The Optimal Load for Maximal Power Production During Lower-Body Resistance Exercises: A Meta-Analysis

Accentuated Eccentric Loading in Countermovement Jumps Vs. Drop Jumps: Effects on Jump Performance and Strength in A Randomized Controlled Trial

This study examined the effects of Accentuated Eccentric Loading Countermovement Jump (AEL CMJ) training on jump performance, lower body strength, sprint performance, and change of direction ability, compared to drop jump (DJ) training. This study used a randomized controlled trial (RCT) with a parallel design. Forty men physical education students (Mean ± SD: age 22.60 ± 3.24 years, body mass 75.21 ± 8.12 kg, height 1.79 ± 0.07 m) were randomly assigned to AEL (n = 14), DJ (n = 13), or a control group (CON, n = 13). The AEL and DJ groups trained three times per week for 8 weeks, while the CON group maintained their usual routines. All groups with similar levels of physical activity outside the training. Pre-, mid- (4 weeks), and post-intervention (8 weeks) assessments measured jump performance (CMJ and squat jump (SJ)), 1RM squat strength, 30 m sprint time, and change of direction (T-test). A mixed-effects model evaluated group and time effects. Significant group × time interactions were observed for CMJ height (P = 0.006), with both AEL and DJ training improving CMJ (AEL: +11.8%, ES = 0.77; DJ: +7.7%, ES = 0.47), SJ height (AEL: +5.7%, ES = 0.37; DJ: +11.3%, ES = 0.66), and 1RM squat (AEL: +7.0%, ES = 0.44; DJ: +8.4%, ES = 0.46) at 8 weeks. Neither training method significantly improved sprint or change of direction performance. Additionally, no significant gains were seen in any indicator at 4 weeks. These results indicate that AEL CMJ and DJ training both effectively enhance vertical jump and strength, positioning AEL CMJ as an effective alternative or complement to DJ training.

Portions of the force-velocity relationship targeted by weightlifting exercises

We compared the force-velocity (F-V) characteristics between jump squat (JS) and weightlifting (hang clean [HC] and HC pull [HCP]) to determine lower limb F-V portions targeted by weightlifting exercises. Ten weightlifters performed JS at 0% (body weight only) to 70% of their one-repetition maximum (1RM) for back squat, and HC and HCP at 30‒90% and 30‒110% of their 1RM for HC, respectively. Force and velocity values at each relative load were plotted to determine the F-V features of JS, HC, and HCP. Linear regression was used to evaluate each participant's JS F-V results to obtain individual F-V relationships. Regression equations evaluated the JS force at a given velocity for each relative load of HC and HCP. HC produced significantly less force than JS at given velocities for 30%, 40%, and 50% 1RM. Furthermore, HCP produced significantly less force than JS at a given velocity for 30% 1RM and exhibited less force than JS at a given velocity for 40% 1RM with moderate effect size. HC and HCP produce comparable forces to JS within the velocity ranges of 60‒90% and 50‒110% 1RM, respectively. Thus, weightlifting exercises target low‒moderate-velocity portion of the lower limb F-V relationship.

Joint kinetic demand for performance in high jump

High jump is a power-demanding motor task. Jumpers extend the take-off leg joints with maximum effort, but kinetic requirements (i.e. torque/power) for each joint are unclear. Here we show the inter-joint differences in the kinetic exertion related to the flight height in high jump trials by 16 male high jumpers (personal best record: 1.90-2.35 m). For the knee joint, both maximum net power and maximum norm of torque were significantly and positively correlated with flight height, with a stronger correlation for maximum net power (r = 0.70) than for maximum norm of torque (r = 0.52). For the hip joint, maximum norm of torque was significantly correlated with flight height (r = 0.62), but maximum net power (r = 0.36) was not. Both torque and power exhibited the proximal-to-distal sequence (from hip to ankle). The norm of ground reaction force peaked almost simultaneously with the hip torque while external net power peaked with knee power. We suggest that the required musculoskeletal function of each joint differs even in the same task. We suggest that it may be effective to adapt the different training programme between joints to improve performance. Jumpers should prioritise torque exertion for the hip and power exertion for the knee.

The Relationship Between the Burpee Movement Program and Strength and Endurance Performance Measures in Active Young Adults: A Cross-Sectional Analysis

OBJECTIVES

This paper aimed to assess the motor performance in the Burpee Movement Program through the acceleration recorded by the Phyphox mobile app and define its relationship to strength and endurance parameters.

METHODS

Altogether, 15 students in physical education teaching completed the 3 × 3 min Burpee Movement Program, consisting of the repeated execution of a single burpee with maximum effort at regular intervals triggered by a sound signal. During the load phase, the intensity of the burpee and the fatigue index expressed in percentages were evaluated by means of the acceleration recorded through a mobile phone. In the second part of testing, we evaluated the performance parameters during a bench press and squat where the intensity was measured using a linear displacement transducer (Tendo Power Analyzer) and aerobic endurance was assessed with a 20 m shuttle run test (20 mSR).

RESULTS

The average intensity of the burpee ranged from 3.12 to 11.12 ms-2. The fatigue index ranged from -21.95% (which represented an increase in performance) to 33.63% (which represented a decrease in performance). The performances in the bench presses ranged from 58 to 480 W and from 175 to 696 W during the squats. The distance in the 20 m shuttle run test (20 mSR) ranged from 540 to 2000 m. The intensity of the burpee showed a significant correlation to the performances achieved in the bench presses and squats r = 0.82 and 0.79. The fatigue index showed a significant correlation to the 20 m shuttle run test (20 mSR) r = -0.67.

CONCLUSIONS

These findings indicate that in, our case, the results from the Burpee Movement Program are significantly associated with the participants' strength and endurance abilities. We recommend using BMP for the development of strength-endurance abilities, but further exploration is needed regarding the potential use of BMP as a diagnostic test.

A systematic review of resistance training methodologies for the development of lower body concentric mean power, peak power, and mean propulsive power in team-sport athletes

This study aimed to systematically review training methods prescribed to develop lower-body power, determine their effectiveness for the development of lower-body mechanical power and their implementation in an annual training cycle amongst team-sport athletes. The absolute and relative outcome values of concentric mean power, peak power and mean propulsive power were extracted from 19 studies. Outcomes were assessed using baseline to post intervention percent change, effect sizes, and the level of evidence concerning the method's effectiveness. A thorough analysis of the literature indicated that, based on the high level of evidence, traditional (e.g., strength training alone) and combination training (e.g., complex and contrast) methods should be considered. Further, optimal load and velocity-based training can be implemented if coaches have access to the appropriate equipment to monitor movement velocity and mechanical power in every session. This is of particular importance in periods of the season where high volumes of technical-tactical training and congested fixture periods are present. Also, flywheel, eccentric overload and weightlifting methods have been shown to be effective although the level of evidence is low. Future research should expand on current training practices whilst adequately reporting actual training loads from sport-specific training and games alongside strength-power training protocols.

Post-activation Performance Enhancement of Countermovement Jump after Drop Jump versus Squat Jump Exercises in Elite Rhythmic Gymnasts

Drop jump (DJ) and squat jump (SJ) exercises are commonly used in rhythmic gymnastics training. However, the acute effects of DJ and SJ on countermovement jump (CMJ) performance have not been investigated. This study aimed to verify the post-activation performance enhancement (PAPE) responses induced by DJ and SJ with optimal power load and evaluate the relationship between peak PAPE effects and strength levels. Twenty female rhythmic gymnasts completed the following exercises in a randomized order on three separate days: 6 repetitions of DJs; 6 repetitions of SJs with optimal power load; and no exercise (control condition). Jump height was assessed before (baseline) and at 30 seconds and 3, 6, and 9 minutes after each exercise. DJs significantly improved jump height by 0.8 cm (effect size (ES) = 0.25; P = 0.003) at 30 seconds post-exercise compared with baseline. Jump height significantly decreased by -0.14 cm (ES = -0.61; P = 0.021) at 9 minutes after the control condition. SJs significantly improved jump height by 1.02 cm (ES = 0.36; P = 0.005) at 9 minutes post-exercise compared to the control condition. Jump height and relative back squat one-repetition maximum were positively related after performing DJs (r = 0.63; P = 0.003) and SJs (r = 0.64; P = 0.002). DJ and SJ exercises effectively improved countermovement jump height. DJ improved jump height early, while SJ produced greater potentiation effects later. Athletes with a higher strength level benefited the most from these exercises.

The effect of optimal load training on punching ability in elite female boxers

Optimal load training is a method of training that aims to maximize power output. This is achieved by arranging optimal loads (optimal ratios of load intensity and load volume) during strength training. The fixed load intensity and number of repetitions employed in traditional strength training. The present study will investigate the applicability of these two load arrangements to female elite boxers. Twenty-four elite female boxers were divided into three groups [optimal load (OL = 8), traditional load (TL = 8) and control group (CG = 8)]. The six-week intervention consisted of strength training with different loading arrangements. The punching ability and strength were tested before and after the intervention. We found that optimal load training enhances a boxer's punching ability and economy, which aligns with the demands of boxing and is suitable for high-level athletes, whose strength training loads require a more individualised and targeted approach.

