategies. However, the treatment for an athlete experiencing EAMC remains gentle static stretching until the EAMC abate. The most effective EAMC prevention strategy is less clear. EAMC prevention strategies should be tailored to an individual’s unique risk factors following a thorough medical evaluation and screening. Clinicians should avoid generalized treatment advice (e.g., drink more fluids or sports drinks) since it can result in disastrous outcomes such as exertional hyponatremia.
Article
Abstract The oral-pharyngeal cavity and the gastrointestinal tract are richly endowed with receptors that respond to taste, temperature and to a wide range of specific nutrient and non-nutritive food components. Ingestion of carbohydrate-containing drinks has been shown to enhance endurance exercise performance, and these responses have been attributed to post-absorptive effects. It is increasingly recognised, though, that the response to ingested carbohydrate begins in the mouth via specific carbohydrate receptors and continues in the gut via the release of a range of hormones that influence substrate metabolism. Cold drinks can also enhance performance, especially in conditions of thermal stress, and part of the mechanism underlying this effect may be the response to cold fluids in the mouth. There is also some, albeit not entirely consistent, evidence for effects of caffeine, quinine, menthol and acetic acid on performance or other relevant effects. This review summarises current knowledge of responses to mouth sensing of temperature, carbohydrate and other food components, with the goal of assisting athletes to implement practical strategies that make best use of its effects. It also examines the evidence that oral intake of other nutrients or characteristics associated with food/fluid intake during exercise can enhance performance via communication between the mouth/gut and the brain.
Article
Marosek, SEH, Antharam, V, and Dowlatshahi, K. Quantitative analysis of the acetic acid content in substances used by athletes for the possible prevention and alleviation of exercise-associated muscle cramps. J Strength Cond Res 34(6): 1539-1546, 2020-Athletes regularly consume commercially available food and sports shot products, carbohydrate beverages, and water to improve their physical exertion and to possibly prevent or relieve exercise-associated muscle cramps (EAMCs)-often experienced during practice, training, or competition. Acetic acid, a component of interest within these products, has been recognized for its potential role in cramp reduction. Acetic acid is postulated to mitigate cramping by decreasing alpha motor neuron activity through oropharyngeal stimulation and inhibitory neurotransmitter production, while aiding in the role acetylcholine plays in muscle contraction and relaxation. The purpose of this research is to analytically assess the most viable sources of acetic acid from substances that athletes ingest before or when experiencing these cramps. The range of samples investigated were based on their widespread use in the athletic world: dill and sweet pickle juices, yellow mustard, sweet relish, apple cider vinegar, Hot Shot, PJ Shot, PJ Sport, E-Lyte Sport, Powerade, Gatorade, Smartwater, and Propel (with electrolytes). As hypothesized, pH and enzymatic assay or spectroscopic analyses revealed that yellow mustard, sweet relish, all pickle juices, and the pickle juice products were composed of moderate amounts of acetic acid. Based on established studies resulting in EAMC relief, acetic acid consumption, and the appropriate serving size, the yellow mustard, PJ Shot, and all pickle juices would be the most practical and palatable sources of acetic acid for strength and conditioning professionals to recommend that athletes consume for the possible prevention or alleviation of muscle cramps.
Article
Exercise-associated muscle cramps (EAMC) are common and frustrating for athletes and the physically active. We critically-appraised the EAMC literature to provide evidence-based treatment and prevention recommendations. While the pathophysiology of EAMC appears controversial, recent evidence suggests EAMC are due to a confluence of unique intrinsic and extrinsic factors rather than a singular etiology. The treatment of acute EAMC continues to include self-application or clinician-guided gentle static stretching until EAMC abatement. Once the painful EAMC are alleviated, clinicians can continue treatment on the sidelines by focusing on patient-specific risk factors that the clinician believes may have contributed to the genesis of EAMC. For EAMC prevention, clinicians should first perform a thorough medical history followed by identification of the patients' unique risk factors that could have coalesced to elicit EAMC. Individualizing EAMC prevention strategies will likely be more effective than generalized advice (e.g., drink more fluids).
Article
New findings: What is the topic of this review? The nutritional strategies that athletes use during competition events to optimize performance and the reasons they use them. What advances does it highlight? A range of nutritional strategies can be used by competitive athletes, alone or in combination, to address various event-specific factors that constrain event performance. Evidence for such practices is constantly evolving but must be combined with understanding of the complexities of real-life sport for optimal implementation. Abstract: High-performance athletes share a common goal despite the unique nature of their sport: to pace or manage their performance to achieve the highest sustainable outputs over the duration of the event. Periodic or sustained decline in the optimal performance of event tasks, involves an interplay between central and peripheral phenomena that can often be reduced or delayed in onset by nutritional strategies. Contemporary nutrition practices undertaken before, during or between events include strategies to ensure the availability of limited muscle fuel stores. This includes creatine supplementation to increase muscle phosphocreatine content and consideration of the type, amount and timing of dietary carbohydrate intake to optimize muscle and liver glycogen stores or to provide additional exogenous substrate. Although there is interest in ketogenic low-carbohydrate high-fat diets and exogenous ketone supplements to provide alternative fuels to spare muscle carbohydrate use, present evidence suggests a limited utility of these strategies. Mouth sensing of a range of food tastants (e.g., carbohydrate, quinine, menthol, caffeine, fluid, acetic acid) may provide a central nervous system derived boost to sports performance. Finally, despite decades of research on hypohydration and exercise capacity, there is still contention around their effect on sports performance and the best guidance around hydration for sporting events. A unifying model proposes that some scenarios require personalized fluid plans while others might be managed by an ad hoc approach (ad libitum or thirst-driven drinking) to fluid intake.
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.
Article
Both extreme heat and cold can be challenging for athletes during training and competition. One role of the team physician is to educate coaches and athletes on the risks of exposure to these conditions and how to best prevent and manage their adverse effects. Heat illness varies in degree from mild to severe, with the most severe forms being potentially fatal. Cold exposure can result in systemic effects and peripheral injury to the extremities.
