Effects of 8 weeks of vibration training at different frequencies (1 or 15 Hz) in senior sportsmen on force and force development and of 1 year of training on muscle fibers

Authors: Kern H1,2, Kovarik J1, Franz C1, Vogelauer M1, Löfler S2, Sarabon N3, Grim-Stieger M1, Biral D4, Adami N5, Carraro U4,5, Zampieri S5,6, Hofer Ch2

Source: Neurol Res. 2010 Feb;32(1):26-31

Keywords: Vibration training, strength training, isometric torque, force development, muscle fiber size, muscle damage, senior sportsmen, aging

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 120u) 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-embMHC antibodies.
Discussion: 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.

Affiliations:

1 Department of Physical Medicine and Rehabilitation, Wilhelminenspital Wien, Vienna, Austria
2 Ludwig Boltzmann Institute of Electrical Stimulation and Physical Rehabilitation, Vienna, Austria
3 Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia
4 Italian C.N.R. Institute of Neuroscience, c/o Department of Biomedical Sciences, University of Padova, Padova, Italy
5 Laboratory of Translational Myology, Interdepartmental Research Institute of Myology, University of Padova,
Padova, Italy
6 Division of Rheumatology, Department of Clinical and Experimental Medicine, University of Padova, Padova,
Italy