Peak Landing Forces Research Articles

Unilateral Plyometric Jump Training Shows Significantly More Effective than Bilateral Training in Improving Both Time to Stabilization and Peak Landing Force in Single-Leg Lend and Hold Test: A Randomized Multi-Arm Study Conducted Among Young Male Basketball Players.

Enhancing peak landing forces and ensuring faster stabilization in the lower limbs during jumping activities can significantly improve performance and decrease the risk of injury among basketball players. This study aimed to compare the effects of unilateral (uPJT) and bilateral plyometric jump training (bPJT) programs on various performance measures, including countermovement jump (CMJ), squat jump (SJ), and single-leg land and hold (SLLH) test outcomes, assessed using force plates. A randomized multi-arm study design was employed, comprising two experimental groups (n = 25; uPJT and n = 25; bPJT) and one control group (n = 25), conducted with youth male regional-level basketball players (16.3 ± 0.6 years old). Participants underwent assessment twice, both before and after an 8-week intervention training period. The uPJT program exclusively involved plyometric drills (e.g., vertical jump exercises; horizontal jump exercises) focusing on single-leg exercises, whereas the bPJT program utilized drills involving both legs simultaneously. The outcomes analyzed included CMJ peak landing force, CMJ peak power, SJ peak force, SJ maximum negative displacement, SLLH time to stabilization, and SLLH peak landing force. The control group exhibited significantly greater SLLH time to stabilization compared to both the uPJT (p < 0.001) and bPJT (p < 0.030) groups. Additionally, time to stabilization was also significantly higher in bPJT than in uPJT (p = 0.042). Comparisons between groups in regards SLLH peak landing force after intervention revealed that the value was significantly smaller in uPJT than in bPJT (p = 0.043) and control (p < 0.001). In the remaining outcomes of CMJ and SJ, both uPJT and bPJT showed significant improvement compared to the control group (p > 0.05), although there was no significant difference between them. In conclusion, our study suggests that utilizing uPJT is equally effective as bPJT in enhancing performance in bilateral jump tests. However, it significantly outperforms bPJT in improving time to stabilization and peak landing forces during single-leg land and hold test. uPJT could be advantageous not for maximizing performance but also for potentially decreasing injury risk by enhancing control and balance during single-leg actions, which are common in basketball.

Small-Sided Games with Baskets Are Significantly More Effective at Enhancing Neuromuscular Force Parameters Compared to Ball Possession Games: A Randomized Controlled Study in Young Male Basketball Players.

The aim of this study was to compare the effects of 8 weeks of small-sided basketball games (SSG) training using baskets (SSGbk) and ball possession games without baskets (SSGbpg) on various neuromuscular parameters in young male basketball players. Specifically, the study examined unilateral isometric knee flexor strength (KFS), unilateral isometric knee extensor strength (KES), bilateral countermovement jump peak power and peak landing force (CMJ), and leg land and hold test (LHT) peak landing force. This randomized controlled study included two experimental groups (SSGbk and SSGbpg) and one control group. Fifty regional competitive-level male youth basketball players (16.7 ± 0.5 years) were assigned to the groups. The experimental groups participated in two additional SSG weekly training sessions over 8 weeks. Both experimental groups were exposed to the same 2v2 to 4v4 formats of play and training volume, with the only difference being that one group performed ball possession games while the other participated in games targeting to score in the basket. Players were evaluated twice: once at baseline in the week prior to the intervention period, and again in the week post-intervention. The neuromuscular tests were conducted using force platforms. Significant interactions between time and groups were observed in KES (p < 0.001; η p 2 = 0.902), KFS (p < 0.001; η p 2 = 0.880), and CMJ peak power (p < 0.001; η p 2 = 0.630). Significant differences between groups were found post-intervention for the variables of KES (p = 0.017; η p 2 = 0.159), KFS (p = 0.011; η p 2 = 0.174), CMJ peak power (p = 0.017; η p 2 = 0.160), CMJ peak landing force (p = 0.020; η p 2 = 0.154), and LHT peak power (p = 0.012; η p 2 = 0.171). In conclusion, our study highlights that the SSGbk significantly increases neuromuscular adaptations in young male basketball players. Conversely, our findings do not support the efficacy of SSGbpg in targeting these specific physical fitness variables. Therefore, the use of SSGs must be carefully considered, particularly in selecting task conditions, to ensure efficacy in interventions.

Vertical Jump Testing after Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis.

