(16) NEUROMUSCULAR AND FATIGUE RESPONSES FOLLOWING DIFFERENT BLOOD FLOW RESTRICTED EXERCISE PROTOCOLS IN TRAINED ADULTS

Purpose: Blood flow restriction (BFR) combined with resistance exercise provides robust physiological responses, but the heterogeneity among protocols makes it difficult to isolate potential mechanisms underlying BFR exercise. Therefore, the purpose of this investigation was to compare 3 commonly implemented BFR resistance exercise protocols on neuromuscular function, muscle thickness (MT), and fatigue responses in trained adults.

Methods:   Ten (22 ± 4.1 years) participants (n=4 women, n=6 men), performed 3 different BFR protocols that were randomly performed on separate days (≥48hrs). For all 3 BFR protocols, participants completed, submaximal (30% of MVIC), isokinetic (90°-s^-1), unilateral, leg extension muscle actions with BFR (60% of total arterial occlusion pressure), but performed different sets and repetition schemes (75 reps [1x30, 3x15], 3 failure [3 sets to failure], 1 fail [1 set to failure]). Surface electromyography (sEMG) was assessed during the first and last 5 repetitions of each protocol and leg extension MVIC torque and MT of the RF were assessed immediately prior to and after each protocol. A 3 (Condition [75 reps, 3 sets, 1 set]) × 2 (Time [first 5 repetitions, last 5 repetitions]) repeated measures ANOVA was used to assess the EMG responses. Separate 3 (Condition [75 reps, 3 fail, 1 fail]) × 2 (Time [pretest, posttest]) repeated measures ANOVAs were used to examine MVIC torque and MT.

Results: There were no significant (p= 0.121-0.430, η_p²= 0.218-0.087) Condition × Time interactions for any of the variables. There were, however, main effects for Time for MVIC, MT, and EMG amplitude and frequency. Specifically, collapsed across Condition, there were pretest to posttest decreases in MVIC torque (pretest: 125 ± 46.2Nm.1 to posttest: 67. 6± 35.5Nm) and pretest to posttest increases in MT (2.7 ± 0.41cm to 3.0 ± 0.49cm). Across each protocol, sEMG amplitude increased (47.29 ± 31.6µV to 107.4 ± 76.18µV), while sEMG frequency decreased (79.7 ± 10.6Hz to 60 ± 8.66Hz).

Conclusion: There were similar fatigue-induced decreases in maximal strength and increases in MT among all 3 BFR protocols. Furthermore, there were no differences in any of the sEMG responses among the 3 protocols which included within protocol increases in sEMG amplitude and decreases in sEMG frequency. PRACTICAL APPLICATIONS: Acute BFR resistance exercise exhibits a potent effect on neuromuscular and muscle function regardless of exercise protocol. Interestingly, despite differences in set and repetition schemes, commonly implemented BFR protocols induced comparable physiological responses. Thus, coaches, practitioners, and clinicians may consider implementing a variety of BFR protocols among individuals with previous exercise experience.

Acknowledgements: None