Objective: To investigate the effect of short-term vibration frequencies on muscle force generation capabilities.Method: Six healthy participants were recruited for this study and only their dominant leg was tested. The subjects were tested under five conditions of vibration frequencies with constant amplitude: 0 Hz (no vibration), 30 Hz, 60 Hz, and 90 Hz, and the vibration amplitude was 10 mm for all frequency conditions. The vibration was applied to the rectus femoris (RF). The subjects were then instructed to maintain a steadystate isometric knee joint torque (100 Nm) for the first 6 s. After the steady-state torque production, the subjects were required to produce isometric knee joint torque by leg extension as hard as possible with a start signal within the next 3 s. The vibration was applied for ~4 s starting from 1 s before initiation of the change in the steady-state knee joint torque. Results:The results showed that the maximum voluntary torque (MVT) of the knee joint increased with the vibration frequencies. On average, the MVTs were 756.47 Nm for 0 Hz (no vibration) and 809.61 Nm for 90 Hz. There was a significant positive correlation (r = 0.71) between the MVTs and integrated electromyograms (iEMGs). Further, the co-contraction indices (CCIs) were computed, which represent the ratio of the iEMGs of the antagonist muscle to the iEMGs of all involved muscles. There was a significant negative correlation (r = 0.62) between the CCIs and MVTs, which was accompanied by a significant positive correlation (r = 0.69) between the iEMGs of the vibrated muscle (RF). There was no significant correlation between the MVTs and iEMGs of the antagonist muscle. Conclusion:The results of this study suggest that the short-term vibration on the muscle increases the level of muscle activation possibly owing to the increased Ia afferent activities, which enhances the muscle force generation capability.

No abstract

No abstract

PURPOSE: To investigate the effect of muscle vibration on performance accuracy and multi-muscle coordination pattern during voluntary isometric knee extension torque production.METHODS: The subjects were tested under two conditions of external vibration frequencies (90 Hz vibration (VIB)&no-vibration (NVIB)) with three levels of torque magnitudes of 20% (MVT₂₀), 40% (MVT₄₀), and 60% of maximal voluntary torque (MVT₆₀). The subjects were instructed to perform a submaximal isometric ramp task and matched the produced torque with the torque template shown in the screen as accurately as possible. External vibration was applied to the rectus femoris (RF).RESULTS: The performance error (RMSENORM) was reduced in 60% of MVT (MVT₆₀) in both ramp and SS phases, and the iEMGAGO was significantly reduced by vibration under the same torque conditions in the SS phase. In addition, the muscle-mode (M-mode) composition was found to be different in the VIB and NVIB in the SS phase. We found that the VIB condition showed co-contraction M-modes and mixed M-modes. However, there was no significant difference in the ramp phase under all conditions.CONCLUSIONS: The neurophysiological changes due to muscle vibration may positively affect the task characteristics and steps that require accurate torque generation and provide information for the quantitative understanding of multi-muscle coordination of vibration.

The overall goal of this study lies in the multi-mode structural vibration control for systems, based on spatial information. In order to accomplish this task, a neural network was designed to identify the shape of the dominant vibration mode by using properly located piezoelectric sensors. The network then chose a set of scaling gains for a fuzzy logic controller that had been optimally tuned for that particular mode's shape. Next, a fuzzy logic controller was employed to control the vibratory system. The novel technique was experimentally verified on an aluminum cantilever beam system that was augmented with two lead zirconate titanate (PZT) actuators and two PZT sensors. The optimized control strategy was then compared to traditional fuzzy logic control. Finally the mass of the plant was increased by over a factor of 1.5 and the same controller was used to adequately stop vibration.