Fatigue Responses during Repeated Sprints Matched for Initial Mechanical Output

MENDEZ-VILLANUEVA, ALBERTO1,2; HAMER, PETER1,3; BISHOP, DAVID1,4

Medicine & Science in Sports & Exercise: December 2007 - Volume 39 - Issue 12 - pp 2219-2225
doi: 10.1249/mss.0b013e31815669dc
APPLIED SCIENCES: Physical Fitness and Performance

Purpose: To compare muscle fatigability during two sets of repeated cycling sprints matched for initial mechanical output in a nonfatigued and fatigued state.

Methods: Eight young men performed 10, 6-s all-out sprints on a cycle ergometer interspersed with 30 s of recovery, followed, after 6 min of passive recovery, by five 6-s sprints, again interspersed by 30 s of recovery.

Results: On the basis of total work (TW), performance in sprint 11 (79.8 ± 4.8 J·kg−1) was not significantly different to performance in sprint 4 (80.3 ± 5.3 J·kg−1; P = 0.81). The decrease in TW for the five sprints after sprint 4 (i.e., sprints 4 to 8) averaged 14.5% (P < 0.001), which was significantly less than the decrement in TW from sprints 11 to 15 (20.3%; P < 0.05). Despite no significant differences in TW values achieved in sprints 4 and 11, the amplitude of the electromyogram (EMG) signal (i.e., root mean square (RMS)) recorded during sprint 11 (0.398 ± 0.03 V) was 12.0% lower (P < 0.05) than in sprint 4 (0.452 ± 0.02 V). In contrast, values of EMG median frequency (MF) recorded during sprint 4 (85.5 ± 5.5 Hz) and 11 (89.3 ± 7.2 Hz) were not significantly different (P = 0.33). However, the rate of decrease in EMG activity (i.e., RMS and MF) was similar for the two set of sprints.

Conclusions: These findings suggest that previous fatiguing repeated-sprint exercise, followed by a rest period, induces greater fatigability during subsequent repeated-sprint exercise, regardless of the initial mechanical output, and that these changes are associated with acute neuromuscular adjustments.

1School of Human Movement and Exercise Science, The University of Western Australia, Perth, AUSTRALIA; 2Faculty of Physical Activity and Sport Sciences, University of Alcala, Madrid, SPAIN; 3School of Health Science, The University of Notre Dame, Fremantle, AUSTRALIA; and 4Team Sport Research Group, Faculty of Motor Sciences, University of Verona, Verona, ITALY

Address for correspondence: Alberto Mendez-Villanueva, Ph.D, Facultad de Ciencias de la Actividad Física y el Deporte, Universidad de Alcalá, Campus Universitário, Ctra. Madrid-Barcelona Km. 3,600, 28871 Alcalá de Henares (Madrid), Spain; E-mail: amendezvillanueva@yahoo.com.

Submitted for publication April 2007.

Accepted for publication July 2007.

©2007The American College of Sports Medicine