Article

Use of an Overhead Goal Alters Vertical Jump Performance and Biomechanics

May 2005
The Journal of Strength and Conditioning Research 19(2):394-9

DOI:10.1519/15834.1

Source
PubMed

Authors:

Kevin R Ford

High Point University

Gregory Myer

Emory University

Rose Smith

University of Cincinnati

Robyn Mchugh

Cincinnati Children's Hospital Medical Center

Show all 6 authorsHide

This study examined whether an extrinsic motivator, such as an overhead goal, during a plyometric jump may alter movement biomechanics. Our purpose was to examine the effects of an overhead goal on vertical jump height and lower-extremity biomechanics during a drop vertical jump and to compare the effects on female (N = 18) versus male (N = 17) athletes. Drop vertical jump was performed both with and without the use of an overhead goal. Greater vertical jump height (p = 0.002) and maximum takeoff external knee flexion (quadriceps) moment (p = 0.04) were attained with the overhead goal condition versus no overhead goal. Men had significantly greater vertical jump height (p < 0.001), maximum takeoff vertical force (p = 0.009), and maximum takeoff hip extensor moment (p = 0.02) compared with women. A significant gender x overhead goal interaction was found for stance time (p = 0.02) and maximum ankle (p = 0.04) and knee flexion angles (p = 0.04), with shorter stance times and lower angles in men during overhead goal time. These results indicate that overhead goals may be incorporated during training and testing protocols to alter lower-extremity biomechanics and can increase performance.

Different External Cues Elicit Specific Kinetic Strategies During a Drop Jump in Well-Trained Adolescent Soccer Players

Article

Full-text available

Jan 2025
J STRENGTH COND RES

Barillas, SR, Lloyd, RS, Pedley, JS, and Oliver, JL. Different external cues elicit specific kinetic strategies during a drop jump in well-trained adolescent soccer players. J Strength Cond Res 39(1): e30-e39, 2025-The purpose of this study was to examine how different external cues that focus on jump height and ground contact time influence kinetic outcomes from a drop jump (DJ) in well-trained young soccer players. Following familiarization, 21 adolescent male soccer players performed 2 DJ trials under 4 different cue conditions: a height cue instructed subjects to jump to the ceiling, a ground contact cue instructed subjects to get off the ground as fast as possible, a combined condition joined both cues together, whereas a neutral cue with no external focus was used as a control condition. The height and contact time cues elicited specific kinetic responses that were significantly different to other conditions (p < 0.05); the height cue increasing impulses (d = 1.17-1.21) and jump height (d = 0.68), with the contact cue shortening ground contact time (GCT) (d = 1.27), increasing vertical stiffness (d = 1.48) and increasing force (d = 1.20-1.36). When combining the height and contact cue, a combination of significant (p < 0.05) kinetic responses were also observed, albeit to a lesser effect. Specifically, the combined cue increased impulse (d = 0.71-0.76) and jump height (d = 0.57) compared with a contact cue and a height cue, increased reactive strength index (d = 0.34), force (d = 0.69-0.83), and vertical stiffness (d = 0.75) while also reducing GCT (d = 0.69). Practitioners working with well-trained adolescent soccer players can use different external cues to effectively influence the kinetic strategies employed during a DJ.

Effects of attentional focus strategy on drop jump for athletes with different experience levels: Performance, kinetics and kinematics

Article

Full-text available

Oct 2024

The attentional focus strategy (AFS) affects drop jump (DJ) performance; however, its effects on DJ kinetics and kinematics are unclear. This study examines the effects of AFS on DJ performance, kinetics and kinematics. Forty collegiate males were divided into a DJ experienced group and a DJ inexperienced group, and they performed two trials of DJs after listening to instructions designed to elicit internal (INT), external (EXT) or neutral (NEUT) focus of attention. In the experienced group, the reactive strength index (RSI) was larger with the NEUT than with the INT. Hip joint torque and positive hip joint power in the concentric phase was smaller with the NEUT than with the INT, and the hip joint angle at the lowest centre of mass was larger with the NEUT than with the INT (p < .05). In the inexperienced group, RSI was larger with the EXT than with the INT. Further, the hip joint torque in the concentric phase was smaller with the EXT than with the INT; positive ankle joint power was larger with the EXT than with the INT; and the hip joint angles at the lowest centre of mass and take-off were larger with the EXT than with the INT (p < .05). These results showed that the AFS affected the DJ performance, kinetics and kinematics and suggested that effective DJ training may be achieved with the NEUT for DJ experienced and with the EXT for DJ inexperienced.

