ACUTE EFFECTS OF VARIOUS WHOLE-BODY VIBRATION FREQUENCIES ON LOWER-BODY POWER IN TRAINED AND UNTRAINED SUBJECTS

Ronnestad, BR. Acute effects of various whole-body vibration frequencies on lower-body power in trained and untrained subjects. J Strength Cond Res 23(4): 1309-1315, 2009-The purpose of this study was to investigate the acute effects of whole-body vibration (WBV) with different vibration frequencies on power production during squat jump (SJ) and countermovement jump (CMJ) with submaximal external loads in strength trained and untrained subjects. Subjects were randomly exposed to WBV with frequencies of 20, 35, or 50 Hz (amplitude: 3 mm), or no vibration. Peak average power during SJ and CMJ was assessed on a Smith machine while standing on a vibration platform. Both the trained and untrained group increased peak average power during SJ at an WBV frequency of 50 Hz (6.8 +/- 1.9 and 7.3 +/- 1.7%, respectively; p < 0.05). This increase was larger than in the other test conditions, in which no changes occurred (p < 0.05). Untrained subjects increased peak average power during CMJ with 4.4 +/- 1.3% (p < 0.05) while vibrating at a frequency of 50 Hz, but there was no difference for the strength trained subjects. Furthermore, there was no difference in peak average power in CMJ and SJ while vibrating at frequencies of 20 and 35 Hz compared with no vibration in either of the groups. In conclusion, WBV with a frequency of 50 Hz increases peak average power in both trained and untrained subjects, whereas vibration frequencies of 20 and 35 Hz do not have this effect. Thus, if the purpose of using WBV is to increase the stimulus to the neuromuscular system to a greater extent than traditional explosive strength/power training, the WBV frequency should be 50 Hz and the exercises should be explosive and submaximally loaded (like traditional explosive strength/power training).