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Purpose: Postactivation performance enhancement (PAPE), which refers to the phenomena associated with the attainment of enhanced performance in sport-specific tasks after a conditioning activity, is an important objective of warming-up practices in many sports. This is even more relevant for sprinters, as potential increases in sprinting speed will directly influence their competitive results. This systematic review with meta-analysis evaluated the effects of different PAPE protocols (ie, using plyometrics, strength-power exercises, and resisted/assisted sprints) on the sprinting performance (ie, sprint time or sprint speed) of competitive sprinters. Methods: Initially, 1205 records published until last December 18 were identified, using the following databases: PubMed/MEDLINE, Scopus, and Clarivate Web of Science. After removing duplicates and screening titles and abstracts, 14 high-quality studies met the inclusion criteria for the meta-analysis. Results: Overall, there were no significant changes in sprint performance after implementing various types of conditioning activities (standardized mean difference [SMD] = 0.16 [95% CI, −0.02 to 0.33]; Z = 1.78; P =.08; I2 = 0%). In addition, when comparing prechanges and postchanges between experimental, control, and other conditions, no significant differences were found in sprint speed or time across all studies (SMD = 0.09 [95% CI, −0.10 to 0.28]; Z = 0.92; P =.36; I = 0%). Conclusions: Results revealed that different types of conditioning activities may not be capable of acutely enhancing the sprint speed of competitive sprinters. This aligns with previous observations indicating that sprinting is a highly stable physical capacity, a phenomenon that is even more consistent among elite sprinters. Coaches and sport scientists should collaborate to develop more efficient PAPE protocols for these highly specialized athletes, with special attention to study design and individualization, while considering their effects on acceleration versus top speed. [ABSTRACT FROM AUTHOR]

Despite previous support for plyometric training, optimal dosing strategies remain unclear. Purpose: To investigate vertical and horizontal jump kinetic performance following a low-volume plyometric stimulus with progressively increased session jump volume. Methods: Sixteen academy rugby players (20.0 [2.0] y; 103.0 [17.6] kg; 184.3 [5.5] cm) volunteered for this study. Vertical and horizontal jump sessions were conducted 1 week apart and consisted of a 40-jump low-volume plyometric stimulus using 4 exercises, after which volume was progressively increased to 200 jumps, using countermovement jump (CMJ) for vertical sessions and horizontal broad jump (HBJ) for horizontal sessions. Jump performance was assessed via force-plate analysis at baseline (PRE-0), following the low-volume plyometric stimulus (P-40), and every subsequent 10 jumps until the end of the session (P-50, P-60, P-70,... P-200). Results: The low-volume stimulus was effective in potentiating HBJ (2% to 5%) but not CMJ (0% to −7%) performance (P <.001). The HBJ performance enhancements were maintained throughout the entire high-volume session, while CMJ realized small but significant decrements (−5% to −7%) in jump height P-50 to P-80 before recovering to presession values. Moreover, increases in eccentric impulse (5% to 24%; P <.001) in both sessions were associated with decreased or maintained concentric impulse, indicating a breakdown in performance-augmenting mechanisms and less effective power transfer concentrically after moderate volumes. Conclusion: Practitioners should consider kinetic differences between HBJ and CMJ with increasing volume to better inform and understand session dosing strategies. [ABSTRACT FROM AUTHOR]

This study aimed to determine, through the use of a highly sensitive statistical tool, whether real changes in performance were present; and compare the rates of meaningful variations in strength, speed, and power parameters at different time-points during the competitive season in national team rugby players. Thirtytwo players were assessed 5 times across the season using the following tests: squat jump and countermovement jump tests; 30-m sprint velocity; and one-repetition maximum (1RM) in the half-squat and bench-press exercises. A repeated-measures analysis of variance was conducted to test for differences between successive time-points. Individual coefficients of variation values were used to set target scores for post-measurements and examine whether changes in performance parameters were greater than the natural test variance, thus providing an indication of whether "true changes" occurred. No significant changes were detected in the vertical jump height, 1RM measures, and sprint velocity and momentum throughout the 11-month period ( P > 0.05). True changes occurred much more frequently for strength-power measures than for sprint velocity and momentum. Elite rugby union players did not exhibit significant variations in neuromuscular performance across the competitive period, when a group-based analysis was conducted. However, at the individual level, "true changes" in strength-power- (but not in speed-) related qualities were consistently observed over the competitive season. [ABSTRACT FROM AUTHOR]

