The acute effects of an ascending squat protocol on performance during horizontal plyometric jumps

Acute Effects of Low vs. High Inertia During Flywheel Deadlifts with Equal Force Impulse on Vertical Jump Performance

BACKGROUND

Flywheel resistance training has gained popularity due to its ability to induce eccentric overload and improve strength and power. This study examined the acute effects of low- (0.025 kg·m2) versus high-inertia (0.10 kg·m2) flywheel deadlifts, matched for force impulse, on the countermovement jump (CMJ) performance, reactive strength index (RSI) during drop jumps (DJs), and rating of perceived exertion (RPE).

METHODS

Sixteen trained participants (twelve men, and four women) performed three conditions in a randomized, counterbalanced order: low-inertia (LOW), high-inertia (HIGH), and control (CTRL). In the LOW and HIGH conditions, we used force plates to measure and equalize the force impulse in the two conditions (HIGH: 20182 ± 2275 N∙s vs. LOW: 20076 ± 2526 N∙s; p > 0.05), by calculating the number of deadlift repetitions required to achieve it (HIGH: 5 repetitions and LOW: 9.8 ± 0.4 repetitions). The RSI and CMJ performance were measured pre-exercise, immediately post-exercise, and at 3, 6, 9, and 12 min post-exercise.

RESULTS

Both the RSI and CMJ performance improved equally after LOW and HIGH flywheel deadlifts compared to baseline and CTRL (p < 0.01). Specifically, the RSI increased from baseline at 3 to 12 min in both conditions (LOW: 12.8 ± 14.9% to 15.4 ± 14.8%, HIGH: 12.1 ± 17.0% to 12.2 ± 11.7%, p < 0.01), while the CMJ increased from 3 to 9 min in LOW (4.3 ± 3.2% to 4.6 ± 4.7%, p < 0.01) and from 6 to 9 min in HIGH (3.8 ± 4.2% to 4.2 ± 4.9%, p < 0.05). No significant differences were observed between LOW and HIGH conditions (p > 0.05), suggesting similar effectiveness of both inertial loads for enhancing performance. The RPE increased similarly after both conditions from baseline to immediately post-conditioning (LOW: from 2.2 ± 1.2 to 5.8 ± 1.4, HIGH: from 1.5 ± 1.0 to 6.1 ± 1.5, p < 0.01) and decreased by the end of the session, although values remained higher than baseline (LOW: 4.1 ± 1.4, p < 0.01, HIGH: 4.5 ± 2.0, p < 0.01).

CONCLUSIONS

These findings highlight the potential of flywheel deadlift exercise as an effective method to potentiate explosive performance of the lower limbs, regardless of inertia, provided that the total force impulse is equal.

Acute Effects of Fast vs. Slow Bench Press Repetitions with Equal Time Under Tension on Velocity, sEMG Activity, and Applied Force in the Bench Press Throw

Background: The tempo of resistance exercises is known to influence performance outcomes, yet its specific effects on post-activation performance enhancement (PAPE) remain unclear. This study aimed to investigate the effects of fast versus slow repetitions at a load of 70% of one-repetition maximum (1-RM) in the bench press exercise, focusing on velocity, surface electromyographic (sEMG) activity, and applied force while equating time under tension on bench press throw performance. Methods: Eleven men (age: 23.5 ± 5.4 years, height: 1.79 ± 0.04 m, body mass: 79.1 ± 6.4 kg, maximum strength 1-RM: 91.0 ± 12.0 kg) participated. Two experimental conditions (FAST and SLOW) and one control (CTRL) were randomly assigned. Participants performed two sets of six repetitions as fast as possible (FAST condition) and two sets of three repetitions at a controlled tempo (SLOW condition) at half the concentric velocity of FAST, as determined in a preliminary session. Before and after the bench press participants performed bench press throws tests (Pre, 45 s, 4, 8, and 12 min after). Results: sEMG activity and peak force during the bench press were higher in FAST vs. SLOW conditioning activity (p < 0.001), with time under tension showing no significant differences between conditions (p > 0.05). Mean propulsive velocity (MPV) during the bench press throw improved equally in both FAST and SLOW conditions compared with baseline from the 4th to the 12th min of recovery (FAST: +6.8 ± 2.9% to +7.2 ± 3.3%, p < 0.01, SLOW: +4.0 ± 3.0% to +3.6 ± 4.5%, p < 0.01, respectively). Compared to the CTRL, both conditions exhibited improved MPV values from the 4th to 12th min (p < 0.01). Peak velocity improvements were observed only after the FAST condition compared to the baseline (p < 0.01) with no differences from SLOW. For all muscles involved and time points, sEMG activity during bench press throws was higher than CTRL in both experimental conditions (p < 0.01), with no differences between FAST and SLOW. Peak force increased in both FAST and SLOW conditions at all time points (p < 0.05), compared to CTRL. Conclusions: These findings suggest that post-activation performance enhancement is independent of movement tempo, provided that the resistive load and total time under tension of the conditioning activity are similar. This study provides valuable insights into the complex training method for athletes by demonstrating that varying tempo does not significantly affect post-activation performance enhancement when load and TUT are equated.

Effects of Drop Jump Training on Physical Fitness in Highly Trained Young Male Volleyball Players: Comparing Maximal Rebound Height and Standard Drop Height Training

BACKGROUND

Drop height has previously been used as an effective programming parameter in plyometric jump training. Less is known about the usage of maximal rebound jump height from a distinct drop height as a parameter for individualized plyometric jump training. Hence, the aim of this study was to contrast the effects of two different drop jump (DJ) training modalities using either the individualized maximal rebound height (MRHT) or a standard (SDHT) drop height on selected measures of physical fitness in young volleyball players.

METHODS

Thirty male young volleyball players aged 14 to 16 years were randomly assigned to an MRHT (n = 15) or an SDHT (n = 15) group. The MRHT group performed DJ exercises using a drop height according to the individual's maximal rebound jump height from 30 cm, 40 cm, and 50 cm drop heights. The SDHT group performed DJs following a standardized drop height (30 cm) across the 8-week intervention period. The overall training volume was similar between MRHT and SDHT with one to three sets of 8 to 10 repetitions of DJ exercises per session. Before and after training, jump height and the reactive strength index (RSI) were taken as dependent variables from 30, 40, and 50 cm drop heights. In addition, dynamic balance (Y-balance test) as well as linear sprint and change-of-direction (CoD) speed were assessed.

RESULTS

Significant group × time interactions were found for jump height, balance, RSI, and linear sprint (p < 0.001; d = 0.12-3.42) but not CoD speed. Post hoc tests showed significant jump height improvements in favor of the MRHT group for drop heights from 30 cm (Δ20.4%, p < 0.001, d = 3.69), 40 cm (Δ20.3%, p < 0.001, d = 2.90), and 50 cm (Δ18.3%, p < 0.001, d = 3.37) and RSI50 (Δ30.14%, p < 0.001, d = 2.29). MRHT but not SDHT resulted in significant 5 m (Δ9.2%, p < 0.001, d = 1.32) and 20 m (Δ7.4%, p < 0.01, d = 2.30) linear sprint speed improvements.

CONCLUSIONS

The findings demonstrate that MRHT but not SDHT improved DJ height, RSI, and linear sprint speed. Due to the importance of vertical jumps and short accelerations for overall competitive performance in volleyball, our results suggest that young male players should perform MRHT as part of plyometric jump training if the goal is to improve acceleration, reactive strength, and vertical jump performance.

