Article

OBJECTIVE: To examine the immediate effects of 2 vibration protocols with
different vibration frequencies that yielded the same maximum acceleration
(106.75ms(-2)) on muscle peak torque and stiffness of knee extensor and flexor.
DESIGN: Randomized crossover study with repeated measures. SETTING: Laboratory
setting. PARTICIPANTS: Recreationally active male adults (N=10). INTERVENTION:
Participants performed 10 bouts of 60-second static half squats intermitted with
a 60-second rest period between bouts on a platform with no vibration (control)
and a vibration frequency of 26Hz or 40Hz. MAIN OUTCOME MEASURES: Concentric and
eccentric peak torques of knee extensor and flexor were examined within 5 minutes
before and after vibration by isokinetic test. Young's modulus as an index of
tissue stiffness was determined at quadriceps and hamstring pre- and
postvibration by using an ultrasound indentation method. RESULTS: The 2-way
repeated-measures analysis of variance indicated a significant interaction effect
between vibration and vibration frequency for knee extensor concentric peak
torque (P=.003). The vibration-induced changes of knee extensor concentric peak
torque in vibration frequency of 26Hz (14.5Nm) and 40Hz (12.0Nm) were found to be
significantly greater than that in controls (-29.4Nm) (P<.05). The change in
eccentric peak torque of knee flexor after vibration tended to be greater in 26Hz
of vibration frequency when compared with controls (26Hz of vibration frequency
vs controls: 13.9+/-7.1 vs -11.4+/-5.3Nm, P=.08). No statistically significant
differences were obtained in tissue stiffness in the quadriceps and hamstring
with any of the conditions. CONCLUSIONS: Our data suggest that whole-body
vibration at a frequency of 26Hz and 40Hz preclude the decline in concentric peak
torque of knee extensor observed after 10 bouts of 60 seconds of static half
squats. A change in muscle mechanical stiffness property as induced by whole-body
vibration is not supported by our data.
CI - Copyright (c) 2010 American Congress of Rehabilitation Medicine. Published by
Elsevier Inc. All rights reserved.

Langue : ANGLAIS