Cross-transfer Effects On Muscle Strength, Size, And Quality Following Unilateral Blood Flow Restriction Training

PURPOSE: Unilateral resistance training (RT) has shown to induce contralateral strength improvements in the untrained homologous muscle. Notably, low-load blood flow restriction (BFR) RT has shown superior increases in muscle strength and hypertrophy compared to low-load non-BFR RT. Previous literature has also reported that BFR RT has systemic cross-transfer effects of strength on other working skeletal muscles compared to low-load non-BFR RT. METHODS: Fourteen untrained participants were randomized into two groups: (BFR; n = 8) (177.6 ± 4.1 cm, 84.8 ± 15.1 kg, 21.3 ± 1 years) or control (non-BFR; n = 6) (173.2 ± 7.5 cm, 77.9 ± 10.3 kg, 23 ± 2.6 years). Subjects completed 4 weeks (8 sessions) of unilateral isokinetic dorsiflexion RT at 30% of their daily peak torque at a velocity of 60°/s. Isokinetic peak torque, echo intensity (EI), and muscle cross-sectional area (mCSA) were taken bilaterally pre and post RT. Statistical analyses included 3 separate 3-way mixed factorial ANOVAs (Group [BFR, non-BFR] x Time [pre, post] x Leg [right, left]). RESULTS: For isokinetic strength, there were no significant interactions or main effects (p > .05). For EI, there were no significant interactions (p > .05); however, collapsed across time and leg, there was a significant main effect for group (p = .017; BFR (91.7 ± 1.6), non-BFR (84.8 ± 1.9); mean ± SE). Furthermore, there was no significant interaction for mCSA (p > .05), but there was a significant main effect for time (p < .001; pre (6.9 ± .26) to post (7.5 ± .26)) and a significant main effect for leg (p < .001; right (7.5 ± .26), left (6.8 ± .26)). CONCLUSIONS: The BFR group was found to have elevated echo intensity values throughout the intervention, yet there was no RT-induced change in muscle quality. Interestingly, low-load RT with and without BFR induced hypertrophy in both the trained and untrained legs without increases in isokinetic dorsiflexion strength. President's Excellence in Research Scholars Internal Grant