Recently, there has been a call for vertical jump testing via force-plate analysis to be included in the assessment of individuals after anterior cruciate ligament reconstruction (ACLR) and as part of return-to-play criteria. However, a synthesis of current literature is needed to help guide clinicians on what tests to perform, which force-plate metrics to assess, and how these may change over the time course of rehabilitation. Four online databases were searched from inception to July 2022. The Downs and Black checklist was used to assess study quality. Multilevel meta-analyses and meta-regressions were undertaken in conjunction with a best evidence synthesis. Forty-two articles were included, capturing 2375 participants with a history of ACLR. Reconstructed limbs displayed 1) lower peak eccentric forces, concentric forces, landing forces, and lower eccentric and concentric impulses (standardized means difference [SMD] = -1.84 to -0.46) than uninjured contralateral limbs during bilateral countermovement jumps (CMJ) and drop vertical jumps (DVJ); 2) lower jump heights and reactive strength indices (RSI), and longer contact times than uninjured contralateral limbs during unilateral CMJ and DVJ (SMD = -0.86 to 0.26); and 3) lower jump heights, RSI, and longer contact times during bilateral and unilateral CMJ, and unilateral DVJ, than uninjured controls (SMD = -1.19 to 1.08). Meta-regression revealed that time postsurgery was a significant moderator ( P < 0.05) for 1) bilateral CMJ height, peak concentric force, and peak landing force; 2) between-limb differences in unilateral CMJ height; and 3) differences in unilateral DVJ height, RSI, and contact time between reconstructed limbs and healthy controls with no history of injury. Individuals with a history of ACLR display chronic deficits in vertical jumping performance during a range of bilateral and unilateral tasks, which may have implications for return-to-play criteria and the design of interventions targeted at restoring long-term deficits in explosive lower limb strength after ACLR.

Development of an algorithm-based approach using neuromuscular test results to indicate an increased risk for non-contact lower limb injuries in elite football players

ObjectivesThis retrospective cohort study explored an algorithm-based approach using neuromuscular test results to indicate an increased risk for non-contact lower limb injuries in elite football players.MethodsNeuromuscular data (eccentric hamstring strength,...

Performance and symmetry measures during vertical jump testing at return to sport after ACL reconstruction

ObjectiveVertical jump tests are more sensitive in revealing asymmetries in performance metrics at the time of return to sport after anterior cruciate ligament (ACL) reconstruction (ACLR) than horizontal hop tests....

Impact of the Anatomical Accelerometer Placement on Vertical Jump Performance Characteristics.

With rapid technological development over recent years, the use of wearable athlete monitoring devices has substantially gained popularity. Thus, the purpose of the present study was to examine the impact of the anatomical placement of an accelerometer on biomechanical characteristics of countermovement vertical jump with and without an arm swing when compared to the force plate as a criterion measure. Seventeen recreationally active individuals (ten males and seven females) volunteered to participate in the present study. Four identical accelerometers sampling at 100 Hz were placed at the following anatomical locations: upper-back (UB), chest (CH), abdomen (AB), and hip (HP). While standing on a uni-axial force plate system sampling at 1000 Hz, each participant completed three non-sequential maximal countermovement vertical jumps with and without an arm swing. All devices recorded the data simultaneously. The following variables of interest were obtained from ground reaction force curves: peak concentric force (PCF), peak landing force (PLF), and vertical jump height (VJH). The findings of the present study reveal that the most appropriate anatomical locations to place the accelerometer device when attempting to estimate PCF, PLF, and VJH during a countermovement vertical jump with no arm swing are CH, AB, and UB, and during a countermovement vertical jump with an arm swing are UB, HP, and UB, respectively. Overall, these findings may help strength and conditioning professionals and sports scientists to select appropriate anatomical locations when using innovative accelerometer technology to monitor vertical jump performance characteristics.

Efficacy of Proprioceptive Training on Plantar Pressure and Jump Performance in Volleyball Players: A Proof-of-Principle Study.

