HORMONAL RESPONSES TO WHOLE-BODY VIBRATION

  1. Bosco, M. Iacovelli, O. Tsarpela, M. Cardinale, M. Bonifazi, J. Tihanyi, M. Viru, A. De Lorenzo, A

European Journal Applied Physiology (2000) 81: 449±454

Ronald Peters, MD Comment:

Whole-body vibration creates powerful cellular energy changes that benefit health in many ways, including raising testosterone and growth hormone while lowering the chronic stress hormone cortisol.  This article postulates that the benefits are similar to the effect of “explosive” power training, such as jumping and bouncing.  All of this occurs while simply standing on the vibrating platform. 

Whole-body vibration is scientifically proven to benefit the following:

  • Fitness training: aerobics, weight training and flexibility
  • Metabolism and weight loss
  • Chronic illness rehabilitation and prevention
  • Bone density (osteoporosis)
  • Multiple sclerosis and Parkinson’s disease
  • Pain management
  • Fibromyalgia and more

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Abstract

The aim of this study was to evaluate the acute responses of blood hormone concentrations and neuro-muscular performance following whole-body vibration (WBV) treatment. Fourteen male subjects [mean (SD) age 25 (4.6) years] were exposed to vertical sinusoidal WBV, 10 times for 60 s, with 60 s rest between the vibration sets (a rest period lasting 6 min was allowed after 5 vibration sets). Neuromuscular performance tests consisting of countermovement jumps and maximal dynamic leg presses on a slide machine, performed with an extra load of 160% of the subject’s body mass, and with both legs were administered before and immediately after the WBV treatment. The average velocity, acceleration, average force, and power were calculated, and the root mean square electromyogram (EMG rms) were recorded from the vastus lateralis and rectus femoris muscles simultaneously during the leg-press measurement. Blood samples were also collected, and plasma concentrations of testosterone (T), growth hormone (GH) and cortisol (C) were measured. The results showed a significant increase in the plasma concentration of testosterone and growth hormone, whereas cortisol levels decreased. An increase in the mechanical power output of the leg extensor muscles was observed together with a reduction in EMG rms activity. Neuromuscular efficiency improved, as indicated by the decrease in the ratio between EMG rms and power. Jumping performance, which was measured using the countermovement jump test, was also enhanced. Thus, it can be argued that the biological mechanism produced by vibration is similar to the effect produced by explosive power training (jumping and bouncing). The enhancement of explosive power could have been induced by an increase in the synchronization activity of the motor units, and/or improved co-ordination of the synergistic muscles and increased inhibition of the antagonists. These results suggest that WBV treatment leads to acute responses of hormonal profile and neuromuscular performance. It is therefore likely that the effect of WBV treatment elicited a biological adaptation that is connected to a neural  potentiation effect, similar to those reported to occur following resistance and explosive power training. In conclusion, it is suggested that WBV influences proprioceptive feedback mechanisms and specific neural components, leading to an improvement of neuromuscular performance. Moreover, since the hormonal responses, characterized by an increase in testosterone and growth hormone concentration and a decrease in cortisol concentration, and the increase in neuromuscular electiveness were simultaneous but independent, it is speculated that the two phenomena might have common underlying mechanisms.

INTRODUCTION

Recent studies have documented the effect of vibration on the neuromuscular apparatus. Acute  treatment with whole-body vibration (WBV) has been shown to increase leg muscle force (F ) and power, and movement velocity. After 10 min of vibration treatment the velocity/F and W_ /F curves were shifted to the right (Bosco et al. 1999a). In 12 well-trained boxers, treated with 5 repetitions of 1-min vibration that was applied while their arms were kept in a semi-flexed position, an increase in the mechanical W_ of the arm was observed. The root mean square of the associated electromyogram (EM Grms) did not change following the vibration treatment, but the ratio of EMG/W decreased, showing an enhancement of neural efficiency (Bosco et al. 1999b). Apart from these acute effects, vibration may induce chronic adaptation changes in the mechanical behavior of human skeletal muscles: a daily series of five vertical sinusoidal vibrations lasting 90 s each and imposed for a period of 10 days caused pronounced improvement of jumping performance (Bosco et al. 1998). These results suggest that vibration elicits short-term and long-term neurogenic adaptation. In accordance with this, previous studies have demonstrated a facilitation of the excitability of the patellar tendon reflex by vibration applied to quadriceps muscle (Burke et al. 1996), vibration-induced drive of alpha-motoneurons via the Ia loop (Rothmuller and Cafarelli 1995), and activation of the muscle spindle receptors (Kasai et al. 1992). However, muscle tissue can also be affected by vibration (Necking et al. 1992). In rats, a vibration-induced enlargement of slow- and fast-twitch fibers has been demonstrated (Necking et al. 1996).

A question arises as to whether vibration effects include adaptive changes and changes in endocrine functions. It has been shown that short-term intensive exercises such as 60-s consecutive jumps (Bosco et al. 1996a), anaerobic cycle exercises (Adlercreutz et al. 1976; NaÈveri et al. 1985; Buono et al. 1986; Farrell et al. 1987; Brooks et al. 1988; Kraemer et al. 1989; Schwarz and Kindermann 1990) and weightlifting (Kraemer et al. 1990; Schwab et al. 1993) evoke rapid hormonal responses. At the same time, certain relationships seem to exist between plasma concentrations of hormones and short-term performance: athletes with better explosive strength and sprint-running performances have a higher basal concentration of testosterone (T, Kraemer et al. 1995; Bosco et al. 1996b). It has been demonstrated that exercise-induced hormonal responses are significant not only for acute adaptation, but also for triggering long-term training effects (Inoue et al. 1994; Viru 1994; Kraemer et al. 1996). Similarly, the vibration-induced hormonal changes may be significant for chronic improvement of neuromuscular function in repeated exposure to vibration.

The aim of the present study was to test the possibility that WBV induces changes in the plasma concentration of hormones that are known to be associated with the adaptation of muscular activity.

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