Effect of Heading a Soccer Ball as an External Focus During a Drop Vertical Jump Task

Article

Full-text available

Apr 2023

Background Research has demonstrated that performing a secondary task during a drop vertical jump (DVJ) may affect landing kinetics and kinematics. Purpose To examine the differences in the trunk and lower extremity biomechanics associated with anterior cruciate ligament (ACL) injury risk factors between a standard DVJ and a DVJ while heading a soccer ball (header DVJ). Study Design Descriptive laboratory study. Methods Participants comprised 24 college-level soccer players (18 female and 6 male; mean ± SD age, 20.04 ± 1.12 years; height, 165.75 ± 7.25 cm; weight, 60.95 ± 8.47 kg). Each participant completed a standard DVJ and a header DVJ, and biomechanics were recorded using an electromagnetic tracking system and force plate. The difference (Δ) in 3-dimensional trunk, hip, knee, and ankle biomechanics between the tasks was analyzed. In addition, for each biomechanical variable, the correlation between the data from the 2 tasks was calculated. Results Compared to the standard DVJ, performing the header DVJ led to significantly reduced peak knee flexion angle (Δ = 5.35°; P = .002), knee flexion displacement (Δ = 3.89°; P = .015), hip flexion angle at initial contact (Δ = −2.84°; P = .001), peak trunk flexion angle (Δ = 13.11°; P = .006), and center of mass vertical displacement (Δ = −0.02m; P = .010), and increased peak anterior tibial shear force (Δ = −0.72 N/kg; P = .020), trunk lateral flexion angle at initial contact (Δ = 1.55°; P < .0001), peak trunk lateral flexion angle (Δ = 1.34°; P = .003), knee joint stiffness (Δ = 0.002 N*m/kg/deg; P = .017), and leg stiffness (Δ = 8.46 N/kg/m; P = .046) compared to those in standard DVJs. In addition, individuals' data for these variables were highly and positively correlated between conditions ( r = 0.632-0.908; P < .001). Conclusion The header DVJ task showed kinetic and kinematic parameters that suggested increased risk of ACL injury as compared with the standard DVJ task. Clinical Relevance Athletes may benefit from acquiring the ability to safely perform header DVJs to prevent ACL injury. To simulate real-time competition situations, coaches and athletic trainers should incorporate such dual tasks in ACL injury prevention programs.

Effect of an overhead goal on landing error scoring system and jump height measures

Article

Nov 2022
PHYS THER SPORT

Objectives Compare overall Landing Error Scoring System (LESS) scores, risk categorisation, specific LESS errors, and double-leg jump-landing jump heights between overhead goal and no goal conditions. Design Randomised cross-over. Setting Laboratory. Participants 76 (51% male). Main outcome measures Participants landed from a 30-cm box to 50% of their body height and immediately jumped vertically for maximum height. Participants completed three trials under two random-ordered conditions: with and without overhead goal. Group-level mean LESS scores, risk categorisation (5-error threshold), specific landing errors, and jump heights were compared between conditions. Results Mean LESS scores were greater (0.3 errors, p < 0.001) with the overhead goal, but this small difference was not clinically meaningful. Similarly, although the number of high-risk participants was greater with the overhead goal (p = 0.039), the 9.2% difference was trivial. Participants jumped 2.7 cm higher with the overhead goal (p < 0.001) without affecting the occurrence of any specific LESS errors. Discussion Performing the LESS with an overhead goal enhances sport specificity and elicits greater vertical jump performances with minimal change in landing errors and injury-risk categorisation. Adding an overhead goal to LESS might enhance its suitability for injury risk screening, although the predictive value of LESS with an overhead goal needs confirmation.

Presence of an Overhead Goal Does Not Improve the Effectiveness of Jump Training

Article

Sep 2022

Akbaş, A, Marszałek, W, and Król, H. Presence of an overhead goal does not improve the effectiveness of jump training. J Strength Cond Res XX(X): 000-000, 2022-This study investigated the effectiveness of jump training with and without an overhead goal (OG) on a modified countermovement jump (CMJ) tested in a similar manner, with and without OG. Fifty-two men divided into 3 groups-trained with OG, trained without OG, and untrained-were examined: before the commencement of training; after 2, 4, and 6 weeks of training; and 2 weeks after the discontinuation of training. Each session consisted of 50 modified CMJ and was performed 3 times per week. Countermovement jump height, mean power, peak power, countermovement depth, and take-off phase time were quantified, and the statistical level was set at p < 0.05. Although the results showed the beneficial effect of OG on jump height (p < 0.01), the training with OG did not bring significantly better results than training without OG. In addition, the group trained without OG improved after 2 weeks in both testing conditions (with and without OG), whereas the group trained with OG improved after 2 weeks when tested with OG and only after 6 weeks when tested without OG. We believe the use of OG in jump training may be detrimental when the OG is withdrawn from the testing procedure because of its strong motivational and feedback features. Consequently, athletes in disciplines which require them to jump toward an object located over their head during a game, e.g., a ball or crossbar, should be tested with the presence of OG. Despite this, OG is still an important factor in maximizing jump performance.

