Countermovement Jump Peak Research Articles

The Effect Of Cluster-sets Resistance Priming Training On Delayed Potentiation Of Athletes

Cluster sets (CS) resistance training can induce greater post-activation potentiation (PAP) effects than traditional sets (TS) by reducing fatigue. The neuromuscular performance response demonstrated in delayed potentiation (DLP) effects is similar to that in PAP, they are all based on the relationship between potentiation and fatigue. However, it is not clear whether CS resistance training can induce greater DLP effects. OBJECTIVE The aim of the study was to compare the delayed potentiation (DLP) effects induced by cluster sets (CS) versus traditional sets (TS) resistance priming (RP) training. METHODS Sixteen male collegiate athletes were recruited for the study in a crossover design. All the subjects performed a CS (30s interval between reps, 4 minutes interval between sets) and a TS (no rest between reps, 4 minutes interval between sets) RP training sessions (3 sets of 3 repetitions of barbell back squat at 85%1RM) in random order separated by 72 hours. countermovement jump (CMJ),20-meters sprint, and T-test were evaluated at baseline and 6 hours after the RP training sessions. RESULTS 6 hours after the RP sessions, both the CS and TS significantly improved the CMJ height (CS: 50.44 ± 8.35 cm, ES = 0.48; TS: 48.35 ± 8.05 cm, ES = 0.23), CMJ take-off velocity (CS: 3.21 ± 0.28 m/s, ES = 0.56; TS: 3.16 ± 0.27 m/s, ES = 0.38), CMJ push-off impulse (CS: 237.3 ± 26.99Ns, ES = 0.38; TS: 233.8 ± 24.96Ns, ES = 0.26), 20-meters sprint (CS: 2.967 ± 0.139 s, ES = 0.85; TS: 3.007 ± 0.122 s, ES = 0.58) and T-test (CS:9.805 ± 0.535 s, ES = 0.99; TS: 9.921 ± 0.64 s, ES = 0.73) performance compared with baseline values. The CMJ peak power (64.42 ± 8.92 W/kg, ES = 0.3) were significant better following the CS compared with baseline values. The CMJ height (ES = 0.25), CMJ peak power (ES = 0.2), 20-meters sprint (ES = 0.31) were significant better following the CS compared with the TS training session. No inter-condition significant difference was observed in CMJ take-off velocity (ES = 0.18), CMJ push-off impulse (ES = 0.13), and T-test (ES = 0.2). CONCLUSIONS Compared with TS, CS RP training resulted in greater DLP effects after 6 hours, and significantly improving athletes’ lower limb speed performance and power output.

Relationships Between Lower Extremity Power and Fastball Spin Rate and Ball Velocity in Professional Baseball Pitchers.

Wong, R, Laudner, K, Amonette, W, Vazquez, J, Evans, D, and Meister, K. Relationships between lower extremity power and fastball spin rate and ball velocity in professional baseball pitchers. J Strength Cond Res 37(4): 823-828, 2023-Lower extremity power has been hypothesized to increase ball spin and velocity during pitching in baseball. Therefore, the purpose of this study was to determine the relationship between lower extremity power and fastball spin rate in professional baseball pitchers. A secondary purpose was to determine the relationship between lower extremity power and ball velocity. Fifty-three asymptomatic professional pitchers participated (24.5 ± 3.6 years; 189.9 ± 6.1 cm; 92.6 ± 10.3 kg). Each athlete performed 3 separate bilateral jump tests on force plates: countermovement jump (CMJ), squat jump (SJ), and drop jump (DJ). The average fastball spin rate and ball velocity for each pitcher was calculated using a 3-dimensional Doppler radar and video system over the course of a competitive season. Standard multiple regression analyses ( p ≤ 0.05) revealed significant relationship between ball spin and summation of variables for the CMJ (peak force, peak power, rate of power development, and jump height) ( R2 = 0.20, F = 3.1, p = 0.03). However, no individual variable was significantly associated ( p > 0.09). There was also a significant amount of variance in ball spin explained by summation of variables for the SJ (peak force, peak power, rate of power development, and jump height) ( R2 = 0.19, F = 2.8, p = 0.04); rate of power development was the only variable that significantly predicted ball spin within this model ( B = 0.27; 95% confidence interval [CI]: 0.003-0.75, p = 0.05). Ball spin was not associated with summation of DJ variables (peak power, rate of power development, jump height, reactive strength index, and total peak power in watts) ( R2 = 0.18, F = 2.0, p = 0.09). For ball velocity, there were no significant relationships for the summation of either the CMJ variables ( R2 = 0.10, p = 0.28) or the SJ variables ( R2 = 0.07, p = 0.44). However, there was a significant amount of variance in ball velocity explained by summation of variables for the DJ ( R2 = 0.30, F = 3.93, p = 0.005). The reactive strength index was the sole unique contribution to this model ( B = 1.18; 95% CI: -10.34 to 2.36, p = 0.002). These findings highlight the relevance of increased lower extremity power on increasing fastball spin rate and ball velocity.

