Short-term effects of whole-body vibration on maximal voluntary isometric knee extensor force and rate of force rise

Abstract

Whole-Body vibration (WBV) may lead to muscle contractions via reflex activation of the primary muscle spindle (Ia) fibres. WBV has been reported to increase muscle power in the short term by improved muscle activation. The present study set out to investigate the acute effects of a standard WBV training session on voluntary activation during maximal isometric force production (MVC) and maximal rate of force rise (MRFR) of the knee extensors. Twelve students underwent a single standard WBV training session: 5x1 min vibration (frequency 30 Hz, amplitude 8 mm) with 2 min rest in between. During vibration, subjects stood barefoot on the vibration platform with their knees at an angle of 110 degrees. At 90 s following vibration, maximal voluntary knee extensor force was reduced to 93 (5)% [mean (SD), P<0.05] of baseline value and recovered within the next 3 h. Voluntary activation remained significantly depressed (2-4%). Neither the electrically induced MRFR nor voluntary MRFR were significantly affected by WBV. In addition, six WBV training sessions in 2 weeks ( n=10) did not enhance either voluntary muscle activation during MVC [99 (2)% of the baseline value] or voluntary MRFR [98 (9)% of the baseline value]. It is concluded that in the short term, WBV training does not improve muscle activation during maximal isometric knee extensor force production and maximal rate of force rise in healthy untrained students.

Determining the Optimal Whole-Body Vibration Dose–response Relationship for Muscle Performance

“…On the other hand, our data differ with those reported by Bullock et al (11), who used a duration of 60 seconds and also found no changes in jump height (SJ and CMJ) in a group of 7 elite skeleton athletes. In the study, authors used a recovery time of 3 minutes between sets, which has been deemed excessive (20). Adams et al…”

“…We used the combination of parameters determined to be the most effective by previous studies: a frequency of 30 Hz (14,19) and a recovery time of 2 minutes between sets for both studies (20). Because of the mechanical characteristics of the machine used, peak-to-peak displacement was fixed as 4 mm; greater muscle activity and strength were attained when this displacement was combined with the aforementioned frequency (1,19,20). Vibration was applied using a vibrating platform producing sinusoidal oscillations (Nemes, Ergotest, Rome, Italy).…”

“…In a previous study, our working group assessed the effects of 3 different frequencies (20,30, and 40 Hz), with a fixed amplitude of 4 mm, on jumping ability and power in the lower limbs; we concluded that 30 Hz yields the greatest increase in muscle performance (19).…”

“…Thus, research has focused on finding the optimal combination of these variables to reach maximal muscular response. For this purpose, frequency, amplitude, and duration were the main parameters analyzed (1,4,20,23,35,37).…”

Whole-Body-Vibration–Induced Increase in Leg Muscle Activity During Different Squat Exercises

“…Several studies showed that whole-body vibration (WBV) training, in which subjects perform unloaded exercises on a vibrating platform, resulted in improved muscle strength or muscle performance (3,11,19,20,24,25). Some other studies reported no changes in muscle strength after WBV training (9,10).…”