Acute effects of whole-body vibration on unilateral isometric knee extensors maximal torque and fatigability during an intermittent endurance task in adult males

Whole-body vibration (WBV) has been employed for performance-enhancing purposes. WBV may positively affect muscular endurance and its underlying neural mechanisms due to an enhanced muscular blood circulation and oxygen uptake. However, the effects of WBV on endurance-related torque signal complexity have been understudied. This study aims to investigate the acute effects of WBV on i) maximal isometric torque production; ii) isometric knee extensors fatigability and iii) torque signal complexity during an isometric endurance task. Thirty adult males performed an isometric intermittent endurance protocol on their dominant lower limb after performing: static half squat with WBV (WBV), static half squat without WBV (HS), and no exercise protocol (CC). For each repetition the maximal torque was identified. The maximal torque of the first repetition was identified as the PeakT. The Mean torque (MTorque) and fatigue index (pFatigue) were calculated as the mean and the percentage decay in torque across the entire set of eighteen repetitions (MTorque_{0-100 %}, pFatigue_{0-100 %}), and across shorter blocks of six repetitions (MTorque_{0-33 %}, pFatigue_{0-33 %}; MTorque_{34-66 %}, pFatigue_{34-66 %}, and MTorque_{67-100 %}, pFatigue_{67-100 %}). Torque fluctuations were analysed computing Sample Entropy (SampEn) and the coefficient of variation (CV). PeakT was significantly higher in CC than in WBV (p < 0.01) and in HS (p < 0.01). PeakT was significantly higher in HS than in WB (p < 0.05). MTorque_{0-100 %}, MTorque_{0-33 %}, MTorque_{34-66 %,} and MTorque_{67-100 %} were significantly higher in CC than in WBV (all p-values <0.01) and in HS (p < 0.01). MTorque_{67-100 %} was significantly higher in HS than in WB (p = 0.049). pFatigue_{34-66 %} was significantly higher in WBV than in CC (p < 0.05) whereas pFatigue_{67-100 %} was significantly higher in CC than in WB (p < 0.01) and in HS (p < 0.01). No effect of condition was observed for SampEn and CV. Acute WBV does not lead to beneficial effects on maximal torque production and isometric knee extensors fatigability. These acute detrimental effects may be related to long-term WBV-related adaptations.