Article
MINETTO, M. A., A. HOLOBAR, A. BOTTER, and D. FARINA. Origin and development of muscle cramps. Exerc. Sport Sci. Rev., Vol. 41, No. 1, pp. 3-10, 2013. Cramps are sudden, involuntary, painful muscle contractions. Their pathophysiology remains poorly understood. One hypothesis is that cramps result from changes in motor neuron excitability (central origin). Another hypothesis is that they result from spontaneous discharges of the motor nerves (peripheral origin). The central origin hypothesis has been supported by recent experimental findings, whose implications for understanding cramp contractions are discussed.
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Small volumes of pickle juice (PJ) relieve muscle cramps within 85 seconds of ingestion without significantly affecting plasma variables. This effect may be neurologic rather than metabolic. Understanding PJ's gastric emptying would help to strengthen this theory. To compare gastric emptying and plasma variables after PJ and deionized water (DIW) ingestion. Crossover study. Laboratory. Ten men (age  =  25.4 ± 0.7 years, height  =  177.1 ± 1.6 cm, mass  =  78.1 ± 3.6 kg). Rested, euhydrated, and eunatremic participants ingested 7 mL·kg⁻¹ body mass of PJ or DIW on separate days. Gastric volume was measured at 0, 5, 10, 20, and 30 minutes postingestion (using the phenol red dilution technique). Percentage changes in plasma volume and plasma sodium concentration were measured preingestion (-45 minutes) and at 5, 10, 20, and 30 minutes postingestion. Initial gastric volume was 624.5 ± 27.4 mL for PJ and 659.5 ± 43.8 mL for DIW (P > .05). Both fluids began to empty within the first 5 minutes (volume emptied: PJ  =  219.2 ± 39.1 mL, DIW  =  305.0 ± 40.5 mL, P < .05). Participants who ingested PJ did not empty further after the first 5 minutes (P > .05), whereas in those who ingested DIW, gastric volume decreased to 111.6 ± 39.9 mL by 30 minutes (P < .05). The DIW group emptied faster than the PJ group between 20 and 30 minutes postingestion (P < .05). Within 5 minutes of PJ ingestion, plasma volume decreased 4.8% ± 1.6%, whereas plasma sodium concentration increased 1.6 ± 0.5 mmol·L⁻¹ (P < .05). Similar changes occurred after DIW ingestion. Calculated plasma sodium content was unchanged for both fluids (P > .05). The initial decrease in gastric volume with both fluids is likely attributable to gastric distension. Failure of the PJ group to empty afterward is likely due to PJ's osmolality and acidity. Cardiovascular reflexes resulting from gastric distension are likely responsible for the plasma volume shift and rise in plasma sodium concentration despite nonsignificant changes in plasma sodium content. These data support our theory that PJ does not relieve cramps via a metabolic mechanism.
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ZUSAMMENFASSUNG Nierenersatztherapie beeinflusst den Alltag der betroffenen Patienten deutlich. Trotzdem können verschiedene Reiseangebote wahrgenommen werden. Bei Flugreisen sollten Dialysepatienten bereits bei der Reisevorbereitung einige organisatorische Aspekte berücksichtigen, Anpassungen der Medikation können erforderlich werden, während des Fluges können Notfälle im Zusammenhang mit der Dialysebehandlung auftreten. Diese Besonderheiten bei Dialysepatienten als Flugpassagiere werden genauer dargestellt.
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Context Despite recent evidence to suggest that exercise-associated muscle cramps (EAMC) might be primarily of neuromuscular origin, the authors surmise that most information available to certified athletic trainers (ATCs) emphasizes the role of dehydration and electrolyte imbalance in EAMC. Objective To investigate ATCs' perceptions of EAMC. Design 7-question, Web-based, descriptive, cross-sectional survey. Subjects 997 ATCs. Main Outcome Measures Responses to 7 questions regarding the cause, treatment, and prevention of EAMC. Results Responders indicated humidity, temperature, training, dehydration, and electrolyte imbalance as causative factors of EAMC. Fluid replacement and stretching the involved muscle were identified as very successful in treating and preventing EAMC. Proper nutrition and electrolyte replacement were also perceived as extremely successful prevention strategies. Conclusions ATCs' perceptions of the cause, treatment, and prevention of EAMC are primarily centered on dehydration and electrolyte imbalance. Other prominent ideas concerning EAMC should be implemented in athletic training education.
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Health care professionals advocate that athletes who are susceptible to exercise-associated muscle cramps (EAMCs) should moderately increase their fluid and electrolyte intake by drinking sport drinks. Some clinicians have also claimed drinking small volumes of pickle juice effectively relieves acute EAMCs, often alleviating them within 35 seconds. Others fear ingesting pickle juice will enhance dehydration-induced hypertonicity, thereby prolonging dehydration. To determine if ingesting small quantities of pickle juice, a carbohydrate-electrolyte (CHO-e) drink, or water increases plasma electrolytes or other selected plasma variables. Crossover study. Exercise physiology laboratory. Nine euhydrated, healthy men (age = 25 +/- 2 years, height = 179.4 +/- 7.2 cm, mass = 86.3 +/- 15.9 kg) completed the study. Resting blood samples were collected preingestion (-0.5 minutes); immediately postingestion (0 minutes); and at 1, 5, 10, 15, 20, 25, 30, 45, and 60 minutes postingestion of 1 mL/kg body mass of pickle juice, CHO-e drink, or tap water. Plasma sodium concentration, plasma magnesium concentration, plasma calcium concentration, plasma potassium concentration, plasma osmolality, and changes in plasma volume were analyzed. Urine specific gravity, osmolality, and volume were also measured to characterize hydration status. Mean fluid intake was 86.3 +/- 16.7 mL. Plasma sodium concentration, plasma magnesium concentration, plasma calcium concentration, plasma osmolality, and plasma volume did not change during the 60 minutes after ingestion of each fluid (P >or= .05). Water ingestion slightly decreased plasma potassium concentration at 60 minutes (0.21 +/- 0.14 mg/dL [0.21 +/- 0.14 mmol/L]; P <or= .05). At these volumes, ingestion of pickle juice and CHO-e drink did not cause substantial changes in plasma electrolyte concentrations, plasma osmolality, or plasma volume in rested, euhydrated men. Concern that ingesting these volumes of pickle juice might exacerbate an athlete's risk of dehydration-induced hypertonicity may be unwarranted. If EAMCs are caused by large electrolyte loss due to sweating, these volumes of pickle juice or CHO-e drink are unlikely to restore any deficit incurred by exercise.
