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This Article Full Text Full Text (PDF) All Versions of this Article: 91/1/171    most recent expphysiol.2005.032094v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Pucci, A. R Articles by Cafarelli, E Search for Related Content PubMed PubMed Citation Articles by Pucci, A. R Articles by Cafarelli, E

¹ School of Kinesiology and Health Science, York University, Toronto, ON, Canada ² Department of Kinesiology and Health Education, University of Texas at Austin, Austin, TX, USA

This study measured changes in maximal voluntary contraction (MVC) force, percentage maximal activation, maximal surface EMG, M-wave amplitude and average motor unit firing rates during the initial 3 weeks of isometric resistance training of the quadriceps muscle. Ten men participated in a resistance training programme three times a week for 3 weeks and 10 men participated as a control group. In the training group, MVC increased by 35% (from 761 ± 77 to 1031 ± 78 N) by the end of the 3 weeks. There were no changes in mean motor unit firing rates during submaximal or maximal voluntary contractions of 50 (15.51 ± 1.48 Hz), 75 (20.23 ± 1.85 Hz) or 100% MVC (42.25 ± 2.72 Hz) with isometric resistance training. There was also no change in maximal surface EMG relative to the M-wave amplitude. However, there was a small increase in maximal activation (from 95.7 ± 1.83 to 98.44 ± 0.66%) as measured by the twitch interpolation technique. There were no changes in any of the parameters measured in the control group. It is suggested that mechanisms other than increases in average motor unit firing rates contributed to the increase in maximal force output with resistance training. Such mechanisms may include a combination of increased motor unit recruitment, enhanced protein synthesis, and changes in motor unit synchronization and muscle activation patterns across the quadriceps synergy.

(Received 1 September 2005; accepted after revision 4 October 2005; first published online 6 October 2005)
Corresponding author L. Griffin: Department of Kinesiology and Health Education, University of Texas at Austin, 1 University Station, D3700, Bellmont 222, Austin, TX 78712, USA. Email: l.griffin{at}mail.utexas.edu