Effects of Simultaneously Combined Whole-Body Electrostimulation and Plyometric Training on Vertical Jump Performance, 20 m Sprint-Time and Handgrip Strength

Abstract Introduction. The aim of the present study was to investigate the effects of a 6-week low intensity plyometric training (PT) + whole-body electrostimulation (WBES) combined program, compared with traditional PT, on vertical jump performance, 20 m sprint-time and handgrip strength. Material and methods. 10 male and 10 female Physical Education students were randomly allocated to a control (CON) or an experimental (EXP) group. Both groups performed a 6-week low intensity PT 3 days per week, and during the third day, PT was simultaneously combined with WBES in the EXP group. Countermovement jump (CMJ) height, CMJ peak power, 20 m sprint-time and handgrip strength were measured before (pre-test) and after (post-test) the training period. Repeated measures ANOVA was performed to identify differences after the training program. Effect sizes (ES) were assessed using Hedge’s g. Results. No significant differences between groups were observed at post-test. CMJ height and CMJ peak power significantly increased in both groups, with greater ES in the EXP group (p < 0.001, g = 0.68; p < 0.001, g = 0.70, respectively). 20 m sprint-time significantly improved in both groups, with greater ES in the CON group (p < 0.001, g = −1.68). Handgrip strength also increased in both groups, but ES were minimal. Conclusions. Both training methods demonstrated to be a good strategy to improve CMJ performance and 20 m sprint-time. The most effective training method for improving CMJ performance was PT + WBES combined program, and traditional PT obtained better results in 20 m sprint-time.

Strength and Biomechanical Risk Factors for Noncontact ACL Injury in Elite Female Footballers: A Prospective Study.

This study aimed to determine if a preseason field-based test battery was prospectively associated with noncontact anterior cruciate ligament (ACL) injury in elite female footballers. In total, 322 elite senior and junior female Australian Rules Football and soccer players had their isometric hip adductor and abductor strength, eccentric knee flexor strength, countermovement jump (CMJ) kinetics, and single-leg hop kinematics assessed during the 2019 preseason. Demographic and injury history details were also collected. Footballers were subsequently followed for 18 months for ACL injury. Fifteen noncontact ACL injuries occurred during the follow-up period. Prior ACL injury (odds ratio [OR], 9.68; 95% confidence interval (95% CI), 2.67-31.46), a lower isometric hip adductor to abductor strength ratio (OR, 1.98; 95% CI, 1.09-3.61), greater CMJ peak take-off force (OR, 1.74; 95% CI, 1.09-3.61), and greater single-leg triple vertical hop average dynamic knee valgus (OR, 1.97; 95% CI, 1.06-3.63) and ipsilateral trunk flexion (OR, 1.60; 95% CI, 1.01-2.55) were independently associated with an increased risk of subsequent ACL injury. A multivariable prediction model consisting of CMJ peak take-off force, dynamic knee valgus, and ACL injury history that was internally validated classified ACL injured from uninjured footballers with 78% total accuracy. Between-leg asymmetry in lower limb strength and CMJ kinetics were not associated with subsequent ACL injury risk. Preseason field-based measures of lower limb muscle strength and biomechanics were associated with future noncontact ACL injury in elite female footballers. These risk factors can be used to guide ACL injury screening practices and inform the design of targeted injury prevention training in elite female footballers.

Effects of Plyometric Jump Training in Sand or Rigid Surface on Jump-Related Biomechanical Variables and Physical Fitness in Female Volleyball Players.