Acute Effect of Heavy Load Back Squat and Foam Rolling on Vertical Jump Performance

Purpose: In a rested state, foam rolling has been shown to improve blood flow to the working tissues. When inducing post-activation performance enhancement (PAPE), previous research suggests a longer recovery period between the conditioning activity and performance assessment in weaker participants (back squat <2.0 × body mass). It is possible that a cool-down effect may take place between the conditioning activity and performance assessment for these participants. Therefore, the purpose of this investigation was to determine if foam rolling could help mitigate any cool-down effect to help participants capitalize on PAPE. Methods: Seventeen physically active participants completed baseline jumps followed by rest (control), back squat exercise (heavy squats), rest and foam rolling (FR), and heavy squats followed by foam rolling (combo). VJ performance was assessed three times post-treatment with 2 min between each assessment. Results: VJ height and impulse were greater at baseline than at any other time point across all sessions (p < .001). Impulse for the control and FR sessions were greater than the squats session (p < .015). Impulse for the combo session was less than the FR session (p = .04). Conclusions: Foam rolling did not have a significant impact on attenuating any cool-down effect. In addition, our heavy squats protocol appears to induce too much fatigue that possibly masked the effects of PAPE.

The Connection Between Resistance Training, Climbing Performance, and Injury Prevention

BACKGROUND

Climbing is an intricate sport composed of various disciplines, holds, styles, distances between holds, and levels of difficulty. In highly skilled climbers the potential for further strength-specific adaptations to increase performance may be marginal in elite climbers. With an eye on the upcoming 2024 Paris Olympics, more climbers are trying to maximize performance and improve training strategies. The relationships between muscular strength and climbing performance, as well as the role of strength in injury prevention, remain to be fully elucidated. This narrative review seeks to discuss the current literature regarding the effect of resistance training in improving maximal strength, muscle hypertrophy, muscular power, and local muscular endurance on climbing performance, and as a strategy to prevent injuries.

MAIN BODY

Since sport climbing requires exerting forces against gravity to maintain grip and move the body along the route, it is generally accepted that a climber`s absolute and relative muscular strength are important for climbing performance. Performance characteristics of forearm flexor muscles (hang-time on ledge, force output, rate of force development, and oxidative capacity) discriminate between climbing performance level, climbing styles, and between climbers and non-climbers. Strength of the hand and wrist flexors, shoulders and upper limbs has gained much attention in the scientific literature, and it has been suggested that both general and specific strength training should be part of a climber`s training program. Furthermore, the ability to generate sub-maximal force in different work-rest ratios has proved useful, in examining finger flexor endurance capacity while trying to mimic real-world climbing demands. Importantly, fingers and shoulders are the most frequent injury locations in climbing. Due to the high mechanical stress and load on the finger flexors, fingerboard and campus board training should be limited in lower-graded climbers. Coaches should address, acknowledge, and screen for amenorrhea and disordered eating in climbers.

CONCLUSION

Structured low-volume high-resistance training, twice per week hanging from small ledges or a fingerboard, is a feasible approach for climbers. The current injury prevention training aims to increase the level of performance through building tolerance to performance-relevant load exposure and promoting this approach in the climbing field.

Reliability of isokinetic decay slope is superior to using fatigue indices for shoulder horizontal abduction

INTRODUCTION

Reliable and valid measurements for shoulder muscular endurance should be available for clinical use. The posterior shoulder endurance test offers a potential clinical assessment, but its construct validity isn't available. Since a criterion measure of muscular endurance is not available, this study's purpose was to determine a reliable method for testing shoulder muscular endurance using an isokinetic dynamometer.

METHODS

The test-retest reliability, standard error measurement, and minimal detectable change were calculated on four different paradigms to quantify muscular fatigue using two isokinetic speeds (60°sec-1,180°sec-1). Calculation paradigms included peak torque fatigue index (FI), average torque FI, area-under-the-curve FI, and peak torque decay slope. Testing occurred on two days. Repeated measures analysis of variance compared the two peak torque decay slopes across both testing days.

RESULTS

Superior reliability was found within the decay slope measurements at both 60°sec-1 (ICC = 0.941) and 180°sec-1 (ICC = 0.764) speeds, with the 60°sec-1 decay slope being the highest reliability between the two angular velocities. There was a greater amount of fatigue in the 60°sec-1 decay slope compared to the 180°sec-1 decay slope.

CONCLUSION

Using the decay slope of isokinetic shoulder horizontal abduction at 60°sec-1 is a reliable method to validate other muscular endurance clinical measures. Rehabilitation specialists should utilize the decay slope of the isokinetic dynamometry to monitor responsiveness.

The Influence of Maximum Squatting Strength on Jump and Sprint Performance: A Cross-Sectional Analysis of 492 Youth Soccer Players

This study aims to analyze the influence of relative strength performance, determined by parallel back squats (REL SQ), on 30 m sprinting (LS) and on jumping performance (squat [SJ], countermovement [CMJ]) in a large sample (n = 492) of elite youth soccer players. The soccer players were divided into subgroups based on their strength performance: strength level 1 (0.0−0.5 REL SQ), strength level 2 (>0.5−1.0 REL SQ), strength level 3 (>1.0 to 1.5 REL SQ), strength level 4 (>1.5 to 2.0 REL SQ), and strength level 5 (>2.0 REL SQ). The results of this study show that REL SQ explains 45−53% (r = |0.67−0.73|) of the variance of SJ, CMJ, and LS for the total sample. Strength levels 2−4 showed similar coefficients of correlation in jumping performance (r = |0.42−0.55|) and strength levels 2 and 3 in sprint performance (r = |0.41|). The respective extreme strength levels showed lower coefficients of correlation with the sprinting and jumping performance variables (r = |0.11−0.29|). No coefficients could be calculated for strength level 5 because no athlete achieved an appropriate strength level (>2.0 REL SQ). The data from this study show a clear influence of REL SQ on sprint and jump performance, even in a large sample.

Effect of Post-Activation Potentiation on Sprint Performance after Combined Electromyostimulation and Back Squats

Post-activation potentiation (PAP) is a phenomenon which can improve force performance executed after a previous conditioning activity. PAP is usually evoked through heavy resistance, but many new methods are being suggested that acutely improve performance in post-activation potentiation protocols. The purpose of this study was to examine the effect of simultaneous application of Smith machine back squats (BS) with electromyostimulation (EMS) on sprint performance. Sixteen male (age = 22.9 ± 2.3 years, body mass = 79.9 ± 13.8 kg, BS one-repetition maximum (1 RM) = 120.5 ± 17.3) amateur football and rugby players volunteered for this study. Participants randomly performed PAP protocols (CON = no load, BS = 3 × 85% of 1 RM BS, EMS = 3 × weightless squat with electric current and BS + EMS = 3 × 85% 1 RM BS with electric current) on four different days with at least 48 h intervals. Participants rested passively for 7 min after preloads and performed the 30 m sprint test. Sprint times for 10 and 30 m were recorded for each condition. As a result, no significant difference was found in the 10 m (p = 0.13) and 30 m (p = 0.10) sprint performance between the preload protocols. The effect size was found to be trivial (ηp2: 0.13 for 10 m; ηp2: 0.11 for 30 m). In individual results, the 10 m sprint performance of five participants and 30 m sprint performance of two participants decreased in BS, EMS, or BS + EMS conditions compared with CON. No PAP effect in other participants was observed. In conclusion, preloads did not affect 10 m and 30 m sprint performance of football and rugby players. It can be said that the applied PAP protocols or physical exertion alone may cause fatigue in some individuals.

