The effect of warm-up on high-intensity, intermittent running using nonmotorized treadmill ergometry.

The aim of this study was to investigate the effect of previous warming on high-intensity intermittent running using nonmotorized treadmill ergometry. Ten male soccer players completed a repeated sprint test (10 x 6-second sprints with 34-second recovery) on a nonmotorized treadmill preceded by an active warm-up (10 minutes of running: 70% VO2max; mean core temperature (Tc) 37.8 +/- 0.2 degrees C), a passive warm-up (hot water submersion: 40.1 +/- 0.2 degrees C until Tc reached that of the active warm-up; 10 minutes +/- 23 seconds), or no warm-up (control). All warm-up conditions were followed by a 10-minute static recovery period with no stretching permitted. After the 10-minute rest period, Tc was higher before exercise in the passive trial (38.0 +/- 0.2 degrees C) compared to the active (37.7 +/- 0.4 degrees C) and control trials (37.2 +/- 0.2 degrees C; p < 0.05). There were no differences in pre-exercise oxygen consumption and blood lactate concentration; however, heart rate was greater in the active trial (p < 0.05). The peak mean 1-second maximum speed (MxSP) and group mean MxSP were not different in the active and passive trials (7.28 +/- 0.12 and 7.16 +/- 0.10 m x s(-1), respectively, and 7.07 +/- 0.33 and 7.02 +/- 0.24 m x s(-1), respectively; p > 0.05), although both were greater than the control. The percentage of decrement in performance fatigue was similar between all conditions (active, 3.4 +/- 1.3%; passive, 4.0 +/- 2.0%; and control, 3.7 +/- 2.4%). We conclude that there is no difference in high-intensity intermittent running performance when preceded by an active or passive warm-up when matched for post-warm-up Tc. However, repeated sprinting ability is significantly improved after both active and passive warm-ups compared to no warm-up.

The effects of acute creatine supplementation on multiple sprint cycling and running performance in rugby players.

The benefits of creatine (CR) supplementation are well documented, particularly during repeated bouts of high-intensity muscular activity. Most published experiments use mass-supported (cycle ergometry) activities as a means of evaluating creatine's efficacy, therefore minimizing any possible adverse effects of increased body mass associated with CR supplementation. This study aims to use both mass-supported and mass-dependent activities to assess the effectiveness of acute CR supplementation on a group of highly trained rugby players. A randomized, double-blind, crossover research design was utilized, with subjects receiving 20 g.d(-1) x 5 d of both CR and a glucose placebo (PL). Subjects were assessed via 10 x 6-second Wingate test and a 10 x 40-m sprint test on separate days, presupplementation and postsupplementation. A 28-d washout period separated the two treatments. No significant treatment (p > 0.05) or treatment by test interaction effects (p > 0.05) were observed for peak or minimum power output (W), peak or minimum running velocity (m.s(-1)), or fatigue index (%). No significant differences (p > 0.05) were found postsupplementation for body mass and percentage body fat. Although statistical significance was not achieved for any of the measured parameters, there were small improvements in performance that may be of benefit to rugby players.

The oxygen uptake response running to exhaustion at peak treadmill speed.

PURPOSE: Peak treadmill speed (V(max)), which is the final speed reached and sustained for a minute during a speed-incremented continuous maximal oxygen uptake ([OV0312]O(2max)) test, is an effective predictor of endurance performance. This study assesses the reliability of V(max) and [OV0312]O(2max), and examines the oxygen uptake response while running to exhaustion at V(max). METHODS: Eleven recreationally active runners completed two speed-incremented [OV0312]O(2max) tests (test 1 and test 2) to determine [OV0312]O(2max) and V(max). In addition, the subjects completed a constant speed test (test 3) at V(max) to determine time to exhaustion (T(max)). RESULTS: No significant differences existed between test 1 and test 2 for [OV0312]O(2max) (P = 0.68) and V(max) (P = 0.10). Means (+/- SD) for [OV0312]O(2max) and V(max) were 51.1 +/- 5.8 mL.kg-1.min-1 and 17.4 +/- 1.3 km.h-1, respectively; 95% limits of agreement for V(max) were -0.1 +/- 1.4 km.h-1. However, as heteroscedasticity was present in the [OV0312]O(2max) test data, 95% ratio limits of agreement were reported (1.01 *// 1.08). During test 3, 6 of the 11 subjects attained an oxygen uptake equivalent to their previously recorded [OV0312]O(2max). The time to attain [OV0312]O(2max) was 155.0 +/- 48.0 s, which represented 66.5% of T(max) (237.0 +/- 35.0 s). Although 5 of the 11 subjects did not attain an oxygen uptake response equivalent to that previously recorded, no significant difference existed between the oxygen uptakes for the three tests (P = 0.52). CONCLUSION: The results of this study indicate that V(max) and [OV0312]O(2max) attained during a speed incremented maximal oxygen uptake test were reliable. However, while running at V(max), not all the subjects attained an oxygen uptake response equivalent to that previously recorded during incremental tests 1 and 2.