Characterisation of the transient mechanical response and the electromyographical activation of lower leg muscles in whole body vibration training (original) (raw)
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2021
PurposeTo characterise the mechanical and neuromuscular response of lower limb muscles in subjects undergoing Whole Body Vibration (WBV) at different frequencies while holding two static postures.MethodsTwenty-five participants underwent WBV at 15, 20, 25 and 30 Hz while holding a static ‘hack squat’ and on ‘fore feet’ posture. Surface electromyography (sEMG) and soft tissue accelerations were collected from Gastrocnemius Lateralis (GL), Soleus (SOL) and Tibialis Anterior (TA) muscles.ResultsOnly specific WBV settings led to a significant increase in muscle contraction. Specifically, the WBV-induced activation of SOL and GL was maximal in fore-feet and in response to higher frequencies. Estimated displacement at muscle bellies revealed a resonant pattern never highlighted before. After stimulation starts, muscle oscillation reaches a peak followed by a drop and a further stabilisation (few seconds after the peak) that suggests the occurrence of a neuromuscular activation to reduce t...
Journal of Strength and Conditioning Research, 2015
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 (sEMG RMS) 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 sEMG RMS of the lower limb muscles. Significant increases in sEMG RMS were found with a vertical acceleration threshold of 18 m$s 22 and higher. The present results emphasize that WBV exercises should be performed on a platform that induces vertical accelerations of 18 m$s 22 and higher.
Variation in neuromuscular responses during acute whole-body vibration exercise
Purpose: Leg muscle strength and power are increased after whole-body vibration (WBV) exercise. These effects may result from increased neuromuscular activation during WBV; however, previous studies of neuromuscular responses during WBV have not accounted for motion artifact. Methods: Sixteen healthy adults performed a series of static and dynamic unloaded squats with and without two different directions of WBV (rotational vibration, RV; and vertical vibration, VV; 30 Hz; 4 mm p-p ). Activation of unilateral vastus lateralis, biceps femoris, gastrocnemius, and tibialis anterior was recorded using EMG. During RV and VV, increases in EMG relative to baseline were compared over a range of knee angles, contraction types (concentric, eccentric, isometric), and squatting types (static, dynamic). Results: After removing large, vibration-induced artifacts from EMG data using digital band-stop filters, neuromuscular activation of all four muscles increased significantly (P e 0.05) during RV and VV. Average responses of the extensors were significantly greater during RV than VV, whereas responses of the tibialis anterior were significantly greater during VV than RV. For all four muscles, responses during static squatting were greater than or equal to responses during dynamic squatting, whereas responses during eccentric contractions were equal to or smaller than responses during concentric and isometric contractions. Neuromuscular responses of vastus lateralis, gastrocnemius, and tibialis anterior were affected by knee angle, with greatest responses at small knee angles. Conclusions: Motion artifacts should be removed from EMG data collected during WBV. We propose that neuromuscular responses during WBV may be modulated by leg muscle cocontraction as a postural control strategy and/or muscle tuning by the CNS intended to minimize soft-tissue vibration.
2021
Lower limb muscles actively contribute to maintain body posture but also act to attenuate soft tissues oscillations that occur during everyday life. This elicited activity can be exploited as a mean of neuromuscular training or rehabilitation. In this study, Whole Body Vibrations (WBV) at different frequencies were delivered to healthy subjects while holding static postures to test the transient muscles mechanical responses. Twenty-five participants underwent WBV at 15, 20, 25 and 30 Hz while holding either a static ‘hack squat’ or ‘fore feet’ posture. Soft tissue accelerations and surface electromyography (sEMG) were recorded from Gastrocnemius Lateralis (GL), Soleus (SOL) and Tibialis Anterior (TA) muscles. Estimated displacement at muscle bellies revealed a resonant pattern, different across frequencies and postures (p
European Journal of Applied Physiology, 2013
This study aimed to assess the influence of different whole body vibration (WBV) determinants on the electromyographic (EMG) activity during WBV in order to identify those training conditions that cause highest neuromuscular responses and therefore provide optimal training conditions. In a randomized cross-over study, the EMG activity of six leg muscles was analyzed in 18 subjects with respect to the following determinants: (1) vibration type (side-alternating vibration (SV) vs. synchronous vibration (SyV), (2) frequency (5-10-15-20-25-30 Hz), (3) knee flexion angle (10°-30°-60°), (4) stance condition (forefoot vs. normal stance) and (5) load variation (no extra load vs. additional load equal to one-third of the body weight). The results are: (1) neuromuscular activity during SV was enhanced compared to SyV (P \ 0.05); (2) a progressive increase in frequency caused a progressive increase in EMG activity (P \ 0.05); (3) the EMG activity was highest for the knee extensors when the knee joint was 60°flexed (P \ 0.05); (4) for the plantar flexors in the forefoot stance condition (P \ 0.05); and (5) additional load caused an increase in neuromuscular activation (P \ 0.05). In conclusion, large variations of the EMG activation could be observed across conditions. However, with an appropriate adjustment of specific WBV determinants, high EMG activations and therefore high activation intensities could be achieved in the selected muscles. The combination of high vibration frequencies with additional load on an SV platform led to highest EMG activities. Regarding the body position, a knee flexion of 60°and forefoot stance appear to be beneficial for the knee extensors and the plantar flexors, respectively.