Background: This study aims to assess the effects of 8 weeks of plyometric jump training (PJT) conducted on sand or a rigid court surface on jump-related biomechanical variables and physical fitness in female indoor volleyball players. Methods: Seventeen participants were randomly divided into a sand surface group (SsG, n = 8) and rigid surface group (RsG, n = 9). Both groups completed equal indoor volleyball training routines. Participants were assessed pre and post the 8-week PJT for jump-related biomechanical variables (countermovement jump (CMJ) RSI; drop jump (DJ) reactive strength index (RSI); spike jump (SJ) height; CMJ height; CMJ rate of force development (RFD); CMJ velocity at take-off; DJ height and CMJ peak force), 20 m linear sprint time, t test for change-of-direction sprint (CODs) time, Wingate test peak power (PP), cardiorespiratory endurance, and leg-press one-repetition maximum (1RM). Results: A two-way mixed analysis of variance (group × time) revealed that there was a significant group × time interaction between DJ height (p = 0.035) and CMJ peak force (p = 0.032) in favour of RsG and SsG, respectively. A significant interaction was also observed for cardiorespiratory endurance (p = 0.01) and 1RM (p = 0.002), both favouring the SsG. No other group × time interaction was observed. Conclusions: The type of surface used during PJT induced specific adaptations in terms of jump-related biomechanical variables and physical fitness in female indoor volleyball players. Based on the individual needs of the athletes, practitioners may prescribe one type of surface preferentially over another to maximize the benefits derived from PJT.

Impact of prior ACL, hamstring or groin injury on lower limb strength and jump kinetics in elite female footballers

Introduction: Prior injury is a risk factor for lower limb injury in female footballers. An improved understanding of the impact of the most common and severe injuries on lower limb strength and biomechanics may help to optimise rehabilitation strategies and decrease subsequent injury rates. The aim of this cross-sectional study was to compare lower limb strength and countermovement jump (CMJ) kinetics between elite female footballers with and without a history of anterior cruciate ligament reconstruction (ACLR), hamstring strain, or hip/groin injury. Methods: 369 elite female Australian football, soccer and rugby league players aged 15–35 years underwent assessments of isometric hip adductor and abductor strength, eccentric knee flexor strength, and CMJ vertical ground reaction forces. Players reported their lifetime history of ACLR, and whether they had sustained a hamstring strain, or hip/groin injury in the previous 12-months. Strength and jump/landing kinetics, including between-leg asymmetry, were compared between players with and without prior injury. Logistic regression was used to determine the variables that best distinguished between players with and without prior injury. Results: Players with a unilateral history of ACLR (n=24) displayed asymmetry (injured<uninjured leg) in eccentric knee flexor strength (mean difference=-6.9%, 95%CI=-9.1 to -4.8%), isometric hip abductor strength (mean difference=-2.4%, 95%CI=-4.4 to -0.4%), and peak landing force (mean difference=-5.9%, 95%CI=-11.0 to -0.9%). Together, between-leg asymmetry in eccentric knee flexor strength, isometric hip abductor strength, and CMJ peak landing force distinguished between players with and without prior ACLR with 93% accuracy. No differences in strength or CMJ kinetics were observed between players with and without a history of hamstring or hip/groin injury. Discussion: Elite female footballers with a history of ACLR, but not hamstring or hip/groin injury, exhibit persistent between-leg asymmetries in lower limb strength and jump kinetics following a return to sport. To address the effects of prior injury, ACLR rehabilitation programs for elite female footballers should consider targeting between-leg asymmetries in eccentric knee flexor strength, isometric hip abductor strength, and CMJ kinetics. Conflict of interest statement: Funding for travel costs associated with data collection was provided by Vald Performance (Brisbane, Australia) and SMA Research Grant. My co-authors and I acknowledge that we have no conflict of interest of relevance to the submission of this abstract.

Risk factors for ACL, hamstring strain, and hip/groin injuries in elite Australian female footballers: A prospective study.

