Drop Jumps Research Articles

The effects of post-activation performance enhancement and different warm-up protocols on swim start performance

This study aimed to examine the effects of post-activation performance enhancement (PAPE) on swim start performance and lower body power performance after different warm-up protocols. Ten male national-level swimmers performed three different warm-ups: (i) a swim-specific warm-up (SW, control protocol); (ii) PAPE (an experimental protocol); and (iii) SW followed by PAPE (SW + PAPE, an experimental protocol). PAPE consisted of performing three series of 5 drop jumps. A repeated-measures ANOVA showed significant differences between the protocols in the swim start performance (F = 8.89; P < 0.001) and countermovement jump (F = 2.22; P = 0.047). SW + PAPE induced greater improvements in swim start time to 15 m (ES = − 0.47, P = 0.017) and entry time (ES = − 1.83, P < 0.001), the countermovement jump reactive strength index modified (ES = − 1.83, P < 0.001), eccentric rate of force development (ES = 0.69, P = 0.047), and index of explosive strength (ES = 0.94, P = 0.005) compared to SW. The current findings of this study indicate that the drop jump PAPE protocol, in addition to SW, is an effective tool because it could improve athletes' capacity for a more efficient swim start and their countermovement jump performance. Furthermore, the results of this study indicate that PAPE induced by drop jumps could be time-efficient and practically applicable in facilities with limited resources.

Neuromuscular, kinetic and kinematic differences in drop jumping between male adolescents with and without intellectual disability

BackgroundIndividuals with intellectual disability (ID) have lower performance in vertical jumps compared to individuals without ID. Training programmes including drop jump (DJ) exercises to gap this deficit are required. However, there is a lack of knowledge on biomechanical variables may influence DJ performance in young people with ID. Research questionAre there differences in the neuromuscular, kinetic and kinematic parameters in DJ between male adolescents with and without ID (WID and NID, respectively). MethodsThirteen male adolescents WID (Wisk III intelligence quotient: 55.6 ± 11.2) and thirteen age-matched boys NID executed DJ from 30 cm on a force-plate. The vastus lateralis (VL) and biceps femoris (BF) electromyogram (EMG) as well as the knee kinematics and kinetics were obtained. ResultsWID had significantly (p < .05) lower DJ height, knee power, peak angular velocity and stiffness compared to NID. VL activity was higher and BF/VL co-activation was lower in WID than NID. SignificanceThe deficit in DJ performance shown in WID was accompanied with lower power and stiffness, as well as lack of coordination in the lower limb muscles. Improving these variables, with specific and targeted training interventions, may diminish the performance gap with their age-matched counterparts.

Time-course analysis following initial warm-up to inform pre-pitch entry preparations of soccer substitutes

The purpose of this study was to investigate the time-course of decrements in physical performance following a pre-match warm-up in soccer players. Knowledge of this information could be used to inform re-warm-ups and pre-pitch entry practices of soccer substitutes. Data were collected over five sessions with 12 male youth professionals (15–17 yrs). Across the five sessions each player performed countermovement jumps (CMJ) and drop jumps (30 and 40 cm), pre-warm-up, immediately post-warm-up, and following 10-, 20-, 30-, 40-, and 50-min of inactivity. Physical performance was assessed by jump height and calculation of reactive strength index (RSI). Hierarchical generalised linear models (HGLMs) were fitted within a Bayesian framework to identify plausible time to achieve 10 to 50% decrements of the initial pre to post warm-up improvement. Mean improvements of 5.4 cm (95%CrI: 4.8 to 6.0), 0.24 ms−1 (95%CrI: 0.19 to 0.29), and 0.32 ms−1 (0.27 to 0.36) were obtained for the CMJ, and RSI measured from the 30 and 45 cm box, respectively. Decrements for all assessments were non-linear with the steepest rates of decline measured in the initial periods following warm-up. High probabilities were calculated ( p ≥ 0.979) that up to 50% of the initial warm-up improvement for the CMJ would be lost between 20 and 30 min. The results of this study provide a guide for future research and practitioners managing the pre-pitch entry of soccer substitutes. It is suggested that practitioners consider and assess the effectiveness of exposing players to a re-warm-up between 20- and 30-min prior to pitch entry to maintain performance capabilities.

