Acute Effects of Blood Flow Restriction on Muscle Activity and Endurance During Fatiguing Dynamic Knee Extensions at Low Load

Abstract

The purpose of this study was to investigate muscle activity and endurance during fatiguing low-intensity dynamic knee extension exercise with and without blood flow restriction. Eleven healthy subjects with strength training experience performed 3 sets of unilateral knee extensions with no relaxation between repetitions to concentric torque failure at 30% of the 1 repetition maximum. One leg was randomized to exercise with cuff occlusion and the other leg to exercise without occlusion. The muscle activity in the quadriceps was recorded with electromyography (EMG). Ratings of perceived exertion (RPE) and acute pain were collected immediately, and delayed onset muscle soreness (DOMS) was rated before and at 24, 48, and 72 hours after exercise. The results demonstrated high EMG levels in both experimental conditions, but there were no significant differences regarding maximal muscle activity, except for a higher EMG in the eccentric phase in set 3 for the nonoccluded condition (p = 0.005). Significantly more repetitions were performed with the nonoccluded leg in every set (p < 0.05). The RPE and acute pain ratings were similar, but DOMS was higher in the nonoccluded leg (p < 0.05). We conclude that blood flow restriction during low-intensity dynamic knee extension decreases the endurance but does not increase the maximum muscle activity compared with training without restriction when both regimes are performed to failure. The high levels of muscle activity suggest that performing low-load dynamic knee extensions in a no-relaxation manner may be a useful method in knee rehabilitation settings when large forces are contraindicated. However, similarly to fatiguing blood flow restricted exercise, this method is associated with ischemic muscle pain, and thus its applications may be limited to highly motivated individuals.

Effects of low-intensity concentric and eccentric exercise combined with blood flow restriction on indices of exercise-induced muscle damage

“…Currently, no studies have analyzed muscle soreness associated with BFR resistance exercise in the upper body. Reported muscle soreness in BFR exercise studies have ranged from 33 to 55 mm (VAS, 0-100 mm), following both eccentric and concentric exercise to failure [22,23] but have also been found to be as low as 1.6 on a verbal analog scale (0-10) after only performing ECC-BFR exercise to failure [9]. The muscle soreness levels in this BFR study were smaller than most other BFR studies (20 mm vs. 33-55 mm).…”

Exercise and Blood Flow Restriction

“…Several other studies measuring muscle activation via electromyography (EMG) during unfatigued contractions demonstrated significantly greater responses with the application of BFR (91,100,101). Conversely, Wernbom et al (97) in examining 3 sets of low--intensity (30% of 1RM) unilateral knee extensions with BFR (100 mm Hg; 135--mm cuff width) and without BFR, found similar EMG activity patterns, with the exception that without BFR, set 3 demonstrated greater EMG activity during the eccentric phase, when all sets were performed to repetition failure. Similarly, Kacin and Strazer (38) evaluated vastus medialis and rectus femoris EMG activity during dynamic knee extensions performed to repetition failure under 2 different conditions: (a) (Con) 15% of MVC without BFR, (b) (Isch) 15% of MVC with BFR at 230 mm Hg.…”

“…However, distinctions have been made between ROS produced chronically during resting conditions, where radicals are primarily generated by the mitochondrial electron transport chain in the beta--oxidation of fatty acids, and those generated transiently by contracting muscles during exercise (6). The ROS have been shown to promote growth in both smooth muscle and cardiac muscle (87), and several researchers have speculated that they might be involved in the hypertrophic response pursuant to BFR (92,94,97). Hornberger et al (35) demonstrated that selenoprotein--deficient transgenic mice exhibited significantly greater increases in exercise--induced muscle growth compared with that in wildtype controls, suggesting an ROS--mediated hypertrophic effect through redox sensitive signaling pathways.…”

Strength training with vascular occlusion: a review of possible adaptive mechanisms

“…Despite evidence concerning fatigue as an active variable in TVO to alter the pattern of recruitment, Wernbom et al [20] found no difference in the pattern of electromyographic (EMG) activity, either in concentric or eccentric contractions of individuals who underwent knee extensions to failure with and without occlusion. In addition, long periods of TVO can reduce EMG activity owing to a probable increase in sensory feedback or increased perceived exertion during occluded exercise, which inhibits motor activity [9].…”