INFLUENCE OF MUSCLE ARCHITECTURE AND SIZE ON MECHANOMYOGRAPHIC AMPLITUDE OF THE VASTUS LATERALIS

Sergio Perez Jr.1, Stephanie A. Sontag1, Trent J. Herda2, Adam J. Sterczala3, Jonathan D. Miller2, Mandy E. Parra4, Hannah L. Dimmick5, Michael A. Trevino1 1Oklahoma State University, Stillwater, Oklahoma; 2University of Kansas, Lawrence, Kansas; 3University of Pittsburg, Pittsburg, Pennsylvania; 4University of Mary Hardin-Baylor, Belton, Texas; 5University of Calgary, Calgary, Alberta PURPOSE: The purpose of this study was to examine if relationships exist between muscle architecture and mechanomyographic amplitude (MMGRMS)-torque relationships of the vastus lateralis (VL). METHODS: 11 healthy males (means ± SD; age: 20.18 ± 2.04 years; height: 178.51 ± 4.28 cm; body mass: 78.63 ± 9.11 kg) and 12 healthy females (age: 21.33 ± 3.00 years; height: 164.58 ± 6.60 cm; body mass: 60.38 ± 10.24 kg) completed this investigation. B-mode ultrasonography was used to measure pennation angle, muscle thickness, and subcutaneous fat (sFAT) of the VL. Subjects performed three, three-second maximal voluntary contractions (MVCs) of the knee extensors on an isokinetic dynamometer and the highest torque output was designated as the MVC. A MMG sensor was placed on the VL. Participants then performed an isometric submaximal muscle action that included a 7 s linearly increasing segment up to 70% MVC and a 12 s plateau. For the linearly increasing segment, linear regressions models were fit to the log-transformed MMGRMS-torque relationships and the slope (b term) was calculated. MMGRMS was averaged during the steady torque segment. Pearson’s product moment correlation coefficients were calculated comparing the b terms and MMGRMS at steady torque to pennation angle, muscle thickness, and sFAT of the VL. Alpha was set at 0.05. RESULTS: The b terms were significantly correlated with pennation angle (p \u3c 0.001, r = 0.772) and muscle thickness (p = 0.004, r = 0.571), but not with sFAT (p = 0.263). In addition, MMGRMS at steady torque was significantly correlated with pennation angle (p = 0.018, r = 0.500) and muscle thickness (p = 0.014, r = 0.515), but not with sFAT (p = 0.154). CONCLUSION:The mechanical behavior of the muscle, as measured with MMGRMS, was sensitive to differences in pennation angle and muscle thickness of the VL during a high-intensity contraction. MMGRMS may provide a relatively simple measurement to obtain information regarding muscle architecture. Future research should investigate if MMGRMS can quantify potential changes in pennation angle and muscle thickness as a result of exercise training, aging, or disease