Establishing a relationship between repetitions left in reserve and the mean absolute velocity (RIR-velocity relationship) during resistance training (RT) could allow for objective monitoring, prescription, and real- time adjustment of the training load and set-volume. Therefore, we examined the goodness of fit and prediction accuracy of general and individual RIR-velocity relationships in the free-weight back squat exercise. The effects of sex, training status and history, as well as personality traits, on the goodness of fit and the accuracy of these relationships were also investigated. Forty-six resistance-trained people (15 females and 31 males) performed a one-repetition maximum (1RM) test, and two repetitions to failure (RTF) tests 72 h apart. We found greater goodness of fit of individual RIRvelocity relationships compared to general RIR-velocity relationships. Individual, but not general RIR-velocity relationships established in the first testing session yielded acceptable prediction accuracy of RIR (mean error <2 repetitions) in the subsequent testing session, regardless of the load used. Similar results were obtained when both general and individual RIR-velocity relationships were averaged across the loads, suggesting that a single RIR- velocity relationship covering a range of loads can be used instead of traditional RT methods, potentially allowing for better fatigue management and more efficient adaptation. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine responses at 3 and 27 hours after low-load jump squat (LL) and maximal isometric half-squat (ISO) priming stimuli. Fifteen resistance-trained males performed LL (4 3 3 at 20% 1 repetition maximum [1RM]), ISO (4 3 3 seconds), and control (CON) activities (standardized warm-up) in a randomized and counterbalanced order. Countermovement jump (CMJ) and isometric midthigh pull tests were conducted to assess performance changes after priming and CON activities. No clear changes in CMJ measures were found after priming activities compared with CON. However, small effect size improvements were found after priming stimuli completed on the same day. A 2.9% decrease in concentric phase duration (CI 5 0.3-5.9, p 5 0.333, Cliff's delta520.156) and a 9.1% increase in RSImod (CI 50.2-12.3, p50.151, Cliff's delta520.218) occurred at 3 hours after LL compared with CON. Braking phase duration (CI 5 0.8-10.6, p 5 0.333, Cliff's delta520.213) was 2.9% shorter at 3 hours after ISO compared with CON. No clear changes in isometric peak force occurred after priming activities compared with CON. Additionally, questionnaires were completed to assess perceptual state and perceived effectiveness of the priming stimulus to influence performance. An increase in the "effect of activity" was perceived at 3 hours after LL and ISO (p 5 0.013-0.044, Cliff's delta 5 0.578-0.6) and at 27 hours after ISO (p 5 0.99, Cliff's delta 5 0.173) compared with CON. An increase in "muscular heaviness" was also reported at 3 hours after ISO compared with CON (p 5 0.199, Cliff's delta 5 0.320). The collective findings suggest limited benefits over the day after LL and ISO priming stimuli. However, as there was substantial variation in individual responses, the relative nature of priming responses should be considered when prescribing similar strategies in practical environments. [ABSTRACT FROM AUTHOR]

Purpose: The optimal power load is defined as the load that maximizes power output in a given exercise. This load can be determined through the use of various instruments, under different testing protocols. Specifically, the "optimum power load" (OPL) is derived from the load–velocity relationship, using only bar force and bar velocity in the power computation. The OPL is easily assessed using a simple incremental testing protocol, based on relative percentages of body mass. To date, several studies have examined the associations between the OPL and different sport-specific measures, as well as its acute and chronic effects on athletic performance. The aim of this brief review is to present and summarize the current evidence regarding the OPL, highlighting the main lines of research on this topic and discussing the potential applications of this novel approach for testing and training. Conclusions: The validity and simplicity of OPL-based schemes provide strong support for their use as an alternative to more traditional strength–power training strategies. The OPL method can be effectively used by coaches and sport scientists in different sports and populations, with different purposes and configurations. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to map responses over 32 hours following high-load (HL) and moderate-load (ML) half-squat priming. Methods: Fifteen participants completed control, HL (87% 1RM), and ML (65% 1RM) activities in randomized, counterbalanced order. Countermovement jump (CMJ), squat jump (SJ), saliva testosterone, saliva cortisol, and perceptual measures were assessed before and 5 minutes, 8 hours, 24 hours, and 32 hours after each activity. Results are presented as percentage change from baseline and 95% confidence interval (CI). Cliff delta was used to determine threshold for group changes. Results: SJ height increased by 4.5% (CI = 2.2–6.8, Cliff delta = 0.20) 8 hours following HL. CMJ and SJ improved by 6.1% (CI = 2.1–7.8, Cliff delta = 0.27) and 6.5% (CI = 1.2–11.8, Cliff delta = 0.30), respectively, 32 hours after ML. No clear diurnal changes in CMJ or SJ occurred 8 hours following control; however, increases of 3.9% (CI = 2.9–9.2, Cliff delta = 0.26) and 4.5% (CI = 0.9–8.1, Cliff delta = 0.24), respectively, were observed after 32 hours. Although diurnal changes in saliva hormone concentration occurred (Cliff delta = 0.37–0.92), the influence of priming was unclear. Perceived "physical feeling" was greater 8 hours following HL (Cliff delta = 0.36) and 32 hours after ML and control (Cliff delta = 0.17–0.34). Conclusions: HL priming in the morning may result in small improvements in jump output and psychophysiological state in the afternoon. Similar improvements were observed in the afternoon the day after ML priming. [ABSTRACT FROM AUTHOR]