The Effects of Drop Vertical Jump Task Variation on Landing Mechanics: Implications for Evaluating Limb Asymmetry

Article

Full-text available

Jan 2024

Limb asymmetry is an important consideration when evaluating rehabilitation progress or re-injury risk. The drop vertical jump (DVJ) task is commonly used to assess landing mechanics; however, the extent to which task setup influences limb asymmetry is unknown. Our purpose was to examine limb asymmetries across DVJ variations. We hypothesized that more demanding variations involving greater jump distance and target use would elicit greater landing asymmetries. Participants performed six DVJ variations while lower extremity joint kinematics and kinetics were collected. Joint angles and internal moments of the hip, knee and ankle were computed at initial contact and over the decent phase of the initial landing. The horizontal jump distance and the verbal instructions provided on how to jump off the box influenced limb asymmetries. The DVJ variation without a horizontal jump distance resulted in significant differences at the hip and knee; specifically, greater hip and knee flexion asymmetry (7.0° and 15.2° differences, respectively) were observed between limbs at initial contact. Instructions restricting take-off and landing strategies reduced asymmetry; this indicates that verbal instructions are critical to avoid altering natural landing mechanics. To best utilize DVJ as a tool, study protocols should be standardized to allow for more generalizable research and clinical findings.

The effects of different vertical jump height on electromyographic, kinematic and kinetic variables

Article

Full-text available

Jan 2022

Countermovement jump (CMJ) is an element of many sports techniques and has an important role in the overall performance, both when performed at maximal and submaximal intensity. This paper aims to investigate changes in biomechanical and neuromuscular variables that are responsible for controlling different submaximal intensities of the CMJ. 8 healthy and uninjured volleyball players from the first league of the Republic of Serbia, average age 21.9 ± 1.9 years, average body height 191.6 ± 9.2 cm, average body weight 83.1 ± 7.1 kg were included in the study. Subjects performed CMJ at three different jump heights (approximately 65%, 80%, and 95% of the maximal height). For the analysis of electromyographic data, the value of root mean square analysis was used separately for the amortization phase and the jump phase, for the following muscles: m. gluteus maximus (GlutM), m. rectus femoris (RF), m. biceps femoris (BF), m. vastus lateralis (VL), m. tibialis anterior (TA) and m. gastrocnemius medialis(GastM).Kinematic and kinetic variableswere monitored: vertical center of mass displacement in the amortization phase [m], the center of mass height at take-off point [m], jump height [m], jump speed [m/s], angular displacement in the ankle, knee and hip joint [rad], maximal vertical ground reaction force [N/ kg], vertical stiffness [kN/m/kg], the torque of the ankle, knee and hip joint [Nm/kg]. The change in jump height (65, 80 and 95%) did not have a significant effect on the change in activation for most muscles (p≥0.05), except for GastM where a tendency towards increase was observed (p=0.066). During jump phase, the activation of VL, BF, GlutM, TA muscles significantly increased compared to the amortization phase (p≤0.05). The torque in the hip joint increased significantly with increasing jump height (65<80=95%) (p=0.028). During amortization phase, the values of vertical center of mass displacement increased significantl y between each jump height (65<80<95%) (p≤0.05), while the values of vertical stiffness decreased with increasing jump height, where significant differences were observed between 80% and 95% of maximal jump height (65=80<95%) (p=0.012). Angular displacements in the knee and hip joint increased significantly with increasing jump height (65<80<95%) (p≤0.05) while no changes in angular displacement in the ankle joint were observed (p≥0.05). The results of the research show that the increase in the jump height is related to an increase in the amortization phase, due to an increase in angular displacements in the knee and hip joint, as well as an increase in torque of the hip joint.

Kinetic Responses to External Cues Are Specific to Both the Type of Cue and Type of Exercise in Adolescent Athletes

