Sergio Perez Jr.1, Stephanie Sontag1, Trent Herda2, Adam Sterczala3, Jonathan Miller2, Mandy Parra4, Hannah Dimmick5, Michael A. Trevino1

1Oklahoma State University, Stillwater, Oklahoma; 2University of Kansas, Lawrence, Kansas; 3University of Pittsburgh, Pittsburgh, Pennsylvania; 4Baker University, Baldwin City, Kansas; 5University of Calgary, Calgary, Alberta

PURPOSE: To examine mechanomyographic mean power frequency (MMGMPF)-torque relationships for the vastus lateralis (VL) in sedentary males and females. METHODS: Eleven females (mean ± SD; age = 22.7 ± 5.5 yrs) and eight sedentary males (age=19.4 ± 0.7 yrs) volunteered for this study. An MMG sensor was placed over the VL and subcutaneous fat (sFAT) was measured via ultrasonography at the sensor site. Participants completed 3 isometric maximal voluntary contractions (MVCs) of the knee extensors on an isokinetic dynamometer followed by an isometric trapezoid muscle action at 40% MVC. For linearly increasing and decreasing muscle actions, linear regressions models were fit to the log-transformed MMGMPF-force relationship and the slope (b term) was calculated. MMGMPF was averaged during the steady force segment. A 2way mixed factorial ANOVA (sex [male vs. female] x segment [ramp up vs. ramp down]) examined differences in the b terms during the linearly increasing and decreasing muscle actions. Independent samples t-tests examined sex-related differences in skinfold measurements and MMGMPF during steady torque. Pearson’s product moment correlations were used to determine relationships among sFAT and the b terms and MMGMPF. Alpha was set at 0.05. RESULTS: For the b terms, there was no significant two way interaction (p = 0.714) or main effect for sex (p = 0.259). There was a significant main effect for segment (p = 0.001). The b terms were greater during the linearly increasing (0.154 ± 0.131) than decreasing (0.006 ± 0.113) segment when collapsed across sex. During steady torque, MMGMPF was significantly greater (p = 0.002) for males (26.36 ± 2.57 Hz) than females (20.91 ± 3.64 Hz), while sFAT was significantly greater (p = 0.001) for females (1.59 ± 0.69 cm) than males (0.57 ± 0.32 cm). sFAT was significantly correlated with MPF during the plateau (p < 0.001, r = -0.736), but not the b terms for either segment (p > 0.05). CONCLUSION: MMGMPF distinguished between muscle activation and deactivation strategies, but not between sexes. MMGMPF during steady torque was greater for males; however, this may be due to the influence sFAT low-pass filtering the MMG signal to a greater extent for females. Higher targeted torques may be necessary to distinguish muscle activation and deactivation strategies between sexes.

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