Introduction: Female footballers are at high risk of sustaining lower limb injuries, with some of the most prevalent and severe injuries being hamstring strains, hip/groin pain, and knee ligament sprains. However, there is currently limited evidence to guide injury prevention strategies and injury risk assessment testing in female footballers. The aim of this study was to assess risk factors for ACL, hamstring, and hip/groin injuries in elite female footballers. Methods: Data were collected from 321 elite female Australian Football, soccer, and Rugby League players during pre-season. Players underwent field-based assessments of isometric hip adductor and abductor strength (ForceFrame), eccentric knee flexor strength during the Nordic hamstring exercise (NordBord), countermovement jump (CMJ) on dual forceplates (ForceDecks), and a single-leg triple vertical hop (TVH) using a makerless motion capture system (HumanTrak). Players were subsequently followed for injuries for 18 months. Risk factors were identified prospectively using simple and multiple logistic regression and decision tree learning. Results: A total of 12 anterior cruciate ligament (ACL) ruptures, 17 hamstring strains, and 12 hip/groin injuries were recorded. Risk factors for ACL injury included prior ACL injury (standardised odds ratio [OR]=12.3, P<.001), lower body weight normalised adductor torque (OR=2.1, P=.028), greater body weight normalised CMJ peak force (OR=1.9, P=.013), lower CMJ impulse (OR=2.0, P=.037), greater triple vertical hop knee frontal plane projection angle (OR=2.3, P=.014), and greater triple vertical hop lateral trunk flexion (OR=1.7, P=.038). Multiple logistic regression and decision tree models classified ACL injured players with high accuracy (sensitivity=67% and 75% respectively, and specificity=88% and 100% respectively). Risk factors for time-loss hamstring injury included smaller stature (OR=1.8, P=.030), greater between-leg asymmetry in CMJ peak force (OR=2.0, P=.011) and eccentric impulse (OR=1.9, P=.016). There were no statistically significant risk factors for hip/groin injury. Discussion: This is the first study to explore risk factors for lower limb injury in elite female Australian football codes. These results provide insight into the potential modifiable factors associated with subsequent injury in elite female footballers, which may inform player testing batteries and the design of targeted injury risk reduction strategies. Conflict of interest statement: Funding for travel was provided by Vald Performance (Brisbane, Australia) and SMA Research Foundation. My co-authors and I acknowledge that we have no conflict of interest of relevance to the submission of this abstract.

Impact of prior anterior cruciate ligament, hamstring or groin injury on lower limb strength and jump kinetics in elite female footballers

ObjectiveTo compare lower limb strength and countermovement jump (CMJ) kinetics between elite female footballers with and without a history of anterior cruciate ligament reconstruction (ACLR), hamstring strain, or hip/groin injury. DesignCross-sectional. SettingField-based. Participants369 elite female Australian football, soccer and rugby league players aged 15–35. Main outcome measuresIsometric hip adductor and abductor strength, eccentric knee flexor strength, and CMJ vertical ground reaction forces, including between-leg asymmetry. Players reported their lifetime history of ACLR, and whether they had sustained a hamstring strain, or hip/groin injury in the previous 12-months. ResultsPlayers with a unilateral history of ACLR (n = 24) had significant between-leg asymmetry in eccentric knee flexor strength (mean = −6.3%, 95%CI = −8.7 to −3.9%, P < .001), isometric hip abductor strength (mean = −2.5%, 95%CI = −4.3 to −0.7%, P = .008), and CMJ peak landing force (mean = −5.5%, 95%CI = −10.9 to −0.1%, P = .046). Together, between-leg asymmetry in eccentric knee flexor strength, isometric hip abductor strength, and CMJ peak landing force distinguished between players with and without prior ACLR with 93% accuracy. ConclusionElite female footballers with a history of ACLR, but not hamstring or hip/groin injury, exhibit persistent between-leg asymmetries in lower limb strength and jump kinetics following a return to sport.

The mobility limitation in healthy older people is due to weakness and not slower muscle contractile properties.

