Relationship Between Lower Limb Muscle Activity and Platform Acceleration During Whole-Body Vibration Exercise

Abstract

The purpose of this study was to identify the influence of different magnitudes and directions of the vibration platform acceleration on surface electromyography (sEMG) during whole-body vibration (WBV) exercises. Therefore, a WBV platform was used that delivers vertical vibrations by a side-alternating mode, horizontal vibrations by a circular mode, and vibrations in all 3 planes by a dual mode. Surface electromyography signals of selected lower limb muscles were measured in 30 individuals while they performed a static squat on a vibration platform. The WBV trials included 2 side-alternating trials (Side-L: 6 Hz, 2.5 mm; Side-H: 16 Hz, 4 mm), 2 circular trials (Circ-L: 14 Hz, 0.8 mm; Circ-H: 43 Hz, 0.8 mm), and 4 dual-mode trials that were the combinations of the single-mode trials (Side-L/Circ-L, Side-L/Circ-H, Side-H/Circ-L, Side-H/Circ-H). Furthermore, control trials without vibration were assessed, and 3-dimensional platform acceleration was quantified during the vibration. Significant increases in the root mean square of the sEMG (sEMGRMS) compared with the control trial were found in most muscles for Side-L/Circ-H (+17 to +63%, p ≤ 0.05), Side-H/Circ-L (+7 to +227%, p ≤ 0.05), and Side-H/Circ-H (+21 to +207%, p < 0.01) and in the lower leg muscles for Side-H (+35 to +138%, p ≤ 0.05). Furthermore, only the vertical platform acceleration showed a linear relationship (r = 0.970, p < 0.001) with the averaged sEMGRMS of the lower limb muscles. Significant increases in sEMGRMS were found with a vertical acceleration threshold of 18 m·s(-2) and higher. The present results emphasize that WBV exercises should be performed on a platform that induces vertical accelerations of 18 m·s(-2) and higher.

The EMG activity–acceleration relationship to quantify the optimal vibration load when applying synchronous whole-body vibration

“…In addition, in the present study the displacement of the vibrating plate was not constant but 24 tended to increase, increasing the vibration frequency, and therefore we underline, as previously reported (Lienhard et al 2015), that the acceleration load rather than a vibration 1 frequency should be considered as the most important parameter for optimization of the 2 beneficial effects of WBV.…”

“…Interestingly, Lienhard et al (2015) have found a linear relationship between the vertical 10 platform acceleration and the lower body sEMG RMS . However, by this study the relationship 11 has not been specified in each leg muscle but, for analysis, it has been considered the average 12 value of different leg muscles.…”

“…When applying WBV as an alternative exercise modality in sport and rehabilitation, one of 5 the major points of concern, not yet completely addressed in the literature (Padulo et al, 2014a, b), is the process of individualizing the optimal magnitude of vibration (or 1 acceleration) relative to the subjects' responsiveness (Cardinale and Bosco, 2003;Cardinale 2 and Lim, 2003;Carlucci et al, 2013;Ritzmann et al, 2013;Lienhard et al, 2015). The 3 changes in the acceleration load transmitted to the body can be obtained by manipulating 4 various combinations of frequency and amplitude, that will in turn activate muscles.…”

“…The 3 changes in the acceleration load transmitted to the body can be obtained by manipulating 4 various combinations of frequency and amplitude, that will in turn activate muscles. 5 Several studies have used sEMG RMS to measure the level of neuromuscular activity (Di 6 Giminiani et al, 2009Giminiani et al, , 2013Dickin et al, 2013, Ritzmann et al, 2013Lienhard et al, 2015), 7 which has been used to identify the conditions that maximize acute neuromuscular responses 8 (Dickin et al, 2012;Dickin and Heath, 2014;Suroviec et al, 2014;Ritzmann et al, 2013;9 Lienhard et al, 2015) to dampen the vibration waves and consequently to avoid the adverse 10 effects of chronic exposure linked to the transmissibility of these waves from the tibia to the 11 cranium (Wakeling et al 2002;Muir et al 2013). The neuromuscular response to WBV 12 appears to be caused by a tonic vibration reflex (TVR) (Ritzmann et al, 1010;Pollock et al, 13 2012;Zaidell et al, 2013) that is similar to the reflex induced by directly applying vibration to 14 the muscle-tendon unit (Eklund and Hagbarth, 1966;Bongiovanni and Hagbarth, 1990).…”

“…Because of the controversial point of adjusting for the presence of 3 the motion artifact (Abercromby et al, 2007;Fratini et al, 2009;Ritzmann et al, 2010;Xu et 4 al., 2015;Sebik et al, 2013;Lienhard et al, 2015), we decided to avoid digital filtering 5 preventing from a plausible signal artifact and introducing a very likely mathematical artifact. 6 We think, that it is still preferable to account for the motion artifact in terms of study design 7 in the following way: first we limited the occurrence of the motion artifact securing the 8 electrodes and cables with elastic bands; secondly the choice of a non-parametric statistical 9 analysis allowed us to address the plausible presence of motion artifact as well.…”