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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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It is the position of the American College of Sports Medicine that adequate fluid replacement helps maintain hydration and, therefore, promotes the health, safety, and optimal physical performance of individuals participating in regular physical activity. This position statement is based on a comprehensive review and interpretation of scientific literature concerning the influence of fluid replacement on exercise performance and the risk of thermal injury associated with dehydration and hyperthermia. Based on available evidence, the American College of Sports Medicine makes the following general recommendations on the amount and composition of fluid that should be ingested in preparation for, during, and after exercise or athletic competition: 1) It is recommended that individuals consume a nutritionally balanced diet and drink adequate fluids during the 24-hr period before an event, especially during the period that includes the meal prior to exercise, to promote proper hydration before exercise or competition. 2) It is recommended that individuals drink about 500 ml (about 17 ounces) of fluid about 2 h before exercise to promote adequate hydration and allow time for excretion of excess ingested water. 3) During exercise, athletes should start drinking early and at regular intervals in an attempt to consume fluids at a rate sufficient to replace all the water lost through sweating (i.e., body weight loss), or consume the maximal amount that can be tolerated. 4) It is recommended that ingested fluids be cooler than ambient temperature [between 15 degrees and 22 degrees C (59 degrees and 72 degrees F])] and flavored to enhance palatability and promote fluid replacement. Fluids should be readily available and served in containers that allow adequate volumes to be ingested with ease and with minimal interruption of exercise. 5) Addition of proper amounts of carbohydrates and/or electrolytes to a fluid replacement solution is recommended for exercise events of duration greater than 1 h since it does not significantly impair water delivery to the body and may enhance performance. During exercise lasting less than 1 h, there is little evidence of physiological or physical performance differences between consuming a carbohydrate-electrolyte drink and plain water. 6) During intense exercise lasting longer than 1 h, it is recommended that carbohydrates be ingested at a rate of 30-60 g.h(-1) to maintain oxidation of carbohydrates and delay fatigue. This rate of carbohydrate intake can be achieved without compromising fluid delivery by drinking 600-1200 ml.h(-1) of solutions containing 4%-8% carbohydrates (g.100 ml(-1)). The carbohydrates can be sugars (glucose or sucrose) or starch (e.g., maltodextrin). 7) Inclusion of sodium (0.5-0.7 g.1(-1) of water) in the rehydration solution ingested during exercise lasting longer than 1 h is recommended since it may be advantageous in enhancing palatability, promoting fluid retention, and possibly preventing hyponatremia in certain individuals who drink excessive quantities of fluid. There is little physiological basis for the presence of sodium in n oral rehydration solution for enhancing intestinal water absorption as long as sodium is sufficiently available from the previous meal.
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OBJECTIVE: To present recommendations for the prevention, recognition, and treatment of exertional heat illnesses and to describe the relevant physiology of thermoregulation. BACKGROUND: Certified athletic trainers evaluate and treat heat-related injuries during athletic activity in "safe" and high-risk environments. While the recognition of heat illness has improved, the subtle signs and symptoms associated with heat illness are often overlooked, resulting in more serious problems for affected athletes. The recommendations presented here provide athletic trainers and allied health providers with an integrated scientific and practical approach to the prevention, recognition, and treatment of heat illnesses. These recommendations can be modified based on the environmental conditions of the site, the specific sport, and individual considerations to maximize safety and performance. RECOMMENDATIONS: Certified athletic trainers and other allied health providers should use these recommendations to establish on-site emergency plans for their venues and athletes. The primary goal of athlete safety is addressed through the prevention and recognition of heat-related illnesses and a well-developed plan to evaluate and treat affected athletes. Even with a heat-illness prevention plan that includes medical screening, acclimatization, conditioning, environmental monitoring, and suitable practice adjustments, heat illness can and does occur. Athletic trainers and other allied health providers must be prepared to respond in an expedient manner to alleviate symptoms and minimize morbidity and mortality.
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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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This observational study was designed to determine whether football players with a history of heat cramps have elevated fluid and sodium losses during training. During a "two-a-day" training camp, five Division I collegiate football players (20.2 +/- 1.6 y, 113 +/- 20 kg) with history of heat cramps (C) were matched (weight, age, race and position) with a cohort of teammates (19.6 +/- 0.6 y, 110 +/- 20 kg) who had never cramped (NC). Change in body weight (adjusted by fluid intake) determined gross sweat loss. Sweat samples (forearm patch) were analyzed for sodium and potassium concentrations. Ad libitum fluid intake was measured by recording pre- and post-practice bottle weights. Average sweat sodium loss for a 2.5-h practice was projected at 5.1 +/- 2.3 g (C) vs. 2.2 +/- 1.7 g (NC). When averaged across two practices within the day, fluid intake was similar between groups (C: 2.6 +/- 0.8 L vs. NC: 2.8 +/- 0.7 L), as was gross sweat loss (C: 4.0 +/- 1.1 L vs. NC: 3.5 +/- 1.6 L). There was wide variability in the fluid deficit incurred for both C and NC (1.3 +/- 0.9 vs. 0.7 +/- 1.2%) due to fluid intake. Sweat potassium was similar between groups, but sweat sodium was two times higher in C versus NC (54.6 +/- 16.2 vs. 25.3 +/- 10.0 mmol/L). These data indicate that sweat sodium losses were comparatively larger in cramp-prone football players than in NC. Although both groups consumed sodium-containing fluids (on-field) and food (off-field), both appeared to experience an acute sodium deficit at the end of practices based on sweat sodium losses. Large acute sodium and fluid losses (in sweat) may be characteristic of football players with a history of heat cramping.