Effects of an external pneumatic compression device vs static compression garment on peripheral circulation and markers of sports performance and recovery.

To identify the effects of a single 30min partial lower leg external pneumatic compression (EPC) treatment compared to a static compression (SC) garment or a no treatment control (CTL) on markers of recovery and performance following a muscle damaging protocol. Thirty healthy, active males(23 ± 3years; 180.2 ± 9.0cm; 81.6 ± 11.3kg) performed 100 drop jumps from a 0.6m box followed by a randomized, single 30min treatment of either a partial lower leg EPC device worn below the knee and above the ankle (110mmHg), SC garment (20-30mmHg) covering the foot and calf just below the knee, or no treatment CTL, and then returned 24 and 48h later. Participants were assessed for measures of muscle soreness, fatigue, hemodynamics, blood lactate, muscle thickness, circumferences, and performance assessments. The drop jump protocol significantly increased muscle soreness (p < 0.001), fatigue (p < 0.001), blood flow (p < 0.001), hemoglobin (p < 0.001), and muscle oxygen saturation (SMO2; p < 0.001). Countermovement jump and squat jump testing completed after treatment with either EPC, SC, or CTL revealed no differences for jump height between any condition. However, EPC treatment maintained consistent braking force and propulsive power measures across all timepoints for countermovement jump testing. EPC and SC treatment also led to better maintenance of squat jump performance for average relative propulsive force and power variables at 24 and 48h compared to CTL. A single 30min partial leg EPC treatment may lead to more consistent jump performance following a damaging bout of exercise.

Prospective Study on Dynamic Postural Stability in Youth Competitive Alpine Skiers: Test-Retest Reliability and Reference Values as a Function of Sex, Age and Biological Maturation.

This study aimed 1) to assess the test-retest reliability of dynamic postural stability index (DPSI) assessments using a ski-specific jump protocol that consists of single-leg landings on a three-dimensional force plate after forward-performed double-leg drop jumps from a box over a hurdle (DJSLLs), 2) to provide reference values for female and male youth competitive alpine skiers; 3) to explore their changes in DPSI over 3 years during adolescence; and 4) to investigate potential associations of DPSI with age and biological maturation. Using three-dimensional force plates, 16 healthy subjects were tested on the same day (test-retest reliability experiment; five test-retest assessments of right leg landings), and 76 youth skiers aged 13–15 years were tested 3 times within 2 years (main experiment; average of two trials per leg each time). The test-retest reliability experiment revealed an ICC(3,1) and 95% CI of 0.86 [0.74, 0.94] for absolute DPSI assessment. The within-subject SEM of absolute DPSI was 16.30 N [13.66 N, 20.65 N], and the standardized typical error was moderate (0.39 [0.33, 0.50]). Both absolute and relative DPSI values were comparable between male and female youth competitive alpine skiers. The mean absolute DPSI in year 1 (195.7 ± 40.9 N), year 2 (196.5 ± 38.9 N) and year 3 (211.5 ± 41.3 N) continuously increased (i.e., worsened) (p < 0.001). Mean relative, i.e. body weight force normalized, DPSI values significantly decreased, i.e., improved, from year 1 to 2 (0.42 ± 0.01 vs. 0.36 ± 0.004; p < 0.001) and year 1 to 3 (0.42 ± 0.01 vs. 0.36 ± 0.01; p < 0.001). Absolute DPSI correlated with age and biological maturation, while no such correlations were found for relative DPSI values. Our findings suggest that DPSI is a reliable and sensitive measure of dynamic postural control during DJSLLs and that relative DPSI improves annually in competitive youth skiers when accounting for body weight. Future work should consider biological maturation testing during the growth spurt, and normalizing to body weight force could be a possible solution.