Eliciting Postactivation Potentiation With Hang Cleans Depends on the Recovery Duration and the Individual's 1 Repetition Maximum Strength

ABSTRACT

Dinsdale, AJ and Bissas, A. Eliciting postactivation potentiation with hang cleans depends on the recovery duration and the individual's 1 repetition maximum strength. J Strength Cond Res 35(7): 1817-1824, 2021-Acutely coupling biomechanically similar resistance exercises (e.g., back squats) with subsequent explosive movements (e.g., countermovement jumps [CMJs]) can elicit an enhancement in explosive force and power production, which is known as postactivation potentiation (PAP). However, limited information exists with regard to the coupling of hang cleans with the CMJ. The purpose of this study was to determine the effectiveness of the hang clean at eliciting PAP through the systematic appraisal of the implemented recovery interval. Twelve explosively trained male track and field athletes completed 8 randomized protocols. These consisted of a structured warm-up, 3 baseline CMJs performed on a force platform, 3 reps of hang cleans set at 90% of 1 repetition maximum (1RM), a randomized rest, and 3 post-CMJs. The rest intervals were set at 0 (T0), 1 (T1), 2 (T2), 3 (T3), 4 (T4), 5 (T5), and 6 (T6) minutes after completing the hang cleans. A repeated-measures analysis of variance showed that the hang cleans did not elicit PAP, although there were significant (p < 0.05) decreases in jump height (JH) for T0 (-4%), T2 (-3%), and T3 (-3.3%). Interestingly, when splitting the subjects based on absolute 1RM hang clean (above 80 kg = strong and below 80 kg = weak), significant differences (p < 0.05) in JH were observed between the groups at T1 (strong -1.2% and weak +3.8%) and T5 (strong +5.1% and weak -1.9%). Our results suggest that to elicit PAP when using hang-clean protocols, it is important to establish first the function between individual strength levels and recovery duration as this may lead to contrasting optimal performance windows for different explosively trained athletes.

Does one heavy load back squat set lead to postactivation performance enhancement of three-point explosion and sprint in third division American football players?

Background

American football players need the ability to provide maximal muscular power in a modicum of time. Postactivation performance enhancement (PAPE), which is characterized by an acute improvement of a performance measure following conditioning contractions, could be of value for American football players. The aim of the present study was to determine the effect of a heavy load back squat PAPE protocol on three-point explosion (TPE; an essential blocking technique and drill) and 40-yard dash (40YD) performance compared to a traditional warm-up in American football players.

Methods

In a crossover study design, eighteen male competitive regional league American football players (mean ± SD: body mass 93.9 ± 15.5 kg, height 181.4 ± 6.8 cm, age 24.8 ± 3.9 years) performed a TPE on a double blocking sled (weight: 150 kg) and a 40YD (36.6 m with a 5 and 10 m split) 8 min after two different warm-up conditions. One condition was a traditional, football specific warm-up (TWU) consisting of game related movements (e.g. backward lunges, lateral power steps), whereas the other condition (PAPE) consisted of three explosive back squats with a load of 91 % one-repetition maximum.

Results

There was no significant difference in TPE between TWU and PAPE. For the 40YD, we found significantly shorter sprint times in the PAPE condition with medium effect sizes for the 5 m (p = 0.007; r = 0.45) and 10 m (p = 0.020; r = 0.39) but not for the whole 36.6 m distance (p = 0.084; r = 0.29) compared to the TWU condition.

Conclusions

The used heavy load back squat PAPE protocol improved sprint performance over short distances (≤ 10 m) but not complex movements like the three-point explosion.

Postactivation Potentiation Improves Acute Resistance Exercise Performance and Muscular Force in Trained Men

ABSTRACT

Conrado de Freitas, M, Rossi, FE, Colognesi, LA, de Oliveira, JVNS, Zanchi, NE, Lira, FS, Cholewa, JM, and Gobbo, LA. Postactivation potentiation improves acute resistance exercise performance and muscular force in trained men. J Strength Cond Res 35(5): 1357-1363, 2021-The purpose of this study was to investigate the effects of heavy back squat (90% one repetition maximum [1RM]) postactivation potentiation (PAP) on acute resistance exercise performance and force production in recreationally trained men, and to verify the relationship between maximal strength and the PAP response. Ten resistance-trained men randomly completed 4 experimental trials: (a) back squats without PAP (No-PAP), (b) back squats with PAP, (c) maximum voluntary isometric contraction (MVIC) of the quadriceps without PAP, and (d) MVIC with PAP. Back squats were performed with 4 sets at 70% of 1 RM with 2 minutes of rest interval. The number of squats repetitions performed was recorded for each set, and a total number of repetitions were calculated to analyze performance. Maximum voluntary isometric contraction was measured using electronic dynamometer, and the peak force and mean force were recorded. Blood lactate concentration was analyzed presquat and postsquat exercise. Repetitions performed in the first set was significantly (p < 0.001) greater in the PAP condition (22.00 ± 5.14) compared with No-PAP (15.50 ± 5.10), which resulted in significantly (p = 0.001) more total repetitions performed in the PAP (56.20 ± 17.3) condition compared with No-PAP (48.80 ± 14.5). Maximum voluntary isometric contraction peak was higher in PAP than in No-PAP (PAP = 765.7 ± 147.8 vs. No-PAP = 696.8 ± 131.5 N, p = 0.006). No significant correlations were observed between back squat 1RM relative to body mass and the PAP response in squat and MVIC. There were no significant differences in lactate concentration between conditions. In conclusion, PAP resulting from a heavy load prior back squat exercise improved total volume during resistance exercise. In addition, PAP was effective to increase force production during MVIC, but there was no relationship between relative 1RM values and the PAP response in trained men.

Human thrust in aquatic environment: The effect of post-activation potentiation on flutter kick

Herein, we analyse by experimental techniques the human kicking thrust and measure the effect of a warm-up routine that includes post-activation potentiation (PAP) sets on front-crawl flutter kick thrust, kinematics, and performance. Sixteen male competitive swimmers with 22.13 ± 3.84 years of age were randomly assigned in a crossover manner to undergo a standard warm-up (non-PAP; control condition) and a warm-up that included PAP sets (PAP; experimental condition) consisting in 2 × 5 repetitions of unloaded countermovement jump. Participants performed a 25 m all-out trial in front-crawl with only flutter kicks eight min after each warm-up. Kinetics (i.e., peak thrust, mean thrust, and thrust-time integral) and kinematics (i.e., speed, speed fluctuation and kicking frequency) were experimentally collected by an in-house customized system composed of differential pressure sensors, speedo-meter, and underwater camera. Peak thrust (P = 0.02, d = 0.66) and mean thrust (P = 0.10, d = 0.40) were increased by 15% in PAP compared to non-PAP. Large and significant differences were noted in speed (P = 0.01, d = 0.54) and speed fluctuation (P = 0.02, d = 0.58), which improved by 10% in PAP compared with non-PAP. In conclusion, a warm-up that includes PAP sets improves kicking thrust, kinematics and performance.

