Instability and blood flow restriction: do they contribute to resistance training adaptations?

Abstract The aim of this study was to investigate changes in muscle size, strength, and dynamic balance after resistance training on an unstable surface with and without blood flow restriction and on a stable surface. Twenty-nine untrained men were assigned according to baseline vastus lateralis muscle thickness to one of the three resistance training groups: stable surface (TRAD), unstable surface (UST), and unstable surface with blood flow restriction (UST-BFR). Each group performed three sets of 8–12 repetition maximum (RM) in the back squat and the leg press 45° exercises. Vastus lateralis muscle thickness, back squat and leg-press 1‑RM and dynamic balance were assessed before and after 8 weeks of training. Two-way repeated measures analysis of covariance (ANCOVA), having group as a factor and prevalues as covariates, was used to analyze muscle thickness, 1‑RM, and dynamic balance. Significance level was set at p ≤ 0.05. Groups were not different at posttraining for any variable, except dynamic balance, where UST improved over TRAD ( p = 0.019). Based on these findings, we propose that strength and conditioning coaches and practitioners should consider incorporating resistance training on unstable surfaces to enhance dynamic balance while still achieving gains in muscle size and strength.