Effects of KAATSU on muscular function during isometric exercise

Abstract

Generally, a threshold intensity of 65% 1-RM will induce muscle hypertrophy; however, recent studies using low-intensity (20% 1-RM) exercise combined with vascular restriction (KAATSU) have demonstrated increases in muscle size and strength. PURPOSE: To investigate the EMG and MMG responses, and percent voluntary activation (PVA) of the vastus lateralis (VL) following exposure to low-intensity intermittent isometric exercise in combination with moderate vascular restriction. METHODS: Twelve males (Age = 23.7 ± 4.1 yrs) participated in 1 familiarization trial and 2 experimental trials (with or without KAATSU) each separated by 48 h. Testing order was: a) Resting blood pressure after 5 min rest; b) 5 min warm-up on a cycle ergometer (50 W, 50-70 rpm); c) 2 pre- exercise 5-s isometric MVCs, 1 min rest between trials; d) 5 sets of 20 intermittent isometric contractions (2-s on / 1-s off) at 20% of MVC, 30-s interset rest periods; and e) 2 post-exercise isometric 5-s MVCs. RESULTS: There were no significant interactions or main effects for time or session for pre- and post-exercise isometric MVCs, with and without KAATSU, for the following parameters: MVC, PVA, EMG amplitude, EMG mean power frequency (MPF), MMG amplitude, and MMG MPF. Average normalized EMG amplitude increased significantly from repetitions 1-4 to 5-8 to 9-12 and MMG amplitude increased significantly from set 1 to 2 for both the KAATSU and no-KAATSU sessions. CONCLUSION: Intermittent isometric contractions at 20% 1-RM, with or without vascular restriction, are not intense enough to cause significant muscular fatigue.