Acute effects of various whole body vibration frequencies on 1RM in trained and untrained subjects.

The purpose of this study was to compare the acute effects of whole body vibration (WBV) at different vibration frequencies on 1 repetition maximum (1RM) in recreationally strength trained subjects and untrained subjects. While performing a 1RM test in half squat, trained (8 men) and untrained (5 men and 3 women) subjects were randomly exposed to WBV with a frequency of 20 Hz, 35 Hz, 50 Hz (amplitude, 3 mm), or control conditions with no vibration. 1RM in half squat was assessed in a Smith Machine while subjects were standing on a vibration platform. Both untrained and recreationally strength trained subjects increased their 1RM at a vibration frequency of 50 Hz compared with no vibration (p < 0.05), and untrained subjects increased their 1RM to a larger extent than recreationally trained subjects (8.7% vs. 4.9%; p < 0.05). However, there was no difference in 1RM while vibrating at a frequency of 20 Hz and 35 Hz compared with no vibrations in either of the groups. In conclusion, WBV with a frequency of 50 Hz increases 1RM in both recreationally strength trained and untrained subjects, whereas vibration frequencies of 20 Hz and 35 Hz do not have this effect. Untrained subjects increased their 1RM at WBV at 50 Hz to a larger extent than recreationally strength trained subjects. Therefore, if the purpose is to increase the stimulus to the neuromuscular system to a greater extent than traditional strength training, the WBV frequency should be 50 Hz and the exercises should be heavily loaded (as in traditional strength training).