IntroductionBecause of evidence supporting their effectiveness for improving strength, flexibility and power, whole body vibration platforms have become increasingly available in fitness centers and athletic training facilities. These platforms generally provide repeated vertical fluctuations at a user-selected rate and amplitude (distance). One study reported that frequencies of 20-30 Hz (cycles per second) produced the greatest gains in flexibility and strength. Amplitude adjustment generally ranges from 1-15 mm (0.04-0.60").
While it is easy to train previously untrained people to increase strength and power, it is more difficult to produce improvement in those already trained. Thus, the study described below provided a challenge to whole-body vibration training.
Experimental MethodIn a study by Wyon, Guinan, and Hawkey published in the Journal of Strength and Conditioning Research (vol 24, no 3, pp. 866-870, 2010) 18 female undergraduate dance majors, who were currently engaged in 12-16 hours of dance training per week, were divided into the following two groups that were tested before and after a 6-week experimental period:
Experimental Group: In addition to their normal dance training, these subjects did whole-body vibration training two times a week separated by 2 rest days. The training consisted of twice holding each of the following positions for 30 sec while on a vibration platform set at a frequency of 35 Hz and amplitude of 4 mm (0.16").
Half-squat with knees pointing outwards
Right leg leading lunge
Left leg leading lunge
Maximal height calf raise
Forward torso bend (at least 90 degrees) with knees straight
Control Group: In addition to their normal dance training, this group held each of the same positions as the experimental group, but on a stable floor rather than on a vibration platform.
ResultsThe experimental groups improved 2.3 cm (0.9" or 6%) in their maximal vertical jump, while the control group actually declined by 1.5 cm (0.6" or 4%). This difference was statistically significant.
Whole-body vibration training appears to hold promise for training athletes and dancers. The experimental training required only 5 minutes twice a week. Because the physical demands on in-season dancers and athletes are great, strength and power training is usually limited to avoid overtraining. However, whole-body vibration training seems to be able to improve performance without excessively stressing the athlete. An added advantage is the previous evidence that such training can improve bone mineral density. Low bone density has been a problem with female dancers and athletes who maintain low bodyfat, such as gymnasts and distance runners.