Backward Double Integration is a Valid Method to Calculate Maximal and Sub-Maximal Jump Height

ABSTRACT The backward double integration method uses one force plate and could calculate jump height for countermovement jumping, squat jumping and drop jumping by analysing the landing phase instead of the push-off phase. This study compared the accuracy and variability of the forward double integration (FDI), backwards double integration (BDI) and Flight Time + Constant (FT+C) methods, against the marker-based rigid-body modelling method. It was hypothesised that the jump height calculated using the BDI method would be equivalent to the FDI method, while the FT+C method would have reduced accuracy and increased variability during sub-maximal jumping compared to maximal jumping. Twenty-four volunteers performed five maximal and five sub-maximal countermovement jumps, while force plate and motion capture data were collected. The BDI method calculated equivalent mean jump heights compared to the FDI method, with only slightly higher variability (2–3 mm), and therefore can be used in situations where FDI cannot be employed. The FT+C method was able to account for reduced heel-lift distance, despite employing an anthropometrically scaled heel-lift constant. However, across both sub-maximal and maximal jumping, it had increased variability (1.1 cm) compared to FDI and BDI and should not be used when alternate methods are available.

High-Efficiency Directional Ejection of Coalesced Drops on a Circular Groove.

Coalescence-induced drop jumping has received significant attention in the past decade. However, its application remains challenging as a result of the low energy conversion efficiency and uncontrollable drop jumping direction. In this work, we report the high-efficiency coalescence-induced drop jumping with tunable jumping direction via rationally designed millimeter-sized circular grooves. By increasing the surface-droplet impact site area and restricting the oscillatory deformation, the energy conversion efficiency of the jumping droplet reaches 43.5%, 600% as high as the conventional superhydrophobic surfaces. The droplet jumping direction can be tuned from 90° to 60° by varying the principal curvature of the circular groove, while the energy conversion efficiency remains unchanged. We show through theoretical analysis and numerical simulations that the directional jumping mainly originates from reallocation of droplet momentum enabled by the asymmetric liquid bridge impact. Our study demonstrates a simple yet effective method for fast, efficient, and directional droplet removal, which warrants promising applications in jumping droplet condensation, water harvesting, anti-icing, and self-cleaning.

Differences in Vertical Performance Caused by Drop Jumping on Surfaces with Different Stiffness

It is well established that muscle activation regulates leg stiffness to optimize stretch shortening cycle (SSC) performance. There is a significant interaction between the surface properties, muscle activation and leg stiffness. The aim of this study was to examine the potentiating adjustments after drop jumps (DJs) executed on two surfaces with different elasticity. Twenty-two adults randomly performed 3 protocols: Protocols with three pre-conditioning DJs performed on a springboard (PSB), Protocol (PG) with three pre-conditioning DJs performed on a stiff ground surface and Protocol without any type of pre-conditioning (C). Vertical jump performance was evaluated at four time points: before (COND0), immediately after pre-conditioning (COND10), and after 1 (COND60) and 2 min (COND120) of rest. Dynamics, kinematics and electromyographic parameters of the ankle were evaluated. ANOVA with repeated measures revealed statistically significant increase in Hpeak, Ppeak and Kleg was observed (p&lt;0.05), over split-intervals and rest periods for Protocol (PSB) while no differences were recorded in jump kinematics. Both protocols (PSB and PG) significantly decreased CI during the pre-activation and eccentric phase, whereas the CI was increased during the concentric phase. The positive effect observed in jump performance could not be attributed to co-activity of the ankle joint, indicating that jumping on an elastic surface, may be beneficial in cases where increased leg stiffness is a determining factor for final performance.

Optimal Loading Height: A Practical Research of Drop Jump from Biomechanics.

Plyometrics training is paid great attention by coaches and researchers because of its significant effect on the level of lower limb explosive athletes. Many coaches and reseachers use the biomechanical methods to determine optimal loading height for drop jump. The researchers' findings in determining optimal loading height were highly biased and were not applied effectively to training practices. This paper reviews the development process of optimal loading height in deep-jump training, combs the relevant concepts and biomechanical mechanisms of optimal loading height in deep-jump training, and looks forward to the future research.

