Fatiguing effects of indirect vibration stimulation in upper limb muscles: pre, post and during isometric contractions superimposed on upper limb vibration

Abstract

Whole-body vibration and upper limb vibration (ULV) continue to gain popularity as exercise intervention for rehabilitation and sports applications. However, the fatiguing effects of indirect vibration stimulation are not yet fully understood. We investigated the effects of ULV stimulation superimposed on fatiguing isometric contractions using a purpose developed upper limb stimulation device. Thirteen healthy volunteers were exposed to both ULV superimposed to fatiguing isometric contractions (V) and isometric contractions alone Control (C). Both Vibration (V) and Control (C) exercises were performed at 80% of the maximum voluntary contractions. The stimulation used was 30 Hz frequency of 0.4 mm amplitude. Surface-electromyographic (EMG) activity of the Biceps Brachii, Triceps Brachii and Flexor Carpi Radialis were measured. EMG amplitude (EMGrms) and mean frequency (MEF) were computed to quantify muscle activity and fatigue levels. All muscles displayed significantly higher reduction in MEFs and a corresponding significant increase in EMGrms with the V than the Control, during fatiguing contractions (p < 0.05). Post vibration, all muscles showed higher levels of MEFs after recovery compared to the control. Our results show that near-maximal isometric fatiguing contractions superimposed on vibration stimulation lead to a higher rate of fatigue development compared to the isometric contraction alone in the upper limb muscles. Results also show higher manifestation of mechanical fatigue post treatment with vibration compared to the control. Vibration superimposed on isometric contraction not only seems to alter the neuromuscular function during fatiguing efforts by inducing higher neuromuscular load but also post vibration treatment.

Indirect Vibration of the Upper Limbs Alters Transmission Along Spinal but Not Corticospinal Pathways

“…The ULV was maintained at a displacement amplitude of 0.353 mm, a frequency of 30 Hz and acceleration of 1.286 m/s 2 . A built-in load cell assessed force during isometric elbow and wrist flexion (Pujari, 2016;Pujari et al, 2019b). For trials involving ULV, the vibration was turned on and data collection started within ∼1 min, remained on for the duration of data collection (∼5 min) and the vibration was turned off immediately after data were collected (>1 min).…”

Indirect Vibration of the Upper Limbs Alters Transmission Along Spinal but not Corticospinal Pathways

“…The ULV was maintained at a displacement amplitude of 0.353 mm, a frequency of 30 Hz and acceleration of 1.286 m/s 2 . A built-in load cell assessed force during isometric elbow and wrist flexion (Pujari, 2016; Pujari et al, 2019b). For trials involving ULV, the vibration was turned on and data collection started within ~ 1 min, remained on for the duration of the trial (~5min) and the vibration was turned off immediately after data were collected (>1 min).…”

Development and Characterization of a Wearable, Low-cost, Focal Muscle Vibration Device for Neurorehabilitation Applications

“…After the relation of battery voltages with device frequencies was established, an electronic circuit was designed to control the frequencies of the vibration device. Based on previous evidence [6,8,12,14] 60, 80, 100, and 120 Hz frequencies were chosen as the desired output frequencies, the corresponding voltages were determined by using the characterization data in the previous step. The electronic circuitry consisted of a voltage regulator and a power-resistor based voltage divider scheme for these voltages.…”

“…Vibration stimulation applied to muscles is well-known to stimulate neuromuscular, musculoskeletal, cardiovascular and endocrine systems [1]. On this ground, vibration exercise, especially Whole-Body Vibration (WBV) and Upper Limb Vibration (ULV) has been extensively investigated for muscle performance related therapies [1][2][3][4][5][6], with devices to improve muscle performance being reported almost a decade ago [5,8].…”