Effects of an acute bout of low-load resistance training with blood flow restriction: -with special reference to muscle damage, hypertrophic signaling and satellite cells
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Main findings: Blood flow restriction reduces muscle endurance at low exercise loads (20-40% of 1RM) but not necessarily at moderate to higher loads (>50% of 1RM) in the knee extension exercise. The intramuscular pressures in the quadriceps are probably quite high already at low-to-moderate loads in this exercise, sufficient to induce relative ischemia as long as the muscle is under tension. Fatiguing low-load dynamic knee extension exercise both with and without blood flow restriction induces DOMS. Fatiguing low-load dynamic knee extension exercise both with and without blood flow restriction induces high muscle activity in the quadriceps. Not only the concentric but also the eccentric muscle activity increases as the point of torque failure draws closer. Very likely, this indicates a high degree of muscle fiber recruitment, possibly also during eccentric muscle actions. Multiple sets of low-load resistance exercise to failure with BFR induce decrements in maximum torque capacity and signs of increased sarcolemmal permeability and damage at the muscle fiber level. These phenomena were also observed in the freeflow leg, but to a lesser degree. Multiple sets of low-load resistance exercise to failure with BFR appear to induce long-lasting (>24 hours) increases in hypertrophic signaling, and rapid increases in satellite cell numbers. These phenomena were also observed in the free-flow leg, but to a somewhat lesser degree with regard to signaling.Paper I: Wernbom M, Augustsson J, Thomeé R. Effects of vascular occlusion on muscular endurance in dynamic knee extension exercise at different submaximal loads. J Strength Cond Res 2006: 20: 372-377.Paper II: Wernbom M, Järrebring R, Andreasson MA, Augustsson J. Acute effects of blood flow restriction on muscle activity and endurance during fatiguing dynamic knee extensions at low load. J Strength Cond Res 2009; 23: 2389-95.Paper III: Contractile function and sarcolemmal permeability after acute low-load resistance exercise with blood flow restriction. Manuscript.Paper IV: Resistance exercise with blood flow restriction increases protein signaling and satellite cell numbers in human skeletal muscle. Manuscript.
Avhandling (doktorgrad) - Norges idrettshøgskole, 2011.