Following a bout of high-intensity exercise of short duration (preload stimulus), the muscle is in both a fatigued and a potentiated (referred to as postactivation potentiation) state. Consequently, subsequent muscle performance depends on the balance between these 2 factors. To date, there is no uniform agreement about the optimal recovery required between the preload stimulus and subsequent muscle performance to gain optimal performance benefits. The aim of the present study was to determine the optimal recovery time required to observe enhanced muscle performance following the preload stimulus. Twenty-three professional rugby players (13 senior international players) performed 7 countermovement jumps (CMJs) and 7 ballistic bench throws at the following time points after a preload stimulus (3 repetition maximum [3RM]): baseline, approximately 15 seconds, and 4, 8, 12, 16, and 20 minutes. Their peak power output (PPO) was determined at each time point. Statistical analyses revealed a significant decrease in PPO for both the upper (856 +/- 121 W vs. 816 +/- 121 W, p < 0.001) and the lower (4,568 +/- 509 W vs. 4,430 +/- 495 W, p = 0.005) body when the explosive activity was performed approximately 15 seconds after the preload stimulus. However, when 12 minutes was allowed between the preload stimulus and the CMJ and ballistic bench throws, PPO was increased by 8.0 +/- 8.0% and 5.3 +/- 4.5%, respectively. Based on the above results, we conclude that muscle performance (e.g., power) can be significantly enhanced following a bout of heavy exercise (preload stimulus) in both the upper and the lower body, provided that adequate recovery (8-12 minutes) is given between the preload stimulus and the explosive activity.

There is a general agreement that the most valid method of measuring peak lower-body mechanical power output (LBPP) in a countermovement jump (CMJ) is by analysis of the corresponding vertical component of the ground reaction force (VGRF)-time history of the jump. However, there is no published standard protocol. The purpose of this study was to establish a standard protocol. The variables necessary to define a valid and reliable CMJ method were: (a) vertical force range, (b) force sampling and integration frequency, (c) method of integration, (d) determination of body weight (BW), and (e) determination of the initiation of the CMJ. Countermovement jumps off a force platform (FP) were performed by 15 male professional rugby players. The 5 variables were then optimized to maximize the reliability and validity of the measure of LBPP. Errors of <1% (p ≤ 0.05) in the measurement of LBPP were obtained using the following specification: (a) 6 times BW (using a 16-bit analog to digital converter), (b) 1,000 Hz, (c) Simpson's rule or the trapezoidal rule, (d) mean VGRF for 1 second of quiet standing immediately before jump signal, and (e) 30 ms before the instant BW ± 5 SD is exceeded after the jump signal. Peak lower-body power output was most sensitive to variables 4 and 5. It was concluded that this study has established a standard protocol for the criterion method of measuring peak power in a CMJ using an FP. As all other estimates and less reliable methods of determining LBPP in a CMJ rely on the FP method for calibration, it is proposed that this protocol be used as the basis of future criterion measures using a FP.

Following a bout of heavy resistance training, the muscle is in both a fatigued and potentiated state with subsequent muscle performance depending on the balance between these two factors. To date, there is no uniform agreement about the optimal acute recovery required between the heavy resistance training and subsequent muscle performance to gain performance benefits. The aim of the present study was to determine the recovery time required to observe enhanced muscle performance following a bout of heavy resistance training. Twenty professional rugby players performed a countermovement jump at baseline and approximately 15 s, 4, 8, 12, 16, 20, and 24 min after a bout of heavy resistance training (three sets of three repetitions at 87% one-repetition maximum squat). Power output, jump height, and peak rate of force development were determined for all countermovement jumps. Despite an initial decrease in countermovement jump performance after the heavy resistance training (P<0.001), participants' performance increased significantly following 8 min recovery (P<0.001) (i.e. jump height increased by 4.9%, s=3.0). The findings suggest that muscle performance during a countermovement jump can be markedly enhanced following bouts of heavy resistance training provided that adequate recovery (approximately 8 min) is allowed between the heavy resistance training and the explosive activity.

After a bout of high-intensity exercise of short duration (preload stimulus), the muscle is in both a fatigued and potentiated (referred to as postactivation potentiation [PAP]) state. Consequently, subsequent muscle performance depends on the balance of these 2 factors. Although research has shown PAP to be an effective method of increasing power during both the squat jumps, little data exist on its effect on more functional activities such as sprinting. The present study aimed to determine the effect of PAP on sprint performance in professional rugby players. Sixteen professional male rugby players performed 5 10-m sprints (with a 5-m split): baseline, 4, 8, 12, and 16 minutes after the preload stimulus (1 set of 3 repetitions of the back squat at 91% 1 Repetition Maximum [RM]). There was no significant time effect over the duration of the study with regard to 5-m (p = 0.175) and 10-m sprint times (p = 0.401). However, when individual responses to PAP were taken into account, a significant improvement in sprint performance was observed over both 5 (Baseline: 1.09 +/- 0.06s vs. Best time: 1.05 +/- 0.05s, p = 0.002) and 10 m (Baseline: 1.83 +/- 0.08s vs. Best time: 1.79 +/- 0.08s, p = 0.003) compared with the baseline sprint. We conclude that sprinting performance is enhanced after a preload stimulus providing adequate and individualized recovery is given between the 2 activities, and this may have important implications for training speed.