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Context: Recommendations for heat illness prevention provided by sports medicine associations do not always account for sex differences, specific age populations, regional environmental conditions, equipment worn during activity, or the athlete's size or preexisting level of fitness. Objective: To evaluate the rate of exertional heat illness (EHI) among collegiate football athletes and to monitor environmental conditions during American football practice for a 3-month period. Design: Epidemiologic study in which we reviewed the occurrence rates of EHI and wet bulb globe temperature readings during a 3-month period of American collegiate football practice sessions. Setting: Five universities in the southeastern region of the United States. Patients or other participants: Collegiate football players at the 5 universities. Main outcome measure(s): Wet bulb globe temperatures were recorded from August through October 2003, at the beginning, middle, and end of each practice session. The EHIs were identified and recorded, and athlete-exposures (AEs) were calculated. Results: A total of 139 EHIs and 33 196 AEs were reported (EHI rate = 4.19/1000 AEs). The highest incidence of EHIs was in August (88%, EHI rate = 8.95/1000 AEs) and consisted of 70% heat cramps (6.13/1000 AEs), 23% heat exhaustion (2.06/ 1000 AEs), and 7% heat syncope (0.58/1000 AEs). No cases of heat stroke or hyponatremia were identified. The highest risk of EHI occurred during the first 3 weeks of the study; mean wet bulb globe temperature declined significantly as the study continued ( P < .001). Temperatures in the final 5 weeks of the study were significantly cooler than in the first 5 weeks ( P < .05). Conclusions: Heat cramps were the most common EHI and occurred most often during the first 3 weeks of practice. Athletic trainers should take all necessary preventive measures to reduce the risk of EHI.
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This Position Stand provides guidance on fluid replacement to sustain appropriate hydration of individuals performing physical activity. The goal of prehydrating is to start the activity euhydrated and with normal plasma electrolyte levels. Prehydrating with beverages, in addition to normal meals and fluid intake, should be initiated when needed at least several hours before the activity to enable fluid absorption and allow urine output to return to normal levels. The goal of drinking during exercise is to prevent excessive (>2% body weight loss from water deficit) dehydration and excessive changes in electrolyte balance to avert compromised performance. Because there is considerable variability in sweating rates and sweat electrolyte content between individuals, customized fluid replacement programs are recommended. Individual sweat rates can be estimated by measuring body weight before and after exercise. During exercise, consuming beverages containing electrolytes and carbohydrates can provide benefits over water alone under certain circumstances. After exercise, the goal is to replace any fluid electrolyte deficit. The speed with which rehydration is needed and the magnitude of fluid electrolyte deficits will determine if an aggressive replacement program is merited.
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Muscle cramps are involuntary, painful, spasmodic contractions of the skeletal muscle. Although cramps are a common clinical complaint, their etiology and management have not been well established. Exercise-associated muscle cramps occur during or immediately following exercise, and they are associated with muscular fatigue and shortened muscle contraction. The main challenges for treating physicians are to identify whether the complaint represents a true muscle cramp as well as to rule out the presence of an underlying serious clinical condition. Muscle cramps may be a symptom of any of several conditions, including radiculopathies, Parkinson's disease, hypothyroidism, diabetes mellitus, vascular problems, electrolyte disorders, and metabolic myopathies. Cramps also may occur as a side effect of certain drugs (eg, lipid-lowering agents, antihypertensives, beta-agonists, insulin, oral contraceptives, alcohol). Most athletes who experience exercise-associated muscle cramps are healthy individuals without systemic illness. Therapy should focus on preventing premature fatigue by means of appropriate nutrition and adequate training.
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The oral cavity and pharynx are anatomically separate but functionally integrated regions of the head. The two regions are involved in complex motor responses that include feeding, chewing, swallowing, speech, and respiration. The multiple sensory receptors that innervate these two regions provide the first link in reflexes that control muscles of the entire head, upper gastrointestinal tract, and airway. Most of the reflexes affect the diversity of muscles that compose the tongue, which is vital to all stages of feeding and which continually affects the patency of the airway. Oral-pharyngeal reflexes are evident in the mammalian fetus and continually emerge as the animal or human matures. Some of the first reflexes in the oral region are geared toward nourishment. As the central nervous system matures and the oral and pharyngeal regions develop morphologically, new reflexes develop. Many of these reflexes are protective both of the tissue in the oral cavity, such as the tongue, and of the upper airway in preventing aspiration. While simple reflexes can be evoked in isolation, most reflexes combine with more complex oral and pharyngeal responses such as chewing and vocalization. Oral-pharyngeal reflexes demonstrate a range in complexity. Some sensory stimuli will evoke a series of responses, as is often evident in the infant, and other stimuli will evoke a complex multiple-level recruitment of muscles in a sequence, as in pharyngeal swallowing. Certain sensory inputs evoke an entire motor behavior pattern, such as taste avoidance or facial expression. The oral-pharyngeal reflexes are critical to maintaining life and ultimately serve functions that the oral and pharyngeal regions have in common, such as communication, feeding, and breathing.
