The Impacts Of Combined Blood Flow Restriction Training And Betaine Supplementation On Exercise-associated Serum Hormones

PURPOSE: Both blood flow restriction (BFR) training and betaine supplementation are touted for their ability to independently augment serum growth hormone (GH), as well as subsequent insulin-like growth factor-1 (IGF-1) concentrations. Furthermore, betaine supplementation may augment blood flow restriction (BFR) training-mediated metabolic stress and mechanical tension via osmolyte-associated protein protection and attenuated fatigue. Therein, the purpose of this investigation was to compare the impacts of a potential BFR-betaine synergy on circulating post-exercise GH and IGF-1 concentrations. METHODS: Eighteen recreationally trained males (25 ± 5y) were randomized in double-blind fashion to supplement 6 g/day of either betaine anhydrous (BET) or identically dosed cellulose placebo (PLA) for 14-days. Subsequently, all subjects performed four standardized sets of one-leg press and two additional sets to muscular failure on both legs in a counter-balanced and crossover design. Specifically, one leg performed standard high-load (HL; 70%1RM) exercise and contralateral limb underwent BFR (LL-BFR; 20%1RM) training at 80% arterial occlusion pressure. Serum growth hormone (GH) and insulin-like growth factor-1 concentrations were analyzed before (PRE) and 30-minutes post-exercise (POST30M), subsequently quantified via ELISA. The changes in serum hormones from baseline (∆GH and ∆IGF-1) were assessed via separate two-way mixed model ANOVA with repeated measures at a significance level of p < .05. RESULTS: Analysis failed to detect any main or interaction effects for ∆GH. Despite statistically equivocal main exercise condition and interaction effects, the supplement-specific change from baseline in serum IGF-1 was significantly (p = .042; ηp2 = .247) higher in BET (105.4 ± 34.0 ng/mL to 114.6 ± 32.6 ng/mL) versus PLA (136.6 ± 45.1 to 129.1 ± 37.7 ng/mL). Incidentally, serum ∆IGF-1 failed normality assumptions, and thus the aforementioned significant finding was confirmed via an exercise condition-collapsed non-parametric Mann-Whitney U test (p = .029; R2 = .132). CONCLUSIONS: Although the data fails to support a BFR-betaine synergy, they otherwise support BFR as a viable training modality and further substantiate the growing literature regarding betaine’s ostensibly anabolic potential.