Postactivation Potentiation in Blood Flow-Restricted Complex Training

Cleary, CJ and Cook, SB. Postactivation potentiation in blood flow-restricted complex training. J Strength Cond Res 34(4): 905-910, 2020-Complex training uses a high-load (HL) resistance exercise to elicit postactivation potentiation (PAP) that is typically observed through enhanced plyometric performance. Blood flow-restricted (BFR) resistance exercise uses low loads to induce similar muscular adaptations to HL resistance exercise; however, the efficacy and feasibility of BFR complex training are unknown. Fifteen college-aged men (mean ± SD; age: 20.3 ± 0.9 years; relative back-squat one-repetition maximum [1RM]: 1.78 ± 0.3 kg·kg) with at least 2 years of resistance training experience completed 3 sessions: a familiarization session with 1RM testing, and 2 complex training sessions of 3 presquat vertical jumps (VJs), condition-specific back squats (HL: 5 repetitions at 85% 1RM, BFR: 30 repetitions at 30% 1RM), and a single postsquat VJ. Postactivation potentiation was calculated as (postsquat VJ height ÷ max presquat VJ height) [BULLET OPERATOR] 100. Electromyography (EMG) of the vastus lateralis and hamstrings was collected, quantified to root mean square values, and normalized to peak 1RM activity. Postsquat VJ height was significantly reduced in both conditions, and PAP did not occur because it was less than 100% (HL: 96.1 ± 5.1%, BFR: 90.8 ± 7.8%, p = 0.010). Vastus lateralis and hamstrings EMG amplitude was highest (p < 0.001) in the HL condition. High-load and BFR complex training decreased subsequent VJ height in these individuals, and this might have been due to an ineffective complex training protocol and individual factors such as training status and relative strength.

Effects of two drop-jump protocols with different volumes on vertical jump performance and its association with the force-velocity profile

PURPOSE

This study aimed to evaluate the changes in countermovement jump (CMJ) height after two drop-jump (DJ) protocols with different volumes, and to explore the possibility of predicting the changes in CMJ height based on the vertical force-velocity (F-v) profile.

METHOD

Thirty-four male athletes (age: 21.9 ± 2.0 years) were tested on three occasions. The F-v profile during the CMJ exercise was determined in the first session. Two DJ protocols (low-volume [1 set of 5 DJ trials from a 30 cm height] and high-volume [3 sets of 5 DJ trials from a 30 cm height]) were randomly performed during the second and third sessions, and the unloaded CMJ height was evaluated before (Pre), 4 min (Post4), 8 min (Post8), and 12 min (Post12) after the DJ protocol.

RESULTS

CMJ height was significantly higher at Post4 (2.5 cm [95% confidence interval (CI) = 2.0-3.0 cm]; ES = 0.35), Post8 (2.1 cm [95% CI = 1.4-2.8 cm]; ES = 0.29) and Post12 (2.2 cm [95% CI = 1.4-3.0 cm]; ES = 0.30) compared to Pre. The only significant interaction (protocol × time) was caused by a higher increment in CMJ height at Post4 for the low-volume (8.1 ± 3.7%) compared to the high-volume (5.8 ± 3.9%) protocol. The F-v profile did not explain a significant part of the change in CMJ height (variance explained < 10%).

CONCLUSIONS

These results suggest that low-volume DJ protocols could be more efficient to acutely increase CMJ performance, while the change in CMJ height was not affected by the F-v profile.

Post-Activation Potentiation: Is there an Optimal Training Volume and Intensity to Induce Improvements in Vertical Jump Ability in Highly-Trained Subjects?

The aim of this study was to compare the acute effects of performing half squats (HSs) with different loading intensities (1, 3, and 5 repetitions maximum [RM], and 60% 1RM) and a different number of sets (1, 2, and 3) on the countermovement jump (CMJ) performance of 18 highly‐trained male subjects. Participants were submitted to four experimental conditions (1RM, 3RM, 5RM, and 60% 1RM) in randomized order. The CMJ was assessed before and after each set. Differences in CMJ performance between the distinct experimental conditions and individual responses in CMJ performance induced by the different protocols were analyzed via the magnitude‐based inference method. Overall, significant improvements were detected in individual CMJ heights after each activation protocol. It can be concluded that the use of 1 to 3 sets of HSs performed at moderate‐to‐high loads may be an effective strategy to improve jump performance in highly‐trained subjects. Nonetheless, despite the high efficiency of the protocols tested here, coaches and researchers are strongly encouraged to perform individualized assessments within the proposed range of loads and sets, to find optimal and tailored post‐activation potentiation protocols.

Postactivation Potentiation of Bench Press Throw Performance Using Velocity-Based Conditioning Protocols with Low and Moderate Loads

This study examined the acute effects of the bench press exercise with low and moderate loads as well as with two predetermined movement velocity loss percentages on bench press throw performance and surface electromyographic (sEMG) activity. Ten trained men completed 5 main trials in randomized and counterbalanced order one week apart. Mean propulsive velocity (MPV), peak velocity (PV) and sEMG activity of prime movers were evaluated before and periodically for 12 minutes of recovery under five conditions: using loads of 40 or 60% of 1 RM, until mean velocity dropped to 90 or 70%, as well as a control condition (CTRL). MPV and PV were increased 4-12 min into recovery by 4.5-6.8% only after the 60%1RM condition during which velocity dropped to 90% and total exercise volume was the lowest of all conditions (p < 0.01, Hedges’ g = 0.8-1.7). When peak individual responses were calculated irrespective of time, MPV was increased by 9.2 ± 4.4 (p < 0.001, Hedges’ g = 1.0) and 6.1 ± 3.6% (p < 0.001, Hedges’ g = 0.7) under the two conditions with the lowest total exercise volume irrespective of the load, i.e. under the conditions of 40 and 60% 1RM where velocity was allowed to drop to 90%. sEMG activity of the triceps was significantly greater when peak individual responses were taken into account only under the 60%1RM condition when velocity dropped to 90% (p < 0.05, Hedges’ g = 0.4). This study showed that potentiation may be maximized by taking into account individual fatigue profiles using velocity-based training.

Post-Activation Potentiation: Is there an Optimal Training Volume and Intensity to Induce Improvements in Vertical Jump Ability in Highly-Trained Subjects?

The aim of this study was to compare the acute effects of performing half squats (HSs) with different loading intensities (1, 3, and 5 repetitions maximum [RM], and 60% 1RM) and a different number of sets (1, 2, and 3) on the countermovement jump (CMJ) performance of 18 highly-trained male subjects. Participants were submitted to four experimental conditions (1RM, 3RM, 5RM, and 60% 1RM) in randomized order. The CMJ was assessed before and after each set. Differences in CMJ performance between the distinct experimental conditions and individual responses in CMJ performance induced by the different protocols were analyzed via the magnitude-based inference method. Overall, significant improvements were detected in individual CMJ heights after each activation protocol. It can be concluded that the use of 1 to 3 sets of HSs performed at moderate-to-high loads may be an effective strategy to improve jump performance in highly-trained subjects. Nevertheless, despite the high efficiency of the protocols tested here, coaches and researchers are strongly encouraged to perform individualized assessments within the proposed range of loads and sets, to find optimal and tailored post-activation potentiation protocols.

