Neuromuscular, Swelling, And Perceived Effort Responses Following Isotonic Versus Isokinetic Blood Flow Restriction Exercise

Abstract

PURPOSE: The application of blood flow restriction (BFR) with resistance training has been applied to various exercise modalities, but no previous investigations have examined isotonic BFR vs isokinetic BFR. Therefore, the purpose of this study was to examine the neuromuscular, swelling, and rating of perceived exertion (RPE) responses following isotonic and isokinetic BFR exercise. METHODS: Fifteen (22 ± 2 years) women randomly performed (on separate days) 75 (1x30, 3x15) submaximal (30% of one repetition maximum [isotonic] or 30% maximal voluntary isometric contraction (MVIC) [isokinetic]) unilateral leg extensions with BFR (60% of total arterial occlusion pressure). Before and immediately after each exercise, subjects performed MVICs while electromyography (EMG) was simultaneously recorded from the vastus lateralis (VL) muscle. Ultrasound muscle thickness (MT) was assessed from the VL prior to and after the MVICs. RPE was recorded during all 4 sets. Separate 2 (Condition [Isotonic, Isokinetic]) × 2 (Time [pretest, posttest]) repeated measures ANOVAs were used to examine the EMG and MT responses. A separate 2 (Condition [Isotonic, Isokinetic]) × 4 (Time [set 1, set 2, set 3, set 4]) repeated measures ANOVAs was used to assess RPE. Paired samples t-tests were used to analyze percent change in MVIC torque. RESULTS: There was no significant (p = 0.294-0.823) interaction or main effect for normalized EMG amplitude. For EMG frequency and MT there were significant interactions (p = 0.008) that indicated greater decreases in EMG frequency following isotonic (13%) than isokinetic (6%) but similar increases in MT (22%). For RPE, there was no significant (p = 0.368) interaction, but there were significant (p = 0.004) main effects for Time (set 4 > set 3 > set 2 > set 1) and Condition (isotonic > isokinetic) (p = 0.018). Additionally, there was a greater (34.9%) decrease in MVIC following the isotonic than isokinetic (15.2%) condition. CONCLUSIONS: Isotonic BFR exercise elicited greater fatigue-induced changes in EMG frequency, MVIC, and perceived effort than isokinetic condition. Therefore, relative to isokinetic, isotonic BFR exercise may provide a more potent acute exercise response and discomfort, but this may not translate to chronic adaptations as there were similar EMG amplitude responses between conditions.