Using Barbell Acceleration to Determine the 1 Repetition Maximum of the Jump Shrug

ABSTRACT

Techmanski, BS, Kissick, CR, Loturco, I, and Suchomel, TJ. Using barbell acceleration to determine the 1 repetition maximum of the jump shrug. J Strength Cond Res 38(8): 1486-1493, 2024-The purpose of this study was to determine the 1 repetition maximum (1RM) of the jump shrug (JS) using the barbell acceleration characteristics of repetitions performed with relative percentages of the hang power clean (HPC). Fifteen resistance-trained men (age = 25.5 ± 4.5 years, body mass = 88.5 ± 15.7 kg, height = 176.1 ± 8.5 cm, relative 1RM HPC = 1.3 ± 0.2 kg·kg-1) completed 2 testing sessions that included performing a 1RM HPC and JS repetitions with 20, 40, 60, 80, and 100% of their 1RM HPC. A linear position transducer was used to determine concentric duration and the percentage of the propulsive phase (P%) where barbell acceleration was greater than gravitational acceleration (i.e., a>-9.81 m·s-2). Two 1 way repeated measures ANOVA were used to compare each variable across loads, whereas Hedge's g effect sizes were used to examine the magnitude of the differences. Concentric duration ranged from 449.7 to 469.8 milliseconds and did not vary significantly between loads (p = 0.253; g = 0.20-0.39). The P% was 57.4 ± 7.2%, 64.8 ± 5.9%, 73.2 ± 4.3%, 78.7 ± 4.0%, and 80.3 ± 3.5% when using 20, 40, 60, 80, and 100% 1RM HPC, respectively. P% produced during the 80 and 100% 1RM loads were significantly greater than those at 20, 40, and 60% 1RM (p < 0.01, g = 1.30-3.90). In addition, P% was significantly greater during 60% 1RM compared with both 20 and 40% 1RM (p < 0.01, g = 1.58-2.58) and 40% was greater than 20% 1RM (p = 0.003, g = 1.09). A braking phase was present during each load and, thus, a 1RM JS load was not established. Heavier loads may be needed to achieve a 100% propulsive phase when using this method.

Dose-Response Modelling of Resistance Exercise Across Outcome Domains in Strength and Conditioning: A Meta-analysis

BACKGROUND

Resistance exercise is the most common training modality included within strength and conditioning (S&C) practice. Understanding dose-response relationships between resistance training and a range of outcomes relevant to physical and sporting performance is of primary importance for quality S&C prescription.

OBJECTIVES

The aim of this meta-analysis was to use contemporary modelling techniques to investigate resistance-only and resistance-dominant training interventions, and explore relationships between training variables (frequency, volume, intensity), participant characteristics (training status, sex), and improvements across a range of outcome domains including maximum strength, power, vertical jump, change of direction, and sprinting performance.

METHODS

Data were obtained from a database of training studies conducted between 1962 and 2018, which comprised healthy trained or untrained adults engaged in resistance-only or resistance-dominant interventions. Studies were not required to include a control group. Standardized mean difference effect sizes were calculated and interventions categorized according to a range of training variables describing frequency (number of sessions per week), volume (number of sets and repetitions performed), overall intensity (intensity of effort and load, categorised as low, medium or high), and intensity of load (represented as % of one-repetition maximum [1RM] prescribed). Contemporary modelling techniques including Bayesian mixed-effects meta-analytic models were fitted to investigate linear and non-linear dose-responses with models compared based on predictive accuracy.

RESULTS

Data from a total of 295 studies comprising 535 groups and 6,710 participants were included with analyses conducted on time points ≤ 26 weeks. The best performing model included: duration from baseline, average number of sets, and the main and interaction effects between outcome domain and intensity of load (% 1RM) expressed non-linearly. Model performance was not improved by the inclusion of participant training status or sex.

CONCLUSIONS

The current meta-analysis represents the most comprehensive investigation of dose-response relationships across a range of outcome domains commonly targeted within strength and conditioning to date. Results demonstrate the magnitude of improvements is predominantly influenced by training intensity of load and the outcome measured. When considering the effects of intensity as a % 1RM, profiles differ across outcome domains with maximum strength likely to be maximised with the heaviest loads, vertical jump performance likely to be maximised with relatively light loads (~ 30% 1RM), and power likely to be maximised with low to moderate loads (40-70% 1RM).

Combined Accentuated Eccentric Loading and Rest Redistribution in High-Volume Back Squat: Acute Kinetics and Kinematics

ABSTRACT

Chae, S, Long, SA, Lis, RP, McDowell, KW, Wagle, JP, Carroll, KM, Mizuguchi, S, and Stone, MH. Combined accentuated eccentric loading and rest redistribution in high-volume back squat: Acute kinetics and kinematics. J Strength Cond Res 38(4): 640-647, 2024-The purpose of this study was to explore acute kinetic and kinematic responses to combined accentuated eccentric loading and rest redistribution (AEL + RR). Resistance-trained men ( n = 12, 25.6 ± 4.4 years, 1.77 ± 0.06 m, and 81.7 ± 11.4 kg) completed a back squat (BS) 1 repetition maximum (1RM) and weight releaser familiarization session. Three BS exercise conditions (sets × repetitions × eccentric/concentric loading) consisted of (a) 3 × (5 × 2) × 110/60% (AEL + RR 5), (b) 3 × (2 × 5) × 110/60% (AEL + RR 2), and (c) 3 × 10 × 60/60% 1RM (traditional sets [TS]). Weight releasers (50% 1RM) were attached to every first repetition of each cluster set (every first, third, fifth, seventh, and ninth repetition in AEL + RR 5 and every first and sixth repetition in AEL + RR 2). The AEL + RR 5 resulted in significantly ( p < 0.05) greater concentric peak velocity (PV) (1.18 ± 0.17 m·s -1 ) and peak power (PP) (2,304 ± 499 W) compared with AEL + RR 2 (1.11 ± 0.19 m·s -1 and 2,148 ± 512 W) and TS (1.10 ± 0.14 m·s -1 and 2,079 ± 388 W). Furthermore, AEL + RR 5 resulted in significantly greater PV and PP across all 10 repetitions compared with TS. Although AEL + RR 5 resulted in significantly greater concentric mean force (MF) (1,706 ± 224 N) compared with AEL + RR 2 (1,697 ± 209 N) and TS (1,685 ± 211 N), no condition by set or repetition interactions existed. In conclusion, AEL + RR 5 increases PV and PP but has little effect on MF. Coaches might consider prescribing AEL + RR 5 to increase especially peak aspects of velocity and power outcomes.

Will Music Give Me Power? Effects of Listening to Music during Active and Passive Rest Intervals on Power Output during Resistance Exercise

The study aimed to evaluate the impact of listening to preferred music during active/passive rest on power output and heart rate in barbell squats (BS) and bench presses (BP). Fifteen participants (13 males and 2 females), moderately resistance trained, were engaged in four randomized experimental sessions with varying rest intervals (active/passive) and music presence (listening or not). Each session involved three sets of three repetitions of BS and BP at a 50% one-repetition maximum. ANOVA showed a significant main effect of the set for BP relative mean and peak power output (p < 0.001; both). The post hoc comparisons indicated a significantly higher BP relative mean and peak power output in set_2 (p < 0.001; effect size [ES] = 0.12 and p < 0.001; ES = 0.10) and set_3 (p < 0.001; ES = 0.11 and p = 0.001; ES = 0.16) in comparison to set_1. Moreover, a main effect of the set indicating a decrease in BS relative peak power output across sets was observed (p = 0.024) with no significant differences between sets. A significantly higher mean heart rate during active rest in comparison to passive rest was observed (p = 0.032; ES = 0.69). The results revealed no significant effect of listening to music on relative power output and heart rate during BS and BP.

Acute Effects of Varied Back Squat Activation Protocols on Muscle-Tendon Stiffness and Jumping Performance

ABSTRACT

Krzysztofik, M, Wilk, M, Pisz, A, Kolinger, D, Tsoukos, A, Zając, A, Stastny, P, and Bogdanis, GC. Acute effects of varied back squat activation protocols on muscle-tendon stiffness and jumping performance. J Strength Cond Res 37(7): 1419-1427, 2023-Intensity, movement velocity, and volume are the principal factors to successfully use postactivation performance enhancement. Therefore, 15 resistance-trained volleyball players completed 3 different back squat configurations as a conditioning activity (CA) in randomized order: (a) 3 sets of 3 repetitions at 85% 1RM (HL); (b) a single set of back squats at 60% 1RM until 10% mean velocity loss (VB); (c) and 2 sets of back squats at 60% 1RM until 10% mean velocity loss (2VB) on subsequent countermovement jump performance, Achilles tendon, and vastus lateralis stiffness with concomitant front thigh skin surface temperature assessment. The measurements were performed 5 minutes before the CA and at 2, 4, 6, 8, and 10 minutes. The jump height was significantly increased in the second minute and at peak, post-CA compared with baseline for all conditions ( p = 0.049; ES = 0.23 and p < 0.001; ES = 0.37). Skin surface temperature was significantly increased for all post-CA time points compared with baseline in the 2VB condition ( p from <0.001-0.023; ES = 0.39-1.04) and in the fourth minute and at peak post-CA in HL condition ( p = 0.023; ES = 0.69 and p = 0.04; ES = 0.46), whereas for the VB condition, a significant decrease in peak post-CA was found ( p = 0.004; ES = -0.54). Achilles tendon stiffness was significantly decreased for second, fourth, eighth, 10th, and peak post-CA in comparison to baseline for all conditions ( p from p = 0.004-0.038; ES = -0.47 to -0.69). Vastus lateralis stiffness was significantly decreased for peak post-CA compared with baseline for all conditions ( p = 0.017; ES = -0.42). We recommend using a single set of barbell squats with a 10% velocity loss as a mechanism of fatigue control to acutely improve jump height performance and avoid unnecessary increases in training volume.

