A Comparison of the Acute Muscular Response and Long-term Adaptation to Resistance Training Using Traditional High Loads or Very Low Loads with Different Degrees of Blood Flow Restriction in the Lower Body
Purpose: To compare acute and chronic responses to lower body resistance exercise using: high-load (70/0), very low-load alone (15/0), with moderate (15/40), or higher (15/80) blood flow restriction. Conditions labeled (% One-repetition maximum/% arterial occlusion pressure). Acute: Trained participants (12 males, 11 females) completed knee extension exercise (4 sets to failure capped at 90 repetitions) with each condition. Muscle thickness and torque were assessed before (Pre), after (Post), and fifteen minutes after (Post-15) exercise; surface electromyography (EMG) during. Chronic: Untrained participants (20 males, 20 females) performed the same exercise, with one condition assigned to each leg, twice per week for eight weeks. Muscle thickness, strength, and endurance were assessed. Acute Results: Torque decreased Pre to Post [-108.12 (-129.48, -86.76) Nm], recovered at Post-15 [76.83 (57.89, 95.77) Nm], but remained lower than Pre [-31.28 (-42.03, -20.54) Nm]. At Post, 15/80 torque was lowest and 70/0 highest [102.37 (73.13, 131.60) versus 205.28 (178.14, 232.42) Nm]. At Post-15, 15/0 was lowest [ex. 209.45 (171.77, 247.13) versus 70/0 = 231.63 (196.91, 266.34) Nm]. Muscle thickness increased Pre to Post [0.468 (0.388, 0.548) cm], decreased Post to Post-15 [-0.104 (-0.138, -0.071) cm], and remained elevated over Pre [0.364 (0.284, 0.444) cm]. Generally, EMG amplitude of the first three repetitions increased across sets, while during the last three repetitions it did not. Chronic Results: 70/0 increased 1RM [3.15 (2.04, 4.25) kg]. The endurance change was greatest for 15/80 [ex. 6.2 (4.3, 8.0) versus 70/0 = 4.0 (2.2, 5.9) and 15/0 = 4.2 (2.4, 6.0) kg]. Isometric MVC [10.5 (3.8, 17.1) Nm] and Isokinetic MVC 180?/s [8.61 (5.54, 11.68) Nm] increased, while Isokinetic MVC 60?/s was unchanged [2.45 (-1.84, 6.74) Nm]. Generally, all conditions increased muscle thickness similarly (Pre < Post). The workload required to reach failure in acute and chronic decreased with restriction (15/80 < 15/40 < 15/0 < 70/0). Conclusions: In trained and untrained individuals the reduced workload observed using greater restriction does not appear to compromise the hypertrophic stimulus when using very low-loads. Perhaps this provides utility in a variety of settings where hypertrophy is desired, but individuals are disinclined to greater workloads.
Blood flow restriction, High-load, Low-load, Muscle, Occlusion, Kinesiology
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