The Acute Effects of Whole Body Vibration on Shoulder Flexibility

Abstract

Whole body vibration (WBV) was first developed to reduce muscle atrophy and increase bone density in astronauts. It is now being used for training patients and athletes. WBV repeatedly stimulates the body's natural stretch reflex typically controlled by muscle spindles. These vibrations also cause a rapid increase in intramuscular temperature. Perhaps an oscillating pattern of mechanical stimulation at a specific frequency may enhance soft tissue flexibility. PURPOSE: The purpose of this study was to investigate the acute effects of WBV on shoulder flexibility. METHODS: Prior to testing, subjects (N = 25, 20.3 ± 0.9 yrs.) performed two pre-test unilateral stretches. They involved the anterior deltoid/pectoralis major and posterior deltoid/scapular retractors. Exercises were led by the investigators, held for 15-seconds and performed three times (total=45sec/exercise). Following the stretching exercises, the back scratch flexibility test (Distance-cm) between the tips of the middle fingers was used to measure flexibility. Subjects used their dominant arm to reach above and behind their back, and their non-dominant arm to reach behind their back. If the fingers touched a score of zero was assigned. Fingers that did not touch received a negative value and those that overlapped received a positive value. Three measures were taken and the average score was used. Following the pretest, and kneeling in a modified push-up position, subjects placed their hands on a WBV platform. Subjects received omni-directional vibration at 0.5g's for 120 seconds. Immediately following WBV subjects completed the back scratch flexibility test. Again three measures were taken and the average recorded. A dependent t-test assessed at p< 0.05, was used to assess differences in flexibility following WBV. RESULTS: The results of the study indicated that a statistically significant difference was found between the Pre and Post (-5.80 ± 12.20 vs. -3.05 ± 11.42 cm) shoulder flexibility measures (t (25) = -8.37, p < 0.05). CONCLUSIONS: The results of this study suggest that a single bout of WBV can improve shoulder flexibility. This study has implications for those in the rehabilitation or sports settings whose goal is to increase range of motion of the shoulder joint.