A novel gravity-induced blood flow restriction model augments ACC phosphorylation and PGC-1$α$ mRNA in human skeletal muscle following aerobic exercise: A randomized crossover study


This study tested the hypothesis that a novel, gravity-induced blood flow restricted (BFR) aerobic exercise (AE) model will result in greater activation of the AMPK–PGC-1$α$ pathway compared with work rate-matched non-BFR. Thirteen healthy males (age: 22.4 ± 3.0 years; peak oxygen uptake: 42.4 ± 7.3 mL/(kg˙min)) completed two 30-min work rate-matched bouts of cycling performed with their legs below (CTL) and above their heart (BFR) at $α$2 weeks apart. Muscle biopsies were taken before, immediately, and 3 h after exercise. Blood was drawn before and immediately after exercise. Our novel gravity-induced BFR model led to less muscle oxygenation during BFR compared with CTL (O2Hb: P = 0.01; HHb: P < 0.01) and no difference in muscle activation (p = 0.53). Plasma epinephrine increased following both BFR and CTL (p < 0.01); however, only norepinephrine increased more following BFR (p < 0.01). PGC-1$α$ messenger RNA (mRNA) increased more following BFR ($α$6-fold) compared with CTL ($α$4-fold; p = 0.036). VEGFA mRNA increased (p < 0.01) similarly following BFR and CTL (p = 0.21), and HIF-1$α$ mRNA did not increase following either condition (p = 0.21). Phosphorylated acetyl-coenzymeAcarboxylase (ACC) increased more following BFR (p<0.035) whereas p-PKA substrates, p-p38 MAPK, and acetyl-p53 increased (p < 0.05) similarly following both conditions (p > 0.05). In conclusion, gravity-induced BFR is a viable BFR model that demonstrated an important role of AMPK signalling on augmenting PGC-1$α$ mRNA. Novelty • Gravity-induced BFR AE reduced muscle oxygenation without impacting muscle activation, advancing gravity-induced BFR as a simple, inexpensive BFR model. • Gravity-induced BFR increased PGC-1$α$ mRNA and ACC phosphorylation more than work rate-matched non-BFR AE. • This is the first BFR AE study to concurrently measure blood catecholamines, muscle activation, and muscle oxygenation.

Applied Physiology, Nutrition and Metabolism