Effects of Flywheel vs. Free-Weight Squats and Split Squats on Jumping Performance and Change of Direction Speed in Soccer Players

The objective of this study was to compare (i) The effects of a flywheel and free-weight resistance training program; and (ii) The effects of performing lateral and frontal split squats as part of a flywheel-resistance training program on jumping performance, the 5-0-5 change of direction test time, and the one-repetition maximum (1RM) back squat in soccer players. Twenty-four male amateur soccer players participated in this study and were randomly and equally assigned to one of three different test groups: forward split-squat group (FSQ); lateral split-squat group (LSQ); and free-weight training group (TRAD). Athletes in the FSQ group performed a squat and a forward split squat on a flywheel device, while those in the LSQ group performed a squat and a lateral split squat (instead of a forward split squat) on a flywheel device. Each training lasted 4 weeks. The main finding was that all training groups, such as TRAD, FSQ, and LSQ, significantly improved broad jump length (p = 0.001; effect size [ES] = 0.36), 5-0-5 COD time with a turn on the dominant limb (p = 0.038; ES = 0.49), and 1RM back squat (p = 0.001; ES = 0.4). In turn, both flywheel-resistance training groups (FSQ and LSQ) significantly improved their counter-movement jump height (p = 0.001; ES = 0.8 and p = 0.002; ES = 0.58; respectively) with no effect in the TRAD (p = 0.676; ES = 0.07) training group. Both free-weight and flywheel-resistance training lasting 4 weeks performed in-season contributed to significant improvement in 1RM back squat, broad jump performance, and 5-0-5 change of direction testing time, while flywheel-resistance training might be superior in counter-movement jump height enhancement in soccer players. Moreover, the manner in which split squats were performed was not a factor influencing the obtained results.

National Strength and Conditioning Association Position Statement on Weightlifting for Sports Performance

ABSTRACT

Comfort, P, Haff, GG, Suchomel, TJ, Soriano, MA, Pierce, KC, Hornsby, WG, Haff, EE, Sommerfield, LM, Chavda, S, Morris, SJ, Fry, AC, and Stone, MH. National Strength and Conditioning Association position statement on weightlifting for sports performance. J Strength Cond Res XX(X): 000-000, 2022-The origins of weightlifting and feats of strength span back to ancient Egypt, China, and Greece, with the introduction of weightlifting into the Olympic Games in 1896. However, it was not until the 1950s that training based on weightlifting was adopted by strength coaches working with team sports and athletics, with weightlifting research in peer-reviewed journals becoming prominent since the 1970s. Over the past few decades, researchers have focused on the use of weightlifting-based training to enhance performance in nonweightlifters because of the biomechanical similarities (e.g., rapid forceful extension of the hips, knees, and ankles) associated with the second pull phase of the clean and snatch, the drive/thrust phase of the jerk and athletic tasks such as jumping and sprinting. The highest force, rate of force development, and power outputs have been reported during such movements, highlighting the potential for such tasks to enhance these key physical qualities in athletes. In addition, the ability to manipulate barbell load across the extensive range of weightlifting exercises and their derivatives permits the strength and conditioning coach the opportunity to emphasize the development of strength-speed and speed-strength, as required for the individual athlete. As such, the results of numerous longitudinal studies and subsequent meta-analyses demonstrate the inclusion of weightlifting exercises into strength and conditioning programs results in greater improvements in force-production characteristics and performance in athletic tasks than general resistance training or plyometric training alone. However, it is essential that such exercises are appropriately programmed adopting a sequential approach across training blocks (including exercise variation, loads, and volumes) to ensure the desired adaptations, whereas strength and conditioning coaches emphasize appropriate technique and skill development of athletes performing such exercises.

Neuromechanical Consequences of Eccentric Load Reduction During the Performance of Weighted Jump Squats

PURPOSE

To quantify the acute effects of a spectrum of eccentric load reductions on neuromechanical adjustments during the performance of weighted jump squats (WJSs).

METHODS

On separate days, 16 well-trained participants performed WJS trials with various eccentric load reductions (0% [body mass only], 25%, 50%, 75%, and 100% [standard WJS] of concentric load) with a mechanical braking unit, while concentric load was set at 30% of peak isometric squat force in all trials. A force platform and a motion-capture system were used to assess neuromuscular performance.

RESULTS

Peak power output was 6.2% (4.7%) higher when load was reduced by 50% versus 0% (55.4 [7.8] vs 51.9 [7.6] W/kg; P = .001). Compared with no braking (0.326 [0.059] m), jump height was ∼13% to 17% higher for all eccentric load reduction conditions (all P < .001). Vertical ground reaction forces were progressively lower for 25%, 50%, 75%, and 100% loading conditions (-22.1% [14.6%], -32.3% [10.8%], -42.0% [13.2%], and -46.1% [14.7%]; all P ≤ .001) in reference to body mass only.

CONCLUSION

Eccentric load reduction is advantageous compared with traditional isoinertial loading for improving both jump height and peak power output during the concentric portion of maximal-effort WJS. This practice also decreases mechanical constraints in the lower extremities, which may become beneficial for load-compromised individuals.

With Great Power Comes Great Responsibility: Common Errors in Meta-Analyses and Meta-Regressions in Strength & Conditioning Research

BACKGROUND AND OBJECTIVE

Meta-analysis and meta-regression are often highly cited and may influence practice. Unfortunately, statistical errors in meta-analyses are widespread and can lead to flawed conclusions. The purpose of this article was to review common statistical errors in meta-analyses and to document their frequency in highly cited meta-analyses from strength and conditioning research.

METHODS

We identified five errors in one highly cited meta-regression from strength and conditioning research: implausible outliers; overestimated effect sizes that arise from confusing standard deviation with standard error; failure to account for correlated observations; failure to account for within-study variance; and a focus on within-group rather than between-group results. We then quantified the frequency of these errors in 20 of the most highly cited meta-analyses in the field of strength and conditioning research from the past 20 years.

RESULTS

We found that 85% of the 20 most highly cited meta-analyses in strength and conditioning research contained statistical errors. Almost half (45%) contained at least one effect size that was mistakenly calculated using standard error rather than standard deviation. In several cases, this resulted in obviously wrong effect sizes, for example, effect sizes of 11 or 14 standard deviations. Additionally, 45% failed to account for correlated observations despite including numerous effect sizes from the same study and often from the same group within the same study.

CONCLUSIONS

Statistical errors in meta-analysis and meta-regression are common in strength and conditioning research. We highlight five errors that authors, editors, and readers should check for when preparing or critically reviewing meta-analyses.

The Use of Elastic Bands in Velocity-Based Training Allows Greater Acute External Training Stimulus and Lower Perceived Effort Compared to Weight Plates

The objective was to compare the mean propulsive velocity (MPV), maximum power (PMAX), heart rate, and rate of perceived exertion (RPE) during the parallel squat using elastic bands (EB) or weight plates (WP) to load the bar. The effect of relative strength on the dependent variables was analysed. Additionally, the potential of the RPE to predict external load parameters was assessed. Eighteen trained volunteers squatted at 40%, 55%, 70%, and 85% of their one-repetition maximum with EB and WP (a total of eight sets) in random order. Dependent variables were measured at the first and last repetition (i.e., 10% velocity loss). Two identical sessions were conducted to assess the reliability of measurements. Compared to WP, EB allowed a significantly greater number of repetitions, MPV, and PMAX, and significantly lower RPE. The RPE of the first repetition was a significant predictor of the external load of the set. The RPE showed good repeatability and was not influenced by the relative strength of athletes. In conclusion, compared to WP, the use of EB allows for greater external load with reduced internal load responses in a wide spectrum of load-based intensities. The potential implications of these novel findings are discussed in the manuscript.

Omnidirectional Triboelectric Nanogenerator for Wide-Speed-Range Wind Energy Harvesting

The environmentally friendly harvesting of wind energy is an effective technique for achieving carbon neutrality and a green economy. In this work, a core-shell triboelectric nanogenerator (CS-TENG) for harvesting wind energy is demonstrated and the device structure parameters are optimized. The core-shell structure enables the CS-TENG to respond sensitively to wind from any direction and generate electrical output on the basis of the vertical contact-separation mode. A single device can generate a maximum power density of 0.14 W/m3 and can power 124 light-emitting diodes. In addition, wind energy can be harvested even at a wind speed as low as 2.3 m/s by paralleling CS-TENGs of different sizes. Finally, a self-powered water quality testing system that uses the CS-TENG as its power supply is built. The CS-TENG exhibits the advantages of a simple structure, environmentally friendly materials, low cost, and simple fabrication process. These features are of considerable significance for the development of green energy harvesting devices.

