title: Effects of 8 weeks of vibration training at different frequencies (1 or 15 Hz) in senior sportsmen on torque and force development and of 1 year of training on muscle fibers.
abstract: OBJECTIVE
  To examine the effects of 8 weeks of vibration training at different frequencies (1 and 15 Hz) on maximal isometric torque and force development in senior sportsmen, and of 1 year of heavy-resistance and vibration trainings on muscle fibers.
  
  
  METHODS
  Seven healthy senior sportsmen (mean age: 69.0 +/- 5.4 years) performed an 8 weeks of strength training of knee extensors. Vibrations were applied vertically to the axis of movement during training. One leg of each subject was trained at a frequency of 1 Hz, while the other leg was trained at 15 Hz. Measures of isometric peak torque (at knee-angles of 60, 90 and 120 degrees ) and force development were recorded before and after training. Four sportsmen continued a year-long heavy-resistance training adding every second week a session of vibration training. After training, muscle biopsies were harvested from their quadriceps muscles and used for structural analyses. Morphometry of muscle fibers was performed by light microscopy. Immunohistochemistry using anti-MHCemb and anti-N-CAM antibodies was performed to measure potential muscle damage. Data from muscle morphometry were compared to that of a series of vastus lateralis biopsies harvested from 12 young sportsmen and four healthy elderly.
  
  
  RESULTS
  Our results showed a significant increase in isometric peak torque at both 1 and 15 Hz vibration frequency in all three measured angles of the knee. There was no significant difference between the two frequencies, but we could find a higher increase in percentage of maximum power after the 1 Hz training. The results of force development showed a slight increase at the 1 Hz training in measured time frames from 0 to 50 and 200 ms, without statistical significance. A trend to significance was found at the 1 Hz training at the time window up to 200 ms. The 15 Hz training showed no significant changes of force development. Muscle biopsies show that the muscles of these well trained senior sportsmen contain muscle fibers which are 35% larger than those of sedentary elderly and, unexpectedly, 10% larger than those of young sportsmen. Despite 1 year of heavy resistance and vibration training, no evidence of muscle damage or denervation/reinnervation could be observed by light microscopy analyses, ATPase histochemistry and immunohistochemistry using anti-N-CAM or anti-MHC-emb antibodies.
  
  
  CONCLUSIONS
  Integration of vibration to conventional strength training in elderly sportsmen induces similar improvement of isometric peak torque and force development independently from the vibration frequency after 8 weeks of training, and long-term results in the surprising evidence of hypertrophic muscle fibers larger than those of young active sportsmen. The observation that the vibration training with low frequency is safe opens the possibility to test these rehabilitation procedures in sedentary elderly.
authors.affiliation: Department of Physical Medicine and Rehabilitation, Wilhelminenspital Wien, Vienna, Austria.
authors.forename: H
authors.initials: H
authors.lastname: Kern
authors.forename: J
authors.initials: J
authors.lastname: Kovarik
authors.forename: C
authors.initials: C
authors.lastname: Franz
authors.forename: M
authors.initials: M
authors.lastname: Vogelauer
authors.forename: S
authors.initials: S
authors.lastname: Löfler
authors.forename: N
authors.initials: N
authors.lastname: Sarabon
authors.forename: M
authors.initials: M
authors.lastname: Grim-Stieger
authors.forename: D
authors.initials: D
authors.lastname: Biral
authors.forename: N
authors.initials: N
authors.lastname: Adami
authors.forename: U
authors.initials: U
authors.lastname: Carraro
authors.forename: S
authors.initials: S
authors.lastname: Zampieri
authors.forename: Ch
authors.initials: Ch
authors.lastname: Hofer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D056352:Athletes; D006801:Humans; D007150:Immunohistochemistry; D007717:Knee / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D055070:Resistance Training / Q000379:methods*; D013997:Time Factors; D019415:Torque; D014732:Vibration / Q000627:therapeutic use*; D055815:Young Adult