The effects of 11 weeks whole body vibration training on jump height, contractile properties and activation of human knee extensors.

The purpose of the present study was to investigate whether 11 weeks of whole body vibration (WBV) training applied in a way that is commonly seen in practice, i.e. without additional loads, would improve muscle activation and/or contractile properties of the knee extensor muscles and counter movement jump height in healthy subjects. Ten subjects belonging to the experimental group trained three times a week and stood bare-foot with a 110 degrees knee angle on a vibration platform (30 Hz, 8 mm amplitude). They underwent five to eight sets of 1-min vibration with 1 min rest in between. Ten control subjects followed the same training programme but stood (110 degrees knee angle) beside the platform. Before, during and following the training period the subjects were tested. Values [mean (SEM)] obtained in the last test were expressed as percentages of the baseline value and presented for control and experimental groups. Quadriceps femoris isometric muscle force [105.4 (6.2)%, 99.9 (2.0)%; P=0.69], voluntary activation [107.1 (6.0)%, 101.1 (2.3)%; P=0.55] and maximal rate of voluntary force rise [95.4 (6.0)%, 103.3 (7.7)%; P=0.57] did not improve. The maximal rate of force rise during electrical stimulation was increased [102.3 (4.5)%, 123.6 (7.5)%; P=0.02]. Counter movement jump height was not affected by WBV [103.7 (1.8)%, 103.0 (2.8)%; P=0.71]. In conclusion, 11 weeks of standard two-legged WBV training without additional training loads did not improve functional knee extensor muscle strength in healthy young subjects.