Load-power relationship in older adults: The influence of maximal mean and peak power values and their associations with lower and upper-limb functional capacity

Identifying the relative loads (%1RM) that maximize power output (Pmax-load) in resistance exercises can help design interventions to optimize muscle power in older adults. Moreover, examining the maximal mean power (MPmax) and peak power (PPmax) values (Watts) would allow an understanding of their differences and associations with functionality markers in older adults. Therefore, this research aimed to 1) analyze the load-mean and peak power relationships in the leg press and chest press in older adults, 2) examine the differences between mean Pmax-load (MPmax-load) and peak Pmax-load (PPmax-load) within resistance exercises, 3) identify the differences between resistance exercises in MPmax-load and PPmax-load, and 4) explore the associations between MPmax and PPmax in the leg press and chest press with functional capacity indicators. Thirty-two older adults (79.3 ± 7.3 years) performed the following tests: medicine ball throw (MBT), five-repetition sit-to-stand (STS), 10-m walking (10 W), and a progressive loading test in the leg press and chest press. Quadratic regressions analyzed 1) the load-mean and peak power relationships and identified the MPmax-load, MPmax, PPmax-load, and PPmax in both exercises, 2) the associations between MPmax and PPmax in the chest press with MBT, and 3) the associations between MPmax and PPmax in the leg press with STSpower and 10Wvelocity. In the leg press, the MPmax-load was ∼66% 1RM, and the PPmax-load was ∼62% 1RM, both for women and men (p &gt; 0.05). In the chest press, the MPmax-load was ∼62% 1RM, and the PPmax-load was ∼56% 1RM, both for women and men (p &gt; 0.05). There were differences between MPmax-load and PPmax-load within exercises (p &lt; 0.01) and differences between exercises in MPmax-load and PPmax-load (p &lt; 0.01). The MPmax and PPmax in the chest press explained ∼48% and ∼52% of the MBT-1 kg and MBT-3 kg variance, respectively. In the leg press, the MPmax and PPmax explained ∼59% of STSpower variance; however, both variables could not explain the 10Wvelocity performance (r2 ∼ 0.02). This study shows that the Pmax-load is similar between sexes, is resistance exercise-specific, and varies within exercises depending on the mechanical power variable used in older adults. Furthermore, this research demonstrates the influence of the MBT as an upper-limb power marker in older adults.

Resistance Training Variables for Optimization of Muscle Hypertrophy: An Umbrella Review

This umbrella review aimed to analyze the different variables of resistance training and their effect on hypertrophy, and to provide practical recommendations for the prescription of resistance training programs to maximize hypertrophy responses. A systematic research was conducted through of PubMed/MEDLINE, SPORTDiscus and Web of Science following the preferred reporting items for systematic reviews and meta-analyses statement guidelines. A total of 52 meta-analyses were found, of which 14 met the inclusion criteria. These studies were published between 2009 and 2020 and comprised 178 primary studies corresponding to 4,784 participants. Following a methodological quality analysis, nine meta-analyses were categorized as high quality, presenting values of 81–88%. The remaining meta-analyses were rated as moderate quality, with values between 63–75%. Based on this umbrella review, we can state that at least 10 sets per week per muscle group is optimal, that eccentric contractions seem important, very slow repetitions (≥10 s) should be avoided, and that blood flow restriction might be beneficial for some individuals. In addition, other variables as, exercise order, time of the day and type of periodization appear not to directly influence the magnitude of muscle mass gains. These findings provide valuable information for the design and configuration of the resistance training program with the aim of optimizing muscle hypertrophy.

Effects of Individualized Versus Traditional Power Training on Strength, Power, Jump Performances, and Body Composition in Young Male Nordic Athletes

PURPOSE

This study aimed to examine the effects of individualized-load power training (IPT) versus traditional moderate-load power training (TPT) on strength, power, jump performance, and body composition in elite young Nordic athletes.

METHODS

In a randomized crossover design, 10 young male athletes (ski jumpers, Nordic combined athletes) age 17.5 (0.6) years (biological maturity status: +3.5 y postpeak height velocity) who competed on a national or international level performed 5 weeks of IPT (4 × 5 repetitions at 49%-72% 1-repetiton maximum [RM]) and TPT (5 × 5 repetitions at 50%-60% 1-RM) in addition to their regular training. Testing before, between, and after both training blocks comprised the assessment of muscle strength (loaded back squat 3-RM), power (maximal loaded back squat power), jump performance (eg, drop-jump height, reactive strength index), and body composition (eg, skeletal muscle mass).

RESULTS

Significant, large-size main effects for time were found for muscle strength (P < .01; g = 2.7), reactive strength index (P = .03; g = 1.6), and drop-jump height (P = .02; g = 1.9) irrespective of the training condition (IPT, TPT). No significant time-by-condition interactions were observed. For measures of body composition, no significant main effects of condition and time or time-by-condition interactions were found.

CONCLUSIONS

Our findings demonstrate that short-term IPT and TPT at moderate loads in addition to regular training were equally effective in improving measures of muscle strength (loaded back squat 3-RM) and vertical-jump performance (reactive strength index, drop jump, and height) in young Nordic athletes.

Effects of Inertial Load on Sagittal Plane Kinematics of the Lower Extremity During Flywheel-Based Squats

ABSTRACT

Worcester, KS, Baker, PA, and Bollinger, LM. Effects of inertial load on sagittal plane kinematics of the lower extremity during flywheel-based squats. J Strength Cond Res 36(1): 63-69, 2022-Increasing load increases flexion of lower extremity joints during weighted squats; however, the effects of inertial load on lower extremity kinematics during flywheel-based resistance training (FRT) squats remain unclear. The purpose of this study was to evaluate sagittal plane kinematics of lower extremity joints during FRT squats at various inertial loads. Nine recreationally resistance-trained subjects (3M, 6F) completed a bout of FRT squats with inertial loads of 0.050, 0.075, and 0.100 kg·m2. Two-dimensional sagittal plane kinematics were monitored with retroreflective markers at a rate of 60 Hz. Joint angles and angular velocities of the knee, trunk + hip, trunk inclination, and ankle were quantified throughout concentric and eccentric actions. Effects of inertial load were determined by repeated-measures analysis of variance with α = 0.05. Average power and average vertical velocity decreased with increasing inertial load, whereas average force increased. Minimal and maximal sagittal plane joint angles of the knee, trunk + hip, trunk inclination, and ankle were not significantly different among inertial loads. However, peak joint angular velocities of the knee and trunk + hip tended to decrease with increasing inertial load. Conversely trunk inclination and ankle dorsiflexion velocities were not significantly different among inertial loads. Increasing inertial load from 0.050 to 0.100 kg·m2 significantly reduces average power during FRT squats primarily by decreasing movement velocity, which seems to be specific to the knee and hip joints. It is possible that lower concentric energy input at high inertial loads prevents increased joint flexion during FRT squats.

The Optimum Power Load: A Simple and Powerful Tool for Testing and Training

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.

Electromyography, Stiffness and Kinematics of Resisted Sprint Training in the Specialized SKILLRUN® Treadmill Using Different Load Conditions in Rugby Players

This study’s aim was to analyze muscle activation and kinematics of sled-pushing and resisted-parachute sprinting with three load conditions on an instrumentalized SKILLRUN^® treadmill. Nine male amateur rugby union players (21.3 ± 4.3 years, 75.8 ± 10.2 kg, 176.6 ± 8.8 cm) performed a sled-push session consisting of three 15-m repetitions at 20%, 55% and 90% body mas and another resisted-parachute session using three different parachute sizes (XS, XL and 3XL). Sprinting kinematics and muscle activity of three lower-limb muscles (biceps femoris (BF), vastus lateralis (VL) and gastrocnemius medialis (GM)) were measured. A repeated-measures analysis of variance (RM-ANOVA) showed that higher loads during the sled-push increased (VL) (p ≤ 0.001) and (GM) (p ≤ 0.001) but not (BF) (p = 0.278) activity. Furthermore, it caused significant changes in sprinting kinematics, stiffness and joint angles. Resisted-parachute sprinting did not change kinematics or muscle activation, despite producing a significant overload (i.e., speed loss). In conclusion, increased sled-push loading caused disruptions in sprinting technique and altered lower-limb muscle activation patterns as opposed to the resisted-parachute. These findings might help practitioners determine the more adequate resisted sprint exercise and load according to the training objective (e.g., power production or speed performance).

