Effects of blood flow restricted exercise training on muscular strength and blood flow in older adults

Background: In young adults, blood flow restricted exercise (BFRE) at relatively low intensities can increase muscle strength as effectively as conventional high intensity training. Ischemic exercise can also increase collateral blood flow in skeletal muscle. However, the effects of chronic BFRE on muscle strength and blood flow in older adults remain unknown. The purpose of this study was to compare the effects of 4 weeks of BFRE training on skeletal muscle strength and blood flow between young and older subjects and between older adults performing BFRE and conventional high intensity resistance exercise. Methods: Maximum voluntary contraction (MVC), forearm girth, peak forearm blood flow (FBF) and forearm vascular conductance (FVC) were assessed before and after 4 weeks of forearm resistance training with BFRE in older adults (O-BFRE, 63 +/- 1 y, n = 9) and younger adults (Y-BFRE, 22 +/- 1 y, n = 8) and with high intensity training at 75% maximum voluntary contraction in older adults (O-HI, 63 +/- 1 y, n = 10). Results: MVC increased in all groups (O-BFRE, 33.4 +/- 4.7 to 36.3 +/- 4.7 kg; Y-BFRE, 37.2 +/- 4.9 to 43.0 +/- 5.0 kg; O-HI, 34.0 +/- 4.4 to 39.8 +/- 4.4 kg; all p < 0.05). Forearm girth increased in O-BFRE (26.3 +/- 1.1 to 26.7 +/- 1.1 cm; p < 0.05) and Y-BFRE (23.9 +/- 0.9 to 25.1 +/- 1.5 cm; p < 0.05) but not in O-HI (25.9 +/- 1.0 to 26.1 +/- 1.0 cm; p = 0.26). Peak forearm vascular conductance increased in Y-BFRE (0.190 +/- 0.016 to 0.311 +/- 0.031 units; p = 0.01) but not in O-BFRE (0.157 +/- 0.024 to 0.193 +/- 0.029 units; p = 0.48) and O-HI (0.188 +/- 0.035 to 0.227 +/- 0.035 units; p = 0.18). Conclusion: These data suggest that chronic BFRE training is effective in increasing muscular strength, muscle size and vascularity in young adults but, in older adults, increases only muscular strength and size. Longer training durations or higher volumes may be required to evoke similar vascular adaptations in older adults.