Author(s): GORDON, D., DUNN, A., PEARSON, J.1, WOJCIECHOWSKI, G.1, FRENCH, C.1, DESANLIS, J.2, GERNIGON, M.2, Institution: ANGLIA RUSKIN UNIVERSITY, Country: UNITED KINGDOM, Abstract-ID: 372

INTRODUCTION:
Blood flow restriction (BFR) training can increase rates of muscular adaptations at equal, and lower training intensities than traditional strength training. BFR induces hypoxia in the working muscle inducing greater fatigue, promoting angiogenesis as well morphological responses. There is currently limited knowledge as to the effects of blood flow restricted recovery on morphological and neuromuscular adaptations. Therefore, the aim of this study was to investigate whether blood flow restricted recovery can elicit strength and neuromuscular adaptations over a 4-week isokinetic strength training program.
METHODS:
Following local institutional ethical approval 20 physically active participants (n = 12 male, n = 8 female) volunteered to participate (mean ± SD: age = 21.0 ± 2.3 years, height = 174.5 ± 9.2 cm, mass = 75.2 ± 14.0 kg. A single-blinded repeated measures matched pairs design was implemented with 3 training conditions: 20 mmHg [SHAM], 40% limb occlusion pressure (40-LOP), and 80% LOP (80-LOP). Participants completed baseline and post testing ankle-brachial index (ABI), 60 cm Drop Jumps, 6 s and isokinetic concentric knee flexion-extension at 60 and 180 °.s-1. During dynamometer testing electromyography (100 Hz) and Near Infrared Spectroscopy (10Hz) were recorded at the mid-point of rectus femoris. Isokinetic training consisted of 12 sessions, 3 times per week for 4 weeks at 60 °.s-1 with blood flow restricted recovery. For sessions 1-6 participants completed 3 sets of 5 repetitions per leg with 120 s recovery between sets; sessions 7-9: 3 sets of 5 repetitions per leg with 90 s recovery between sets; and sessions 10-12: 2 of 5 repetitions with 120 s recovery, and 2 sets with 180 s unrestricted recovery.
RESULTS:
A significant pre to post increase (P = 0.004) in peak torque (60°.s-1) was observed in LOP-40 (Pre: 147 ± 51 Nm, Post: 208 ± 79 Nm) ES= 0.97 ±95% CI -33.1 – 31.2. There was a significant increase in peak torque for LOP-80 (60°.s-1) from 178 ± 36 to 216 ± 33 Nm (P= 0.02), ES= 1.17 ±95% CI -17.0 – 14.7. Significant decreases in tissue oxygenation mean response time (MRT) were observed for LOP-40 (P= 0.01) from 31.2 ± 3.9 s to 23.8 ± 5.7 s, ES= 1.63 ±95% CI -0.7 – 4.0 and LOP-80 (P= 0.01) 38.4 ± 8.6 s to 25.6 ± 8.9 s ES= 1.56 ±95% CI -2.44 – 5.57. Average iEMG increased at 60 °.s-1 from 2892.3 ± 692.6 mV to 3472.6 ± 852.2 mV (P= 0.01) ES=0.80 ±95% CI -377.5 – 375.8. Non-significant changes observed for peak torque, iEMG or MRT at 180 °.s-1. Additionally there was no change across any group for drop jump performance (P> 0.05).
CONCLUSION:
Blood flow restricted recovery promoted significant gains in both peak torque and MRT. Suggesting, that it proffers a modality that allows for maximal force generation during the exercise whilst enhancing the adaptive process by facilitating a hypoxic environment during recovery. Attention now needs be given to establishing optimal LOP and the mechanisms of these adaptations.