Andrew J. Duncan1, Steven B. Machek1,2, Dillon R. Harris2, Jeffrey L. Heileson2, Dylan T. Wilburn2, Emma A. Fletcher2, LesLee K. Funderburk2, Tracey N. Sulak2, Jason M. Cholewa3, & Darryn S. Willoughby, FACSM2,4

1University of the Ozarks, Clarksville, AR; 2Baylor University, Waco, TX; 3University of Lynchburg, Lynchburg, VA;4University of Mary Hardin-Baylor, Belton, TX

Blood flow restriction (BFR) training and betaine supplementation both possibly facilitate myofibril-level mechanotransduction via intracellular cell swelling. PURPOSE: To explore a potential extra-to-intracellular fluid flux-mediated BFR-betaine synergistic effect on intramuscular phosphorylated signaling targets. METHODS: Eighteen resistance trained men (23±5y) visited the laboratory after supplementing with either 6g/day betaine anhydrous (BET) or equivalently-dosed placebo (PLA) for 14-days. Following supplementation, all participants performed six sets (last two to muscular failure) in randomized, counterbalanced, and crossover fashion of either high-load (HL; 70% one-repetition maximum [1RM]) or low-load BFR (LL-BFR; 20%1RM) leg press exercise. Participants underwent vastus lateralis muscle biopsies before and 30-minutes post exercise to assess phosphorylated focal adhesion kinase (FAKTyr397), insulin receptor substrate 1 (PanTyrIRS1), and ribosomal protein S6 kinase beta-1 (p70S6KThr389) via ELISA. Several hydration parameters (whole-body intra-and-extracellular water, as well as muscle tissue-specific ∆Wet-to-Dry weight), exercise condition load-volume, and changes in all aforementioned phosphorylated intracellular signaling targets from baseline (∆FAKTyr397, PanTyrIRS1, and ∆p70S6KThr389) were assessed via separate two-way mixed model repeated measures ANOVA at a significance level of p<.05. RESULTS: Analyses revealed no significant main or interaction effects for any hydration parameter and singularly observed a significant main exercise condition effect for load-volume, whereby HL accumulated a higher load-volume relative to LL-BFR (p<.001). Furthermore, analyses failed to detect any main exercise condition or supplement effects, nor any interactions for FAKTyr397 or PanTyrIRS1. While no significant exercise condition or interaction effects were observed, p70S6KThr389 was significantly (p=.030; ηp2=.262) elevated in BET (11.93±12.29 to 20.58±17.30abs/ng/mL) vs PLA (7.35±0.63 to 7.52±0.81abs/ng/mL). CONCLUSION: Although the present findings do not support an extra-to-intracellular fluid flux-mediated BFR-betaine synergy, they further substantiate previous literature touting efficacy of either distinct modality.

ACKNOWLEDGEMENTS: The present research was partially funded by the American College of Sports Medicine – Texas Chapter, Student Research and Development Award, as well as the Baylor University Health, Human Performance, and Recreation Doctoral Dissertation Research Grant. Furthermore, the authors would like to thank Dr. Mike DeBord from B3 Sciences and Jack Owoc from Vital Pharmaceuticals for generously donating the experimental cuffs and supplement, respectively, to assist in the completion of this investigation.

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