Alex Olmos1, Tony Montgomery1, Kylie Sears1, Taylor Dinyer-McNeely1, Shane Hammer1, Haley Bergstrom2, Ethan Hill3, Pasquale Succi2 and Michael Trevino1

1Oklahoma State University, Stillwater, OK

2University of Kentucky, Lexington, KY

3University of Central Florida, Orlando, FL

PURPOSE: To determine the effects of blood flow restriction (BFR) on electromyographic amplitude (EMGRMS)-force relationships of the biceps brachii. METHODS: Twelve recreationally active males (mean ± SD; age: 25 ± 4 yrs) and twelve recreationally active females (age: 22 ± 5 yrs) participated in this study. Surface EMG was recorded from the biceps brachii during a control (CON) and BFR visit. For each visit, participants performed 2-3 maximal voluntary isometric contractions (MVC) of the elbow flexors and an isometric trapezoidal muscle action at 70% MVC. For BFR, a cuff was inflated to 60% of the pressure required to completely occlude the brachial artery at rest. Individual b- (slopes) and a-terms (anti-log of the y-intercepts) were calculated from the log-transformed EMGRMS-force relationships during the linearly increasing (LI) and decreasing (LD) segments of the trapezoid. EMGRMS during the steady force segment of the trapezoid was normalized (N-EMGRMS) to MVC EMGRMS. Separate, 3-way mixed factorial ANOVAs (sex x condition x segment) were used to examine potential differences for b- and a-terms. A two-way mixed factorial ANOVA (sex x condition) was used to identify differences in N-EMGRMS. RESULTS: For the b- and a-terms, there were no 3-way interactions; however, there were condition x segment interactions for the b- (p = 0.008) and a-terms (p = 0.037). During the LI, b¬-terms were greater for BFR (1.57 ± 0.38) than CON (1.31 ± 0.30; p < 0.001). For BFR, the b-terms were greater during the LI (1.57 ± 0.38) than LD (1.28 ± 0.29; p < 0.001). The only difference for a-terms was between the LI (0.15 ± 0.29) and LD (0.39 ± 0.78; p = 0.045) during BFR. There was no 2-way interaction for N-EMGRMS (p > 0.05); however, there was a main effect for sex (p = 0.025). Females (92.58 ± 31.92%) exhibited greater N-EMGRMS than males (69.54 ± 18.20%) collapsed across conditions. CONCLUSION: The greater b-terms during the LI for BFR compared to CON and a-terms during the LD than LI for BFR, suggests BFR induced greater muscle excitation for the biceps brachii during motor unit activation and deactivation. In addition, the sex-related differences for N-EMGRMS during the steady force segment of both conditions suggests a greater neural cost was necessary for females compared to males when completing a contraction at the same relative high-intensity.

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