Article
muscle cramps during exercise are a common affliction, even in highly fit athletes. And as empirical evidence grows, it is becoming increasingly clear that there are two distinct and dissimilar general categories of exercise-associated muscle cramps. Skeletal muscle overload and fatigue can prompt muscle cramping locally in the overworked muscle fibers, and these cramps can be treated effectively with passive stretching and massage or by modifying the exercise intensity and load. In contrast, extensive sweating and a consequent significant whole-body exchangeable sodium deficit caused by insufficient dietary sodium intake to offset sweat sodium losses can lead to a contracted interstitial fluid compartment and more widespread skeletal muscle cramping, even when there is minimal or no muscle overload and fatigue. Signs of hyperexcitable neuromuscular junctions may appear first as fasciculations during breaks in activity, which eventually progress to more severe and debilitating muscle spasms. Notably, affected athletes often present with normal or somewhat elevated serum electrolyte levels, even if they are Bsalty sweaters,^ because of hypotonic sweat loss and a fall in intravascular volume. However, recovery and maintenance of water and sodium balance with oral or intravenous salt solutions is the proven effective strategy for resolving and averting exercise-associated muscle cramps that are prompted by extensive sweating and a sodium deficit.
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Pickle juice is an unconventional treatment for EAMC; however, we believe that enough athletic trainers are using it to treat and prevent EAMC to justify future research to elucidate optimal treatment parameters and possible mechanisms by which it may be effective. The substantial ambiguity and variability about pickle juice use further suggests that experimental research is required on this treatment. If pickle juice is effective, carefully controlled research must be performed to determine the safest, most effective protocols for its use. If it is not effective or poses a risk to athletes as some health professionals claim, 5 those who use pickle juice must be discouraged from using it.
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Thesis ( M.S..) -- Indiana State University, 2004. " Presented to the School of Graduate Studies Department of Athletic Training." Bibliography: leaves 13-14,39.
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The minimum electrical stimulation frequency (HZ) at which a muscle cramps is termed threshold frequency (TF). TF is theorized to represent one's predisposition to cramping; however, TF and cramp occurrence have never been correlated. We hypothesized that TF would be lower in individuals with a cramp history and lower on the second of two days of testing; genetics may partially explain this lower TF. Cramp TF was measured in 19 subjects with (Group 1), and 12 subjects without (Group 2), a cramp history. Group 1 had a lower TF (14.9 +/- 1.3 vs. 25.5 +/- 1.6 HZ; P < 0.001) and a higher family history of cramping than Group 2 (89% vs. 27%; P < 0.001). TF was lower on day 2 (18.3 +/- 0.26 HZ) than day 1 (19.7 +/- 0.25 HZ; P = 0.03). Lower TFs are correlated with cramp history, supporting the inference that lower TFs may represent increased predisposition toward cramping. TF may be used to identify individuals at risk of cramping.
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Gastrointestinal distress is commonly reported by athletes after ingestion of a beverage. We speculate that ingestion may be occurring after dehydration has taken place. The high prevalence of GI disorders in marathon runners who have lost greater than or equal to 4% body weight supports this theory. To test this theory, the effects of dehydration, and dehydration in combination with endurance running, on gastric emptying (GE) and frequency of gastrointestinal (GI) complaints were tested in this experiment. A complete cross-over study was designed. Sixteen subjects ingested 8 ml.kg BW-1 of a 7% carbohydrate (296 mOsm.kg-1), solution after a euhydration or dehydration regime. Dehydration (4% BW loss) was produced by 60% maximal speed running at 30 degrees C or by intermittent sauna exposure at 100 degrees C. Euhydration experiments were conducted with a 2 h rest period with water administered at 20 and 40 min. Gastric drink volumes were measured every 10 min for 40 min. Emptying curves were compared using semi-log transformation of the percentage emptying data and simple linear regression. The slope of each line was used as a measure of average GE rate. Dehydration-exercise resulted in slower GE than in all other treatments (P less than 0.05). ANOVA revealed significant effects of dehydration (P less than 0.05) and exercise (P less than 0.05), these two effects being additive in delaying GE. GI complaints were reported by 37.5% of the subjects during dehydration-exercise experiments. No GI disturbance was reported in other tests.(ABSTRACT TRUNCATED AT 250 WORDS)
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To study the distribution of glycine immunoreactive neurons in the spinal cord and brain, antisera were raised against glycine conjugated to protein carriers. High-titer rabbit glycine antiserum was purified by affinity chromatography. Testing against other amino acids and peptides with immuno dot blots and ELISA assays showed little apparent cross-reaction with glutamate, aspartate, glutamine, taurine, and 17 other amino acids and related compounds. Similarly, the antiserum showed little apparent recognition of glycine when glycine was incorporated into peptides. A slight cross-reactivity with GABA, beta-alanine, and cysteine was found. Immunocytochemical labeling of tissue sections could be blocked with glycine conjugated to a heterologous carrier protein but not by other amino acids conjugated to that protein. Immunocytochemistry at the light microscope level with immunofluorescence and silver-intensified colloidal gold revealed a wide distribution of glycine-like immunoreactivity throughout all laminae of the rat spinal cord and in all segments studied from the cervical, thoracic, lumbar, and sacral cord. Immunoreactive boutons were found terminating on both cell bodies and on dendrites. Ultrastructural analysis with postembedding colloidal gold immunocytochemistry demonstrated large numbers of immunoreactive boutons making symmetrical type synapses with neuronal perikarya, including motor neurons, and with proximal and distal dendrites. Presynaptic glycine immunoreactive boutons were found in both ventral and dorsal horn. Immunoreactivity was concentrated over regions rich in vesicles, and over mitochondria in immunoreactive boutons, but not over mitochondria in postsynaptic dendrites. Glycine-immunoreactive perikarya were identified both in the dorsal horn and in the ventral horn. Myelinated and unmyelinated glycine-immunoreactive axons were noted both in the gray and white matter of the cord. The density of immunoreactive axons varied in the white matter, with the greatest number of immunoreactive axons found in the white matter adjacent to the gray matter in lateral and ventral white. Significantly fewer immunoreactive axons were found in the white matter of the dorsal columns. Myelin sheaths around axons were unlabeled. The distribution of glycine-immunoreactive boutons correlated well with the distribution of glycine receptor immunoreactivity on postsynaptic elements of the spinal cord, tested with different monoclonal antisera against strychnine-purified glycine receptor. Glycine receptor immunoreactivity was found throughout the gray matter of both rat and primate.(ABSTRACT TRUNCATED AT 400 WORDS)
Article
Exercise-induced muscle cramp has been considered to result from disturbances of fluid and electrolyte balance resulting from excessive sweat loss. Serum biochemical and haematological measurements were made on 82 male marathon runners before and after a 42.2-km race. Fifteen (18%) of the runners reported an attack of muscle cramp which occurred after 35 +/- 6 km (mean +/- S.D.) had been covered. These subjects were not different from the others in terms of racing performance or training status. Serum electrolyte concentrations, including sodium and potassium, were not different between those suffering from cramp and those not so affected either before or after the race, although a significant (P less than 0.001) increase in serum sodium concentrations occurred in both groups. Serum bicarbonate concentrations fell to the same extent (from 28 to 24 mmol l-1) in both groups. Significant decreases in plasma volume, calculated from the changes in circulating haemoglobin and haematocrit, occurred in both groups of subjects, but there was no difference in the extent of the haemoconcentration. The results suggest that exercise-induced muscle cramp may not be associated with gross disturbances of fluid and electrolyte balance.
