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Physical fitness and performance. Fatigue responses during repeated sprints matched for initial mechanical output.

School of Human Movement and Exercise Science, The University of Western Australia, Perth, Australia.
Medicine &amp Science in Sports &amp Exercise (Impact Factor: 4.46). 12/2007; 39(12):2219-25. DOI: 10.1249/mss.0b013e31815669dc
Source: PubMed

ABSTRACT To compare muscle fatigability during two sets of repeated cycling sprints matched for initial mechanical output in a nonfatigued and fatigued state.
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.
On the basis of total work (TW), performance in sprint 11 (79.8 +/- 4.8 J.kg) was not significantly different to performance in sprint 4 (80.3 +/- 5.3 J.kg; 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.
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.

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Available from: David John Bishop, Aug 06, 2014
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    • "To delineate the neural and muscular factors driving performance recovery following repeated sprints a sprint-matching paradigm was introduced, where exercise responses during two sets of repeated cycling sprints (10 x 6-s 'all out' sprints with 30 s recovery followed after 6 min of passive recovery by five 6-s sprints), matched for initial mechanical output in a 'non fatigued' (sprints 4 to 8) and a 'fatigued' state (sprints 11 to 15), were actually compared (Mendez-Villanueva et al. 2007). Results indicated that there was a greater fatigability in the five repetitions of the second versus first set, despite mechanical output produced for the initial bout of both sets (i.e., sprints 4 and 11) being similar. "
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    • "However, it is well-known that the greater the initial force exerted by a muscle during a given task, the more the muscle will fatigue (Enoka and Stuart 1992; Hunter 2009). Thus, it is not surprising to observe that the higher the initial-sprint performance , the larger the performance decrement in subsequent sprint repetitions (Bishop et al. 2003b; Bishop and Spencer 2004; Gaitanos et al. 1993; Mendez-Villanueva et al. 2007, 2008). This is supported by our observation (Fig. 2 "
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    ABSTRACT: To investigate whether the larger reduction in mechanical work observed during repeated-sprint exercise (RSE) in men versus women represents a true, physiological sex dimorphism or is the consequence of the higher initial mechanical work performed by men. Male and female team-sport athletes (n = 35) performed 20, 5-s cycle sprints interspersed with 25 s of rest. Mechanical work and surface electromyograms (EMG) of four muscles were recorded in every sprint. Mechanical work achieved in one sprint (20.7%, P = 0.0006), total work accumulated over the 20 sprints (21.1%, P = 0.009) and percent work decrement (32.2%, P = 0.008) were larger in men than in women. When both sexes were plotted together, there was a positive relationship between the initial-sprint work and the work decrement across sprint repetitions (r = 0.89, P = 0.002). The RSE induced larger (P = 0.009) absolute EMG amplitude changes in men (-155.2 ± 60.3 mVs) than in women (-102.5 ± 45.1 mVs). Interestingly, in a subset of men and women (n = 7 per group) matched for initial-sprint work, the sex difference in percent work decrement (men: -29.5 ± 1.5%; women: -27.2 ± 3.2%; P = 0.72) and EMG changes (men: -17.7 ± 6.9% vs. women: -15.3 ± 7.1%; P = 0.69) no longer persisted. Results show that the proposed greater fatigue in men is likely to be a consequence of their greater absolute initial-sprint performance, rather than a sex difference in fatigue resistance per se. We conclude that, on the basis of the absolute mechanical work completed, women are not more fatigue resistant than men and use comparable muscle recruitment strategies to perform RSE.
    Arbeitsphysiologie 08/2011; 112(4):1429-36. DOI:10.1007/s00421-011-2110-1 · 2.30 Impact Factor
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    • "Pearson's product–moment correlation analysis was used to compare association between running performance and TSI. Because performance at the first sprint is the major determinants of fatigue (and %Dec) during RS (Mendez-Villanueva et al. 2007), correlations including S2 performance or %Dec were adjusted for distance ran during S1 in the post-test using partial correlations. The following criteria were adopted to interpret the magnitude of the correlation (r): \0.1 trivial, 0.1–0.3 "
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    ABSTRACT: The aim of the present study was to examine the effect of an 8-week endurance training program on repeated-sprint (RS) performance and post-sprints muscle reoxygenation rate in 18 moderately trained males (34 ± 5 years). Maximal aerobic speed (MAS), 10 km running and RS (2 × 15-s shuttle-sprints, interspersed with 15 s of passive recovery) performance were assessed before and after the training intervention. Total distance covered (TD) and the percentage of distance decrement (%Dec) were calculated for RS. Between-sprints muscle reoxygenation rate (Reoxy rate) was assessed with near-infrared spectroscopy during RS before and after training. After training, MAS (+9.8 ± 5.8%, with 100% chances to observe a substantial improvement), 10 km time (-6.2 ± 5.3%, 99%), TD (+9.6 ± 7.7%, 98%), %Dec (-25.6 ± 73.6%, 93%) and Reoxy rate (+152.4 ± 308.1%, 95%) were improved. The improvement of Reoxy rate was largely correlated with improvements in MAS [r = 0.63 (90% CL, 0.31;-0.82)] and %Dec [r = -0.52 (-0.15;-0.76)]. Present findings confirm the beneficial effect of endurance training on post-sprint muscle reoxygenation rate, which is likely to participate in the improvement of repeated-sprint ability after training. These data also confirm the importance of aerobic conditioning in sports, where repeating high-intensity/maximal efforts within a short time-period are required.
    Arbeitsphysiologie 02/2011; 111(2):293-301. DOI:10.1007/s00421-010-1654-9 · 2.30 Impact Factor
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