The maximal power generating capacity of a muscle declines with age and has a negative impact on the performance of daily life activities. As muscle power is the product of force and velocity, we recruited 20 young (10 men, 10 women: 20–31 years) and 20 older (10 men, 10 women: 65–86 years) people to investigate which of these components contributes to the lower power and performance in old age. After determination of the maximal isometric knee extension torque (MVC), they performed a countermovement jump (CMJ) in 1) the normal situation (normal), 2) with an extra load of 15% body weight (loaded) and 3) 15% lower body weight (unloaded with a pulley system), and a timed up-and-go test (TUG) in the normal or loaded condition. The TUG and CMJ performance was lower in old than young participants (p<0.001). Below a critical CMJ peak power of ~23.7 W·kg-1 TUG showed a progressive decrease. The CMJ take-off velocity (Voff) in the normal condition was lower in old than young participants (p<0.001). However, the Voff vs. body weight/MVC relationship of the normal, loaded and unloaded data combined was similar in the old and young participants and fitted the Hill equation (R2 = 0.396). This indicates that 1) only when peak power drops below a critical threshold TUG becomes impaired and 2) there was no evidence for intrinsic slowing of the muscle contractile properties in older people, but rather the older people were working on a slower part of the force-velocity relationship due to weaker muscles.

Impulse-Based Dynamic Strength Index: Considering Time-Dependent Force Expression.

Haischer, MH, Krzyszkowski, J, Roche, S, and Kipp, K. Impulse-based dynamic strength index: considering time-dependent force expression. J Strength Cond Res 35(5): 1177-1181, 2021-The dynamic strength index (DSI) is a useful tool to assess an athlete's capacity to effectively use maximum strength during dynamic tasks. Although DSI is traditionally calculated based on peak forces, the ability to express force over time (i.e., impulse) is a better predictor of dynamic performance. The purpose of this study was to investigate the association between DSI calculated based on peak force (fDSI) and impulse (iDSI). Nineteen female collegiate lacrosse players performed countermovement jumps (CMJs) and isometric midthigh pulls (IMTPs). Peak force and impulse were extracted from CMJ and IMTP force-time data. Countermovement jump impulse was calculated by integrating force over the concentric movement time, whereas IMTP impulse was calculated by integrating force over the CMJ-matched movement time. Ratios between CMJ and IMTP peak force and impulse were used to calculate fDSI and iDSI, respectively. A moderate positive correlation existed between iDSI and fDSI (ρ = 0.644 [0.283-0.840], p = 0.003). Based on thresholds established in the literature, the 2 indices suggest conflicting training recommendations for 37% of athletes. Because impulse is a better predictor of dynamic performance, iDSI may represent a more valid method for assessing an athlete's capacity to effectively use maximum strength during dynamic tasks. Practitioners and researchers may want to consider augmenting current training and research practices with an impulse-based DSI.

Countermovement Jump and Squat Jump Force-Time Curve Analysis in Control and Fatigue Conditions.

Hughes, S, Warmenhoven, J, Haff, GG, Chapman, DW, and Nimphius, S. Countermovement jump and squat jump force-time curve analysis in control and fatigue conditions. J Strength Cond Res 36(10): 2752–2761, 2022—This study aimed to reanalyze previously published discrete force data from countermovement jumps (CMJs) and squat jumps (SJs) using statistical parametric mapping (SPM), a statistical method that enables analysis of data in its native, complete state. Statistical parametric mapping analysis of 1-dimensional (1D) force-time curves was compared with previous zero-dimensional (0D) analysis of peak force to assess sensitivity of 1D analysis. Thirty-two subjects completed CMJs and SJs at baseline, 15 minutes, 1, 24, and 48 hours following fatigue and control conditions in a pseudo random cross-over design. Absolute (CMJABS/SJABS) and time-normalized (CMJNORM/SJNORM) force-time data were analyzed using SPM 2-way repeated measures analysis of variance with significance accepted at α = 0.05. The SPM indicated a magnitude of difference between force-time data with main effects for time (p < 0.001) and interaction (p < 0.001) observed in CMJABS, SJABS, and SJNORM, whereas previously published 0D analysis reported no 2-way interaction in CMJ and SJ peak force. This exploratory research demonstrates the strength of SPM to identify changes between entire movement force-time curves. Continued development and use of SPM analysis techniques could present the opportunity for refined assessment of athlete fatigue and readiness with the analysis of complete force-time curves.

Not All Physical Performance Tests Are Related to Early Season Match Running Performance in Professional Rugby League.

