Vibration-induced activation of muscle afferents modulates bioassayable growth hormone release

Abstract

The effects of tendon vibration on bioassayable growth hormone (BGH) secretion from the pituitary gland were investigated in anesthetized adult male rats. The tendons from predominantly fast-twitch ankle extensor muscles (gastrocnemius and plantaris) or a predominantly slow-twitch ankle extensor (soleus) were vibrated by using a paradigm that selectively activates group Ia afferent fibers from muscle spindles. The lower hindlimb was secured with the muscles near physiological length, and the tendons were vibrated for 15 min at 150 Hz and a displacement of 1 mm. Control rats were prepared similarly, but the tendons were not vibrated. Compared with control, vibration of the tendons of the fast ankle extensors markedly increased (160%), whereas vibration of the slow soleus decreased (68%), BGH secretion. Complete denervation of the hindlimb had no independent effects on the normal resting levels of BGH, but it prevented the effects of tendon vibration on BGH secretion. The results are consistent with previous findings showing modulation of BGH release in response to in vivo activation or in situ electrical stimulation of muscle afferents (Bigbee AJ, Gosselink KL, Grindeland RE, Roy RR, Zhong H, and Edgerton VR. J Appl Physiol 89: 2174-2178, 2000; Gosselink KL, Grindeland RE, Roy RR, Zhong H, Bigbee AJ, and Edgerton VR. J Appl Physiol 88: 142-148, 2000; Gosselink KL, Grindeland RE, Roy RR, Zhong H, Bigbee AJ, Grossman EJ, and Edgerton VR. J Appl Physiol 84: 1425-1430, 1998). These data provide evidence that this previously described muscle afferent-pituitary axis is neurally mediated via group Ia afferents from peripheral skeletal muscle. Furthermore, these data show that activation of this group Ia afferent pathway from fast muscles enhances, whereas the same sensory afferent input from a slow muscle depresses, BGH release.

Effects of repeated Achilles tendon vibration on triceps surae stiffness and reflex excitability

“…Ten to 15 min of tendon direct vibration were shown to induce an increase in bioassayable growth hormone (BGH) releases in rats (Gosselink et al, 2004) as in humans (McCall et al, 2000). Those studies are in favor of a muscle afferent-pituitary axis that modulates the release of BGH from primary endings of muscle spindles.…”

Relationship between growth hormone in vivo bioactivity, the insulin-like growth factor-I system and bone mineral density in young, physically fit men and women

“…These existing studies have collectively demonstrated, (1) a dichotomy exists in terms of the relative ''responsiveness" of iGH vs. bioGH [9] and that (2) bioGH is influenced by afferent neuromuscular activity [15,16]. For example, Kraemer et al [9] recently demonstrated that acute resistance exercise elicits an increase in iGH, but not bioGH, while chronic resistance exercise training elicits an increase in bioGH, but not iGH.…”

Hormonal and Metabolic Responses to Whole Body Vibration in Healthy Adults

“…13,20 Bosco et al 13 suggested that the activation of hypothalamic autonomic and neurosecretory centers by collaterals of the central motor command in combination with positive feedback influences from proprio-and metaboreceptors in muscles. Therefore, available data on the effect of WBV on the secretion of cortisol are consistent in human and animal studies in contrast to data on the release of GH that partly provide evidence that mechanical vibration-induced activation of muscle afferents is capable of producing a hormonal response primarily modulating the release of GH in both rats 16 and man. 13,21 The finding that WBV induces an increase of serotonin (5-HT) in the brain in combination with decreased plasma cortisol levels was also previously reported by Ariizumi and Okada 15 in the rat.…”

“…8 The effects of vibration therapy on bone formation were also reported for low acceleration (low magnitude mechanical) signals that do not stimulate the muscular spinal reflex arc, in contrast to side-alternating WBV. 15,16 The studies conducted in humans produced differing results that also deviate from results reported in intensive exercises. The effect of vibration on hormonal secretion was explored in recently published studies focused on men 9 -14 and rodents.…”