Dehydration does not affect muscle cramp frequency

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Herbsman
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Dehydration does not affect muscle cramp frequency

Postby Herbsman » Tue Dec 18, 2012 14:33 pm

http://bjsm.bmj.com/content/early/2012/ ... 1.abstract
Abstract

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.

I haven't read the actual studay as I'm at work. Just thought I'd post it for others to peruse.

Trev The Rev
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Joined: Tue Sep 25, 2012 09:10 am

Re: Dehydration does not affect muscle cramp frequency

Postby Trev The Rev » Tue Dec 18, 2012 14:46 pm

Herbsman wrote:http://bjsm.bmj.com/content/early/2012/12/05/bjsports-2012-091501.abstract
Abstract

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.

I haven't read the actual studay as I'm at work. Just thought I'd post it for others to peruse.


Not what manufacturers of sports drinks want you to believe. According to them you can get cramp crossing the road without taking on board fluids and electrolytes half way across.

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Herbsman
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Re: Dehydration does not affect muscle cramp frequency

Postby Herbsman » Tue Dec 18, 2012 21:51 pm

Now that I've actually read the abstract...
Significant and serious hypohydration with moderate electrolyte losses does not alter cramp susceptibility when fatigue and exercise intensity are controlled


... erm... nothing like race conditions then!

Trev The Rev
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Joined: Tue Sep 25, 2012 09:10 am

Re: Dehydration does not affect muscle cramp frequency

Postby Trev The Rev » Wed Dec 19, 2012 09:35 am

Herbsman wrote:Now that I've actually read the abstract...
Significant and serious hypohydration with moderate electrolyte losses does not alter cramp susceptibility when fatigue and exercise intensity are controlled


... erm... nothing like race conditions then!


This is always the problem with lab based tests.

keef66
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Re: Dehydration does not affect muscle cramp frequency

Postby keef66 » Wed Dec 19, 2012 15:20 pm

That's not what they mean. Controlled is scientist speak for taken into account.

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Herbsman
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Re: Dehydration does not affect muscle cramp frequency

Postby Herbsman » Wed Dec 19, 2012 20:47 pm

keef66 wrote:That's not what they mean. Controlled is scientist speak for taken into account.

Then wouldn't they have said 'controlled for' instead of merely 'controlled'?


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