Article
Observations on hematocrit (Hct) and hemoglobin (Hb) were made in 6 men before and after running long enough to cause a 4% decrease in body weight. Subscripts B and A were used to denote before dehydration and after dehydration, respectively. Relations were derived between BV(b), BV(a), HB(b), Hb(a), Hct(b), and Hct(a) with which the percentage decreases in BV, CV, and PV can be calculated, as well as the concentration of hemoglobin in red cells, g/100 ml-1 (MCHC). When subjects reach the same level of dehydration the water loss from the various body compartments may vary reflecting the difference in salt losses in sweat. Changes in PV calculated from the increase in plasma protein concentration averaged -7.5% compared with -12.2% calculated from changes in Hb and Hct. The difference could be accounted for by a loss of 6% plasma protein from the circulation.
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An analysis has been made in anaesthetised cats of the depression by glycine and related amino acids of the firing of spinal dorsal horn interneurones, Renshaw cells and cortical neurones. In general, electrophoretically administered glycine was a more potent depressant of interneurones than GABA. The reverse was true for cortical neurones, whereas these two amino acids were approximately equally effective upon Renshaw cells. Strychnine blocked the depressant action of a- and ß-amino acids, but not that of ?- and higher ?-amino acids. Only convulsants having a strychnine-like effect on spinal post-synaptic inhibition blocked the action of glycine. The depression of spinal neurones produced by glycine or GABA was not affected by structural analogues of glycine and GABA that were not depressants, or by substances influencing amino acid transport systems. Some evidence was obtained for the enzymic inactivation of electrophoretically administered glycine in spinal tissue. The results are discussed in terms of the involvement of a glycine-like amino acid as a major spinal inhibitory transmitter.
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The anatomic site of origin of muscle fasciculations and cramps has been debated for many years. Many authors have argued for a central origin of the abnormal discharges in the anterior horn cells. However, most of the evidence favors a very distal origin in the intramuscular motor nerve terminals. The factors giving rise to these discharges are not well understood. Fasciculations may be related to chemical excitation of motor nerve terminals, whereas cramps may result from mechanical excitation of motor nerve terminals during muscle shortening.
Article
We investigated the mechanism of cramps in 2 patients: a 48-year-old man with bulbospinal neuronopathy, and a 46-year-old man with amyotrophic lateral sclerosis. Cramps were quite easily induced by volitional exertion and high-frequency stimulation of the peripheral nerves. When an ulnar nerve was blocked with lidocaine at the elbow, no cramp was induced despite the application of high-frequency stimulation at the wrist. Diazepam (GABAA agonist) was effective in the first patient and baclofen (GABAB agonist) in the second, with no cramps induced in spite of increasing stimulation intensity. Impairment of interneurons mediated by GABA as the neurotransmitter is thought to be involved in the mechanism of the cramps.
Article
Muscle cramps induced by voluntary contraction and by electrical stimulation of the peripheral nerve were studied electrophysiologically in 10 healthy subjects. The aim was to verify that cramps can be evoked by electrical stimulation of peripheral nerve and to clarify the physiological mechanism responsible by analyzing the effect of muscular stretching on cramps. Our results showed: (1) Cramps can be induced even after peripheral nerve block by electrical stimulation distal to the block. (2) No cramps were recorded during or following maximal voluntary contraction without muscular shortening, while 7 of 10 subjects showed a true cramp following maximal effort with shortening of the muscle. (3) Muscle stretching caused a sudden interruption of cramps induced by either voluntary contraction or electrical stimulation of the peripheral nerve, even after the induction of nerve block. (4) The lengthening state of the muscle can strongly influence the possibility of evoking cramps by electrical stimulation of nerve. Our study verifies the experimental model proposed by Lambert in 1969, emphasizing the relevance of frequency of stimulation and confirming the hypothesis that cramps are of peripheral origin. The effects of muscle stretch and lengthening on cramp interruption and development also have a peripheral mechanism.
Article
A 17-year-old, nationally ranked, male tennis player (AH) had been experiencing heat cramps during tennis match play. His medical history and previous physical exams were unremarkable, and his in-office blood chemistry profiles were normal. On-court evaluation and an analysis of a 3-day dietary record revealed that AH's sweat rate was extensive (2.5 L.hr-1) and that his potential daily on-court sweat sodium losses (89.8 mmol.hr of play-1) could readily exceed his average daily intake of sodium (87.0-174.0 mmol.day-1). The combined effects of excessive and repeated fluid and sodium losses likely predisposed AH to heat cramps during play. AH was ultimately able to eliminate heat cramps during competition and training by increasing his daily dietary intake of sodium.
