Abstract
The primary goal of this investigation was to examine the physiological responses of blood flow restriction (BFR) resistance exercise (RE) performed with continuous or intermittent BFR and to compare these results to those from conventional high- and low-load RE without BFR. Fourteen men randomly completed the following experimental trials: (1) low-load RE with continuous BFR (cBFR), (2) low-load RE with intermittent BFR (iBFR), (3) low-load RE without BFR (LI), and (4) conventional high-load RE without BFR (HI). For the cBFR, iBFR, and LI exercise trials, participants performed four sets of 30–15–15–15 repetitions of the bilateral leg press (LP) and knee extension (KE) exercises, at an intensity of 20% of their one-repetition maximum (1-RM), at a 1.5-s contraction speed, and with a 1-min rest period between sets. The only difference between the cBFR and iBFR protocols was that the pressure of the cuffs was released during the rest intervals between sets for the iBFR trial. For the HI trial, participants completed four sets of 10 repetitions of the same exercises, at 70% of 1-RM, with a 1-min rest period between sets, and at the same contraction speed. Muscle activity was assessed during each set using superficial electromyography, as well as changes in blood lactate concentration [La–] from baseline at 5 min post exercise and in muscle swelling and plasma volume (%ΔPV) at 5 and 15 min post exercise. There were no significant differences in muscle activity (p < 0.05) across the cBFR, iBFR, and LI protocols at any time point, whereas they were all significantly lower than HI. There were also no significant (p < 0.05) differences across the three low-load RE conditions for [La–],%ΔPV, or muscle swelling. HI elicited significantly (p < 0.05) greater responses than cBFR, iBFR, and LI for all the physiological markers measured. In conclusion, RE combined with cBFR or iBFR induce the same acute physiological responses. However, the largest physiological responses are observed with HI, probably because of the significantly greater exercise volumes. Therefore, releasing the pressure of the restrictive cuffs during the rest periods between sets will not hinder the acute physiological responses from BFR RE.
Highlights
Low-load resistance training combined with blood flow restriction (BFR) has challenged traditional beliefs that loads superior to 65% of one-repetition maximum (1-RM) are required to elicit significant increases in muscle size and strength (American College of Sports Medicine [ACSM], 2011)
Similar results were observed during knee extension (KE), with high-load RE without BFR (HI) (2,052.32 ± 582.66 kg) resulting in significantly (p ≤ 0.01) greater exercise volume than that observed with continuous BFR (cBFR) (1,428.29 ± 261.82 kg), intermittent BFR (iBFR) (1,429.16 ± 271.07 kg), and load RE without BFR (LI) (1,440.94 ± 260.63 kg)
The results from the present study demonstrated that both cBFR and iBFR result in acute muscle swelling following exercise in a similar fashion compared to conventional high-load resistance exercise
Summary
Low-load resistance training combined with blood flow restriction (BFR) has challenged traditional beliefs that loads superior to 65% of one-repetition maximum (1-RM) are required to elicit significant increases in muscle size and strength (American College of Sports Medicine [ACSM], 2011). Previous studies have demonstrated that BFR resistance exercise is capable of eliciting muscle hypertrophy gains and muscle function improvements across a variety of populations (Takarada et al, 2000b; Yasuda et al, 2014; Buford et al, 2015; Jørgensen et al, 2015; Tennent et al, 2017). It has been documented that conventional lowload resistance exercise performed to volitional failure may induce muscle hypertrophy gains and improve muscle function (Mitchell et al, 2012; Ogasawara et al, 2013), large exercise volumes need to be achieved, making this training approach impractical. In addition to low loads, BFR resistance training utilizes low exercise volumes and still has been shown capable of increasing muscle cross-sectional area in a similar fashion to high-load resistance training (Vechin et al, 2015). It has been speculated that it may be due to the activation of the type II muscle fibers (Fatela et al, 2016), the accumulation of metabolites within the intramuscular environment (Suga et al, 2010), anabolic hormone secretion (Takarada et al, 2000a), exercise-induced muscle swelling (Freitas et al, 2017), and the regulation of biomolecular pathways (Fujita et al, 2007; Nakajima et al, 2016)
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