Harrison, PW, Kelly, VG, Jenkins, DG, McGuigan, MR, Holmberg, PM, and James, LP. Does moderate-load priming activity influence maximal upper-body performance and perceptual state?. J Strength Cond Res 37(11): e581-e587, 2023--The results of previous research indicate that resistance exercise "priming" may improve strength-power measures within 48 hours after their completion. Although researchers have primarily examined performance responses after lower-body priming stimuli, investigations examining the effects of upper-body resistance priming exercises are presently limited. Therefore, the aim of this study was to examine upper-body pushing and pulling performance in addition to perceptual responses 3 and 27 hours after moderate-load (ML) upper-body resistance priming exercise. Fourteen resistance-trained men were assigned to complete ML priming (4 3 3 bench press and bench pull at 65% 1RM [repetition maximum]) and control (rest) protocols in a randomized and counterbalanced order. Peak velocity during the bench throw and bench pull tests involving different loads (25, 50, and 75% 1RM) showed no practical change at 3 and 27 hours after the priming session (p 5 0.216-0.99, Cliff's d520.041 to 0.225). Small effect size increases in perceptual measures ("physical feeling," "physical performance," "aggression" [p 5 0.400-0.553, Cliff's d 5 0.183-0.201], and "muscular heaviness" [p 5 0.178, Cliff's d 5 0.231]) were found at 3 hours postpriming. A moderate practical increase was observed in perceived "physical feeling" compared with control (p 5 0.385, Cliff's d 5 0.349) in addition to small effect size increases in perceived "physical performance" and "aggression" (Cliff's d50.243-0.290) at 27 hours after priming activities. These results indicate that upper-body strength-power changes within 27 hours after ML upper-body resistance exercise priming are not practically meaningful. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the effects of a 4-week detraining period on the neuromuscular performance of highly trained soccer players. Pre and post detraining, 18 adult soccer players (age: 27 64.9 years; height: 180.267.1 cm; body mass [BM]: 78.967.6 kg) performed vertical jumps, 20-m linear sprints, curve sprint and change of direction speed tests, and a progressive loading test in the half-squat exercise with loads corresponding to 50, 100, and 150% of the players' BM to assess the peak-force (PF), mean power (MP), and strength-deficit (SDef). Pre and post differences in the variables of interest were analyzed using paired t-tests and effect sizes (ES). No significant changes were detected for vertical jumping height and sprint times. Higher PF at 50 and 100% BM and lower SDef were shown when comparing pre- and post-assessments (ES = 0.66, 0.68, 0.55; p = 0.018, 0.016, and 0.046, respectively). The MP at 50 and 100% BM increased significantly after the detraining phase (ES = 0.56, 0.82; p = 0.049 and 0.007, respectively). The results indicate that these athletes were able to maintain and achieve satisfactory levels of performance after a short period of training cessation. Interestingly, some strength- and power-derived parameters improved significantly after short-term detraining, which may have important implications for training programs aimed at maximizing speed and power performance. It is recommended that coaches test their players not only at the beginning but also at the end of the season, to better evaluate variations in performance and thus create more efficient and tailored training strategies. [ABSTRACT FROM AUTHOR]

Purpose: To test the relationships between maximum and relative strength (MS and RS), absolute and relative peak force (PF and RPF), and strength deficit (SDef), with sprint and jump performance, and to compare these mechanical variables between elite sprinters and professional rugby union players. Methods: Thirty-five male rugby union players and 30 male sprinters performed vertical jumps, 30-m sprint, and half-squat 1-repetition maximum (1RM), where these force-related parameters were collected. Pearson correlation coefficients were used to test the relationships between the variables. An independent t test and magnitude-based inferences compared the mechanical variables between sprinters and rugby players. Results: Almost certain significant differences were observed for jump and sprint performance between groups (P <.0001). The rugby union players demonstrated a likely significant higher MS (P =.03) but a very likely lower RS (P =.007) than the sprinters. No significant differences were observed for PF between them. The sprinters exhibited an almost certain significant higher RPF than the rugby players (P <.0001). Furthermore, the rugby players demonstrated almost certain to likely significant higher SDef from 40% to 70% 1RM (P <.05) compared with the sprinters. Overall, all strength-derived parameters were significantly related to functional performance. Conclusions: Elite sprinters present higher levels of RS and RPF, lower levels of SDef, and better sprint and jump performance than professional rugby players. Relative strength-derived values (RS and RPF) and SDef are significantly associated with speed–power measures and may be used as effective and practical indicators of athletic performance. [ABSTRACT FROM AUTHOR]