Impact of Spotter Sex on One Repetition Maximum Bench Press Performance

ABSTRACT

Nickerson, BS, Salinas, G, Garza, JM, Cho, S, and Snarr, RL. Impact of spotter sex on one repetition maximum bench press performance. J Strength Cond Res 35(9): 2397-2400, 2021-Resistance exercise is popular because of favorable health outcomes associated with increased muscular fitness. For these reasons, 1 repetition maximum (1RM), mean velocity (MV), and peak power (PP) are of interest during the bench press. However, research has yet to evaluate whether spotter sex impacts bench press performance. Therefore, the purpose of this study was to determine the impact of spotter sex on bench press performance during a 1RM testing protocol. Twenty resistance-trained individuals (10 men and 10 women) visited the laboratory on 2 separate occasions. Estimated 1RM was self-reported by subjects before the 1RM protocol. During their visits, subjects had their 1RM (kg), MV (m·s-1), and PP (W) determined on a bench press 1RM protocol while using a male or female spotter. Deception was used by telling subjects the intent of the study was to determine the reliability of a linear position transducer for measuring MV and PP during the 1RM trials. The main findings revealed that measured 1RM values for male weight lifters were significantly higher than estimated 1RM values when using both a male (p = 0.01) and female spotter (p < 0.01). In addition, results revealed MV and PP were significantly higher for the 1RM trials when male weight lifters had a male spotter (both p < 0.01). Alternatively, there were no significant differences in estimated vs. measured 1RM values for women as well as no effect of spotter sex on bench press strength (all p > 0.05). Practitioners should note that sex of a spotter does not seem to impact measured 1RM. However, notable influences may be observed within MV and PP.

Optimal Loading for Force Production in the Straight Bar Deadlift: Force-Time Characteristics in Strength-Trained Adults

ABSTRACT

Lawson, C, Mundy, P, Lyons, M, and Duncan, MJ. Optimal loading for force production in the straight bar deadlift: Force-time characteristics in strength-trained adults. J Strength Cond Res 35(6): 1636-1641, 2021-This study sought to identify whether there is an optimum load in relation to peak force development and rate of force development (RFD) in the straight bar deadlift and to examine whether baseline strength levels influence this optimum load. Twelve strength-trained men (mean age ± SD; 25.1 ± 5.4 years) performed 3 deadlift repetitions at loads of 10% intervals of 20-90% of their predetermined individual 1 repetition maximum (1RM). Peak vertical force (PFz) and RFD were determined from each repetition. The repetition at each percentage of 1RM that produced the greatest PFz was used for analysis. All data were collected on an AMTI force platform. Repeated-measures analysis of variance indicated significant differences in PFz across loads of 20-90% 1RM (p = 0.001) with a linear increase in PFz with increasing % of 1RM. The highest PFz occurred at 90% of 1RM. For RFD, there was a significant main effect for load (p = 0.018) where instantaneous RFD was significantly higher at 80 and 90% 1RM compared with 20% 1RM. When analyses were re-run using baseline strength as a covariate, the results did not change, indicating that baseline strength did not influence the PFz or RFD output. These results suggest that there is no significant difference in RFD between adjacent loads, but that peak force production was greatest at 90% 1RM in the straight bar deadlift.

Barbell Hip-Thrust Exercise: Test-Retest Reliability and Correlation With Isokinetic Performance

ABSTRACT

Dello Iacono, A, Padulo, J, Bešlija, T, and Halperin, I. Barbell hip-thrust exercise: Test-retest reliability and correlation with isokinetic performance. J Strength Cond Res 35(3): 659-667, 2021-The barbell hip-thrust (BHT) exercise is growing in popularity as evident by the large increase in research outputs investigating its utility as a training intervention and a testing tool. The aim of this study was to examine the test-retest reliability of the BHT and its correlation with isokinetic performance. Test-retest reliability was established by correlating the peak force and power outcomes measured with the BHT force-velocity profile test of 20 handball athletes on 2 separate days. The peak force and power measured with the BHT force-velocity profile test of 49 handball athletes were correlated with peak concentric force of the knee flexors and hip extensors measured with an isokinetic device at 2 different velocities (60-180°·s-1). The correlation between the isokinetic testing scores and the BHT force-velocity profile tests were moderate to large (Pearson r ranges: 0.45-0.86, all p values <0.001). Test-retest reliability of the BHT force-velocity profile was very high as shown with intraclass correlations of 0.94 and 0.99 for peak force and 0.97 and 0.99 for peak power measures. The BHT force-velocity profile can serve as a tentative substitute in cases that athletes do not have access to an isokinetic device, given the moderate to large correlations between them. Moreover, the BHT force-velocity profile was shown to be very reliable, thus providing coaches and scientists a range of day-to-day performance variability in this exercise.

Physical and Physiological Predictors of FRAN CrossFit® WOD Athlete's Performance

CrossFit^® training is one of the fastest-growing fitness activities in the world due to its varied functional movement and competition experience. The performance is present in almost every workout of the day (WOD); however, there is a lack of knowledge in the science that did not allow us to fully understand the performance determinants of CrossFit WOD’s like we do for other individual or team sports. The purpose of this study was to analyze the physical and physiological variables of recreational trained CrossFit athletes during one of the most famous WOD, FRAN, and to identify which variables best determine performance. Methods: Fifteen CrossFit practitioners performed, alone on separate days, 1RM and a maximum of repetitions of pull-ups test, 1RM and a maximum of repetitions of thrusters with 95 lb/43.2 kg, FRAN CrossFit WOD, and 2K Row test. Results: Blood lactate concentrate, HR_max, HR_av, and RPE achieved higher values for 2K Row and maximum repetitions of thrusters. Maximum repetition of thrusters and pull-ups, 1RM of thrusters, and 2K Row resulted in moderate to strong correlation with FRAN performance (r = −0.78; r = −0.58; r = −0.67; r = 0.63, respectively). Conclusions and practical applications: FRAN performance was strongly related to maximal and endurance strength training of thrusters, which should be prioritized.

The Implementation of Velocity-Based Training Paradigm for Team Sports: Framework, Technologies, Practical Recommendations and Challenges

While velocity-based training is currently a very popular paradigm to designing and monitoring resistance training programs, its implementation remains a challenge in team sports, where there are still some confusion and misinterpretations of its applications. In addition, in contexts with large squads, it is paramount to understand how to best use movement velocity in different exercises in a useful and time-efficient way. This manuscript aims to provide clarifications on the velocity-based training paradigm, movement velocity tracking technologies, assessment procedures and practical recommendations for its application during resistance training sessions, with the purpose of increasing performance, managing fatigue and preventing injuries. Guidelines to combine velocity metrics with subjective scales to prescribe training loads are presented, as well as methods to estimate 1-Repetition Maximum (1RM) on a daily basis using individual load–velocity profiles. Additionally, monitoring strategies to detect and evaluate changes in performance over time are discussed. Finally, limitations regarding the use of velocity of execution tracking devices and metrics such as “muscle power” are commented upon.

Self-Selected Resistance Exercise Load: Implications for Research and Prescription

ABSTRACT

Barbosa-Netto, S, d'Acelino-e-Porto, OS, and Almeida, MB. Self-selected resistance exercise load: implications for research and prescription. J Strength Cond Res 35(2S): S166-S172, 2021-Resistance training has been widely used for maintaining or improving the quality of life and sports performance. It is not clear, however, whether the load commonly used in these exercises is equivalent to the number of repetitions determined for execution, that is, the level of effort applied to the self-selected load. Ergo, the aim of this study was to identify the number of maximum repetitions that strength training practitioners can perform with the load commonly used (self-selected) to perform 10 repetitions in their training routines. The sample consisted of 160 healthy trained men (25.7 ± 4.5 years, 81.2 ± 10.4 kg, 177.9 ± 6.2 cm). Subjects answered the question "What weight do you usually lift for 10 repetitions on free-weight bench press exercise?" The answer was considered the self-selected 10 repetitions load (S10RL). After a brief warm-up, each individual was instructed to perform as many repetitions as possible at S10RL (repetition maximum [RMS10RL]) at a single bout of free-weight bench press. The RMS10RL was analyzed with the single sample t test, adopting the reference value of 10 repetitions. Individuals performed 16 ± 5RMS10RL (median = 15), which represent a statistical difference for the 10-repetition reference value (p < 0.001). The most prevalent RMS10RL range was from 13 to 15 repetitions (31%), and only 22% performed between 10 and 12 repetitions. It was concluded that most individuals can perform a number of repetitions well above the 10 repetitions predicted for the selected load. Therefore, the training routines are not compatible with maximum effort.

