Stabilizing Motor Reflexive Activation and Acute Growth Hormone Response: ASystematic Review

Objective: Evaluating reflexive (Il and Ia afferent) body-stabilizing activity as a possible mechanism regulating hGH levels. Data Sources: The authors searched MEDLINE, PubMed, Harvard HOLLIS, and EMBASE databases for studies published through 1 January 2016 by using such terms as: vibration, stability, and human growth hormone. Study Selection: The authors included randomized, controlled trials and randomized pre-post observational trials that compared acute alterations of hGH in humans with both genders spanning from post-pubescence to elderly populations. Data Extraction: Three authors independently reviewed articles and abstracted data. Data Synthesis: PRISMA guidelines were followed with 17 articles describing 24 unique study populations meeting the inclusion criteria. A total of 265 participants who engaged in a destabilizing intervention were assayed both against baseline and control (when present). Populations varied in age, with all populations having a mean age of 35.1 [SD, 13.6], and RCTs of 41.6 [SD, 17.2], with the youngest population being 17.8 [SD, 0.88], and the oldest being 70 [SD, 8.8]. Subjects saw acute increases from pre-to-post of 647% [95% CI, 541% to 753%] (P=0.00001). Test group subjects compared to those subjected to control interventions increased hGH levels by 101% [95% CI, 85.7% to 116%] (P=0.006). Statistical analysis excluded one study that altered its blood sample concentrations via centrifuge. Conclusions: The literature published on randomized, controlled trials and randomized acute evaluations of reflexive stability recruitment of muscle and hGH in multiple populations is limited but suggests that there is an association with whole body stability firing and hGH levels. On the basis of this evidence, interventions that encourage increases in whole body stability firing can be recommended to illicit increases in hGH levels.