Purpose: Dozens of variables can be derived from the countermovement jump (CMJ). However, this does not guarantee an increase in useful information because many of the variables are highly correlated. Furthermore, practitioners should seek to find the simplest solution to performance testing and reporting challenges. The purpose of this investigation was to show how to apply dimensionality reduction to CMJ data with a view to offer practitioners solutions to aid applications in high-performance settings. Methods: The data were collected from 3 cohorts using 3 different devices. Dimensionality reduction was undertaken on the extracted variables by way of principal component analysis and maximum likelihood factor analysis. Results: Over 90% of the variance in each CMJ data set could be explained in 3 or 4 principal components. Similarly, 2 to 3 factors could successfully explain the CMJ. Conclusions: The application of dimensional reduction through principal component analysis and factor analysis allowed for the identification of key variables that strongly contributed to distinct aspects of jump performance. Practitioners and scientists can consider the information derived from these procedures in several ways to streamline the transfer of CMJ test information. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the association between the optimum power load in the bench press (BP), shoulder press (SP), and prone bench pull (PBP) exercises and acceleration (ACC) and speed performances in 11 National Team wheelchair basketball (WB) players with similar levels of disability. All athletes were previously familiarized with the testing procedures that were performed on the same day during the competitive period of the season. First, athletes performed a wheelchair 20-m sprint assessment and, subsequently, a maximum power load test to determine the mean propulsive power (MPP) in the BP, SP, and PBP. A Pearson product–moment correlation was used to examine the relationships between sprint velocity (VEL), ACC, and the MPP in the three exercises. The significance level was set as p <.05. Large to very large significant associations were observed between VEL and ACC and the MPP in the BP, SP, and PBP exercises (r varying from.60 to.77; p <.05). The results reveal that WB players who produce more power in these three exercises are also able to accelerate faster and achieve higher speeds over short distances. Given the key importance of high and successive ACCs during wheelchair game-related maneuvers, it is recommended that coaches frequently assess the optimum power load in BP, SP, and PBP in WB players, even during their regular training sessions. [ABSTRACT FROM AUTHOR]

Purpose: To identify the bar velocities that optimize power output in the barbell hip thrust exercise. Methods: A total of 40 athletes from 2 sports disciplines (30 track-and-field sprinters and jumpers and 10 rugby union players) participated in this study. Maximum bar-power outputs and their respective bar velocities were assessed in the barbell hip thrust exercise. Athletes were divided, using a median split analysis, into 2 groups according to their bar-power outputs in the barbell hip thrust exercise ("higher" and "lower" power groups). The magnitude-based inferences method was used to analyze the differences between groups in the power and velocity outcomes. To assess the precision of the bar velocities for determining the maximum power values, the coefficient of variation (CV%) was also calculated. Results: Athletes achieved the maximum power outputs at a mean velocity, mean propulsive velocity, and peak velocity of 0.92 (0.04) m·s−1 (CV: 4.1%), 1.02 (0.05) m·s−1 (CV: 4.4%), and 1.72 (0.14) m·s−1 (CV: 8.4%), respectively. No meaningful differences were observed in the optimum bar velocities between higher and lower power groups. Conclusions: Independent of the athletes' power output and bar-velocity variable, the optimum power loads frequently occur at very close bar velocities. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the peak force (PF), peak power (PP), and peak velocity (PV) outputs produced during half-squat (HS) and jump squat (JS) exercises executed at 20, 40, 60, and 80% of 1 repetition maximum (1RM) in the HS (HS 1RM) and to compute and compare the strength deficit (SDef) achieved in these exercises across these loads. Twenty-four national rugby union players (age: 25.7 ± 3.6 years) performed HS 1RM and a progressive loading test in the HS and JS exercises. The PF, PP, and PV values were obtained in all loads for both exercises, and the SDef was calculated as the percentage difference between the PF at distinct relative intensities and the PF at HS 1RM. The differences in HS and JS variables were determined using an analysis of variance with repeated measures. Higher PF, PP, and PV outputs were generated in the JS in comparison with the HS exercise (p < 0.05); moreover, the SDef magnitudes were significantly lower in the JS (p < 0.01), for all loading conditions. Importantly, the differences in SDef, and as a consequence, PF, PP, and PV decreased progressively with increasing load. Overall, the loaded JS exhibited increased levels of PF, PP, and PV and reduced levels of SDef when compared to the traditional HS performed across a range of loads. The JS is indicated to reduce the SDef and improve the athletes’ ability to apply force at higher velocities. Nevertheless, with heavier loads (i.e.,≥80% HS 1RM), its potential advantages and effectiveness may be seriously compromised. [ABSTRACT FROM AUTHOR]

The purpose of this study was to test the load-velocity relationship in the jump squat (JS) exercise using three different velocity parameters (mean velocity [MV], mean propulsive velocity [MPV], and peak velocity [PV]). Twenty-six male rugby union players (24.3 ± 3.9 years; 1.81 ± 0.09 m; 101.3 ± 15.4 kg) performed a progressive loading test in the JS with loads corresponding to 20, 40, 60, and 80% of the half-squat 1RM (equivalent to 24, 46, 70, and 94% of the estimated JS-1RM). MV, MPV, and PV were continuously recorded during all attempts using a linear velocity transducer. Linear regression models were used to determine the relationships between JS loads and MV, MPV, and PV. Bar-velocity outputs demonstrated high levels of consistency and reliability (coefficient of variation ≤ 5% and intraclass correlation coefficient ≥ 0.90). The predictive power of MV, MPV, and PV were ≥ 91%, for all tested variables (P < 0.0001). The equations and bar-velocity values provided in this study can be used by coaches to precisely determine and prescribe JS training loads, from very-light to heavy loading conditions (i.e., ~20--100% JS 1RM). [ABSTRACT FROM AUTHOR]