2006
The purpose of this study was to analyze if exposure to whole-body vibrations (WBV) of different frequencies with none or additional loads from 20 to 50 kg promotes changes in EMGrms activity of the quadriceps and gastrocnemious muscles. Sixteen male subjects with previous experience in strength training volunteered to participate. Subjects received the treatment while standing on a vibration platform with knees bent at 100o. Normalised EMGrms was recorded in vastus medialis (VM), vastus lateralis (VL), rectus femoris (RF) and gastrocnemious medialis (GM) for 10 secs in the following twenty five conditions: no-vibration (NV), 30, 35, 40 and 50 Hz with body weight or with four different external loads (20, 30, 40 and 50 kg) over the shoulders. In all conditions, average normalised EMGrms from VM was significantly higher than in the NV condition. The same behaviour was observed in VL except in the 50 Hz with 20 kg condition. In RF only six conditions with 40 and 50 Hz were not signifi...
Journal of Education and Training Studies, 2018
A limited number of acute whole body vibration (WBV) studies have investigated the effects of WBV treatments which were applied with different vibration frequencies and amplitude combinations on lower extremity muscle activation of well-trained athletes from different sports branches. To compare the effects of WBV on lower extremity muscle activation via Surface Electromyography (sEMG) of well-trained athletes from different sports branches (soccer, basketball and swimming) during static and dynamic squat exercises. sEMG activities of Tibialis Anterior (TA), Gastrocnemius Medialis (GM), Vastus Medialis (VM), Rectus Femoris (RF), Vastus Lateralis (VL) and Biceps Femoris (BF) muscles of 7 male soccer players, 7 male basketball players, and 6 male swimmers were recorded during WBV applied in static squat and dynamic squat positions with different frequencies (30-35-40 Hz) and amplitude (2-4 mm) combinations separated from each other by 5 min passive rest periods. Each combination was a...
Effects of neuromuscular responses during whole body vibration exercise with different knee angles
Biology of Sport, 2011
The purpose of this study was to compare the effects of whole body vibration (WBV) exercise using different knee angles on three-dimensional acceleration received in the lumbar region and neuromuscular activation of 8 muscles that were selected in order to determine their implications for rehabilitation. Thirty physically active women (mean ± SD; 21.7 ± 1.67 years) were randomized in three groups. The first group performed on the platform with 15, 45 and 90º knee flexions, the second group with 45, 90, 15º, and the third group with 90, 15, 45º. The WBV frequency was 12.6 Hz. The acceleration was recorded by a tri-axial accelerometer (Biopac) attached on the skin at L3 level and the electromyography (EMG) was recorded by surface active electrodes (Biopac) on the extensors and flexors of the knee and lower trunk. The lateral acceleration was 3 times greater (p< 0.05) at the vertical line in 3 angles of flexion, and the vertical line was 2 times greater (p< 0.05). Maximum acceler...
Human Postural Responses to Different Frequency Vibrations of Lower Leg Muscles
We analyzed human postural responses to muscle vibration applied at four different frequencies to lower leg muscles, the lateral gastrocnemius (GA) or tibialis anterior (TA) muscles. The muscle vibrations induced changes in postural orientation characterized by the center of pressure (CoP) on the force platform surface on which the subjects were standing. Unilateral vibratory stimulation of TA induced body leaning forward and in the direction of the stimulated leg. Unilateral vibration of GA muscles induced body tilting backwards and in the opposite direction of the stimulated leg. The time course of postural responses was similar and started within 1 s after the onset of vibration by a gradual body tilt. When a new slope of the body position was reached, oscillations of body alignment occurred. When the vibrations were discontinued, this was followed by rapid recovery of the initial body position. The relationship between the magnitude of the postural response and frequency of vibration differed between TA and GA. While the magnitude of postural responses to TA vibration increased approximately linearly in the 60-100 Hz range of vibration frequency, the magnitude of response to GA vibration increased linearly only at lower frequencies of 40-60 Hz. The direction of body tilt induced by muscle vibration did not depend on the vibration frequency.
Dose-Response
The aim of this study was to characterize acceleration transmission and neuromuscular responses to rotational vibration (RV) and vertical vibration (VV) at different frequencies and amplitudes. Methods: Twelve healthy males completed 2 experimental trials (RV vs VV) during which vibration was delivered during either squatting (30 ; RV vs VV) or standing (RV only) with 20, 25, and 30 Hz, at 1.5 and 3.0 mm peak-to-peak amplitude. Vibrationinduced accelerations were assessed with triaxial accelerometers mounted on the platform and bony landmarks at ankle, knee, and lumbar spine. Results: At all frequency/amplitude combinations, accelerations at the ankle were greater during RV (all P < .03) with the greatest difference observed at 30 Hz, 1.5 mm. Transmission of RV was also influenced by body posture (standing vs squatting, P < .03). Irrespective of vibration type, vibration transmission to all skeletal sites was generally greater at higher amplitudes but not at higher frequencies, especially above the ankle joint. Acceleration at the lumbar spine increased with greater vibration amplitude but not frequency and was highest with RV during standing. Conclusions/Implications: The transmission of vibration during whole-body vibration (WBV) is dependent on intensity and direction of vibration as well as body posture. For targeted mechanical loading at the lumbar spine, RV of higher amplitude and lower frequency vibration while standing is recommended. These results will assist with the prescription of WBV to achieve desired levels of mechanical loading at specific sites in the human body.