Contractile Properties Following Fatigue • 93 Effect of Force Level and Training Status on Contractile Properties Following Fatigue S. Jayne Garland, David Walton, and Tanya D. Ivanova Catalog Data Garland, S.J., Walton, D., and Ivanova, T.D. (2003). Effect of force level and training status on contractile properties following fatigue. Can. J. Appl. Physiol. 28(1): 93-101. ©2003 Canadian Society for Exercise Physiology. Key words: human, muscle fatigue, endurance, submaximal contractions Mots clés: humain, fatigue musculaire, endurance, contractions sous-maximales Abstract/Résumé This study examined the effects of fatigue on the contractile properties of the twitch con- traction evoked by the H-reflex and the maximal M-wave. Untrained subjects demonstrated more pronounced slowing of half relaxation time (HRT) in the H-reflex twitch than in the M-wave twitch and also more slowing of HRT in high force vs. low force contractions. Endurance-trained subjects, however, demonstrated a shortening of the H-reflex twitch. The twitch contractile properties following fatigue are dependent on force level and train- ing status. Cette étude analyse les effets de la fatigue sur les propriétés contractiles de la secousse musculaire associée au réflexe H et à la réponse M. Chez les sujets non entraînés, le temps de demi-relaxation (HRT) associé au réflexe H est plus long que celui associé à la réponse M ; le temps de demi-relaxation est aussi plus long au cours de contractions fortes qu’au cours de contractions faibles. Chez les sujets entraînés à l’endurance, la secousse associée au réflexe H est plus brève. Les propriétés contractiles après une séance d’épuisement dépendent du niveau de force exercée et du niveau d’entraînement. Introduction There have been numerous reports of the decrease in peak force and the slowing of muscle relaxation properties resulting from fatigue (Fitts, 1994). Many of these 93 The authors are with the School of Physical Therapy, Elborn College, The University of Western Ontario, London, ON N6G 1H1; S.J. Garland is also with the Department of Physiology, The University of Western Ontario, London, ON. RAPID COMMUNICATION Can. J. Appl. Physiol. Downloaded from www.nrcresearchpress.com by Depository Services Program on 06/05/13 For personal use only.