Focal Muscle Vibration: A Powerful Clinical Tool to Improve Balance, Strength, and Agility. Some amazing new research has shown that when a contracted muscle is vibrated at a specific frequency and intensity, it can produce long-term changes in athletic performance and balance. In an interesting study of competitive volleyball players, Brunetti et al. (1) show that the application of just 3 sessions of focal muscle vibration (FMV) applied bilaterally over contracted quadriceps muscles produced a 26% increase in muscle power and 13% increase in counter movement jump height. Even more surprising, these changes persisted for more than 6 months. Although the exact mechanism for improved performance remains unclear, most experts agree that FMV enhances output from muscle spindles, which in turn improves the synchronization and coordination between agonist and antagonist muscles producing smoother more efficient joint/muscle interactions.