Post-activation Performance Enhancement in the Bench Press Throw: A Systematic Review and Meta-Analysis

Background: Mechanical power output is recognized as a critical characteristic of an athlete with regard to superior performance during a competition. It seems fully justified that ballistic exercises, in which the external load is projected into a flight phase, as in the bench press throw (BPT), are the most commonly prescribed exercises for the development of power output. In addition, the muscular phenomenon known as post-activation performance enhancement (PAPE), which is an acute improvement in strength and power performance as a result of recent voluntary contractile history, has become the focus of many strength and conditioning training programs. Although the PAPE phenomenon is widely used in the upper-body training regimens, there are still several issues regarding training variables that facilitate the greatest increase in power output and need to be resolved. Objective: The purposes of this meta-analysis were to determine the effect of performing a conditioning activity (CA) on subsequent BPT performances and the influence of different types of CA, intra-complex rest intervals, and intensities during the CA on the upper-body PAPE effect in resistance-trained men. Methods: A search of electronic databases (MEDLINE, PubMed, and SPORTDiscus) was conducted to identify all studies that investigated the PAPE in the BPT up to August 2020. Eleven articles, which met the inclusion criteria, were consequently included for quality assessment and data extraction. All studies included 174 resistance-trained men [age: 25.2 ± 2.1 years; weight: 88.4 ± 7.5 kg; height: 1.82 ± 0.03 m; bench press (BP) relative strength: 1.31 ± 0.14 kg ± kg^-1] as participants. Meta-analyses of standardized mean effect size (ES) between pre-CA mean and post-CA mean from individual studies were conducted using the random-effects model. Results: The effect of PAPE in the BPT was small (ES = 0.33; p < 0.01). The BP exercise as a CA at an intensity of 60-84% one-repetition maximum (1RM) (ES = 0.43) induced slightly greater PAPE effect than a ballistic-plyometric (ES = 0.29) and a BP exercise at ≥85% 1RM and at >100% 1RM as well as a concentric-only BP (ES = 0.23 and 0.22; ES = 0.11, respectively). A single set (ES = 0.37) of the CA resulted in a slightly greater effect than a multiple set (ES = 0.29). Moderate rest intervals induced a slightly greater PAPE effect for intensity below 85% 1RM (5-7 min, ES = 0.48) than shorter (0.15-4 min, ES = 0.4) and longer (≥8 min, ES = 0.36) intra-complex rest intervals. Considering an intensity above 85% 1RM during the CA, a moderate rest interval resulted in a similar PAPE effect (5-7 min, ES = 0.3) compared with longer (8 min, ES = 0.29) intra-complex rest interval, whereas shorter rest intervals resulted in a negative effect on BPT performance (0.15-4 min, ES = -0.13). Conclusion: The presented meta-analysis shows that performing a CA induces a small PAPE effect for the BPT performance in resistance-trained men. Individuals seeking to improve their BPT performance should consider preceding them with a single set of the BP exercise at moderate intensity (60-84% 1RM), performed 5-7 min before the explosive activity.

A Comparison of Kinetic and Kinematic Variables During the Midthigh Pull and Countermovement Shrug, Across Loads

Meechan, D, Suchomel, TJ, McMahon, JJ, and Comfort, P. A comparison of kinetic and kinematic variables during the midthigh pull and countermovement shrug, across loads. J Strength Cond Res 34(7): 1830-1841, 2020-This study compared kinetic and kinematic variables during the midthigh pull (MTP) and countermovement shrug (CMS). Eighteen men (age: 29.43 ± 3.95 years, height: 1.77 ± 0.08 m, body mass: 84.65 ± 18.79 kg, and 1 repetition maximum [1RM] power clean: 1.02 ± 0.18 kg·kg) performed the MTP and CMS at intensities of 40, 60, 80, 100, 120, and 140% 1RM, in a progressive manner. Peak force (PF), mean force (MF), peak velocity, peak barbell velocity (BV), peak power, (PP), mean power (MP), and net impulse were calculated from force-time data during the propulsion phase. During the CMS, PF and MF were maximized at 140% 1RM and was significantly greater than the MTP at all loads (p ≤ 0.001, Hedges g = 0.66-0.90); p < 0.001, g = 0.74-0.99, respectively). Peak velocity and BV were significantly and meaningfully greater during the CMS compared with the MTP across all loads (p < 0.001, g = 1.83-2.85; p < 0.001, g = 1.73-2.30, respectively). Similarly, there was a significantly and meaningfully greater PP and MP during the CMS, across all loads, compared with the MTP (p < 0.001, g = 1.45-2.22; p < 0.001, g = 1.52-1.92). Impulse during the CMS was also significantly greater across all loads (p < 0.001, g = 1.20-1.66) compared with the MTP. Results of this study demonstrate that the CMS may be a more advantageous exercise to perform to enhance force-time characteristics when compared with the MTP, due to the greater kinetics and kinematic values observed.

A Comparison of Kinetic and Kinematic Variables During the Pull From the Knee and Hang Pull, Across Loads

Meechan, D, McMahon, JJ, Suchomel, TJ, and Comfort, P. A comparison of kinetic and kinematic variables during the pull from the knee and hang pull, across loads. J Strength Cond Res 34(7): 1819-1829, 2020-Kinetic and kinematic variables during the pull from the knee (PFK) and hang pull (HP) were compared in this study. Eighteen men (age = 29.43 ± 3.95 years; height 1.77 ± 0.08 m; body mass 84.65 ± 18.79 kg) performed the PFK and HP with 40, 60, 80, 100, 120, and 140% of 1-repetition maximum (1RM) power clean, in a progressive manner. Peak force (PF), mean force (MF), peak system velocity (PSV), mean system velocity (MSV), peak power (PP), mean power (MP), and net impulse were calculated from force-time data during the propulsion phase. During the HP, small-to-moderate yet significantly greater MF was observed compared with the PFK, across all loads (p ≤ 0.001; Hedges g = 0.47-0.73). Hang pull PSV was moderately and significantly greater at 100-140% 1RM (p = 0.001; g = 0.64-0.94), whereas MSV was significantly greater and of a large-to-very large magnitude compared with PFK, across all loads (p < 0.001; g = 1.36-2.18). Hang pull exhibited small to moderate and significantly greater (p ≤ 0.011, g = 0.44-0.78) PP at 100-140%, with moderately and significantly greater (p ≤ 0.001, g = 0.64-0.98) MP across all loads, compared with the PFK. Hang pull resulted in a small to moderate and significantly greater net impulse between 100 and 140% 1RM (p = 0.001, g = 0.36-0.66), compared with PFK. The results of this study demonstrate that compared with the PFK, the HP may be a more beneficial exercise to enhance force-time characteristics, especially at loads of ≥1RM.

Effectiveness of Accentuated Eccentric Loading: Contingent on Concentric Load

PURPOSE

To identify acute effects of a single accentuated eccentric loading (AEL) repetition on subsequent back-squat kinetics and kinematics with different concentric loads.

METHODS

Resistance-trained men (N = 21) participated in a counterbalanced crossover design and completed 4 protocols (sets × repetitions at eccentric/concentric) as follows: AEL65, 3 × 5 at 120%/65% 1-repetition maximum (1-RM); AEL80, 3 × 3 at 120%/80% 1-RM; TRA65, 3 × 5 at 65%/65% 1-RM; and TRA80, 3 × 3 at 80%/80% 1-RM. During AEL, weight releasers disengaged from the barbell after the eccentric phase of the first repetition and remained off for the remaining repetitions. All repetitions were performed on a force plate with linear position transducers attached to the barbell, from which eccentric and concentric peak and mean velocity, force, and power were derived.

RESULTS

Eccentric peak velocity (-0.076 [0.124] m·s-1; P = .01), concentric peak force (187.8 [284.4] N; P = .01), eccentric mean power (-145.2 [62.0] W; P = .03), and eccentric peak power (-328.6 [93.7] W; P < .01) during AEL65 were significantly greater than TRA65. When collapsed across repetitions, AEL65 resulted in slower eccentric velocity and power during repetition 1 but faster eccentric and concentric velocity and power in subsequent repetitions (P ≤ .04). When comparing AEL80 with TRA80, concentric peak force (133.8 [56.9] N; P = .03), eccentric mean power (-83.57 [38.0] W; P = .04), and eccentric peak power (-242.84 [67.3] W; P < .01) were enhanced.

CONCLUSIONS

Including a single supramaximal eccentric phase of 120% 1-RM increased subsequent velocity and power with concentric loads of 65% 1-RM, but not 80% 1-RM. Therefore, AEL is sensitive to the magnitude of concentric loads, which requires a large relative difference to the eccentric load, and weight releasers may not need to be reloaded to induce performance enhancement.

Load-Velocity Relationship in Variations of the Half-Squat Exercise: Influence of Execution Technique

Pérez-Castilla, A, García-Ramos, A, Padial, P, Morales-Artacho, AJ, and Feriche, B. Load-velocity relationship in variations of the half-squat exercise: influence of execution technique. J Strength Cond Res 34(4): 1024-1031, 2020-Previous studies have revealed that the velocity of the bar can be used to determine the intensity of different resistance training exercises. However, the load-velocity relationship seems to be exercise dependent. This study aimed to compare the load-velocity relationship obtained from 2 variations of the half-squat exercise (traditional vs. ballistic) using 2 execution techniques (eccentric-concentric vs. concentric-only). Twenty men performed a submaximal progressive loading test in 4 half-squat exercises: eccentric-concentric traditional-squat, concentric-only traditional-squat, countermovement jump (i.e., ballistic squat using the eccentric-concentric technique), and squat jump (i.e., ballistic squat using the concentric-only technique). Individual linear regressions were used to estimate the 1 repetition maximum (1RM) for each half-squat exercise. Thereafter, another linear regression was applied to establish the relationship between the relative load (%RM) and mean propulsive velocity (MPV). For all exercises, a strong relationship was observed between %RM and MPV: eccentric-concentric traditional-squat (R = 0.949), concentric-only traditional-squat (R = 0.920), countermovement jump (R = 0.957), and squat jump (R = 0.879). The velocities associated with each %RM were higher for the ballistic variation and the eccentric-concentric technique than for the traditional variation and concentric-only technique, respectively. Differences in velocity among the half-squat exercises decreased with the increment in the relative load. These results demonstrate that the MPV can be used to predict exercise intensity in the 4 half-squat exercises. However, independent regressions are required for each half-squat exercise because the load-velocity relationship proved to be task specific.

