Muscle Tissue Oxygenation and Force Production during Low-intensity Resistance Exercise with Blood Flow Restriction

Abstract

We have recently demonstrated that an acute bout of low-intensity resistance exercise combined with blood flow restriction (Kaatsu exercise) stimulates both muscle protein synthesis and translation initiation. Recently, myocardial ischemia-reperfusion has also been shown to activate the signaling pathway of translation initiation. PURPOSE: To investigate the changes in muscle tissue oxygenation during Kaatsu exercise to assess the level of ischemia-reperfusion condition in skeletal muscle. METHODS: Six subjects performed three separate experiments randomly; Control (CON), Kaatsu (KAT, blow restriction via pressure cuff), or High-intensity (HI) exercise group. CON and KAT performed a bout of unilateral knee extension exercise at 20% of 1-repetition maximum (1-RM) strength, while HI group exercised at 70% 1-RM. Vastus lateralis and rectus femoris muscle tissue oxygenation (HbO2) was assessed using near-infrared spectroscopy (NIRS), and isometric muscle strength was assessed immediately before and after the exercise bout. RESULTS: In the KAT, resting HbO2 was reduced significantly (rest, 61.7%; cuff, 54.5%; p<0.05) in response to blood flow restriction. During exercise, HbO2 decreased further in KAT and reached the same level of tissue oxygenation as HI (KAT, 45.6%; HI, 44.8%; p<0.05 vs. rest for both groups) whereas HbO2 did not change in CON. During the recovery period, HbO2 was restored to the resting level both in CON and HI group (63.9 and 69.1% for CON and HI, respectively), whereas it was still significantly depressed in KAT group (51.4%, p<0.05). Muscular strength was significantly reduced after the bout of exercise in KAT and HI (-45 and -25% for KAT and HI, respectively; p<0.05), whereas no change in strength was observed in CON (-1.8%). CONCLUSION: Although a decreased tissue oxygenation during exercise and recovery period may contribute to muscle fatigue, sustained ischemic condition during recovery period in KAT suggests a non-significant ischemia-reperfusion during low intensity resistance exercise with blood flow restriction.