Flywheel resistance training calls for greater eccentric muscle activation than weight training
Changes in muscle activation and performance were studied in healthy men in response to 5 weeks of resistance training with or without “eccentric overload”. Subjects, assigned to either weight stack (grp WS; n = 8) or iso-inertial “eccentric overload” flywheel (grp FW; n = 9) knee extensor resistance training, completed 12 sessions of four sets of seven concentric–eccentric actions. Pre- and post-measurements comprised maximal voluntary contraction (MVC), rate of force development (RFD) and training mode-specific force. Root mean square electromyographic (EMGRMS) activity of mm. vastus lateralis and medialis was assessed during MVC and used to normalize EMGRMS for training mode-specific concentric (EMGCON) and eccentric (EMGECC) actions at 90°, 120° and 150° knee joint angles. Grp FW showed greater (p < 0.05) overall normalized angle-specific EMGECC of vastii muscles compared with grp WS. Grp FW showed near maximal normalized EMGCON both pre- and post-training. EMGCON for Grp WS was near maximal only post-training. While RFD was unchanged following training (p > 0.05), MVC and training-specific strength increased (p < 0.05) in both groups. We believe the higher EMGECC activity noted with FW exercise compared to standard weight lifting could be attributed to its unique iso-inertial loading features. Hence, the resulting greater mechanical stress may explain the robust muscle hypertrophy reported earlier in response to flywheel resistance training.
KeywordsConcentric and eccentric actions Electromyography Iso-inertia Resistance exercise
We thank all the subjects who participated in this study. This study was funded by the Swedish Winter Sports Research Centre, Mid Sweden University, Östersund, the Swedish National Centre for Research in Sports (CIF), and the Swedish National Space Board (SNSB).
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