The investigation of soft-tissue vibrations and landing

The purpose of this study was to examine the effects of muscle tone to an imparted vibration to the vastus lateralis during various mechanical demands (rest vs. back squat). Five healthy male college athletes and five healthy male college recreational athletes were subjected to imparted vibrations on the vastus lateralis muscle during rest (in the supine position) and during a back squat exercise at knee flexion angles of 30 and 35°, while three and five trials were collected respectively. Vibrations were measured from a tri-axial accelerometer securely attached to the skin overlying the vastus lateralis muscle. The model chosen for analysis was that for a damped sinusoidal oscillation. The frequency (j) and damping coefficient (c) were calculated directly from the acceleration signal. A 2x2 (knee angle x activation level) repeated measures analysis of variance (ANOVA) was used to evaluate frequencies and damping coefficients related to the vibrations. An increase in f was associated with an increase in muscular contraction for the Z and Y-directions. No differences were shown between subject populations. The model chosen for analysis was unable to resolve any difference for the damping coefficients. It has been demonstrated that the frequencies and damping coefficients of the quadriceps increased with increased muscular force. The results of this study an inconclusive, but lend support that the frequencies increase with increasing muscular contraction.