Glassbrook, DJ, Fuller, JT, Wade, JA, and Doyle, TLA. Not all physical performance tests are related to early season match running performance in professional rugby league. J Strength Cond Res 36(7): 1944-1950, 2022-This study aimed to determine which physical tests correlate with early season running performance. Sixteen professional rugby league players performed the 30-15 intermittent fitness test (IFT), 1.2-km time trial, 1 repetition maximum (RM) barbell back squat, isometric midthigh pull (IMTP), countermovement jump (CMJ), barbell squat jump (SJ), and ballistic bench press throw (BBP). Bivariate Pearson's correlations and linear regression were used to compare physical tests with peak match running intensities recorded by a portable Global Positioning System and represented by peak match velocity and acceleration, as well as peak 1-, 4-, 6-, and 8-minute instantaneous acceleration/deceleration periods of play. Significant (p < 0.05) negative correlations (r = -0.55 to -0.60) were observed between the IFT and relative 1-, 4-, 6-, and 8-minute peaks, and between the relative 1RM back squat and relative 1-, 4-, 6-, and 8-minute peaks. Significant positive correlations (r = 0.52-0.84) were observed between the following physical tests and match performance pairs: IFT and peak acceleration; relative 1RM back squat and peak acceleration; SJ peak power (relative and absolute) and peak acceleration; CMJ peak force (relative and absolute) and peak acceleration; CMJ peak power (relative and absolute) and peak acceleration and 1-, 4-, 6-, and 8-minute peaks; and relative BBP peak power and peak velocity and peak acceleration. The results of this study highlight that not all generic tests of physical qualities are related to peak match running performance and only those with significant correlations are likely to be able to indicate how players may perform during match-play.

Post Flywheel Squat Potentiation of Vertical and Horizontal Ground Reaction Force Parameters during Jumps and Changes of Direction.

(1) Background: The aim of the study was to determine the post-activation performance enhancement (PAPE) of vertical and horizontal ground reaction force parameters during jumps and change of direction following flywheel squat exercise using two different flywheel inertias. (2) Methods: Eleven male athletes performed a countermovement jump (CMJ), standing broad jump (SBJ), and “modified 505” change of direction (COD) in a control condition and 6 minutes following three sets of six repetitions of flywheel half squats at one of two inertias (0.029 kg·m2 and 0.061 kg·m2). Peak directional ground reaction force, power, and rate of force development were calculated for each test. (3) Results: Higher inertia flywheel squats were able to acutely enhance CMJ peak vertical force (Bayes Factor (BF10) = 33.5, very strong; δ = 1.66; CI: 0.67, 2.70), whereas lower inertia flywheel squats were able to acutely enhance CMJ peak vertical power (BF10 = 3.65, moderate; δ = 0.93; CI: 0.11, 1.88). The vertical squat exercise induced no PAPE effect on resultant SBJ or horizontal COD ground reaction force parameters, nor were any differences observed between the inertias. (4) Conclusions: Researchers and practitioners should consider the kinetic and kinematic correspondence of a pre-load stimulus to the subsequent sport-specific activity (i.e., flywheel squat to CMJ).

Bilateral deficit: relationships with training history and functional performance

The purpose of the study was to investigate the magnitude of bilateral deficit (BLD) in trained males and examine its relationship with functional performance and recent resistance training history. Ten physically active males (age: 23.02±1.27 years) self-reported the number of unilateral and bilateral exercises within their structured resistance training schedule. During two visits to the laboratory, participants performed unilateral and bilateral squat jumps (SJ) and isometric leg extensions (ILE) for the quantification of BLD. Participants also performed bilateral countermovement jumps (CMJ) and a change of direction (COD) test to quantify functional performance. The performance outcomes and information regarding training history were then correlated with the bilateral index (BLI) metric. The key findings were that: (a) a lower BLD in SJ peak power related to a greater CMJ peak force (r=.728; p=.02) and peak power (r=.750; p=.01), (b) the BLI in the ILE was unrelated to performance outcomes, and (c) BLI was unrelated to the mean number of bilateral and unilateral exercises in the structured resistance training programme of participants. In conclusion, lower levels of BLD may be advantageous for bilateral tests of functional performance (i.e. jumps) however there is a need to consider the mechanical similarity between the performance and BLD measure. Finally, the balance of unilateral and bilateral exercises in an individual’s recent resistance training history is not sensitive to the BLI measured during dynamic or isometric assessments.

