Fatigability And Blood Flow Restriction Training Of The Knee Extensors In Older Adults

Blood flow restriction (BFR) training is shown to decrease fatigability and increase exercise-induced blood flow in young adults, but it is unknown if similar adaptations occur in older adults. PURPOSE: Compare the effects of BFR and freely perfused (FP) resistance exercise training on fatigability and exercise-induced blood flow of the knee extensor muscles in older adults. METHODS: 6 older adults (68.1 ± 2.5 yrs, 3 M/3F) completed 24 training sessions (3/week for 8 weeks) of the knee extensors with each leg randomly assigned to either BFR or FP. BFR training was performed at 80% of occlusion pressure while lifting a load equivalent to 25% of the 1-repetition maximum (RM). Each session of BFR training consisted of 2 sets of 15 reps followed by a third set performed until failure. FP training was performed at 25% of 1-RM and matched for total reps with the BFR leg. All reps for both legs were performed as fast as possible, and each set was interspersed by 30s rest. Before and after 8 weeks of training, strength was assessed with maximal voluntary isometric contractions (MVCs) and fatigability was assessed as the reduction in power during a 4-min exercise (1 contraction/3 s) lifting a 20% MVC load. Blood flow through the superficial femoral artery was quantified before and immediately following the exercise via doppler ultrasonography. RESULTS: Power output of the knee extensors did not change following BFR (0.7 ± 4.7%, p = 0.892, d = 0.06) or FP training (4.0 ± 5.9%, p = 0.213, d = 0.58). Fatigability (exercise-induced reduction in power) improved following BFR (13.7 ± 9.5%, p = 0.017, d = 1.44) but not FP training (8.0 ± 9.5%, p = 0.097, d = 0.83). MVC did not change following BFR (3.7 ± 5.4%, p = 0.193, d = 0.61) or FP training (5.6 ± 12.7%, p = 0.327, d = 0.44). Absolute blood flow after the fatiguing exercise did not change after BFR (-5.4 ± 18.4%, p = 0.657, d = 0.19) or FP training (-3.1 ± 19.7%, p = 0.835, d = 0.09). Similarly, blood flow normalized to lean tissue in the thigh did not change following BFR (1.7 ± 22.9%, p = 0.822, d = 0.10) or FP training (1.5 ± 19.1%, p = 0.862, d = 0.08). CONCLUSIONS: These preliminary data suggest that BFR training of the quadriceps with light loads performed as fast as possible can improve fatigability in older adults but does not elicit changes in MVC strength or exercise-induced blood flow through the superficial femoral artery. NIH [R01 AG04826206]