Previous research established that male powerlifters have less range of motion (ROM) in several movements about the shoulder and hip compared with sedentary male subjects. It is unclear if these differences in ROM are related to strength, training type, and years of training experience or if individuals with less ROM have a better propensity to gain strength. The purpose of this study was to compare strength and ROM in male powerlifters and recreationally strength-trained male subjects and to determine if ROM would be an effective predictor of strength in these groups. Twelve powerlifters and 12 recreationally strength-trained control subjects completed 1 repetition maximum (1RM) squat and bench press testing. In a subsequent session, active ROM was measured, and velocity data were collected during submaximal squat repetitions. There was no significant difference (p > 0.05) between the groups for age, height, body mass, training experience, and training frequency. Powerlifters had significantly greater (p ≤ 0.05) training duration and absolute squat and bench press 1RM. Powerlifters had significantly less shoulder extension and horizontal abduction, and hip flexion, extension, and adduction than recreationally strength-trained men. Significant negative relationships were found between 2-lift Wilks score (body mass relative strength) and shoulder extension and horizontal abduction, as well as hip flexion and extension. In powerlifters, significant negative relationships were found between competition Wilks score, shoulder extension, and hip flexion. Because these relationships correspond to the bottom position of the squat and bench press, it may be best to ensure that shoulder extension and hip flexion remain sufficient to achieve competition depth. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effects of strength-training tapers of different intensities but equal volume reductions on neuromuscular performance. Methods: Eleven strength-trained men (21.3 [3.3] y, 92.3 [17.6] kg, relative 1-repetition-maximum deadlift 1.9 [0.2] times bodyweight) completed a crossover study. Specifically, two 4-wk strength-training blocks were followed by a taper week with reduced volume (∼70%) involving either increased (5.9%) or decreased (−8.5%) intensity. Testing occurred pretraining (T1), posttraining (T2), and posttaper (T3). Salivary testosterone and cortisol, plasma creatine kinase, a Daily Analysis of Life Demands in Athletes questionnaire, countermovement jump (CMJ), isometric midthigh pull, and isometric bench press were measured. Results: CMJ height improved significantly over time (P <.001), with significant increases from T1 (38.0 [5.5] cm) to both T2 (39.3 [5.3] cm; P =.010) and T3 (40.0 [5.3] cm; P =.001) and from T2 to T3 (P =.002). CMJ flight time:contraction time increased significantly over time (P =.004), with significant increases from T1 (0.747 [0.162]) to T2 (0.791 [0.163]; P =.012). Isometric midthigh-pull relative peak force improved significantly over time (P =.033), with significant increases from T1 (34.7 [5.0] N/kg) to T2 (35.9 [4.8] N/kg; P =.013). No significant changes were found between tapers. However, the higher-intensity taper produced small effect-size increases at T3 vs T1 for isometric midthigh-pull relative peak force, CMJ height, and flight time:contraction time, while the lower-intensity taper only produced small effect-size improvements at T3 vs T1 for CMJ height. Conclusions: A strength-training taper with volume reductions had a positive effect on power, with a tendency for the higher-intensity taper to produce more favorable changes in strength and power. [ABSTRACT FROM AUTHOR]

The aims of this study were to: 1) provide and compare the height achieved during Smith machine (SM) and free weight (FW) loaded jumps executed over a wide spectrum of loads (40--120% of body mass [BM]); and 2) test the difference between loaded and unloaded squat jump (SJ) and countermovement jump (CMJ) attempts in ten highly trained male sprinters. On the first visit, athletes performed unloaded SJ and CMJ, loaded SJ with loads corresponding to 40, 60, 80, 100, and 120% BM, and loaded CMJ at 100% BM using an Olympic barbell (FW). On the second visit, they performed loaded SJ and CMJ tests under the same loading conditions on the SM device and, subsequently, a half-squat one-repetition maximum (1RM) assessment. The relative strength (RS = 1RM/BM) of the athletes was 2.54 ± 0.15. Loaded SJ performance was similar between SM and FW, and across all loading conditions. Differences in favour of CMJ (higher jump heights compared with SJ) were superior in the unloaded condition but decreased progressively as a function of loading. In summary, sprinters achieved similar SJ heights across a comprehensive range of loads, regardless of the execution mode (FW or SM). The positive effect of the countermovement on jump performance is progressively reduced with increasing load. [ABSTRACT FROM AUTHOR]

