Voluntary activation of the ankle plantar flexors following whole-body vibration

Abstract

This study investigated the effect of whole-body vibration (WBV) on the voluntary activation of the ankle plantar flexors. Twelve healthy young adults were randomly exposed to two treatments on separate occasions. The first (non-WBV) involved stretching of the plantar flexors at end range of dorsiflexion for five 1-min bouts. The second involved the same stretch with WBV (26 Hz) for five 1-min bouts. Attempted maximal voluntary contractions (AMVCs) of the plantar flexors were performed on an isokinetic dynamometer (30 degrees s(-1)) before and after each treatment. A twitch interpolation technique was used to investigate voluntary activation. Post-treatment data were normalised against pre-treatment data. Subjects were classified as maximally (n = 6) or sub-maximally (n = 6) activated using the pre-treatment twitch interpolation data. The effects of WBV were assessed by repeated measure (RM) MANOVA. After WBV, the group of subjects classified as sub-maximally activated increased peak voluntary torque and rate of voluntary torque production (P < 0.05), whereas angular displacement to peak torque reduced (P < 0.05); i.e. peak torque was produced at a longer muscle length. No significant non-WBV treatment effects were found for this group. No significant WBV effects were found for the group of subjects classified as maximally activated. This study found that the response to WBV was dependent on the level of voluntary activation of the ankle plantar flexors during a set of AMVCs.

Immediate effects of whole body vibration on patellar tendon properties and knee extension torque

“…However, the lack of change in torque suggests that this artifact had a limited impact on the similar torque-angle relationship measured after intervention. These findings contrast with reports from Kemertzis et al (2008) and Pellegrini et al (2010) showing a shift in plantarflexor peak torque angle towards a longer muscle length after a single session of WBV. Regardless of mechanisms explaining this shift, these studies indicate that WBV constitutes a sufficient stimulus to alter the torque-angle relation in plantarflexor muscles.…”

“…One may speculate that increasing the intensity of the stimulus transmitted to the quadriceps, by altering vibration parameters, would have yielded similar results to that of Kemertzis et al (2008) and Pellegrini et al (2010). Furthermore, the patellar tendon was selected for the present experiment in accordance with our previous report about WBV training.…”

“…Whilst these hypotheses may hold true, another methodological pitfall may be related to the influence of vibration on musculotendinous mechanical properties. It has been reported that a single session of WBV alters the force-length relationship of plantarflexor muscles, leading to a shift in the optimal joint angle of torque production towards a longer muscle-tendon unit length (Kemertzis et al 2008;Pellegrini et al 2010). Such a shift may partially explain the ambiguous findings from studies where subjects were tested at a single joint angle.…”

“…The authors attributed their results to an increased tissue compliance mediated by stretch-induced damage of musculotendinous structures. However, a few experiments have shown that muscle stiffness remains unchanged (triceps surae; Cronin et al 2004;Siu et al 2010) or is increased (rectus femoris; de Hoyo et al 2013) following a single bout of WBV exercise, suggesting that the shift in peak torque angle observed by Kemertzis et al (2008) and Pellegrini et al (2010) could be related to changes in properties of series elastic elements.…”

Whole-Body Vibration and Blood Flow and Muscle Oxygenation: A Meta-Analysis

“…1,2 Researchers have demonstrated that WBV can improve aspects of physical performance, such as strength [3][4][5] and flexibility, 6,7 whereas evidence regarding the physiologic changes associated with therapeutic WBV remains unclear. [8][9][10][11][12] The influence of WBV on peripheral blood flow and muscle oxygen use is of special interest, as these measures provide insight into the metabolic changes occurring in skeletal muscle.…”