Volleyball players are often subject to micro-traumatisms of the heel fat pad and ankle injuries. Recently, mat-based proprioceptive training has assumed a key role in recovery from these disorders. Therefore, this proof-of-principle study aimed to assess the efficacy of proprioceptive mat training on plantar pressures and athletic performance in volleyball players. The participants included adult semi-professional volleyball players allocated into two groups: an experimental group, with mat-based proprioceptive and balance training, and a control group, with a sham protocol. For the outcome, we evaluated the barefoot plantar pressure, performing an analysis on a baropodometric resistive platform. The countermovement jump and squat jump were measured using an inertial measurement unit. Nineteen subjects were included in the two groups: the active proprioceptive group (n = 10) or the control group (n = 9). The results show a more uniform redistribution of loads with pressure hindfoot relief in the experimental group compared to the control group (p = 0.021, RBC = 0.67). Moreover, we observed a significant increase in peak landing force and high concentric power development in the experimental group compared to the controls. Focused proprioceptive management provided hindfoot load attenuation by stimulating higher peaks of concentric force in the experimental group compared to the sham group. Even though the study included a small sample, the results obtained in this proof-of-principle study suggest a positive role of proprioceptive stimulation in the inter-seasonal scenario for volleyball players to improve their jump performance and reduce the micro-traumatisms of the heel fat pad and the ankle injury rate. However, further studies performed on larger samples are needed to confirm these preliminary results.

The Ecological Validity of Countermovement Jump to On-Court Asymmetry in Basketball.

Jump-based asymmetry is often used as an indicator of sport performance and may be used to discern injury susceptibility. Due to task specificity, however, countermovement jump asymmetry may not be representative of on-court asymmetry. As such, we assessed the association between countermovement jump asymmetry and on-court impact asymmetry metrics (n=3, and n=4, respectively) using linear regressions (α=0.05). Fifteen female basketball athletes completed countermovement jump and on-court sessions across a competitive season. A significant negative association was found between peak landing force asymmetry and both overall and medium acceleration on-court asymmetry (b=-0.1, R 2 =0.08, p<0.001; b=-0.1, R 2 =0.11, p<0.001, respectively), as well as between peak propulsive force asymmetry and on-court medium acceleration asymmetry (b=-0.24, R 2 =0.04, p=0.01). Alternatively, both peak landing and peak propulsive force asymmetry were significantly positively associated with on-court high acceleration asymmetry (b=0.17, R 2 =0.08, p<0.001; b=0.35, R 2 =0.02, p=0.04, respectively). While some overlap may exist, countermovement jump and on-court impact asymmetry appear to be independent. Thus, sport-specific monitoring may be necessary to adequately monitor injury susceptibility using asymmetry.

Kinetic and Kinematic Characteristics of Setting Motions in Female Volleyball Players

While being an integral part of both the offensive and defensive segments of the game, the biomechanical parameters of setting motions remain understudied in the scientific literature. Thus, the purpose of the present study was to examine differences in kinetic and kinematic characteristics between: (a) three types of setting motions (i.e., front, middle, back); (b) two types of setting approaches (i.e., stationary, step-in); and (c) proficient (PRO) and non-proficient (N-PRO) volleyball players. Twenty recreationally active females performed five stationary and five step-in setting approaches to Zone 4–2 in a randomized order. Uni-dimensional force plate sampling at 1000 Hz and high-definition camera recording at 30 fps were used to obtain kinetic and kinematic variables of interest. The total number of setting attempts performed by each subject was 30, accounting for a grand total of 600 attempts. PRO setters had less knee flexion, shoulder flexion, and ankle dorsiflexion at the initial concentric phase of the volleyball setting motion when compared to the N-PRO setters. Moreover, significantly greater peak concentric and landing forces, impulse, rate of force development, and vertical jump height were observed for PRO setters compared to N-PRO setters, while no significant differences were found between different setting targets and approaches.

Impaired Stretch-Shortening Cycle Function Persists Despite Improvements in Reactive Strength After Anterior Cruciate Ligament Reconstruction.

Read, PJ, Pedley, JS, Eirug, I, Sideris, V, and Oliver, JL. Impaired stretch-shortening cycle function persists despite improvements in reactive strength followingafter anterior cruciate ligament reconstruction. J Strength Cond Res 36(5): 1238-1244, 2022-Reactive strength index (RSI) during a single-leg drop jump (SLDJ) has been indicated to determine return-to-sport readiness after anterior cruciate ligament (ACL) reconstruction, but only cross-sectional studies are available. Ground reaction force data and characterization of stretch-shortening cycle (SSC) function also remain sparse. Single-leg drop jump performance, ground reaction force, and SSC function were examined in soccer players with ACL reconstruction (n = 26) and matched controls (n = 25). Injured players were tested at 2 time points (32 and 42 weeks postsurgery). Stretch-shortening cycle function was classified as good (no impact peak and spring like), moderate (impact peak but still spring like or no impact peak and not spring like), or poor (impact peak and not spring like). The involved limb displayed lower-jump height, poorer RSI, less spring-like behavior, earlier peak landing force, and a greater ratio of landing peak to take-off peak force compared with the uninvolved limb and controls at the initial assessment (p < 0.001). Proportionally, more involved limbs were categorized as poor or moderate at the initial assessment (69.2%) and follow-up (50%) in comparison with the control limbs (14%). The reactive strength index was the only variable to change significantly between the initial assessment and follow-up on the involved limb (p < 0.05). No changes in the proportion of ACL reconstructed individuals categorized as poor or moderate SSC function at the follow-up assessment were observed. Residual deficits are present in SLDJ performance, SSC function, and ground reaction force characteristics after ACL reconstruction. The reactive strength index should not be the sole metric, as observed increases did not correspond with changes in SSC function.