Maximal lateral ligament strain and loading during functional activities: Model-based insights for ankle sprain prevention and rehabilitation

BackgroundAlthough it is generally accepted that sports activities present a high risk of lateral ligament injury, the extent to which ligaments are loaded during functional activities is less explored. This is relevant when considering ankle sprain prevention and staged rehabilitation following ligament sprain or reinforcing surgery. Therefore, anterior talofibular ligament, calcaneofibular ligament and posterior talofibular ligament strain and loading were evaluated, based on a newly developed loading index, during movements executed during daily life and rehabilitation. MethodsThree-dimensional motion analysis data was acquired in 10 healthy volunteers during eleven different movements and processed using musculoskeletal modelling. Maximal lateral ligament strain and ligament loading, based on an new index accounting for the ankle and subtalar moment magnitude, ligament strain magnitude and duration, were calculated and statistically compared to ligament strain and loading during walking and a reference clinical (talar tilt) test. FindingsAnterior talofibular, calcaneofibular and posterior talofibular lateral ligament loading were highest during vertical drop jumps, medio-lateral single leg hops and running. Additionally, anterior talofibular loading was high during stair descending, calcaneofibular loading during single leg stance without visual feedback and posterior talofibular loading during anterior single leg hops. During the clinical test, anterior talofibular and calcaneofibular ligament strain were substantially lower than the maximal strain during different movements. InterpretationOur results allow classification of exercises according to the ligament loading index and maximal strain, thereby providing objective data to progressively stage ligament loading during rehabilitation.

Central vs. Peripheral Vision during a Singe-Leg Drop Jump: Implications of Dynamics and Patellofemoral Joint Stress

Landing on a single-leg without receiving direct visual information (e.g., not looking at the ground) may increase the risk of injury. We examined whether visual focus contributed to the changing lower-extremity dynamics and patellofemoral joint stress during a single-leg drop jump task. Twenty healthy volunteers visited the laboratory for three separate sessions. During each session, participants randomly performed either of two types of a single-leg drop jump task from a 30 cm high wooden box. Subsequently, participants looked at the landing spot (central vision condition) or kept their heads up (peripheral vision condition) when performing the task. Sagittal and frontal plane lower-extremity joint angles and joint moments (in the ankle, knee, and hip), including the vertical ground reaction force, and patellofemoral joint stress during the first landing phase (from initial contact to peak knee flexion) were compared. Greater ankle inversion and hip adduction were observed when landing with the peripheral vision condition. However, the magnitudes were negligeable (Cohen’s d effect size &lt;0.35). No statistical difference was observed in other comparisons. Landing on a single-leg from a 30 cm height without receiving full visual attention (peripheral vision condition) does not increase the risk of lower-extremity traumatic and overuse injuries.

Single-Leg Drop Jump Biomechanics After Ankle or Knee Joint Cooling in Healthy Young Adults.

It is unclear if lower-extremity joint cooling alters biomechanics during a functional movement. To investigate the effects of unilateral lower-extremity cryotherapy on movement alterations during a single-leg drop jump. A crossover design. Laboratory. Twenty healthy subjects (10 males and 10 females; 23y, 169cm, 66kg). Subjects completed a single-leg drop jump before and after a 20-minute ankle or knee joint cooling on the right leg, or control (seated without cooling) on 3 separate days. Time to peak knee flexion, vertical ground reaction force, lower-extremity joint angular velocity (sagittal plane only), and angle and moment (sagittal and frontal planes) in the involved leg over the entire ground contact (GC; from initial contact to jump-off) during the first landing. Time to peak knee flexion was compared using an analysis of variance; the rest of the outcome measures were analyzed using functional analyses of variance (P < .05). Neither joint cooling condition changed the time to peak knee flexion (F2,95 = 0.73, P = .49). Ankle joint cooling reduced vertical ground reaction force (55N at 4% of GC), knee joint angular velocity (44°/s during 5%-9% of GC), and knee varus moment (181N·m during 18%-20% of GC). Knee joint cooling resulted in a reduction in knee joint angular velocity (24°/s during 37%-40% of GC) and hip adduction moment (151N·m during 46%-48% of GC), and an increase in hip joint angular velocity (16°/s during 49%-53% of GC) and plantarflexion angle (1.5° during 11%-29% of GC). Resuming activity immediately after lower-extremity joint cooling does not seem to predispose an individual to injury during landing because altered mechanics are neither overlapping with the injury time period nor of sufficient magnitude to lead to an injury.

