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Postactivation potentiation (PAP), an acute and temporary enhancement of muscular performance resulting from previous muscular contraction, commonly occurs after heavy resistance exercise. However, this method of inducing PAP has limited application to the precompetition practices (e.g., warm-up) of many athletes. Very few studies have examined the influence of plyometric activity on subsequent performance; therefore, we aimed to examine the influence of alternate-leg bounding on sprint acceleration performance. In a randomized crossover manner, plyometric-trained men (n = 23) performed seven 20-m sprints (with 10-m splits) at baseline, ∼15 seconds, 2, 4, 8, 12, and 16 minutes after a walking control (C) or 3 sets of 10 repetitions of alternate-leg bounding using body mass (plyometric, P) and body mass plus 10% (weighted plyometric, WP). Mean sprint velocities over 10 and 20 m were similar between trials at baseline. At ∼15 seconds, WP impaired 20-m sprint velocity by 1.4 ± 2.5% when compared with C (p = 0.039). Thereafter, 10- and 20-m sprint velocities improved in WP at 4 minutes (10 m: 2.2 ± 3.1%, p = 0.009; 20 m: 2.3 ± 2.6%, p = 0.001) and 8 minutes (10 m: 2.9 ± 3.6%, p = 0.002; 20 m: 2.6 ± 2.8%, p = 0.001) compared with C. Improved 10-m sprint acceleration performance occurred in P at 4 minutes (1.8 ± 3.3%, p = 0.047) relative to C. Therefore, sprint acceleration performance is enhanced after plyometric exercise providing adequate recovery is given between these activities; however, the effects may differ according to whether additional load is applied. This finding presents a practical method to enhance the precompetition practices of athletes.

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The purpose of this study was to investigate the effects of a 5-week lower-limb unilateral or bilateral strength program on measures of strength, sprinting, and change of direction speed. Eighteen academy rugby players (18.1 ± 0.5 years, 97.4 ± 11.3 kg, 183.7 ± 11.3 cm) were randomly assigned to either a unilateral (UNI) or bilateral (BI) group. The UNI group squatted exclusively with the rear elevated split squat (RESS), whereas the BI group trained only with the bilateral back squat (BS). Both groups trained at a relative percentage of the respective 1 repetition maximum (1RM) twice weekly over a 5-week period. Subjects were assessed at baseline and postintervention for 1RM BS, 1RM RESS, 10-m sprint, 40-m sprint, and pro-agility. There was a significant main effect of time for 1RM BS (F1,16 = 86.5, p < 0.001), ES (0.84 < Cohen d < 0.92), 1RM RESS (F1,16 = 133.0, p < 0.001), ES (0.89 < Cohen d < 0.94), 40-m sprint (F1,16 = 14.4, p = 0.002), ES (0.47 < Cohen d < 0.67) and pro-agility (F1,16 = 55.9, p < 0.001), ES (0.77 < Cohen d < 0.89), but not 10-m sprints (F1,16 = 2.69, p = 0.121), ES (0.14 < Cohen d < 0.38). No significant interactions between group and time were observed for any of the dependent variables. This is the first study to suggest that BI and UNI training interventions may be equally efficacious in improving measures of lower-body strength, 40-m speed, and change of direction in academy level rugby players.

Ferguson C, Whipp BJ, Cathcart AJ, Rossiter HB, Turner AP, Ward SA. Effects of prior very-heavy intensity exercise on indices of aerobic function and high-intensity exercise tolerance. J Appl Physiol 103: [812][813][814][815][816][817][818][819][820][821][822] 2007. First published May 31, 2007; doi:10.1152/japplphysiol.01410.2006.-A recent bout of high-intensity exercise can alter the balance of aerobic and anaerobic energy provision during subsequent exercise above the lactate threshold ( L). However, it remains uncertain whether such "priming" influences the tolerable duration of subsequent exercise through changes in the parameters of aerobic function [e.g., L, maximum oxygen uptake (V O2max)] and/or the hyperbolic power-duration (P-t) relationship [critical power (CP) and the curvature constant (WЈ)]. We therefore studied six men performing cycle ergometry to the limit of tolerance; gas exchange was measured breath-by-breath and arterialized capillary blood [lactate] was measured at designated intervals. On different days, each subject completed 1) an incremental test (15 W/min) for estimation of L and measurement of the functional gain (⌬V O2/ ⌬WR) and V O2peak and 2) four constant-load tests at different work rates (WR) for estimation of CP, WЈ, and V O2max. All tests were subsequently repeated with a preceding 6-min supra-CP priming bout and an intervening 2-min 20-W recovery. The hyperbolicity of the P-t relationship was retained postpriming, with no significant difference in CP (241 Ϯ 39 vs. 242 Ϯ 36 W, post-vs. prepriming), V O2max (3.97 Ϯ 0.34 vs. 3.93 Ϯ 0.38 l/min), ⌬V O2/⌬WR (10.7 Ϯ 0.3 vs. 11.1 Ϯ 0.4 ml ⅐ min Ϫ1 ⅐ W Ϫ1 ), or the fundamental V O2 time constant (25.6 Ϯ 3.5 vs. 28.3 Ϯ 5.4 s). WЈ (10.61 Ϯ 2.07 vs. 16.13 Ϯ 2.33 kJ) and the tolerable duration of supra-CP exercise (Ϫ33 Ϯ 11%) were each significantly reduced, despite a less-prominent V O2 slow component. These results suggest that, following supra-CP priming, there is either a reduced depletable energy resource or a residual fatiguemetabolite level that leads to the tolerable limit before this resource is fully depleted. power-duration relationship; WЈ; oxygen uptake kinetics; slow component; lactate threshold THE TOLERABLE DURATION of muscular exercise, such as cycling or running, is dependent on both the limit (i.e., V O 2max ) and the contour (i.e., V O 2 kinetics) of the oxygen uptake (V O 2 ) response profile. The phase 2 (or fundamental) V O 2 kinetics during constant-load cycle ergometer exercise have been shown to reflect those of muscle O 2 consumption [following a short, transit delay, i.e., phase 1 (3, 20)], with V O 2 attaining a steady state with first-order exponential kinetics. Moderateintensity work rates [i.e., below the lactate threshold ( L )] are highly sustainable, there being no sustained arterial lactate concentration ([L Ϫ ]a) increase (reviewed in Refs. 24, 55). For heavy-intensity work rates that lie between L and critical power [CP; i.e., the power asymptote of the power-duration (P-t) relationship], the emerg...