Effect of jump heights, landing techniques, and participants on vertical ground reaction force and loading rate during landing on three different Korean teeterboards

Korean teeterboard is one of the most physically and technically demanding circus disciplines. Two performers take turns jumping vertically and land with high impact. The aims of this study were to (1) compare the stiffness across three different teeterboards, and (2) compare Peak Landing Force (PLF) and Maximal Loading Rate (MLR) of four acrobats performing jumps from three teeterboards using four landing techniques (normal, smooth, straight legs, and empty board). Pressure sensors were used to determine recorded forces under the feet, while Boosted Regression Trees (BRT) was used to analyze factors contributing to PLF and MLR. Standard static loading protocol was used to estimate teeterboard stiffness. PLF and MLR increased with jump height. PLF and MLR were reached when landing on the teeterboard with the highest stiffness. The “normal” and “straight legs” landing techniques were associated with higher PLF and MLR. The BRT model was able to associate both PLF and MLR with jump height, participant, teeterboard, and landing technique factors. PLF reached 13.5 times the body weight when landing on the stiffer teeterboard using the straight legs technique. Trainers should be aware of the injury risk to teeterboard acrobats during landing.

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.

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.

Lower-limb Force And Fat-free Mass Asymmetries And Their Relationships To Vertical Jump Performance

The countermovement (CMJ) and squat jump (SJ) assess force and power production of the lower-limbs. The relationship of jumping force asymmetries to lower-limb fat-free mass (MM) asymmetries has not been well-studied. PURPOSE: The purpose of this study was to examine the relationship between CMJ and SJ performance and lower-limb MM asymmetries. METHODS: 38 Division II male lacrosse athletes performed the CMJ and SJ on bilateral force plates and their body composition was assessed via segmental bioelectrical impedance analysis. Relationships between peak and left-to-right landing and propulsive forces and MM of the lower-limbs were examined. Left-to-right peak forces were calculated as a percentage by the force plate software as ((left - right) / (left + right)) * 100. A fat-free mass asymmetry variable was manually calculated using this same formula. For both variables, a positive value indicated dominance of the left lower limb and a negative value indicated dominance of the right lower limb. The raw value of each asymmetry variable was used for correlations with other asymmetry variables while the absolute value of each asymmetry variable was used for correlations with variables that only allowed positive values. Alpha was set at 0.05. Normality was assessed with the Shapiro-Wilk test. Due to non-normality of some data, Spearman’s Rho was used for all correlational analysis. Alpha = 0.05. RESULTS: For the CMJ, peak propulsive force (PPF) was related to MM of the left (r = 0.689; p < 0.001) and right (r = 0.657; p < 0.001) lower-limb. The absolute value of the left-to-right peak landing force (PLF) was related to PLF (r = -0.351; p = 0.031). The absolute value of the left-to-right PPF was related to PPF (r = 0.322; p = 0.048). For the SJ, PPF was related to MM of the left lower-limb (r = 0.628; p < 0.001) and MM of the right lower-limb (r = 0.655; p < 0.001). Also for the SJ, left-to-right PPF was related to MM asymmetry (r = 0.386; p = 0.019). No relationships existed between jump height and any other variable for either jump. CONCLUSION: These results suggest that relationships between force asymmetries, overall force, and MM asymmetries in the lower-limbs during jumping are complex. Practically, they suggest that both force production and MM asymmetries are not clearly detrimental to jump performance.

Maturity alters drop vertical jump landing force-time profiles but not performance outcomes in adolescent females.

