Effects of Vascular Restriction on Muscular Function during Intermittent Submaximal Isometric Exercise

Abstract

It is generally accepted that a threshold intensity of 65% 1-RM is needed to induce muscle hypertrophy; however, recent studies using low-intensity resistance exercise (20% 1-RM) combined with vascular restriction (KAATSU) have also been able to demonstrate increases in muscle size and strength. PURPOSE: To investigate EMG and MMG responses of the vastus lateralis (VL) before, during, and after low intensity intermittent isometric exercise in combination with moderate vascular restriction and to examine the percent voluntary activation (PVA) of the VL. METHODS: Twelve healthy males volunteered to participate in this study (mean + SD age = 23.7±4.1 years). Each participant visited the laboratory 3 times: one familiarization trial and two experimental trials, separated by at least 48 h. The two experimental trials consisted of the same testing and isometric exercise protocol; however, the participants experienced either the KAATSU or no-KAATSU conditions in random order. For the experimental trials, the following procedures were performed in order: a) Resting blood pressure assessment after 5 min rest (for the KAATSU trial only), b) five-minute warm-up on a stationary cycle ergometer with a power output of 50 W and a pedaling cadence of 50–70 rpm, c) two pre-exercise 5-s isometric MVCs with 1 min rest between trials, d) five sets of 20 intermittent isometric contractions (2-s on and 1 -s off) at 20% of MVC with a 30-s interset rest period, and e) two post-exercise isometric 5-s MVCs with 1 min rest between trials. RESULTS: For MVC torque, PVA, EMG amplitude, EMG mean power frequency (MPF), MMG amplitude, and MMG MPF, there was no interaction and no main effects for time or session for the pre- and post-exercise isometric MVCs with and without KAATSU. The average normalized EMG amplitude (%MVC) increased 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. CONCLUSIONS: The present study demonstrated no significant change in post-exercise torque values and % activation, suggesting that the exercise task was not intense enough to cause muscular fatigue in either treatment condition.