Abstract
A substantial gain in strength is often observed in the early phase of resistance training. The aim of this study was to address whether improved strength in the early phase of resistance training, can be attributed to increased activation, or to intra-muscular changes of the agonist muscle during maximal isometric torque production. Fourteen male subjects trained maximal isometric dorsiflexion during 5 days. Each subject performed 9 sessions with 25 maximal voluntary contractions in a device that registered the dorsiflexion torque. Surface electromyography (SEMG) of the tibialis anterior (TA) was recorded with a 130-channel grid electrode. SEMG of the extensor digitorum longus, gastrocnemius and soleus muscles were recorded with bipolar electrodes. The main finding was that all subjects gained in strength while the SEMG activation level of the primer agonist, TA, decreased with no apparent intra-muscular spatial changes following 5 days of resistance training. The other muscles that influence dorsiflexion torque did not modify their activation level with training. These findings reject an increase in agonist activation level as the main source for early strength gain, and illustrate the need for further research to reveal the specific sites of neural adaptation and other physiological mechanisms that might contribute to increased strength during the early phase of resistance training.
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Acknowledgements
We would like to thank the Medical technical research center, Medical faculty, NTNU, for partially funding this project. Einar Hassel, Human Movement Sciences program, NTNU, for construction of the strength-recording device, and Paul Jarle Mork, Department of Industrial Economics and Technology, NTNU, for constructive comments and discussion.
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Holtermann, A., Roeleveld, K., Vereijken, B. et al. Changes in agonist EMG activation level during MVC cannot explain early strength improvement. Eur J Appl Physiol 94, 593–601 (2005). https://doi.org/10.1007/s00421-005-1365-9
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DOI: https://doi.org/10.1007/s00421-005-1365-9