The Influence of Repeated Drop Jump Training on Countermovement Jump Performance.

Countermovement jump (CMJ) is used to assess athletic performance of the lower limbs. Drop jump (DJ) is an effect training method that can improve athlete's jumping performance. The main purpose of this study is to explore the effects of different drop jump heights (DJH)30, DJH40, and DJH50 cm for 250 drop jumps (DJs250) on CMJ. Eighteen male athletes were selected as subjects. After the 50th, 100th, 150th, 200th, and 250th DJs, perform 5 groups of CMJ (the average of 3 times for each group) and record them as the 50th, 100th, 150th, 200th, and 250th CMJ jumps (CMJs50, CMJs100, CMJs150, CMJs200, and CMJs250). The BTS motion capture system and two force plates are used to record data. The MATLAB software was used to analyze data through one-way ANOVA repeated measures. If there is a significant difference, the LSD method is used for post hoc comparison. Jump height (JH), contact time (CT), reaction intensity index (RSI), average rate of force development (ARFD), left average rate of force development (LARFD), and right average rate of force development (RARFD) of CMJs50, CMJs100, CMJs150, and CMJs200 at DJH50 were greater than those at DJH40 and DJH30 (all p < 0.05). DJH50 height and DJs200 training times can improve SSC mechanism and improve athlete CMJ performance.

Test–retest reliability of drop jumps in students aged seven and eight: exploratory investigation

Test–retest reliability of drop jumps in students aged seven and eight: exploratory investigation

The association between reactive strength index and reactive strength index modified with approach jump performance.

Jumping performance is one of the key components of volleyball game, thus evaluating jumping ability through different biomechanical variables offers opportunity for performance optimization. The aim of this study was to assess the associations between reactive strength index (RSI), reactive strength index modified (RSImod) and approach jump performance in male volleyball players. Forty volleyball players performed drop jump (DJ) form 40 cm high box, bilateral and unilateral countermovement jumps (CMJ) and approach jump. RSI in DJ was calculated as the ratio between jump height and ground contact time, while the RSI in CMJ tasks (RSImod) was calculated as ratio between jump height and jump time. Our results indicate that the relationships among different RSI variants and approach jump in volleyball players are moderate to strong (r = 0.42–0.73), with the highest correlations being observed for RSImod from bilateral CMJ (r = 0.676–0.727). Those observations are in line with the principle of movement specificity, which suggests that the best performance indicator should be the task that best resembles the demands of the sport-specific movements. Further research is needed to reveal more about the potential of implementing these findings for training optimization through monitoring RSI and RSImod values.

The effect of a core training program on jump performance in female handball players

Objectives: To evaluate changes on bilateral and unilateral jump performance and frontal knee projection angle after an implementation of a core strength program in female handball players.&#x0D; Equipment and methods: This is a randomized controlled trial study. A total of 20 participants [age = 17.2 (1.9) years, height = 1.7 (0.1) m, weight = 62.8 (7) kg ] were recruited and split in: a core training group and a control group. The core training group participated in 8 weeks in-season of a core strength program (2 times/week). Pre- and post-intervention jump height, contact time and reactive strength index were collected during bilateral and unilateral drop vertical jumps. Frontal knee projection angle was measured only at unilateral drop jumps.&#x0D; Results: Core training group increased the bilateral jump height by 18.8% and showed a statistically significant difference in reactive strength index from pre-intervention [0.07 (0.03)] to post-intervention [0.10 (0.04)]. The core training group also improved the unilateral jump height by 20%, but only at the non-dominant leg. This improvement was accompanied by a statistically significant decreased in the frontal knee projection angle from pre-intervention [13.8 (7.38) degrees] to post-intervention [9.3 (6.09) degrees]. Statistical significant difference was set at p ˂0.05.&#x0D; Conclusion: A core strength training increased jump performance and it could play a role in ACL injury prevention programs in female team players.&#x0D; &#x0D;

