Arch Phys Med Rehabil, 2010; 91(10): 1608-15, PMID: 20875522
Immediate effects of 2 different whole-body vibration frequencies on muscle peak torque and stiffness.
Year: 2010
Siu PM, Tam BT, Chow DH, Guo JY, Huang YP, Zheng YP, Wong SH
Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, China. htpsiu@inet.polyu.edu.hk
Abstract
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.Keywords: isokinetic eccentric torque, 26Hz, 40Hz
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