This study evaluates whether an increase in the ipsilateral knee flexor muscle strength transfers to the contralateral knee extensors which are not exposed to vibration, when unilateral-isolated whole body vibration (WBV) is applied to the lower extremity. In the half of volunteers the right leg were exposed vibration, while in the other half the right leg were exposed sham vibration. Muscle strength were measured with the Cybex® (Massachusetts, USA) extremity-testing system.

This study was included 40 healthy volunteers. The change in the quadriceps muscle strength after 20 session of WBV exercises was evaluated this study. In the WBV group, 20 sessions of unilateral lower extremity vibration exercises were performed with the Whole Body Vibration (WBV) device. WBV was applied when the subjects are in the semi-squat position. WBV was implemented with Powerplate® Pro5 (PowerPlate® International Ltd, London, United Kingdom). During 20 sessions, the WBV amplitude and vibration time were increased gradually. In the first session, the subjects were do a 30-second, 30-35, 40- and 45-Hz low-amplitude WBV while the knee and hip joint were in 30 degrees of flexion (in the semi-squat position); 10-second rest period between vibration applications were applied. A total duration of WBV was be two minutes. In the 20th session, the subjects were given a 60-second, 30-, 35-, 40- and 45-Hz high-amplitude WBV while the knee and hip joint were in 45 degrees of flexion; 10-second rest period between vibration applications were applied. A total duration of WBV was eight minutes. During WBV, the left lower extremity was in the knee-hip flexion position but was not exposed the vibration.

The same experimental protocol was applied to the isometric exercise (control) group. Unlike the experimental group, sham vibration was applied to the control group. Before and after 20 session-exercise, both knee extensor isokinetic muscle strength was measured.

Inclusion Criteria:

• Men with ages between 20-50 years
• Being healthy
• Being volunteer
• Right-sided dominant

Exclusion Criteria:

• Non-cooperative subject

All of the participants were told that the vibration stimulation was performed for muscle strengthening. However, participants had no knowledge about the characteristics of the vibration used for muscle-strength enhancement. Vibration was applied in the experimental group, whereas sham vibration was applied in the Control group. The WBV exercise was performed at different days for the Control and Experimental groups to make them blind to each other's applications.All measurements were made by an independent assessor (isokinetic test laboratory assistant) blinded to the trial allocation.