Effects of age and sex on field-based measures of muscle strength and power of the upper and lower body in adolescents

ABSTRACT Field-based tests including the medicine ball chest throw (MBCT) and vertical jump are used to assess muscle performance. To date no study has compared performances of these field-based tests in adolescents across a range of ages. The aim of this study was to examine the effects of age and sex on MBCT and countermovement jump (CMJ) performance in adolescents.This cross-sectional study involved 2192 adolescents (1477 males and 715 females) aged between 12 and 17 years. Trials of the MBCT and CMJ were performed with CMJ peak power estimated. Males had significantly greater MBCT distance, CMJ height and CMJ peak power at each consecutive age group separated by 1 year (p < 0.001). Females generally showed significantly greater performances across a larger age range of at least 2 years for MBCT (p ≤ 0.004) and CMJ peak power (p ≤ 0.018). Males had greater performances than females for MBCT distance, CMJ height, and CMJ peak power from 13 years and above (p < 0.001). Sex differences widened with increasing age for all tests from ~5-8% at 12 years progressing to 24–29% at 16–17 years. This study shows the effects of age and sex is similar for both the MBCT and CMJ tests in adolescents.

Dynamic Strength Index: Relationships with Common Performance Variables and Contextualization of Training Recommendations.

The purposes of this study were to examine the relationships between dynamic strength index (DSI) and other strength-power performance characteristics and to contextualize DSI scores using case study comparisons. 88 male and 67 female NCAA division I collegiate athletes performed countermovement jumps (CMJ) and isometric mid-thigh pulls (IMTP) during a pre-season testing session as part of a long-term athlete monitoring program. Spearman’s correlations were used to assess the relationships between DSI and CMJ peak force, height, modified reactive strength index, peak power and IMTP peak force and rate of force development (RFD). Very large relationships existed between DSI and IMTP peak force (r = -0.848 and -0.746), while small-moderate relationships existed between DSI and CMJ peak force (r = 0.297 and 0.313), height (r = 0.108 and 0.167), modified reactive strength index (r = 0.174 and 0.274), and IMTP RFD (r = -0.341 and -0.338) for men and women, respectively. Finally, relationships between DSI and CMJ peak power were trivial-small for male (r = 0.008) and female athletes (r = 0.191). Case study analyses revealed that despite similar DSI scores, each athlete’s percentile rankings for each variable and CMJ force-time characteristics were unique, which may suggest different training emphases are needed. Based on the explained variance, an athlete’s IMTP performance may have a larger influence on their DSI score compared to the CMJ. DSI scores should be contextualized using additional performance data to ensure each individual athlete receives the appropriate training stimulus during different training phases throughout the year.

Eight Weeks of Strength and Power Training Improves Club Head Speed in Collegiate Golfers.

Oranchuk, DJ, Mannerberg, JM, Robinson, TL, and Nelson, MC. Eight weeks of strength and power training improves club head speed in collegiate golfers. J Strength Cond Res 34(8): 2205-2213, 2020-Club head speed (CHS) is a major determinant of drive distance, a key component of golf performance. The purpose of this study was to determine the indirect effects of an 8-week strength and power program on CHS. Twelve (6 men, 6 women) NCAA Division II golfers (20.3 ± 1.5 years) randomly assigned to an intervention or control group underwent either a periodized strength and power program consisting of high-load barbell movements or a bodyweight and rotational movement focused resistance training program. Outcomes were CHS, countermovement jump (CMJ) height, and 1RM back squat (BS), power clean (PC), and deadlift (DL). Dependent t-tests were used to assess differences in outcome variables pre-to-post for each group, independent t-tests were used to assess differences between groups, and Pearson correlations were used to assess associations between CHS and outcome variables. On average, the intervention group experienced improvements in all outcome variables except peak CHS (p = 0.60); the control group displayed no changes in any outcome variable except a decrease in average CHS (p = 0.028). Compared with the control group, the intervention group experienced greater improvements in average CHS, BS, PC, and average and peak CMJ height (p ≤ 0.05). Additionally, CHS had large associations with PC (r = 0.70, p = 0.012), BS (r = 0.64, p = 0.025), DL (r = 0.54, p = 0.068) and CMJ (r = 0.73, p = 0.007). These results suggest that improving muscular strength and power by increasing PC, BS, and CMJ is associated with increased CHS in collegiate golfers. Integrating a high-load, barbell-focused strength and power program may be beneficial for improving CHS and indirectly, golf performance.