Power-to-Strength Ratio Influences Performance Enhancement with Contrast Training

PURPOSE

The effectiveness of contrast training (CST) for improving explosive exercise performance is modulated by various individual characteristics; however, further work is required to define these factors.

METHODS

Subelite male Australian Football players (n = 22; age, 19 ± 2 yr; body mass, 80.4 ± 9.4 kg; one-repetition maximum [1-RM] half squat, 172 ± 18 kg; mean ± SD) completed two experimental trials involving two sets of squat jumps (six repetitions at 30% 1-RM) performed either alone (CTL condition) or after half squats (six repetitions at 85% 1-RM; CST condition).

RESULTS

Squat jump peak power was similar between CTL and CST during set 1 (mean change: ±90% confidence interval, 2.8% ± 2.0%; effect size [ES]: ±90% confidence interval, 0.13 ± 0.09; P = 0.079) and set 2 (0.3% ± 1.7%; ES, 0.01 ± 0.08; P = 0.781). Peak power enhancement with CST was not related to maximal (1-RM half squat) strength (r = 0.001, P = 0.884), but was negatively correlated with both baseline peak power (r = 0.44, P < 0.001) and power-to-strength ratio (PSR); that is, the ratio between baseline peak power and 1-RM half squat strength (r = 0.65, P < 0.001). Using a median split, analyses were performed in participants with a low PSR (LPSR group; PSR = 15.4-19.1 W·kg; n = 11) or high PSR (HPSR group, PSR = 19.4-24.7 W·kg; n = 11). Peak power was enhanced with CST for the LPSR (8.1% ± 3.9%; ES, 0.44 ± 0.21; P = 0.004) but not HPSR (-2.1% ± 1.3%; ES, -0.14 ± 0.09; P = 0.010) groups.

CONCLUSION

The PSR appears to influence the effectiveness of CST, with performance enhancement more likely in those with a lower PSR.

The Importance of Muscular Strength: Training Considerations

This review covers underlying physiological characteristics and training considerations that may affect muscular strength including improving maximal force expression and time-limited force expression. Strength is underpinned by a combination of morphological and neural factors including muscle cross-sectional area and architecture, musculotendinous stiffness, motor unit recruitment, rate coding, motor unit synchronization, and neuromuscular inhibition. Although single- and multi-targeted block periodization models may produce the greatest strength-power benefits, concepts within each model must be considered within the limitations of the sport, athletes, and schedules. Bilateral training, eccentric training and accentuated eccentric loading, and variable resistance training may produce the greatest comprehensive strength adaptations. Bodyweight exercise, isolation exercises, plyometric exercise, unilateral exercise, and kettlebell training may be limited in their potential to improve maximal strength but are still relevant to strength development by challenging time-limited force expression and differentially challenging motor demands. Training to failure may not be necessary to improve maximum muscular strength and is likely not necessary for maximum gains in strength. Indeed, programming that combines heavy and light loads may improve strength and underpin other strength-power characteristics. Multiple sets appear to produce superior training benefits compared to single sets; however, an athlete's training status and the dose-response relationship must be considered. While 2- to 5-min interset rest intervals may produce the greatest strength-power benefits, rest interval length may vary based an athlete's training age, fiber type, and genetics. Weaker athletes should focus on developing strength before emphasizing power-type training. Stronger athletes may begin to emphasize power-type training while maintaining/improving their strength. Future research should investigate how best to implement accentuated eccentric loading and variable resistance training and examine how initial strength affects an athlete's ability to improve their performance following various training methods.

Impact of Accommodating Resistance in Potentiating Horizontal-Jump Performance in Professional Rugby League Players

This study investigated the efficacy of deadlifts and box squats, with a combination of traditional and accommodating resistance, as a postactivation potentiating stimulus of standing broad jumps (SBJ) in a multiple-set contrast protocol. Twelve professional rugby league players (21.4 [2.5] y; 181.3 [8.3] cm, 91.9 [8.8] kg; 1-repetition-maximum [1RM] back squat/body mass 1.59 [0.21]; 1RM deadlift/body mass 2.11 [0.25]; ≥3-y resistance-training experience) performed baseline SBJ before a contrast postactivation potentiating protocol involving 2 repetitions of 85% 1RM box squat or deadlifts, loaded with a combination of traditional barbell weight (70% 1RM) and elastic-band resistance (∼15% 1RM), followed by 2 SBJs. Exercises were separated by 90 s, and 4 contrast pairs were performed in total. Using a repeated-measures design, all subjects performed the squat followed by the deadlift and finally the control (SBJ only) condition in the same order across consecutive weeks. Changes from baseline in SBJ distance were moderate for the box squat (effect size [ES] = 0.64–1.03) and deadlift (ES = 0.80–0.96) and trivial in the control condition (ES = 0.02–0.11). The magnitude of differences in postactivation potentiating effect were considered moderate (d = 0.61) for set 1, trivial for set 2 (d = 0.10) and set 3 (d = 0.05) in favor of box squats, and moderate for set 4 (d = 0.58) in favor of deadlifts. Accommodating resistance in either box squats or deadlifts is an effective means of potentiating SBJ performance across multiple sets of a contrast protocol with only 90-s rest.

Complex Training: The Effect of Exercise Selection and Training Status on Postactivation Potentiation in Rugby League Players

This study compared the postactivation potentiation (PAP) response of the hex bar deadlift (HBD) and back squat (BS) exercises. The PAP response between different levels of athletes was also compared. Ten professional and 10 amateur rugby league players performed 2 experimental sessions. Participants performed a countermovement jump (CMJ) before and 2, 4, 6, 8, 10, 12, 14, and 16 minutes after a conditioning activity (CA) that contained 1 set of 3 repetitions at 93% 1 repetition maximum of either HBD or BS. A force platform determined peak power output (PPO), force at PPO, velocity at PPO, and jump height of each CMJ. Surface electromyography (EMG) of the vastus lasteralis, rectus femoris, tibialis anterior, and gastrocnemius medialis of each participant's dominant leg was recorded during each CMJ. A further 10 participants performed a control trial without a CA. The HBD expressed PAP between 2 and 6 minutes post-CA, whereas the BS did not. The HBD exhibited a significantly (p ≤ 0.05) greater PAP response than the BS for PPO. There were no significant (p > 0.05) differences between stronger and weaker players. There were no significant (p > 0.05) changes in the EMG variables. These results suggest that HBD is a suitable CA for eliciting PAP in stronger and weaker athletes. Strength and conditioning coaches should consider the CA and time frame between the CA and the plyometric exercise for optimal PAP responses.

Trends Supporting the In-Field Use of Wearable Inertial Sensors for Sport Performance Evaluation: A Systematic Review

Recent technological developments have led to the production of inexpensive, non-invasive, miniature magneto-inertial sensors, ideal for obtaining sport performance measures during training or competition. This systematic review evaluates current evidence and the future potential of their use in sport performance evaluation. Articles published in English (April 2017) were searched in Web-of-Science, Scopus, Pubmed, and Sport-Discus databases. A keyword search of titles, abstracts and keywords which included studies using accelerometers, gyroscopes and/or magnetometers to analyse sport motor-tasks performed by athletes (excluding risk of injury, physical activity, and energy expenditure) resulted in 2040 papers. Papers and reference list screening led to the selection of 286 studies and 23 reviews. Information on sport, motor-tasks, participants, device characteristics, sensor position and fixing, experimental setting and performance indicators was extracted. The selected papers dealt with motor capacity assessment (51 papers), technique analysis (163), activity classification (19), and physical demands assessment (61). Focus was placed mainly on elite and sub-elite athletes (59%) performing their sport in-field during training (62%) and competition (7%). Measuring movement outdoors created opportunities in winter sports (8%), water sports (16%), team sports (25%), and other outdoor activities (27%). Indications on the reliability of sensor-based performance indicators are provided, together with critical considerations and future trends.