Determinants of Y-Shaped Agility Test in Basketball Players

Y-shaped agility test is a reactive agility test that includes both sensory and motor components. However, there is a lack of information about the contribution of these components to reactive agility in basketball players. Therefore, this study investigates: (i) the relationship between Y-shaped agility performance and reaction speed, sprint speed, change of direction speed, muscle strength, and (ii) determinants of this reactive agility test. Eleven male basketball players performed a Y-shaped agility test, 5 m and 20 m sprints, a 505 Agility test, squat, countermovement and drop jumps, and simple and two-choice reaction time tests. The results revealed a significant relationship between the time in Y-shaped agility test and 5 m sprint time (r = 0.795, p = 0.003, R2 = 0.632), 20 m sprint time (r = 0.676, p = 0.022, R2 = 0.457), and reactive strength index (r = −0.619, p = 0.042, R2 = 0.383), but not with simple and choice-based reaction times. These findings indicate that performance in the Y-shaped agility test is more profoundly determined by a motor rather than a sensory component. This may be ascribed to the structure of a predominantly velocity-oriented Y-shaped agility test with a small contribution of responses to visual stimuli. The adaptation of basketball players to training aimed at increasing speed and strength may also play a role. The structure of the Y-shaped agility test should be modified so as to better reflect the sensory component of reactive agility and more sensitively reveal within- and between-group differences.

The impact of breast support garments on fit, support and posture of larger breasted women

Due to current measurement, sizing and fitting approaches, poor bra fit is prevalent amongst larger breasted women. The impact of improving bra fit hasn't yet been explored. This pre-clinical study aimed to explore immediate and short-term biomechanical responses to changing breast support garment. Asymptomatic participants (n=24) performed a static standing task, drop jumps and seated typing whilst kinematic data from the breasts and spine were recorded. Three breast support conditions were assessed: Usual, professionally fitted bra in the immediate term (PFB), and the same professionally fitted bra after four weeks wear (PFB28). Bra fit assessments were included for both bras. All participants failed the bra fit assessment when wearing the Usual bra and 67% (n=16) failed when wearing the PFB. Less bra fit issues were present in the PFB, resulting in immediate biomechanical changes relating to breast support and spinal posture, yet nothing in the short term (PFB28). This research sets the foundations for future work to investigate whether the implementation of better fitting breast support garments can influence musculoskeletal pain amongst larger breasted women, whilst attributing potential improvement of symptoms, objective measures of breast support and spinal posture.

Single leg vertical jump performance identifies knee function deficits at return to sport after ACL reconstruction in male athletes

ObjectivesVertical jump performance (height) is a more representative metric for knee function than horizontal hop performance (distance) in healthy individuals. It is not known what the biomechanical status of athletes...

Drop Jumping on Sand Is Characterized by Lower Power, Higher Rate of Force Development and Larger Knee Joint Range of Motion.

Plyometric training on sand is suggested to result in advanced performance in vertical jumping. However, limited information exists concerning the biomechanics of drop jumps (DJ) on sand. The purpose of the study was to compare the biomechanical parameters of DJs executed on rigid (RIGID) and sand (SAND) surface. Sixteen high level male beach-volleyball players executed DJ from 40 cm on RIGID and SAND. Force- and video-recordings were analyzed to extract the kinetic and kinematic parameters of the DJ. Results of paired-samples t-tests revealed that DJ on SAND had significantly (p < 0.05) lower jumping height, peak vertical ground reaction force, power, peak leg stiffness and peak ankle flexion angular velocity than RIGID. In addition, DJ on SAND was characterized by significantly (p < 0.05) larger rate of force development and knee joint flexion in the downward phase. No differences (p > 0.05) were observed for the temporal parameters. The compliance of SAND decreases the efficiency of the mechanisms involved in the optimization of DJ performance. Nevertheless, SAND comprises an exercise surface with less loading during the eccentric phase of the DJ, thus it can be considered as a surface that can offer injury prevention under demands for large energy expenditure.