Back squat velocity to assess neuromuscular status of rugby league players following a match

ObjectivesBack squat mean concentric velocity (MV) and countermovement jump (CMJ) performance were examined in sub-elite rugby league players post-match to monitor changes in neuromuscular status (NMS) from baseline. Relationships between changes in back squat MV and CMJ performance variables were used to compare back squat MV to an established method to monitor NMS. DesignLongitudinal observational design. Methods18 male sub-elite rugby league players (mean±SD, 20.5±2.4 yr; 180.0±6.7cm; 93.3±11.2kg) performed 3 repetitions of CMJ and back squat with an individualised, pre-determined load at −2h (baseline), +30min, +24h, and +48h in relation to a match. Back squat MV, CMJ height, CMJ peak power, and CMJ peak velocity were measured with a linear position transducer. ResultsSignificant (p<0.05), small to large decreases (ES=0.52–1.24) were observed in back squat MV up to +48h post-match. Significant (p<0.05), small to moderate decreases (ES=0.52–0.70) in CMJ height were also observed up to +24h post-match, returning to baseline at +48h. CMJ peak power and peak velocity post-match changes were not significant compared to baseline (p>0.05). Significant positive correlations were found between changes in back squat MV and CMJ height at +30min (r=0.59; p=0.009) and +48h (r=0.51; p=0.03). ConclusionsThese findings suggest back squat MV may be a suitable alternative or addition to CMJ testing for monitoring NMS in rugby league players.

Neuromuscular predictors of competition performance in advanced international female weightlifters: a cross-sectional and longitudinal analysis

ABSTRACTThe aim of this study was to investigate the physical determinants of weightlifting competition performance based on Isometric Mid-Thigh Pull (IMTP) and Countermovement Jump (CMJ) force-time variables, in a cross-sectional and longitudinal analysis. Ten British advanced international female weightlifters’ competition results and neuromuscular assessment data collected as part of the British Weight Lifting World Class Programme were utilised for the purpose of this study. All data were averaged for two consecutive 1-year periods. The cross-sectional analysis utilised the second year of data, whereas the longitudinal analysis assessed the mean change between the two years. The cross-sectional analysis results reveal IMTP Net Isometric Peak Force (PF) and CMJ Peak Power (PP) predict 94.2%, 95.1% and 91.8% of the variance in Total, Snatch and Clean & Jerk competition performance, respectively (p = <0.5). The longitudinal analysis results revealed that ∆IMTP PF was the only predicting factor of longitudinal change in weightlifting competition performance predicting 41.5%, 41.7% and 42.5% of ∆Total, ∆Snatch and ∆Clean & Jerk, respectively (p = <0.5). The assessments and equations may be utilised by coaches or sports scientists to inform the prescription of training and help predict competition performance.

Measuring lumbar back motion during functional activities using a portable strain gauge sensor-based system: A comparative evaluation and reliability study

Quantifying lumbar back motion during functional activities in real-life environments may contribute to a better understanding of common pathologies such as spinal disorders. The current study therefore aimed at the comparative evaluation of the Epionics SPINE system, a portable device for measuring sagittal lumbar back motion during functional activities. Twenty healthy participants were therefore evaluated with the Epionics SPINE and a Vicon motion capture system in two identical separate research visits. They performed the following activities: standing, sitting, chair rising, box lifting, walking, running and a counter movement jump (CMJ). Lumbar lordosis angles were extracted as continuous values as well as average and range of motion (ROM) parameters. Agreement between the systems was evaluated using Bland-Altman analyses, whereas within- and between-session reliability were assessed using intraclass correlation coefficients (ICC) and minimal detectable changes (MDC). The analysis showed excellent agreement between the systems for chair rising, box lifting and CMJ with a systematic underestimation of lumbar lordosis angles during walking and running. Reliability was moderate to high for all continuous and discrete parameters (ICC ≥ 0.62), except for ROM during running (ICC = 0.29). MDC values were generally below 15°, except for CMJ (peak values up to 20° within and 25° between the sessions). The Epionics SPINE system performed similarly to a Vicon motion capture system for measuring lumbar lordosis angles during functional activities and showed high consistency within and between measurement sessions. These findings can serve researchers and clinicians as a bench mark for future investigations using the system in populations with spinal pathologies.