Velocity Performance Feedback During Ballistic Training: Which Is the Optimal Frequency of Feedback Administration?

This study explored the impact of different frequencies of knowledge of results (KR) on velocity performance during ballistic training. Fifteen males completed four identical sessions (three sets of six repetitions at 30% one-repetition maximum during the countermovement jump and bench press throw) with the only difference of the KR condition provided: no feedback, velocity feedback after the first half of repetitions of each set (HalfKR), velocity feedback immediately after each repetition (ImKR), and feedback of the average velocity of each set (AvgKR). When compared with the control condition, the ImKR reported the highest velocity performance (1.9-5.3%), followed by the HalfKR (1.3-3.6%) and AvgKR (0.7-4.3%). These results support the verbal provision of velocity performance feedback after every repetition to induce acute improvements in velocity performance.

Perception of changes in bar velocity in resistance training: Accuracy levels within and between exercises

Velocity-based training is a method used to monitor resistance-training programs based on repetition velocities measured with tracking devices. Since velocity measuring devices can be expensive and impractical, trainee's perception of changes in velocity (PCV) may be used as a possible substitute. Here, 20 resistance-trained males first completed 1 Repetition Maximum (RM) tests in the bench-press and squat. Then, in three counterbalanced sessions, participants completed four sets of eight repetitions in both exercises using 60%1RM (two-sessions) or 70%1RM. Starting from the second repetition, participants reported their PCV of each repetition as a percentage of the first repetition. Accuracy of PCV was calculated as the difference between PCV and actual changes in velocity measured with a linear-encoder. Three key findings emerged. First, the absolute error in the bench-press and squat was ≈5.8 percentage-points in the second repetition, and increased to 13.2 and 16.7 percentage-points, respectively, by the eighth repetition. Second, participants reduced the absolute error in the second 60%1RM session compared to the first by ≈1.7 in both exercises (p ≤ 0.007). Third, participants were 4.2 times more likely to underestimate changes velocity in the squat compared to the bench-press. The gradual increments in the absolute error suggest that PCV may be better suited for sets of fewer repetitions (e.g., 4-5) and wider velocity-loss threshold ranges (e.g., 5-10%). The reduced absolute error in the second 60%1RM session suggests that PCV accuracy can be improved with practice. The systematic underestimation error in the squat suggests that a correction factor may increase PCV accuracy in this exercise.

When Jump Height is not a Good Indicator of Lower Limb Maximal Power Output: Theoretical Demonstration, Experimental Evidence and Practical Solutions

Lower limb external maximal power output capacity is a key physical component of performance in many sports. During squat jump and countermovement jump tests, athletes produce high amounts of mechanical work over a short duration to displace their body mass (i.e. the dimension of mechanical power). Thus, jump height has been frequently used by the sports science and medicine communities as an indicator of the power output produced during the jump and by extension, of maximal power output capacity. However, in this article, we contend that squat jump and countermovement jump height are not systematically good indicators of power output produced during the jump and maximal power output capacity. To support our opinion, we first detail why, theoretically, jump height and maximal power output capacity are not fully related. Specifically, we demonstrate that individual body mass, push-off distance, optimal loading and the force-velocity profile confound the jump height-power relationship. We also discuss the relationship between squat jump or countermovement jump height and maximal power output capacity measured with a force plate based on data reported in the literature, which added to our own experimental evidence. Finally, we discuss the limitations of existing practical solutions (regression-based estimation equations and allometric scaling), and advocate using a valid, reliable and simple field-based procedure to compute individual power output produced during the jump and maximal power output capacity directly from jump height, body mass and push-off distance. The latter may allow researchers and practitioners to reduce bias in their assessment of lower limb mechanical power output by using jump height as an input with a simple yet accurate computation method, and not as the first/only variable of interest.

Mechanical power production assessment during weightlifting exercises. A systematic review

The assessment of the mechanical power production is of great importance for researchers and practitioners. The purpose of this review was to compare the differences in ground reaction force (GRF), kinematic, and combined (bar velocity x GRF) methods to assess mechanical power production during weightlifting exercises. A search of electronic databases was conducted to identify all publications up to 31 May 2019. The peak power output (PPO) was selected as the key variable. The exercises included in this review were clean variations, which includes the hang power clean (HPC), power clean (PC) and clean. A total of 26 articles met the inclusion criteria with 53.9% using the GRF, 38.5% combined, and 30.8% the kinematic method. Articles were evaluated and descriptively analysed to enable comparison between methods. The three methods have inherent methodological differences in the data analysis and measurement systems, which suggests that these methods should not be used interchangeably to assess PPO in Watts during weightlifting exercises. In addition, this review provides evidence and rationale for the use of the GRF to assess power production applied to the system mass while the kinematic method may be more appropriate when looking to assess only the power applied to the barbell.

The Effects of Cluster-Set and Traditional-Set Postactivation Potentiation Protocols on Vertical Jump Performance

PURPOSE

To compare the effects of 2 postactivation potentiation (PAP) protocols using traditional-set or cluster-set configurations on countermovement jump performance.

METHODS

Twenty-six male basketball players completed 3 testing sessions separated by 72 hours. On the first session, subjects performed barbell jump squats with progressively heavier loads to determine their individual optimum power load. On the second and third sessions, subjects completed 2 PAP protocols in a randomized order: 3 sets of 6 repetitions of jump squats using optimum power load performed with either a traditional-set (no interrepetition rest) or a cluster-set (20-s rest every 2 repetitions) configuration. After a warm-up, countermovement jump height was measured using a force platform before, 30 seconds, 4 minutes, and 8 minutes after completing the PAP protocols. The following kinetic variables were also analyzed and compared: relative impulse, ground reaction force, eccentric displacement, and vertical leg-spring stiffness.

RESULTS

Across both conditions, subjects jumped lower at post 30 seconds by 1.21 cm, and higher in post 4 minutes by 2.21 cm, and in post 8 minutes by 2.60 cm compared with baseline. However, subjects jumped higher in the cluster condition by 0.71 cm (95% confidence interval, 0.37 to 1.05 cm) in post 30 seconds, 1.33 cm (95% confidence interval, 1.02 to 1.65 cm) in post 4 minute, and 1.64 cm (95% confidence interval, 1.41 to 1.88 cm) in post 8 minutes. The superior countermovement jump performance was associated with enhanced kinetic data.

CONCLUSIONS

Both protocols induced PAP responses in vertical jump performance using jump squats at optimum power load. However, the cluster-set configuration led to superior performance across all time points, likely due to reduced muscular fatigue.

Validity and Reliability of a Wearable Inertial Sensor to Measure Velocity and Power in the Back Squat and Bench Press

Orange, ST, Metcalfe, JW, Liefeith, A, Marshall, P, Madden, LA, Fewster, CR, and Vince, RV. Validity and reliability of a wearable inertial sensor to measure velocity and power in the back squat and bench press. J Strength Cond Res 33(9): 2398-2408, 2019-This study examined the validity and reliability of a wearable inertial sensor to measure velocity and power in the free-weight back squat and bench press. Twenty-nine youth rugby league players (18 ± 1 years) completed 2 test-retest sessions for the back squat followed by 2 test-retest sessions for the bench press. Repetitions were performed at 20, 40, 60, 80, and 90% of 1 repetition maximum (1RM) with mean velocity, peak velocity, mean power (MP), and peak power (PP) simultaneously measured using an inertial sensor (PUSH) and a linear position transducer (GymAware PowerTool). The PUSH demonstrated good validity (Pearson's product-moment correlation coefficient [r]) and reliability (intraclass correlation coefficient [ICC]) only for measurements of MP (r = 0.91; ICC = 0.83) and PP (r = 0.90; ICC = 0.80) at 20% of 1RM in the back squat. However, it may be more appropriate for athletes to jump off the ground with this load to optimize power output. Further research should therefore evaluate the usability of inertial sensors in the jump squat exercise. In the bench press, good validity and reliability were evident only for the measurement of MP at 40% of 1RM (r = 0.89; ICC = 0.83). The PUSH was unable to provide a valid and reliable estimate of any other criterion variable in either exercise. Practitioners must be cognizant of the measurement error when using inertial sensor technology to quantify velocity and power during resistance training, particularly with loads other than 20% of 1RM in the back squat and 40% of 1RM in the bench press.

