Neuromuscular and hormonal responses to a single session of whole body vibration exercise in healthy young men

Whole body vibration (WBV) has been proposed as an alternative exercise stimulus to produce adaptive responses similar to resistance exercise. Few studies have analysed acute hormonal responses to WBV. Purpose: To evaluate neuromuscular and hormonal responses to an acute bout of isometric half-squat exercise with and without superimposition of WBV. Methods: Seven healthy males (22.3 ± 2.7 years) performed 10 sets of half squat isometric exercise for 1min with 1-min rest between sets. Two separate trials were conducted either with WBV [30Hz; 3.5 g (1 g = 9.81 m.s²)] or without vibration (Control). Salivary concentration of testosterone and cortisol was collected and maximal isometric unilateral knee extensions (MVC) were completed before, immediately after, 1, 2 and 24 h after treatment. Significant decreases in MVC were observed immediately after (229.4± 53.2Nm), 1h (231.6±59.9Nm), and 2h (233.0±59.1Nm) after WBV compared with baseline (252.7±56.4Nm; P<0.05). No significant change in MVC was recorded in Control. Rate of torque development in the first 200ms (RTD_200ms), and salivary testosterone and cortisol concentrations were unaffected in both conditions. However, there was a trend for change over time in cortisol (P = 0.052), with an increase after WBV and decrease after Control. Conclusion: A 10 min session of intermittent WBV was shown to produce an acute reduction in MVC in healthy individuals, which recovered after 24 h. No significant changes were identified in salivary concentration of testosterone and cortisol suggesting that WBV with low acceleration does not represent a stressful stimulus for the neuroendocrine system.