The Importance of Muscular Strength in Athletic Performance

This review discusses previous literature that has examined the influence of muscular strength on various factors associated with athletic performance and the benefits of achieving greater muscular strength. Greater muscular strength is strongly associated with improved force-time characteristics that contribute to an athlete's overall performance. Much research supports the notion that greater muscular strength can enhance the ability to perform general sport skills such as jumping, sprinting, and change of direction tasks. Further research indicates that stronger athletes produce superior performances during sport specific tasks. Greater muscular strength allows an individual to potentiate earlier and to a greater extent, but also decreases the risk of injury. Sport scientists and practitioners may monitor an individual's strength characteristics using isometric, dynamic, and reactive strength tests and variables. Relative strength may be classified into strength deficit, strength association, or strength reserve phases. The phase an individual falls into may directly affect their level of performance or training emphasis. Based on the extant literature, it appears that there may be no substitute for greater muscular strength when it comes to improving an individual's performance across a wide range of both general and sport specific skills while simultaneously reducing their risk of injury when performing these skills. Therefore, sport scientists and practitioners should implement long-term training strategies that promote the greatest muscular strength within the required context of each sport/event. Future research should examine how force-time characteristics, general and specific sport skills, potentiation ability, and injury rates change as individuals transition from certain standards or the suggested phases of strength to another.

Potentiation Effects of Half-Squats Performed in a Ballistic or Nonballistic Manner

This study examined and compared the acute effects of ballistic and nonballistic concentric-only half-squats (COHSs) on squat jump performance. Fifteen resistance-trained men performed a squat jump 2 minutes after a control protocol or 2 COHSs at 90% of their 1 repetition maximum (1RM) COHS performed in a ballistic or nonballistic manner. Jump height (JH), peak power (PP), and allometrically scaled peak power (PPa) were compared using three 3 × 2 repeated-measures analyses of variance. Statistically significant condition × time interaction effects existed for JH (p = 0.037), PP (p = 0.041), and PPa (p = 0.031). Post hoc analysis revealed that the ballistic condition produced statistically greater JH (p = 0.017 and p = 0.036), PP (p = 0.031 and p = 0.026), and PPa (p = 0.024 and p = 0.023) than the control and nonballistic conditions, respectively. Small effect sizes for JH, PP, and PPa existed during the ballistic condition (d = 0.28-0.44), whereas trivial effect sizes existed during the control (d = 0.0-0.18) and nonballistic (d = 0.0-0.17) conditions. Large statistically significant relationships existed between the JH potentiation response and the subject's relative back squat 1RM (r = 0.520; p = 0.047) and relative COHS 1RM (r = 0.569; p = 0.027) during the ballistic condition. In addition, large statistically significant relationship existed between JH potentiation response and the subject's relative back squat strength (r = 0.633; p = 0.011), whereas the moderate relationship with the subject's relative COHS strength trended toward significance (r = 0.483; p = 0.068). Ballistic COHS produced superior potentiation effects compared with COHS performed in a nonballistic manner. Relative strength may contribute to the elicited potentiation response after ballistic and nonballistic COHS.

Potentiation Following Ballistic and Nonballistic Complexes: The Effect of Strength Level

Suchomel, TJ, Sato, K, DeWeese, BH, Ebben, WP, and Stone, MH. Potentiation following ballistic and nonballistic complexes: the effect of strength level. J Strength Cond Res 30(7): 1825-1833, 2016-The purpose of this study was to compare the temporal profile of strong and weak subjects during ballistic and nonballistic potentiation complexes. Eight strong (relative back squat = 2.1 ± 0.1 times body mass) and 8 weak (relative back squat = 1.6 ± 0.2 times body mass) males performed squat jumps immediately and every minute up to 10 minutes following potentiation complexes that included ballistic or nonballistic concentric-only half-squat (COHS) performed at 90% of their 1 repetition maximum COHS. Jump height (JH) and allometrically scaled peak power (PPa) were compared using a series of 2 × 12 repeated measures analyses of variance. No statistically significant strength level main effects for JH (p = 0.442) or PPa (p = 0.078) existed during the ballistic condition. In contrast, statistically significant main effects for time existed for both JH (p = 0.014) and PPa (p < 0.001); however, no statistically significant pairwise comparisons were present (p > 0.05). Statistically significant strength level main effects existed for PPa (p = 0.039) but not for JH (p = 0.137) during the nonballistic condition. Post hoc analysis revealed that the strong subjects produced statistically greater PPa than the weaker subjects (p = 0.039). Statistically significant time main effects existed for time existed for PPa (p = 0.015), but not for JH (p = 0.178). No statistically significant strength level × time interaction effects for JH (p = 0.319) or PPa (p = 0.203) were present for the ballistic or nonballistic conditions. Practical significance indicated by effect sizes and the relationships between maximum potentiation and relative strength suggest that stronger subjects potentiate earlier and to a greater extent than weaker subjects during ballistic and nonballistic potentiation complexes.

Factors Modulating Post-Activation Potentiation of Jump, Sprint, Throw, and Upper-Body Ballistic Performances: A Systematic Review with Meta-Analysis

BACKGROUND

Although post-activation potentiation (PAP) has been extensively examined following the completion of a conditioning activity (CA), the precise effects on subsequent jump, sprint, throw, and upper-body ballistic performances and the factors modulating these effects have yet to be determined. Moreover, weaker and stronger individuals seem to exhibit different PAP responses; however, how they respond to the different components of a strength-power-potentiation complex remains to be elucidated.

OBJECTIVES

This meta-analysis determined (1) the effect of performing a CA on subsequent jump, sprint, throw, and upper-body ballistic performances; (2) the influence of different types of CA, squat depths during the CA, rest intervals, volumes of CA, and loads during the CA on PAP; and (3) how individuals of different strength levels respond to these various strength-power-potentiation complex components.

METHODS

A computerized search was conducted in ADONIS, ERIC, SPORTDiscus, EBSCOhost, Google Scholar, MEDLINE, and PubMed databases up to March 2015. The analysis comprised 47 studies and 135 groups of participants for a total of 1954 participants.

