Immediate effects of 2 different whole-body vibration frequencies on muscle peak torque and stiffness.
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.


METHODS
Randomized crossover study with repeated measures.


METHODS
Laboratory setting.


METHODS
Recreationally active male adults (N=10).


METHODS
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.


METHODS
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.
Siu
Parco M
PM
Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, China. htpsiu@inet.polyu.edu.hk
Tam
Bjorn T
BT
Chow
Daniel H
DH
Guo
Jing-Yi
JY
Huang
Yan-Ping
YP
Zheng
Yong-Ping
YP
Wong
Stephen H
SH
D018592:Cross-Over Studies; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D026741:Physical Therapy Modalities; D016059:Range of Motion, Articular; D019415:Torque; D014732:Vibration / Q000627:therapeutic use*