Loturco, I, McGuigan, MR, Rodríguez-Rosell, D, Pereira, LA, and Pareja-Blanco, F. A novel strategy to determine the 1-repetition maximum in the jump squat exercise. J Strength Cond Res 36(8): 2330–2334, 2022—This study aimed to determine the maximum relative load of the half-squat (HS; i.e., % HS 1-repetition maximum [1RM]) that can be used in its ballistic variation, namely, the jump squat (JS) exercise, and to examine whether this reference value varies in subjects with different strength levels. In total, 186 elite athletes from 10 distinct sport disciplines participated in this study. A progressive loading test up to HS 1RM was performed during the competitive phase of the season for all athletes. Mean propulsive velocity and propulsive phase duration were also assessed during the 1RM test. Athletes were divided into 3 distinct subgroups: "low," "middle," and "high" strength levels, based on their relative HS 1RM values (kg·kg−1). A 1-way analysis of variance was used to compare the variables assessed between the groups. Significance level was set at p < 0.05. The high group demonstrated the highest relative HS 1RM values, followed by the middle and low groups (all p < 0.05). No significant differences were observed between the groups for the remaining variables (p > 0.05). It was observed that at 86.0 ± 5.4% 1RM, the full concentric action can already be considered as entirely propulsive in the HS exercise for all subjects, independent of their strength levels. Therefore, this relative strength value may be used as a reference for the 1RM in the JS exercise. [ABSTRACT FROM AUTHOR]

Horizontal single-leg drop jumps (SLDJ) have previously been shown to be effective at improving sprinting performance, but the optimal dose is debateable. Therefore, the purpose of this study was to compare moderately-low volume (MLV: 30 -70 ground contacts (GC .session-1)) and ultra-low (ULV: 10 - 28 GC.session-1) volume protocols for improving sprint performance. Two experimental groups (MLV = 11; ULV = 11), consisting of high-level male academy and semi-professional rugby players, underwent twice-weekly horizontal SLDJ training for four weeks, with concurrent rugby and resistance training. Plyometric volumes for both groups were progressed for three weeks with a 30% reduction the fourth week. Maximal vertical jump and sprint assessments were performed pre- and post-intervention. There were no significant differences at baseline for any variable (p > 0.05). An analysis of variance (ANOVA) was performed to detect changes between- and within-subjects. There was a significant training interaction between groups for 10- and 30-m sprint performance. While MLV significantly decreased 10-, 20-, and 30- m times (-0.03 to -0.05s; ES= 0.32 – 0.54), ULV did not significantly change split times at any distance (p > 0.05). There was a small non-significant decrease in maximal velocity only in the ULV group (-1.79%), while both groups were able to produce substantial improvements in vertical jumping performance with no between-group differences (+14.7 – 38.4%; ES: -0.67 to 1.12). In conclusion, adding MLV protocols may preferentially improve sprint performance and maintain maximal velocity characteristics when compared to ULV protocols. However, higher volumes did not additionally improve vertical jump performance more so than low volumes. [ABSTRACT FROM AUTHOR]

McGuigan, MR, Newton, MJ, Winchester, JB, and Nelson, AG. Relationship between isometric and dynamic strength in recreationally trained men. Strength Cond Res 24(9): 2570-2573, 2010--The purpose of this investigation was to examine the relationships between measures of maximal isometric force (peak force [PF]), rate of force development (RFD), vertical jump performance (VJ) and 1-repetition maximum (1RM) strength in recreationally trained men. The subjects in this study were 26 men ([mean [+ or -] SD]: age 22 [+ or -] 1 years; height 175 [+ or -] 7 cm; mass 90 [+ or -] 10 kg). They were tested for PF using the isometric midthigh pull exercise. The 1RM for the squat and bench press exercise were determined as a measure of dynamic strength. Explosive strength was measured as RFD from the isometric force-time curve. Correlations between the variables were calculated using Pearson product moment correlation coefficient. There was a nearly perfect correlation between measures of PF and 1RM squat (r = 0.97, p < 0.05) and 1RM bench press (r = 0.99, p < 0.05). The correlations were very strong between VJ and PF (r = 0.72, p < 0.05) and 1RM bench press (r = 0.70, p < 0.05). There were also strong correlations between VJ and 1RM squat (r = 0.69, p < 0.05). There were no significant correlations with RFD. The results showed that isometric maximum strength determined during the isometric midthigh pull test correlated well with 1RM and VJ testing. However, RFD measured during the same test did not appear to correlate as well with other measures. The isometric midthigh pull provides an efficient method for assessing strength in recreationally trained individuals. Practioners wishing to obtain performance data related to maximum strength may wish to consider isometric testing as a less time intensive method of testing. KEY WORDS isometric strength, power, vertical jump 1 repetition maximum, resistance training