The Effect of Load Placement on the Power Production Characteristics of Three Lower Extremity Jumping Exercises

The purpose of this study was to compare the power production characteristics of the jump squat (JS), hexagonal barbell jump (HEXJ), and jump shrug (JShrug) across a spectrum of relative loads. Fifteen resistance-trained men completed three testing sessions where they performed repetitions of either the JS, HEXJ, or JShrug at body mass (BM) or with 20, 40, 60, 80, or 100% of their BM. Relative peak power (PPRel), relative force at PP (FPP), and velocity at PP (VPP) were compared between exercises and loads. In addition, power-time curves at each load were compared between exercises. Load-averaged HEXJ and JShrug PPRel were statistically greater than the JS (both p < 0.01), while no difference existed between the HEXJ and the JShrug (p = 1.000). Load-averaged JShrug FPP was statistically greater than both the JS and the HEXJ (both p < 0.001), while no statistical difference existed between the JS and the HEXJ (p = 0.111). Load-averaged JS and HEXJ VPP were statistically greater than the JShrug (both p < 0.01). In addition, HEXJ VPP was statistically greater than the JS (p = 0.009). PPRel was maximized at 40, 40, and 20% BM for the JS, HEXJ, and JShrug, respectively. The JShrug possessed statistically different power-time characteristics compared to both the JS and the HEXJ during the countermovement and propulsion phases. The HEXJ and the JShrug appear to be superior exercises for PPRel compared to the JS. The HEXJ may be considered a more velocity-dominant exercise, while the JShrug may be a more force-dominant one.

Maximal power production as a function of sex and training status

Maximal muscular power is achieved at lower percentages of maximal strength (1RM); however, this notion has not been elucidated based on sex or training status. Therefore, the purpose of this investigation was to examine the influence of sex and training status on maximal power production. Sixty men and women (resistance trained or untrained) completed 1RM testing for the two-leg press (2LP) and bench press (BP). Participants then returned to perform single repetitions at 20, 30, 40, 50, 60, 70 and 80% of their 1RM to determine muscular power. Factorial analyses determined significant interactions (training status by sex by intensity) for the BP (F=35.6, p<0.001) and 2LP (F=8.2, p<0.001). Subsequent analyses indicated that during the BP trained men produce maximal power between 30-40% 1RM compared to untrained men at 60-70% 1RM. Trained women produced maximal power at 50% 1RM compared to untrained women at 60-70% 1RM. During the 2LP, trained men produced maximal power at 40% 1RM compared to untrained men at 60% 1RM. Trained women produced maximal power at 50% 1RM compared to 60-70% 1RM in untrained women. These data suggest that resistance trained individuals and men display maximal power at a lower relative intensity than untrained individuals and women.

Force-Time Differences between Ballistic and Non-Ballistic Half-Squats

The purpose of this study was to examine the force-time differences between concentric-only half-squats (COHS) performed with ballistic (BAL) or non-ballistic (NBAL) intent across a range of loads. Eighteen resistance-trained men performed either BAL or NBAL COHS at 30%, 50%, 70%, and 90% of their one repetition maximum (1RM) COHS. Relative peak force (PF) and relative impulse from 0–50 ms (Imp50), 0–90 ms (Imp90), 0–200 ms (Imp200), and 0–250 ms (Imp250) were compared using a series of 2 × 4 (intent × load) repeated measures ANOVAs with Bonferroni post hoc tests. Cohen’s d effect sizes were calculated to provide measures of practical significance between the BAL and NBAL COHS and each load. BAL COHS produced statistically greater PF than NBAL COHS at 30% (d = 3.37), 50% (d = 2.88), 70% (d = 2.29), and 90% 1RM (d = 1.19) (all p < 0.001). Statistically significant main effect differences were found between load-averaged BAL and NBAL COHS for Imp90 (p = 0.006, d = 0.25), Imp200 (p = 0.001, d = 0.36), and Imp250 (p < 0.001, d = 0.41), but not for Imp50 (p = 0.018, d = 0.21). Considering the greater PF and impulse observed during the BAL condition, performing COHS with BAL intent may provide a favorable training stimulus compared to COHS performed with NBAL intent.

A Novel Method to Determine Optimal Load in Elastic-Based Power Training

Buskard, AN, Oh, J, Eltoukhy, M, Brounstein, SR, and Signorile, JF. A novel method to determine optimal load in elastic-based power training. J Strength Cond Res 32(9): 2401-2408, 2018-The benefits of muscular power on sport performance and older adults' abilities to live independently and resist falls is well documented. Consequently, a substantial volume of research has focused on establishing the optimal loading patterns for improving muscular power using resistance exercise; however, to date, this research has only targeted optimal loading during training with free weights or selectorized exercise machines. Conversely, no approach has been developed to establish optimal loads for elastic modalities, such as tubes and bands, commonly used for sports rehabilitation, injury prevention, and training older adults. Therefore, the purpose of this study was to evaluate a new method for determining the optimal tubes to use in power training performed with elastic resistance. Thirty-eight recreationally active college students (age, 23.7 ± 4.5 years) were recruited to perform 3 single-arm bicep curls at a maximum intended velocity using 6 elastic tubes of varying resistance. Testing was performed in a 3-dimensional (3D) motion analysis laboratory using a specially constructed platform with an integrated strain gauge to which each tube was anchored. Force data from the strain gauge and velocity data from the 3D motion capture system were then used to compute power for each tube. An analysis based on individual's cable arm curl 1-repetition maximum (1RM) was then used to generate general guidelines for the most appropriate tube to use for arm curl power training based on upper arm 1RM. Our results demonstrate the feasibility of using this methodology for other exercises, thereby establishing optimal tube use for power training based on each exercise's 1RM.

Mechanical Demands of the Hang Power Clean and Jump Shrug: A Joint-Level Perspective

Kipp, K, Malloy, PJ, Smith, J, Giordanelli, MD, Kiely, MT, Geiser, CF, and Suchomel, TJ. Mechanical demands of the hang power clean and jump shrug: a joint-level perspective. J Strength Cond Res 32(2): 466-474, 2018-The purpose of this study was to investigate the joint- and load-dependent changes in the mechanical demands of the lower extremity joints during the hang power clean (HPC) and the jump shrug (JS). Fifteen male lacrosse players were recruited from a National Collegiate Athletic Association DI team, and completed 3 sets of the HPC and JS at 30, 50, and 70% of their HPC 1 repetition maximum (1RM HPC) in a counterbalanced and randomized order. Motion analysis and force plate technology were used to calculate the positive work, propulsive phase duration, and peak concentric power at the hip, knee, and ankle joints. Separate 3-way analysis of variances were used to determine the interaction and main effects of joint, load, and lift type on the 3 dependent variables. The results indicated that the mechanics during the HPC and JS exhibit joint-, load-, and lift-dependent behavior. When averaged across joints, the positive work during both lifts increased progressively with external load, but was greater during the JS at 30 and 50% of 1RM HPC than during the HPC. The JS was also characterized by greater hip and knee work when averaged across loads. The joint-averaged propulsive phase duration was lower at 30% than at 50 and 70% of 1RM HPC for both lifts. Furthermore, the load-averaged propulsive phase duration was greater for the hip than the knee and ankle joint. The joint-averaged peak concentric power was the greatest at 70% of 1RM for the HPC and at 30%-50% of 1RM for the JS. In addition, the joint-averaged peak concentric power of the JS was greater than that of the HPC. Furthermore, the load-averaged peak knee and ankle concentric joint powers were greater during the execution of the JS than the HPC. However, the load-averaged power of all joints differed only during the HPC, but was similar between the hip and knee joints for the JS. Collectively, these results indicate that compared with the HPC the JS is characterized by greater hip and knee positive joint work, and greater knee and ankle peak concentric joint power, especially if performed at 30 and 50% of 1RM HPC. This study provides important novel information about the mechanical demands of 2 commonly used exercises and should be considered in the design of resistance training programs that aim to improve the explosiveness of the lower extremity joints.

Methods of Power-Force-Velocity Profiling During Sprint Running: A Narrative Review

The ability of the human body to generate maximal power is linked to a host of performance outcomes and sporting success. Power-force-velocity relationships characterize limits of the neuromuscular system to produce power, and their measurement has been a common topic in research for the past century. Unfortunately, the narrative of the available literature is complex, with development occurring across a variety of methods and technology. This review focuses on the different equipment and methods used to determine mechanical characteristics of maximal exertion human sprinting. Stationary cycle ergometers have been the most common mode of assessment to date, followed by specialized treadmills used to profile the mechanical outputs of the limbs during sprint running. The most recent methods use complex multiple-force plate lengths in-ground to create a composite profile of over-ground sprint running kinetics across repeated sprints, and macroscopic inverse dynamic approaches to model mechanical variables during over-ground sprinting from simple time-distance measures during a single sprint. This review outlines these approaches chronologically, with particular emphasis on the computational theory developed and how this has shaped subsequent methodological approaches. Furthermore, training applications are presented, with emphasis on the theory underlying the assessment of optimal loading conditions for power production during resisted sprinting. Future implications for research, based on past and present methodological limitations, are also presented. It is our aim that this review will assist in the understanding of the convoluted literature surrounding mechanical sprint profiling, and consequently improve the implementation of such methods in future research and practice.