RESULTS

The PAP effect is small for jump (effect size [ES] = 0.29), throw (ES = 0.26), and upper-body ballistic (ES = 0.23) performance activities, and moderate for sprint (ES = 0.51) performance activity. A larger PAP effect is observed among stronger individuals and those with more experience in resistance training. Plyometric (ES = 0.47) CAs induce a slightly larger PAP effect than traditional high-intensity (ES = 0.41), traditional moderate-intensity (ES = 0.19), and maximal isometric (ES = -0.09) CAs, and a greater effect after shallower (ES = 0.58) versus deeper (ES = 0.25) squat CAs, longer (ES = 0.44 and 0.49) versus shorter (ES = 0.17) recovery intervals, multiple- (ES = 0.69) versus single- (ES = 0.24) set CAs, and repetition maximum (RM) (ES = 0.51) versus sub-maximal (ES = 0.34) loads during the CA. It is noteworthy that a greater PAP effect can be realized earlier after a plyometric CA than with traditional high- and moderate-intensity CAs. Additionally, shorter recovery intervals, single-set CAs, and RM CAs are more effective at inducing PAP in stronger individuals, while weaker individuals respond better to longer recovery intervals, multiple-set CAs, and sub-maximal CAs. Finally, both weaker and stronger individuals express greater PAP after shallower squat CAs.

CONCLUSIONS

Performing a CA elicits small PAP effects for jump, throw, and upper-body ballistic performance activities, and a moderate effect for sprint performance activity. The level of potentiation is dependent on the individual's level of strength and resistance training experience, the type of CA, the depth of the squat when this exercise is employed to elicit PAP, the rest period between the CA and subsequent performance, the number of set(s) of the CA, and the type of load used during the CA. Finally, some components of the strength-power-potentiation complex modulate the PAP response of weaker and stronger individuals in a different way.

A Preliminary Case Analysis of the Post- Activation Potentiation Effects of Plyometrics on Sprint Performance in Women

This study provided a case analysis of the effects of plyometrics on post-activation potentiation (PAP) of 20-m (0-5, 0-10, 0-20 m intervals) sprint performance in strength-trained females. Three college-aged participants performed a one-repetition maximum (1RM) squat, which was used to set the load for a jump squat with 30% 1RM (JS30). Over three sessions, participants performed three PAP protocols: a control condition of 4 min rest (CC); 3 sets x 5 repetitions of the JS30; and 3 sets x 10 repetitions of the alternate leg bound (ALB). Peak and mean power were recorded during the JS30. Participants performed two baseline sprints prior to each condition, and then six sprints from immediately after for 16 min post. Results indicated that the JS30 and ALB could potentiate sprinting, although responses were highly individual. The two more powerful participants experienced more sprint enhancements across more time points than the less powerful participant. Any performance changes were in the range of 1-4%, which is typical of PAP research. It cannot, however, be confirmed whether the JS30 and ALB were superior to the CC. Nonetheless, the data suggest the JS30 and ALB could potentiate sprinting in females. Further research is needed to confirm these findings.

Postactivation Potentiation of Horizontal Jump Performance Across Multiple Sets of a Contrast Protocol

Seitz, LB, Mina, MA, and Haff, GG. Postactivation potentiation of horizontal jump performance across multiple sets of a contrast protocol. J Strength Cond Res 30(10): 2733-2740, 2016-This study determined whether a postactivation potentiation (PAP) effect could be elicited across multiple sets of a contrast PAP protocol. Fourteen rugby league players performed a contrast PAP protocol comprising 4 sets of 2 paused box squats accommodated with bands alternated with 2 standing broad jumps. The rest period between the squats and the jumps and between the sets was 90 seconds. A control protocol with standing broad jumps only was performed on a separate session. A standing broad jump was performed ∼2 minutes before each protocol and served as a baseline measurement. Standing broad jump distance was significantly greater (4.0 ± 3.4% to 5.7 ± 4.7%) than baseline during the 4 sets of the contrast PAP protocol with the changes being medium in the first, second, and fourth sets (effect size [ES]: 0.58, 0.67, and 0.69, respectively) and large for the third set (ES: 0.81). Conversely, no PAP effect was observed in the control protocol. Additionally, the stronger players displayed a larger PAP effect during each of the 4 sets of the contrast PAP protocol (Cohen's d: 0.28-1.68) and a larger mean effect across these 4 sets (Cohen's d: 1.29). Horizontal jump performance is potentiated after only 90 seconds of rest after an accommodating exercise, and this PAP effect can be elicited across 4 sets. Additionally, the PAP response is largely mediated by the individual's strength level. These results are of great importance for coaches seeking to incorporate PAP complexes involving horizontal jumps in their training programs.

Relationships between maximal strength, muscle size, and myosin heavy chain isoform composition and postactivation potentiation

The purpose of this study was to examine the relationships between maximal voluntary postactivation potentiation (PAP) and maximal knee extensor torque, quadriceps cross-sectional area (CSA) and volume, and type II myosin heavy chain (MHC) isoform percentage in human skeletal muscle. Thirteen resistance-trained men completed a test protocol consisting of 2 isokinetic knee extensions at 180°·s(-)(1) performed before and 1, 4, 7, and 10 min after the completion of 4 maximal knee extensions at 60°·s(-)(1) (i.e., a conditioning activity (CA)). Magnetic resonance imaging and muscle microbiopsy procedures were completed on separate days to assess quadriceps CSA and volume and MHC isoform content. Maximal voluntary PAP response was assessed as the ratio of the highest knee extensor torques measured before and after the CA. There were large to very large correlations between maximal voluntary PAP response and maximal knee extensor torque (r = 0.62) and quadriceps CSA (r = 0.68) and volume (r = 0.63). Nonetheless, these correlations were not statistically significant after adjusting for the influence of type II MHC percentage using partial correlation analysis. By contrast, the strongest correlation was observed for type II MHC percentage (r = 0.77), and this correlation remained significant after adjusting for the other variables. Maximal voluntary PAP response is strongly correlated with maximal knee extensor torque and quadriceps CSA and volume, but is mostly clearly associated with the type II myosin isoform percentage in human skeletal muscle.

Ballistic exercise as a pre-activation stimulus: a review of the literature and practical applications

Post-activation potentiation (PAP) refers to the acute enhancement of muscular function as a direct result of its contractile history. Protocols designed to elicit PAP have commonly employed heavy resistance exercise (HRE) as the pre-activation stimulus; however, a growing body of research suggests that low-load ballistic exercises (BE) may also provide an effective stimulus. The ability to elicit PAP without the need for heavy equipment would make it easier to utilise prior to competition. It is hypothesised that BE can induce PAP given the high recruitment of type II muscle fibres associated with its performance. The literature has reported augmentations in power performance typically ranging from 2 to 5 %. The performance effects of BE are modulated by loading, recovery and physical characteristics. Jumps performed with an additional loading, such as depth jumps or weighted jumps, appear to be the most effective activities for inducing PAP. Whilst the impact of recovery duration on subsequent performance requires further research, durations of 1-6 min have been prescribed successfully in multiple instances. The effect of strength and sex on the PAP response to BE is not yet clear. Direct comparisons of BE and HRE, to date, suggest a tendency for HRE protocols to be more effective; future research should consider that these strategies must be optimised in different ways. The role of acute augmentations in lower limb stiffness is proposed as an additional mechanism that may further explain the PAP response following BE. In summary, BE demonstrates the potential to enhance performance in power tasks such as jumps and sprints. This review provides the reader with some practical recommendations for the application of BE as a pre-activation stimulus.