Rubber-based resistance (RBR) bands and standard link steel (SLS) chains are 2 forms of variable resistance used throughout the strength and conditioning and rehabilitation communities. The purpose of this study was to quantify the tension of RBR bands and the mass of SLS chains as a function of displacement (increasing in 10-cm increments). Five sets of RBR bands (14-, 22-, 30-, 48-, and 67-mm widths) and 5 sets of SLS chains (6-, 8-, 10-, 13-, 16-mm diameters) were measured using a load cell and a force plate. The RBR bands exhibited curvilinear tension-deformation relationships and were best represented ([R.sup.2] greater than or equal to] 0.99) by second-order polynomial functions, whereas the SLS chains exhibited linear mass-displacement relationships and were best represented ([R.sup.2] = 1) by first-order polynomial functions. There were no significant differences (p > 0.05) in force outputs between the load cell and the force plate testing, although the strain gauge is a relatively cheap and viable method of quantifying the variable resistance of chains and bands. The strength and conditioning practitioner when purchasing bands needs to be aware of resting length differences (3.5-5.2%), which resulted in mean tension imbalances of 8-19% in the same color band. This study provides the strength and conditioning coach and clinician with a methodology to quantify variable resistance, which may be useful in the prescription of specific loading intensities. KEY WORDS material properties, standard link steel chains, variable resistance, biomechanics

The purpose of this study was to investigate (a) the cross-sectional relationship of strength, power, and performance variables in trained female athletes and (b) determine if the relationship between these variables changes over the course of a season. Ten female softball players (age = 18.1 [+ or -] 1.6 years, height = 166.5 [+ or -] 8.9 cm, and weight = 72.4 [+ or -] 10.8 kg) from a state Australian Institute of Sport softball team were tested for maximal lower body strength (one repetition maximum [1 RM]), peak force (PF), peak velocity (PV), and peak power (PP) during jump squats unloaded and loaded, unloaded countermovement vertical jump height (VJH) 1 base and 2 base sprint performance and change of direction performance on dominant and nondominant sides. The testing sessions occurred pre, mid, and post a 20-week training period. Relationship between body weight (BW), relative strength (1RM/BW), VJH, relative PP, relative PF, PV, speed, and change of direction variables were assessed by Pearson product--moment correlation coefficient at each testing session. Significant relationships were found across all time points with BW, speed, and change of direction measures (r = 0.70-0.93) and relative strength and measures of speed and change of direction ability (r = 0.73-0.85). There were no significant relationships between VJH and any measure of performance at any time point. In conclusion, BW and relative strength have strong to very strong correlations with speed and change of direction ability, and these correlations remain consistent over the course of the season. However, it seems as if many relationships vary with time, and their relationships should therefore be investigated longitudinally to better determine if these cross-sectional relationships truly reflect a deterministic relationship. KEY WORDS fastpitch, women, agility, correlation, relative strength

The purpose of this study was to investigate the effect of concurrent resistance and endurance cycle training on physiologic and performance parameters of cyclists. Before and after a 6-week training intervention period, 14 well-trained male cyclists completed a maximal graded exercise test, a 30-km dynamic cycling test with 3 intermittent 250-m and 1 -km sprints, and a 1 repetition maximum (1 RM) squat test for the assessment of lower-limb strength. Subjects were allocated into 2 groups: a resistance training group (RT; n = 7) that completed a 6-week undulating, periodized resistance training program (3/wk) in conjunction with their regular cycle training and a control group (CON; n = 7) that maintained their usual cycle training. Upon completion of the training intervention, there was no change in graded exercise test parameters in either group, but the RT group showed a significantly greater increase in 1RM squat strength compared with CON (p < 0.05). Moreover, the change in 30-km time trial and sprinting performance did not differ between RT and CON, except for the final 1-km sprint where the percent change in 1-km final sprint performance was greater in CON (+11%) compared with RT (-5%). In conclusion, although concurrent resistance and endurance training in well-trained cyclists enhanced 1RM strength, it did not improve overall cycle time trial performance and in fact was shown to reduce 1-km final cycle sprint performance compared with a CON group performing their normal cycle training. KEY WORDS power output, sprinting, strength, athlete

The purpose of this investigation was to examine the strength, power, and anthropometric contributors to vertical jump performances that are considered specific to volleyball success, including countermovement vertical jump (CMVJ) and spike jump (SPJ), by examining changes across 12 months in elite volleyball players. Anthropometry (height, mass, [[ZIGMA].sup.7] skinfolds), vertical jump ability (CMVJ, SPJ, and depth jumps from 35 cm), kinetic and kinematic data from an unloaded and loaded (body mass + 50%) jump squat were assessed before and after 12 months of training in 20 elite male volleyball players. To examine the association between the change in each of the strength, power, and anthropometric variables with the changes in CMVJ and SPJ, a correlation analysis of the percent change of each variable with the percent change in CMVJ and SPJ was performed. A significant correlation (r = 0.47; p = 0.04) was observed between changes in CMVJ and SPJ. Significant (p = 0.006-0.02) improvements in CMVJ were associated with increased peak force in the unloaded (r = 0.61 ) and loaded jump squat (r = 0.59) and greater relative power and peak velocity in the loaded jump squat (r = 0.49 and 0.51, respectively). The significant increase in CMVJ was strongly associated (r = 0.865; p < 0.001) with an improved depth-jump ability. Significant (p = 0.003-0.03) increases in SPJ were related to increases in relative power (r = 0.64), peak force (r = 0.46), and peak velocity (r = 0.49) in the loaded jump and improved depth-jumping ability (r = 0.591). This study demonstrates that, in an elite population of volleyball players, stretch shortening cycle performance and the ability to tolerate high stretch loads, as in the depth jump, are critical to improving jumping performance. KEY WORDS spike jump, jump, testing, performance