Article
Chemical stimulation of the pharynx and larynx is effective in eliciting reflex swallowing. A sour taste bolus facilitates the onset of swallowing in patients with neurogenic dysphagia, but the mechanism of the facilitation has not been clarified. We investigated the effect of sour solutions on the elicitation of reflex swallowing in anesthetized rats. The main ducts of salivary glands were ligated to avoid the effect of saliva. A small amount of water, sour solutions, and other taste solutions were applied to the mucosa of the pharyngolaryngeal region. Acetic acid and citric acid, which provide a sour taste, had a stronger effect on evoking reflex swallowing as compared with other taste solutions. The effectiveness of these acids increased with increasing concentrations. We also examined the contribution of the superior laryngeal nerve (SLN) and the pharyngeal branch of the glossopharyngeal nerve (GPNph) to reflex swallowing. Acetic acid was greatly effective in evoking swallowing in both the region innervated by the SLN and the GPNph. On the other hand, water was effective in the SLN region but only slightly effective in the GPNph region. The results indicate that stimulation of the pharyngolaryngeal region with sour solutions facilitates reflex swallowing, suggesting that the facilitation may be due to increases of sensory inputs via the SLN and GPNph.
Article
Gabapentin has recently been used clinically as an antihyperalgesic agent to treat certain neuropathic pain states. The aim of this study is to test whether gabapentin is able to inhibit responses to peritoneal irritation-induced visceral pain and to examine the effect of gabapentin on spinal cord amino acid release. The acetic acid-induced writhing assay was used in rats to determine the degree of antinociception. The rats received an intraperitoneal injection of acetic acid 40 min after intraperitoneal administration of vehicle or gabapentin (50, 100, or 200 mg/kg). Cerebrospinal fluid dialysate was collected by microdialysis from the spinal subarachnoid space in anesthetized rats. Acetic acid-induced release of amino acids into the dialysate, including glutamate, aspartate, serine, glutamine, and glycine, following intraperitoneal injection of acetic acid was evaluated by measurements of changes in the concentrations of these amino acids. The effects of pretreatment with saline or gabapentin (100 mg/kg intraperitoneal) on amino acid release were compared. Gabapentin reduced writhing responses in a dose-related fashion. Dialysate concentrations of glutamate, aspartate, and serine increased significantly following intraperitoneal injection of acetic acid, while glutamine and glycine concentrations were not increased significantly. When compared to saline-treated rats, animals pretreated with 100 mg/kg gabapentin showed suppression of the acetic acid-induced increases in glutamate, aspartate, and serine concentrations. These data demonstrate that gabapentin effectively inhibits acetic acid-induced nociception, and the antinociceptive effect of gabapentin correlates with the suppression of noxious-evoked release of excitatory amino acids in the spinal cord.
Article
OBJECTIVE: Acetic acid solutions, such as pickle juice (PJ), have gained anecdotal popularity among certified athletic trainers and other sports medicine professionals as remedies for exercise-associated muscle cramps. The aims of this study were 2-fold: (1) to report compositional analyses of 2 common types of PJ and (2) to discuss implications for ingestion following current National Athletic Trainers' Association (NATA) fluid-replacement guidelines. DESIGN AND SETTING: Biochemical laboratory analyses of 2 PJ sample types. MEASUREMENTS: Compositional analyses were performed in triplicate and compared with a 1-way analysis of variance. RESULTS: Mean values for PJ with 220 mg of sodium per serving were carbohydrate, 4 +/- 0.2%; osmolality, 713 +/- 6 mOsm.kg H(2)O(-1); pH, 3.8 +/- 0.2; calcium, 0.5 +/- 0.02 g/L; potassium, 1.4 +/- 0.02 g/L; magnesium, 0.1 +/- 0.01 g/L; and sodium, 7.4 +/- 0.1 g/L. Mean values for PJ with 390 mg of sodium per serving were carbohydrate, 3 +/- 0.1%; osmolality, 1446 +/- 9 mOsm.kg H(2)O(-1); pH, 3.5 +/- 0.1 g/L; calcium, 0.1 +/- 0.01 g/L; potassium, 1.2 +/- 0.02 g/L; magnesium, 0.1 +/- 0.01 g/L; and sodium, 17.1 +/- 0.1 g/L. Differences between the 220 and 390 PJ were significant (P <.05) for osmolality, calcium, and sodium. CONCLUSIONS: Both types of PJ exceeded sodium concentration levels set by the current NATA guidelines for fluid replacement. Hypothetical dilution references are presented to assist the athletic trainer with fluid volumes necessary to dilute PJ. Ingestion of PJ or other hypertonic fluids should be followed by ingestion of hypotonic or isotonic fluids to ensure that ingested amounts of sodium fall within the current NATA guidelines. Volumes for proper dilution may be substantial.
Article
Previous study has revealed that water-responsive afferent neurons in the superior laryngeal nerve induced inhibition of motility in the proximal and distal stomach using anaesthetized rats. These gastric responses might facilitate the reservoir function of the stomach. To confirm the gastric responses discovered in rats also occur in humans, we evaluated gastric myoelectrical activities in healthy volunteer subjects during fluid intake using electrogastrography. Before human experiments, we recorded the myoelectrical activities in rats to evaluate the response induced by the administration of water into the larynx. A large deflection in the gastric myoelectrical activities was observed just after the administration of water in anesthetized rats. A similar large deflection was also observed just after voluntary swallowing of 20 ml water in humans. The swallowing of saliva did not induce such response. We further observed the gastric response during reflex swallowing elicited by slow infusion of isotonic saline, water or 0.05 M citric acid on to the posterior tongue. Infusion of water and citric acid but not 0.15 M saline induced significant changes in mean relative ratio of the response. These electrogastrographic responses induced by the infusion of liquids strongly suggest that the gastric motor response facilitates reservoir function of the stomach during liquid intake in humans as well as in rats.
