Abstract
BackgroundTo investigate if the cramp threshold frequency (CTF) can be altered by electrical muscle stimulation in a shortened position.MethodsA 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.ResultsAfter 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).ConclusionsThe present study may be useful for developing new non-pharmacological strategies to reduce cramp susceptibility.Trial RegistryGerman Clinical Trials Register DRKS00005312
Highlights
Muscle cramps, defined as sudden, involuntary contractions of muscles that last a few seconds or longer [1], can occur as a consequence of congenital abnormalities or acquired medical diseases [2]
Even though we did not expect large effects on cramp threshold frequency (CTF), we found huge increments in CTF 96 h after the 6th and the 12th training session in those calf muscles that were stimulated in a shortened position
After a period of three weeks, the CTF of the calf muscles stimulated in a shortened position (CT) was significantly increased from 23.365.7 to 33.366.9 (p,0.001) after three weeks and 35.366.0 (p,0.001) after six weeks of intervention (Fig. 2)
Summary
Muscle cramps, defined as sudden, involuntary contractions of muscles that last a few seconds or longer [1], can occur as a consequence of congenital abnormalities or acquired medical diseases [2]. Despite a broad range of available therapy approaches (e.g. physical exercise, weight loss, stretching, massage, heat therapy, compression garments, night ankle dorsiflexion splints), the review identified only one randomized trial which assessed the effectiveness of a non-drug treatment on lower limb muscle cramps. This trial, though impaired by serious limitations in design, assessed the effectiveness of daytime calf muscle stretching in preventing nighttime muscle cramps [11]. To investigate if the cramp threshold frequency (CTF) can be altered by electrical muscle stimulation in a shortened position
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