The Eccentric Utilization Ratio (EUR), which is the ratio of countermovement jump (CMJ) to squat jump (SJ) performance measures, is a useful indicator of training status in elite athletes and their utilization of the stretch-shortening cycle. This investigation sought to determine if EUR was sensitive to different types of resistance training in untrained college-aged males. Twenty-nine college-aged males completed 8 weeks of training and were randomly allocated to 1 of 3 training programs: weight training (n = 10), plyometrics (n = 10), or weightlifting (n = 9). Testing occurred 3 times (pre, mid, post) with a CMJ and SJ conducted on a force plate integrated with a position transducer. Height, weight, and a 1RM (repetition maximum) squat also were measured. Weightlifting significantly (p < 0.05) helped subjects jump higher and produce more power than plyometrics for height and power for both CMJ and SJ results. This investigation indicated EUR did not significantly change, suggesting that this type of performance indicator may not be useful in a recreationally active population. Alternatively, an 8-week training program might not be a long enough time period to see changes in this group of participants. Results did indicate that high-velocity and high-force training programs, consisting of weightlifting and plyometrics, improved lower-body performance, especially in the areas of jump height and power. KEY WORDS exercise test, muscle development, weightlifting

The purpose of this study was to investigate the effects of different durations of resistance training on body composition and power in children. The study was a 24-week longitudinal design involving 31 preadolescent children who were overweight or obese (ages 7-12 years), divided into 3 groups and resistance trained 3 times per week. Group 8 (G8) trained for 8 weeks, group 16 (G16) trained for 16 weeks, and group 24 (G24) trained for 24 weeks. All participants were measured at weeks 0, 8, 16, and 24 for body composition and power. Subjects in G8 and G16 continued to be tested during the testing weeks after cessation of their training programs. Body composition and bone mineral content were measured by dual-energy X-ray absorptiometry. Significant improvements in body composition were seen in the initial 8-week training phase, and these improvements were maintained for the subsequent 16 weeks. Significant changes in percent body fat (~5-7%) were observed at 8 weeks in all 3 groups. Total fat mass decreased significantly at week 8 in G16 and G24 (5.9%). By week 24, total fat mass was significantly reduced by 8.1% in G24. Significant improvements were observed in static jump power, which improved by 10.5% at week 16 in G24. These results suggest that an 8-week resistance training program is sufficient time to significantly change body composition, strength, and power measures in children who are overweight or obese. However, further improvements are realized with longer-duration resistance training programs. On cessation of the training programs, the G8 and G16 groups maintained the benefits of the exercise program until the end of the study period. KEY WORDS strength training, obesity, exercise

Force platforms are used extensively to measure force and power output during countermovement jump (CMJ). The purpose of this study was to examine measurement reliability and validity of commonly used performance measurements derived from ground reaction force (GRF)--time data during CMJ and the influence of sampling at different frequencies. Twenty-four men performed 2 trials of CMJ on a force platform, and GRF-time data were sampled at a rate of 500 Hz. Data obtained at 500 Hz were considered as the reference, and then data were resampled at 400, 250, 200, 100, 50, and 25 Hz, using interpolation. Commonly used power, force, and velocity performance measures were obtained from GRF-time data. Reliability was assessed by intraclass correlation coefficient (ICC) and coefficient of variation (CV) between the 2 trials within the session. Peak power, peak force, and peak velocity were highly reliable across all sampling frequencies (ICC = 0.92-0.98, CV = 1.3-4.1). Percentage differences from 500-Hz reference values ranged from -0.85 to 0.20% at 400 Hz, -1.88 to 0.89% at 250 Hz, -1.80 to 1.31% at 200 Hz, -3.63 to 3.34% at 100Hz, -11.37 to 6.51% at 50Hz, and -13.17 to 9.03% at 25 Hz. In conclusion, peak power, force, and velocity measurements derived from GRF to assess leg extensor capabilities are reliable within a test session except for peak rate of force development and time to peak power. With regard to sampling frequency, scientists and practitioners may consider sampling as low as 200 Hz, depending on the purpose of measurement, because the percentage difference is not markedly enlarged until the frequency is 100 Hz or lower. KEY WORDS velocity, impulse, momentum, force platform, vertical jump