The temporal profile of postactivation potentiation is related to strength level

The purpose of this investigation was to determine whether stronger individuals are able to express postactivation potentiation (PAP) earlier than weaker individuals during a vertical squat jump test. Eighteen junior elite rugby league players were divided into strong (relative 1 repetition maximum [1RM] back squat ≥ 2 × body mass) and weak (relative 1RM back squat <2.0 × body mass) groups. Each subject performed squat jumps before, 15 seconds, 3, 6, 9, and 12 minutes after a conditioning activity (CA) that contained 1 set of 3 back squats performed at 90% of 1RM. A force plate, which sampled at 1000 Hz, was used to determine the power output and height for each squat jump. Stronger individuals expressed PAP between 3 and 12 minutes post-CA, whereas their weaker counterparts displayed potentiation between 6 and 12 minutes post-CA. Moreover, the stronger group exhibited a significantly (p ≤ 0.05) higher PAP response than the weaker group at all post-CA squat jump tests. The stronger group displayed the greatest potentiation at 6 minutes post-CA, whereas the weaker group displayed the greatest potentiation response at 9 minutes following the CA. Based on these results, stronger individuals appear to be able to express PAP earlier after a CA than weaker individuals. Additionally, stronger individuals express significantly greater postactivation responses than weaker individuals. From a practical standpoint, strength and conditioning coaches should consider the athletes' strength levels when constructing postactivation complexes (CA + performance activity) as strength will dictate the time frame required between the conditioning and the performance activity.

Neuromuscular characteristics of drop and hurdle jumps with different types of landings

The objective of this study was to compare drop (DJ) and hurdle jumps using a preferred, flat foot (FLAT) and forefoot (FORE) landing technique. Countermovement jump height was used to establish the hurdle and the DJ heights. The subjects performed forward hurdles and vertical DJs on a force plate. Measures included vertical ground reaction force (VGRF), contact time, leg stiffness, and rate of force development (RFD). Electromyographic (EMG) activity was measured in the rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius during 3 phases: preactivity, eccentric phase, and concentric phase. All the kinetic variables favored hurdles over DJs. Specifically, hurdle-preferred technique and FORE exhibited the shortest contact time and DJ FLAT the longest. The VGRF was higher in hurdle preferred and FORE than in DJ preferred, FLAT, and FORE. For stiffness and RFD, hurdle preferred and FORE were higher than DJ preferred and FLAT. Hurdle jumps showed higher rectus femoris EMG activity than DJ did during preactivity and eccentric phases but lower activity during the concentric phase. Considering the type of landing, FLAT generally demonstrated the greatest EMG activity. During the concentric phase, DJ exhibited higher rectus femoris EMG activity. Biceps femoris activity was higher with hurdles in all the phases. Gastrocnemius showed the highest EMG activity during the concentric phase, and during the eccentric phase, hurdle preferred and FORE showed the highest results. In conclusion, the hurdle FORE technique was the most powerful type of jump.

The Back Squat and the Power Clean: Elicitation of Different Degrees of Potentiation

Purpose:

To compare the acute effects of back squats and power cleans on sprint performance.

Methods:

Thirteen elite junior rugby league players performed 20-m linear sprints before and 7 min after 2 different conditioning activities or 1 control condition. The conditioning activities included 1 set of 3 back squats or power cleans at 90% 1-repetition maximum. A 2 × 2 repeated-measures ANOVA was used to compare preconditioning and postconditioning changes in sprint performance.

Results:

Both the back-squat and power-clean conditioning activities demonstrated a potentiation effect as indicated by improved sprint time (back squat: P = .001, ES = –0.66; power cleans: P = .001, ES = –0.92), velocity (back squat: P = .001, ES = 0.63; power cleans: P = .001, ES = 0.84), and average acceleration over 20 m (back squat: P = .001, ES = 0.70; power cleans: P = .001, ES = 1.00). No potentiation effect was observed after the control condition. Overall, the power clean induced a greater improvement in sprint time (P = .042, ES = 0.83), velocity (P = .047, ES = 1.17), and average acceleration (P = .05, ES = 0.87) than the back squat.

Conclusions:

Back-squat and power-clean conditioning activities both induced improvements in sprint performance when included as part of a potentiation protocol. However, the magnitude of improvement was greater after the power cleans. From a practical perspective, strength and conditioning coaches should consider using power cleans rather than back squats to maximize the performance effects of potentiation complexes targeting the development of sprint performance.

Repetitive hops induce postactivation potentiation in triceps surae as well as an increase in the jump height of subsequent maximal drop jumps

Postactivation potentiation (PAP) has been defined as the increase in twitch torque after a conditioning contraction. The present study aimed to investigate the effectiveness of hops as conditioning contractions to induce PAP and increase performance in subsequent maximal drop jumps. In addition, we wanted to test if and how PAP can contribute to increases in drop jump rebound height. Twelve participants performed 10 maximal two-legged hops as conditioning contractions. Twitch peak torques of triceps surae muscles were recorded before and after the conditioning hops. Then, subjects performed drop jumps with and without 10 conditioning hops before each drop jump. Recordings included ground reaction forces, ankle and knee angles and electromyographic activity in five leg muscles. In addition, efferent motoneuronal output during ground contact was estimated with V-wave stimulation. The analyses showed that after the conditioning hops, twitch peak torques of triceps surae muscles were 32% higher compared to baseline values (P < 0.01). Drop jumps performed after conditioning hops were significantly higher (12%, P < 0.05), but V-waves and EMG activity remained unchanged. The amount of PAP and the change in drop jump rebound height were positively correlated (r² = 0.26, P < 0.05). These results provide evidence for PAP in triceps surae muscles induced by a bout of hops and indicate that PAP can contribute to the observed performance enhancements in subsequent drop jumps. The lack of change in EMG activity and V-wave amplitude suggests that the underlying mechanisms are more likely intramuscular than neural in origin.

The acute potentiating effects of back squats on athlete performance

Crewther, BT, Kilduff, LP, Cook, CJ, Middleton, MK, Bunce, PJ, and Yang, G-Z. The acute potentiating effects of back squats on athlete performance. J Strength Cond Res 25(12): 3319-3325, 2011-This study examined the acute potentiating effects of back squats on athlete performance with a specific focus on movement specificity and the individual timing of potentiation. Nine subelite male rugby players performed 3 protocols on separate occasions using a randomized, crossover, and counterbalanced design. Each protocol consisted of performance testing before a single set of 3 repetition maximum (3RM) back squats, followed by retesting at ∼15 seconds, 4, 8, 12, and 16 minutes. The 3 tests were countermovement jumps (CMJs), sprint performance (5 and 10 m), and 3-m horizontal sled pushes with a 100-kg load. Relationships between the individual changes in salivary testosterone and cortisol concentrations and performance were also examined. The 3RM squats significantly (p < 0.001) improved CMJ height at 4 (3.9 ± 1.9%), 8 (3.5 ± 1.5%), and 12 (3.0 ± 1.4%) minutes compared with baseline values, but no temporal changes in sprinting and sled times were identified. On an individual level, the peak relative changes in CMJ height (6.4 ± 2.1%, p < 0.001) were greater than the 3-m sled (1.4 ± 0.6%), 5-m (2.6 ± 1.0%), and 10-m sprint tests (1.8 ± 1.0%). In conclusion, a single set of 3RM squats was found effective in acutely enhancing CMJ height in the study population, especially when the recovery period was individualized for each athlete. The study results also suggest that the potentiating effects of squats may exhibit some degree of movement specificity, being greater for those exercises with similar movement patterns. The current findings have practical implications for prescribing warm-up exercises, individualizing training programs, and for interpreting postactivation potentiation research.