title: Cramp Training Induces a Long-Lasting Increase of the Cramp Threshold Frequency in Healthy Subjects.
abstract: OBJECTIVE
  A low cramp threshold frequency (CTF) is associated with an increased cramp susceptibility. Recent data indicate that the CTF can be substantially increased by a cramp training consisting of electrically induced muscle cramps (EIMCs). This study investigated if four cramp training sessions induce sustained effects on the CTF.
  
  
  METHODS
  In ten healthy male subjects, EIMCs were induced in the gastrocnemius medialis of one leg (intervention leg, IL) twice a week, while the opposite leg served as control leg (CL). The stimulation protocol consisted of three sets of six bipolar rectangular wave pulsed currents (5 sec on, 10 sec off) at 30 Hz above the individual CTF.
  
  
  RESULTS
  After four cramp training sessions (2 weeks) the CTF differed (p < 0.001) from pre-values in the IL (pre: 19.2 ± 1.4 Hz post 29.8 ± 8.0 Hz) but not in the CL (pre: 18.2 ± 1.5 Hz post 19.6 ± 2.8 Hz; p > 0.05). Thereafter, the CTF remained elevated in the IL for 22 days (22 days post: 22.2 ± 3.2 Hz; p < 0.05) when compared to pre and was significantly (p < 0.05) higher than that of the CL 5, 10, and 14 days after the intervention.
  
  
  CONCLUSIONS
  The applied cramp training induced a long-term CTF increase of 14 days.
authors.affiliation: Institute of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany.|German Research Center of Elite Sports (momentum), German Sport University Cologne, Cologne, Germany.
authors.forename: Michael
authors.identifier: https://orcid.org/0000-0002-9503-9965
authors.initials: M
authors.lastname: Behringer
authors.affiliation: Institute of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Spieth
authors.affiliation: Institute of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany.|German Research Center of Elite Sports (momentum), German Sport University Cologne, Cologne, Germany.
authors.forename: Johannes Caspar Konrad
authors.initials: JCK
authors.lastname: Montag
authors.affiliation: Institute of Biomechanics and Orthopaedics, German Sport University Cologne, Cologne, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Willwacher
authors.affiliation: Institute of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany.
authors.forename: Molly Leigh
authors.initials: ML
authors.lastname: McCourt
authors.affiliation: Institute of Training Science and Sport Informatics, German Sport University Cologne, Cologne, Germany.|German Research Center of Elite Sports (momentum), German Sport University Cologne, Cologne, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Mester
mesh_terms: D004558:Electric Stimulation; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009120:Muscle Cramp / Q000503:physiopathology* / Q000517:prevention & control*; D018482:Muscle, Skeletal / Q000502:physiology*; D055815:Young Adult
keywords: Cramp prevention; cramp susceptibility; cramp threshold frequency; cramp training; electrically induced muscle cramps