The stretch-shortening cycle (SSC) assists in effective force attenuation upon landing and augments force generation at take-off during a drop vertical jump (DVJ). General performance outcomes such as jump height or peak measures have been used to assess SSC function in youth populations; however, these discrete metrics fail to provide insight into temporal jump-landing characteristics. This study assessed DVJ force-time profiles in 1013middle and high-school female athletes (n=279 prepubertal, n=401 pubertal, and n=333 postpubertal). Maturity status was determined using the Pubertal Maturation Observation Scale. Ground reaction force data were analyzed to extract a range of variables to characterize force-time profiles. SSC function was categorized as poor, moderate, or good dependent on the presence of an impact peak and spring-like behavior. No differences in jump height or ground contact time were observed between maturity groups (p>0.05). Significant differences in absolute peak landing and take-off force were evident between all maturational statuses (p<0.05). Relative to bodyweight normalized forces, only peak take-off force was significantly different between prepubertal and postpubertal groups (p<0.05; d=0.22). Spring-like behavior showed small improvements from pubertal to postpubertal (p<0.05; d=0.25). Most females displayed poor SSC function at prepubertal (79.6%), pubertal (77.3%), and postpubertal (65.5%) stages of maturity. Large increases in absolute forces occur throughout maturation in female athletes; however, only small maturational differences were found in relative force or spring-like behavior. Consequently, most girls display poor SSC function irrespective of maturity.

Can we predict the landing performance of simulated aerials in surfing?

ABSTRACT This study explored which technical and physical attributes could predict superior and/or safe landing performance when surfers performed variations of a simulated aerial task. Fourteen surfers (age 20.6 ± 5.7 years, height 178.1 ± 9.50 cm, mass 70.6 ± 10.8 kg) had their lower limb mobility, squat jump, countermovement jump, and drop-and-stick landing performance assessed. Performance of two aerial variations (Frontside Air (FA) and Frontside Air Reverse (FAR)) was also measured, with variables relating to technical performance (critical feature and subjective ratings) and potential injury risk (relative total peak landing force and loading rates) collected. Multiple linear regressions were used to predict performance of both aerial variations based on a subset of independent variables. Four models could predict performance. Predicted technical capability in the FAR was mostly influenced by lead limb hip extension and lead limb knee flexion range of motion. Potential injury risk when surfers perform an FA and FAR was predicted to be mitigated by increasing lead ankle dorsiflexion range of motion, as well as trail hip extensor mobility to reduce the relative total peak force experienced when landing the FA. These simple outcome measures could be routinely assessed to ensure successful and safe aerial landings in surfing.

Effects of a Competitive Soccer Match on Jump Performance and Interlimb Asymmetries in Elite Academy Soccer Players.

Bromley, T, Turner, A, Read, P, Lake, J, Maloney, S, Chavda, S, and Bishop, C. Effects of a competitive soccer match on jump performance and interlimb asymmetries in elite academy soccer players. J Strength Cond Res 35(6): 1707-1714, 2021-The purpose of this study was to investigate the effects of a competitive soccer match on jump performance and interlimb asymmetries over incremental time points during a 72-hour period. Fourteen elite adolescent players from a professional English category 3 academy performed single-leg countermovement jumps pre, post, 24-, 48-, and 72-hour post-match on a single force platform. Eccentric impulse, concentric impulse, peak propulsive force, jump height, peak landing force, and landing impulse were monitored throughout. Interlimb asymmetries were also calculated for each metric as the percentage difference between limbs. Significant negative changes (p < 0.05) in jump performance were noted for all metrics at all time points, with the exception of jump height. Interlimb asymmetries were metric-dependent and showed very large increases, specifically post-match, with a trend to reduce back toward baseline values at the 48-hour time point for propulsive-based metrics. Asymmetries for landing metrics did not peak until the 24-hour time point and again reduced toward baseline at 48-hour time point. This study highlights the importance of monitoring distinct jump metrics, as jump height alone was not sensitive enough to show significant changes in jump performance. However, interlimb asymmetries were sensitive to fatigue with very large increases post-match. More frequent monitoring of asymmetries could enable practitioners to determine whether existing imbalances are also associated with reductions in physical performance or increased injury risk.

The Acute Effects of Accentuated Eccentric Loading on Drop Jump Kinetics in Adolescent Athletes.