Article
Muscle cramps are a common problem characterized by a sudden, painful, involuntary contraction of muscle. These true cramps, which originate from peripheral nerves, may be distinguished from other muscle pain or spasm. Medical history, physical examination, and a limited laboratory screen help to determine the various causes of muscle cramps. Despite the "benign" nature of cramps, many patients find the symptom very uncomfortable. Treatment options are guided both by experience and by a limited number of therapeutic trials. Quinine sulfate is an effective medication, but the side-effect profile is worrisome, and other membrane-stabilizing drugs are probably just as effective. Patients will benefit from further studies to better define the pathophysiology of muscle cramps and to find more effective medications with fewer side-effects.
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.
Article
This study in humans tested the hypothesis that nociceptive muscle afferent input facilitates the occurrence of muscle cramps. In 13 healthy adults, muscle cramps were experimentally induced in the foot by stimulating the tibialis posterior nerve at the ankle with 2-s bursts of stimuli separated by 30 s, with stimulation frequency increasing by 2-Hz increments from 10 Hz until the cramp appeared. The minimum stimulation frequency that induced the cramp was defined "cramp frequency threshold". In 2 days, elicitation of the cramp was performed in the two-feet with and without (baseline condition) injection of hypertonic (painful condition) or isotonic (control condition) saline into the deep midportion of the flexor hallucis brevis muscle, from where surface EMG signals were recorded. The cramp frequency threshold was lower for the painful condition with respect to its baseline (mean +/- SE, hypertonic saline: 25.7 +/- 2.1 Hz, corresponding baseline: 31.2 +/- 2.8 Hz; P < 0.01) while there was no difference between the threshold with isotonic injection with respect to baseline. EMG average rectified value and power spectral frequency were higher during the cramp than immediately before the stimulation that elicited the cramp (pre-cramp: 13.9 +/- 1.6 muV and 75.4 +/- 3.8 Hz, respectively; post-cramp: 19.9 +/- 3.2 muV and 101.6 +/- 6.0 Hz; P < 0.05). The results suggest that nociceptive muscle afferent activity induced by injection of hypertonic saline facilitates the generation of electrically elicited muscle cramps.
Article
The purpose of this study was to determine the effect of active heat acclimation on the sweat osmolality and sweat sodium ion concentration vs. sweat rate relationship in humans. Eight healthy male volunteers completed 10 days of exercise in the heat. The mean exercising heart rate and core temperature were significantly decreased (P < 0.05) by 18 beats/min and 0.6 degrees C, respectively, following heat acclimation. Furthermore, sweat osmolality and the sweat sodium ion concentration vs. sweat rate relationships were shifted to the right. Specifically, the slopes of the relationships were not affected by heat acclimation. Rather, heat acclimation significantly reduced the y-intercepts of the sweat osmolality and sweat sodium relationships with sweat rate by 28 mosmol/kgH(2)O and 15 mmol/l, respectively. Thus there was a significantly lower sweat sodium ion concentration for a given sweat rate following heat acclimation. These results suggest that heat acclimation increases the sodium ion reabsorption capacity of the human eccrine sweat gland.
Article
Muscle cramp was induced in one head of the gastrocnemius muscle (GA) in eight of thirteen subjects using maximum voluntary contraction when the muscle was in the shortened position. Cramp in GA was painful, involuntary, and localized. Induction of cramp was indicated by the presence of electromyographic (EMG) activity in one head of GA while the other head remained silent. In all cramping subjects, reflex inhibition of cramp electrical activity was observed following Achilles tendon electrical stimulation and they all reported subjective relief of cramp. Thus muscle cramp can be inhibited by stimulation of tendon afferents in the cramped muscle. When the inhibition of cramp-generated EMG and voluntary EMG was compared at similar mean EMG levels, the area and timing of the two phases of inhibition (I(1), I(2)) did not differ significantly. This strongly suggests that the same reflex pathway was the source of the inhibition in both cases. Thus the cramp-generated EMG is also likely to be driven by spinal synaptic input to the motorneurons. We have found that the muscle conditions that appear necessary to facilitate cramp, a near to maximal contraction of the shortened muscle, are also the conditions that render the inhibition generated by tendon afferents ineffective. When the strength of tendon inhibition in cramping subjects was compared with that in subjects that failed to cramp, it was found to be significantly weaker under the same experimental conditions. It is likely that reduced inhibitory feedback from tendon afferents has an important role in generating cramp.
Article
Muscle cramps are difficult to study scientifically because of their spontaneity and unpredictability. Various laboratory techniques to induce muscle cramps have been explored but the best technique for inducing cramps is unclear. Electrical stimulation appears to be the most reliable, but there is a perception that it is extremely painful. Data to support this perception are lacking. We hypothesized that electrical stimulation is a tolerable method of inducing cramps with few side effects. We measured cramp frequency (HZ), pain during electrical stimulation, and soreness before, at 5 s, and 30, 60, and 90 min after cramp induction using a 100-mm visual analog scale. Group 1 received tibial nerve stimulation on 5 consecutive days; Group 2 received it on alternate days for five total treatments. Pain and soreness were mild. The highest ratings occurred on Day 1 and decreased thereafter. Intersession reliability was high. Our study showed that electrical stimulation causes little pain or soreness and is a reliable method for inducing cramps.
Sweat and sodium losses in NCAA football players: a precursor to heat cramps? Threshold frequency of an electrically induced muscle cramp is decreased following exercise associated muscle cramp
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Threshold frequency of an electrically induced muscle cramp is decreased following exercise associated muscle cramp.
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Stone M, Edwards J. Threshold frequency of an electrically induced muscle cramp is decreased following exercise associated muscle cramp. J Athl Train. 2005;40:S113.
Influence of acclimatization on sweat sodium concentration.
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