title: A promising approach to effectively reduce cramp susceptibility in human muscles: a randomized, controlled clinical trial.
abstract: BACKGROUND
  To investigate if the cramp threshold frequency (CTF) can be altered by electrical muscle stimulation in a shortened position.
  
  
  METHODS
  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 6(th) (3 w) and 12(th) (6 w) training session.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  The present study may be useful for developing new non-pharmacological strategies to reduce cramp susceptibility.
  
  
  BACKGROUND
  German Clinical Trials Register DRKS00005312.
authors.affiliation: Institute of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Behringer
authors.affiliation: Institute of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Moser
authors.affiliation: Institute of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany.
authors.forename: Molly
authors.initials: M
authors.lastname: McCourt
authors.affiliation: Institute of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Montag
authors.affiliation: Institute of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Mester
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D006801:Humans; D008297:Male; D009120:Muscle Cramp / Q000517:prevention & control*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D016896:Treatment Outcome; D055815:Young Adult
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