There is considerable conflict within the literature regarding the relevance of isometric testing for the assessment of neuromuscular function within dynamic sports. The aim of this study was to determine the relationship between isometric measures of force development and dynamic performance. Thirty-nine professional rugby league players participated in this study. Forty-eight hours after trial familiarization, participants performed a maximal isometric midthigh pull, with ∼120-130° bend at the knee, countermovement jump (CMJ), and a 10-m sprint. Force-time data were processed for peak force (PF), force at 100 milliseconds (F100ms), and peak rate of force development (PRFD). Analysis was carried out using Pearson's product moment correlation with significance set at p < 0.05. The PF was not related to dynamic performance; however, when expressed relative to body weight, it was significantly correlated with both 10-m time and CMJ height (r = -0.37 and 0.45, respectively, p < 0.05). The F100ms was inversely related to 10-m time (r = -0.54, p < 0.01); moreover, when expressed relative to body weight, it was significantly related to both 10-m time and CMJ height (r = -0.68 and 0.43, p < 0.01). In addition, significant correlations were found between PRFD and 10-m time (r = -0.66, p < 0.01) and CMJ height (r = 0.387, p < 0.01). In conclusion, this study provides evidence that measures of maximal strength and explosiveness from isometric force-time curves are related to jump and sprint acceleration performance in professional rugby league players.

Start performance (as defined by time to 15 m) has been shown to be a key performance indicator during 50-m freestyle swimming; however, there is limited information with regard to the key strength and power variables that influence start performance during sprint swimming. In light of the above, this study aimed to examine the key strength and power predicators of start performance in 50-m freestyle swimming. Eleven male British international sprint swimmers (age 21.3 ± 1.7 years; mass 78.1 ± 11.2 kg; and height 1.8 ± 0.1 m) participated in this study. Within 1 week, swimmers performed the following tests: 3 repetition maximum (3RM) squat strength, countermovement jump (CMJ) on a portable force platform, and a measure of start time performance (time to 15 m under 50-m freestyle conditions). The start time was measured using a standard racing platform to which a portable force platform was mounted, and all starts were recorded using 2 cameras. This setup allowed for the quantification of time to 15 m, peak vertical force (PVF), and peak horizontal force (PHF). Data were analyzed using Pearson's product moment correlation with significance set at p < 0.05. Start time was significantly related to 1RM strength (r = -0.74), jump height (r = -0.69), peak (r = -0.85), and relative power (r = -0.66) (p < 0.05) but not rate of force development (r = -0.56, p > 0.05). Furthermore, lower body strength was a key determinant of jump height (r = 0.69), power (r = 0.78), PVF (r = 0.62), and PHF (r = 0.71) (p < 0.05). This study provides evidence of the importance of lower body strength and power to start time in international 50-m sprint swimmers.

This study examined the validity of 2 kinematic systems for estimating force and power during squat jumps. 12 weight-trained males each performed single repetition squat jumps with a 20-kg, 40-kg, 60-kg and 80-kg load on a Kistler portable force plate. A commercial linear position transducer (Gymaware [GYM]) and accelerometer (Myotest® [MYO]) were attached to the bar to assess concentric peak force (PF) and peak power (PP). Across all loads tested, the GYM and MYO estimates of PF and PP were moderately to strongly correlated ( P≤0.05-0.001) with the force plate measurements ( R=0.59-0.87 and R=0.66-0.97), respectively. The mean PF and PP values were not significantly different between the 2 kinematic systems and the force plate, but the estimates did produce some systematic bias and relatively large random errors, especially with the 20-kg load (PF bias >170 N, PF error >335 N, PP bias >400 W, PP error >878 W). Some proportional bias was also identified. In summary, the estimation of PF and PP by a linear position transducer and accelerometer showed moderate to strong relative validity and equivalent absolute validity, but these estimates are limited by the presence of bias and large random errors.

The ability to develop high levels of muscular power is considered an essential component of success in many sporting activities; however, the optimal load for the development of peak power during training remains controversial. Our aim in the present study was to determine the optimal load required to observe peak power output during the ballistic bench throw (BBT) and squat jump (SJ) in professional rugby players. Forty-seven, professional, male, rugby players of (mean +/- SD) mass 101.3 +/- 12.8 kg and height 1.82 +/- 0.08 m volunteered and gave informed consent for this study, which was approved by a university ethics committee. Players performed BBT at loads of 20, 30, 40, 50, and 60% of their predetermined 1 repetition maximum (1RM) and SJ at loads of 0, (body mass only), 20, 30, 40, 50, and 60% of their predetermined 1RM in a randomized and balanced order. Power output (PO) was determined by measurement of barbell displacement with subsequent calculation of velocity, force, and power. Relative load had a significant effect on PO for both the BBT (effect size eta(2): 0.297, p < 0.001) and SJ (Effect Size eta(2): 0.709, p < 0.001). Peak power output was produced when the athletes worked against an external load equal to 30% 1RM for the upper body and 0% 1RM for the lower body.