Lloyd, RS, Howard, SW, Pedley, JS, Read, PJ, Gould, ZI, and Oliver, JL. The acute effects of accentuated eccentric loading on drop jump kinetics in adolescent athletes. J Strength Cond Res 36(9): 2381-2386, 2022-The purpose of the study was to determine the acute effects of accentuated eccentric loading (AEL) on drop jump kinetics in adolescent athletes. Fifteen male rugby players (mean ± SD: age = 16.2 ± 1.01, body mass = 73.38 ± 9.94, and height = 178.91 ± 6.74) completed 3 trials of a drop jump with and without an accentuated eccentric load using a dumbbell release technique that equated to 15% body mass. The addition of the AEL stimulus resulted in significant, moderate increases in jump height (p < 0.05; Wilcoxon r = 0.47) and braking and propulsive impulse (p < 0.05, Hedges' g = 0.43; p < 0.05, g = 0.61, respectively) but did not significantly influence reactive strength index. Concurrently, there were significant, moderate increases in ground contact times (p < 0.05; r = 0.45) and reductions in spring-like correlations (p < 0.05; g = 0.94). Neither the magnitude nor timing of peak landing force were significantly altered in the AEL protocol (p < 0.05, g = 0.38; p < 0.05, r = 0.10, respectively). Cumulatively, these data indicate that implementation of AEL resulted in meaningful improvements in jump height, driven by significant increases in braking and propulsive impulse. Despite extensions in ground contact times and reductions in spring-like behavior, neither peak landing force nor time to peak force were negatively altered by the AEL. These results indicate that adolescent athletes can realize superior vertical jump heights during drop jumps using AEL, without displaying marked changes in the magnitude or timing of peak landing force.

A Novel Method to Categorize Stretch-Shortening Cycle Performance Across Maturity in Youth Soccer Players.

Pedley, JS, Lloyd, RS, Read, PJ, Moore, IS, Myer, GD, and Oliver, JL. A novel method to categorize stretch-shortening cycle performance across maturity in youth soccer players. J Strength Cond Res 36(9): 2573-2580, 2022-This study used a novel method to categorize stretch-shortening cycle (SSC) function during a drop jump (DJ) using the force-time curve. This method was then used to determine the effect of maturity status upon SSC function and effect of SSC function on DJ performance. Prepeak, circa-peak, and postpeak height velocity male youth soccer players completed a preseason 30-cm DJ onto a force plate. Stretch-shortening cycle function was categorized as poor (impact peak and not spring-like), moderate (impact peak and spring-like), or good (no impact peak and spring-like). Interactions between SSC function and maturity status, and SSC function and kinetic variables were explored. Youth soccer players displaying good SSC function were older and more mature than those with poor SSC function; however, 9.9% of post peak height velocity still displayed poor SSC function. Players with good SSC function recorded significantly shorter ground contact times, reduced time between peak landing and takeoff force, reduced center of mass displacement, and significantly greater takeoff forces than players with moderate and poor SSC function (all p < 0.05). SSC function during a standardized DJ improves with maturation, but a portion of mature players still demonstrate poor SSC function. Good SSC function was associated with improved DJ outcome measures except jump height. Tailored training interventions based on SSC competency may be required to optimally enhance SSC function.

Interlimb Asymmetries With High And Low External Training Loads In Male Collegiate Basketball Athletes

Tracking and monitoring bilateral limb asymmetries is an increasingly common practice to provide information associated with athlete performance, injury risk, as well as guiding return-to-play or return-to-performance protocols following injury. It is speculated external training loads (eTL) during sport specific practice may influence subsequent changes in inter-limb asymmetries. PURPOSE: Therefore, the purpose of the present study was to evaluate acute differences in lower inter-limb asymmetries during a bilateral countermovement jump (CMJ) immediately following high versus low eTL basketball practices in a group of NCAA men’s collegiate basketball players. METHODS: Twelve NCAA Division I collegiate men’s basketball players performed three CMJs on dual cell force platforms immediately prior to and immediately following basketball practices of high and low eTL. A dependent T-test was used to determine mean differences in practice intensities. A 2-way (condition x time) repeated measures analysis of variance (ANOVA) was performed to examine differences in Concentric Impulse (ConcImp), Concentric Peak Force (ConcPF), Eccentric Peak Force (EccPF), Takeoff Peak force (TakeoffPF), and Peak Landing Force (PeakLandF) captured during the CMJ between conditions and across time, with significance set at p ≤ 0.05. RESULTS: There was a significant difference in practice intensities (High: PlayerLoad/min = 5.3 ± 0.9, Low: PlayerLoad/min = 4.7 ± 1.4; p ≤ 0.001). There were no significant condition or time main effects (p > 0.05), and there were no significant condition by time interactions for ConcImp, ConcPF, EccPF, TakeoffPF, and PeakLandF (p > 0.05). CONCLUSION: Although there were significant differences experienced in eTL intensities between practices (PL/min), these differences did not result in alteration of acute lower inter-limb asymmetries during the bilateral CMJ.