Whole-body vibration effects on the muscle activity of upper and lower body muscles during the baseball swing in recreational baseball hitters.

The purpose of this study was to evaluate the effects of whole-body vibration (WBV) on the muscle recruitment of selected upper and lower body muscles during the baseball swing. Participants were recreationally trained males (n = 16, 22 +/- 2 years, 181.4 +/- 7.4 cm, 84.7 +/- 9.0 kg), with previous baseball experience. Subjects participated in three randomized sessions on separate days, consisting of three sets of five swings offa hitting tee. Exercises (upper and lower body dynamic and static movements) with or without WBVexposure were performed between swing sets. During each swing, the gastrocnemius, biceps femoris, gluteus maximus, pectoralis major, latissimus dorsi, and triceps brachii were evaluated for electromyographic (EMG) activity. EMG values were normalized to EMG measured during maximal voluntary isometric contraction. Statistical analysis revealed no significant differences in EMG activity across the three treatments. In addition, the results displayed a specific muscle recruitment order during the swing, starting with the lower body followed by the upper body muscles. This study was the first to report the recruitment order during the baseball swing. Although acute exposure to WBV did not significantly alter the muscle recruitment, these results may prove useful for practitioners looking to enhance baseball swing performance.

The effects of specific preconditioning activities on acute sprint performance.

Previous research suggests that specific preconditioning activities such as whole-body vibration (WBV) and resistance training may play an important role in ensuing dynamic activities. The purpose of this study was to examine the effects of 2 preconditioning activities, WBV and power cleans (PC), on acute sprint performance. Two studies were conducted in which 14 (WBV) and 9 (PC) male track and field athletes were subjects. The WBV treatment consisted of 4 bouts of 5 seconds of high-knee running on a vibrating platform at 0, 30, 40, or 50 Hz. The PC treatment consisted of 3 PC reps at 90% 1RM. In both cases, acute sprint performance was the dependent variable of interest. For WBV, split times were recorded at 10, 20, and 40 m. Reaction times (RXN) as well as 5-, 10-, and 40-m split times were recorded for the PC study. Results indicated no significant differences between treatment and nontreatment groups for both studies. However, significant correlations were present between RXN and 5-m splits (r = 0.65) and RXN and 10-m splits (r = 0.63), although they decreased as a function of sprint distance to r = 0.43 at 40 m. These results suggest little efficacy for the use of WBV and PC as a means of augmenting acute sprint performance. However, a trend within the 30-Hz protocol may suggest that WBV as part of a warm-up for sprinting activities greater than 40 m (i.e., 100 m) could potentially result in a decreased sprint time of nearly 1/10th of a second, which is worth future consideration.