Article

Full-text available

Jul 2022

Barillas, SR, Oliver, JL, Lloyd, RS, and Pedley, J. Kinetic responses to external cues are specific to both the type of cue and type of exercise in adolescent athletes. J Strength Cond Res XX(X): 000-000, 2022-The purpose of this study was to examine how external cues influence kinetics during isometric and dynamic tasks in adolescent athletes. Fifteen adolescent male soccer players performed an isometric midthigh pull (IMTP), unloaded and loaded squat jumps (SJs) (15 and 30% of body mass), countermovement jump (CMJ), and drop jump (DJ) using a neutral or external force-specific or velocity-specific cues. Cue type had limited effects on outcomes in the IMTP or SJs, with mostly trivial (g < 0.20), nonsignificant differences (p > 0.05) across kinetic variables. In the CMJ and DJ, a force cue significantly (p < 0.05) increased jump height (g = 0.43 & 0.52) compared with a velocity cue, but in the DJ, a force cue significantly increased jump height (g = 0.52) compared with both a neutral and velocity cue. However, a velocity cue significantly (p < 0.05) reduced ground contact time (g = 0.73-1.52) and time to peak force (g = 0.50-1.29) in both the CMJ and DJ when compared with a force and neutral cue and increased force and power-related measures (g = 0.33-1.12) in the CMJ and DJ when compared with a force cue. In adolescent athletes, the type of external cue had limited effects on kinetic measures in an IMTP and SJ but differential effects on both a CMJ and DJ, suggesting cues have more effect with increasing movement velocity. Consequently, practitioners working with adolescent athletes should consider both the type of exercise and the desired outcome when providing external cues.

Comparing the Effect of a Simulated Defender and Dual-Task on Lower Limb Coordination and Variability during a Side-Cut in Basketball Players with and without Anterior Cruciate Ligament Injury

Article

Jan 2022
J BIOMECH

Anterior Cruciate Ligament (ACL) injuries commonly occur when attention is simultaneously on the environment (other players, objects) and maintaining neuromuscular control. Therefore, our purpose was to investigate lower-extremity coordination following ACLR during a run-to-cut with ecological validity to sport competition. Sixteen male basketball players with ACLR (20.8 ± 3.42 years, time since surgery: 9.5 ± 2.4 months) were contrasted with 16 healthy male control basketball players (21.3 ± 3.17 years) during a run-to-cut maneuver under two conditions: 1) standard, run and initiate a ∼40° side-cut and 2) simulated sport, run-to-cut with the presence of a defender and engaged in a dual-task to intercept a ball. Lower limb kinematics were used to calculate continuous relative phase metrics for evaluation of coordination pattern and variability. Independent t-test and effect size were used to evaluate the difference between the two groups and across condition via change score. The simulated sports cutting maneuver coordination patterns were significantly different between groups for hip-ankle, hip-knee, knee-knee, and knee-ankle coupling (p<.05). Only hip-knee coupling had a significant condition change score (p=.01) with ACLR increasing (51.8 ± 79.1%) and healthy controls (-16.04 ± 64.1%) decreasing hip flexion-extension and keen abduction-adduction coupling. There was no significant difference in normal cut coordination between groups. The addition of simulated sport visual attention and dual task motor planning during the run-to-cut might elicit different lower limb movement patterns in ACLR athletes compared to the healthy counterparts, potentially contributing to the elevated reinjury risk in those with ACLR history when returning to sport.

Using an overhead target increases volleyball-specific vertical jump performance

Article

Jul 2021

In volleyball, spikes and block jumps are among the most important movements when earning points and impacting performance. Many studies have found a greater jump height after acutely augmented feedback and extrinsic focus of attention on vertical jump height. However, there are limited studies on the long-term effects of using an overhead target on volleyball-specific vertical jumps (block and spike jumps). Therefore, the aim of the current study was to investigate the effects of using an overhead target on the vertical jump heights of volleyball players. Twenty-five professional male volleyball players (age: 24.443.78 years; height: 1.828.79 cm; body mass: 80.969.37 kg) were randomly assigned either to the experimental group with an overhead target (OHT) (n=9), group without an overhead target (WOHT) (n=8), or the control group (n=8). The OHT group performed vertical jumps with an overhead target before their regular training program, while the WOHT group completed vertical jumps without an overhead target before their regular training program. Meanwhile, the control group performed only their regular training program, which was a five-week (three days per week) program. All participants’ spike jump (SPJ) and block jump (BJ) results were assessed before and after the intervention. A repeated-measures analysis of variance (3×2) did not reveal any significant between group interactions for SPJ and BJ (F=7.32, p<0.11 and F=1.59, p<0.22 respectively), but significant results were found for the time effect (F=96.33, p<0.01 and F=132.25, p<0.01 respectively) and group × time interaction (F=42.59, p<0.01 and F=61.52, p<0.01, respectively). While the pre- and post-tests for BJ and SPJ values did not change in the control group (p>0.05), both of these values increased in the OHT group (60.005.95 to 67.445.98 cm, p<0.01 for d=1.24 and 49.006.74 to 56.225.29 cm p<0.01 for d=1.19, respectively) and WOHT group (57.504.86 to 60.504.99 cm, p<0.01 for d=0.60 and 47.754.65 to 50.253.69 cm, p<0.01 for d=0.59). It has been suggested that trainers and professionals can use an overhead target to increase the BJ and SPJ heights of professional volleyball players.

Evaluating the Spectrum of Cognitive-Motor Relationships During Dual-Task Jump Landing

Article

Jul 2021

Cognitive function plays a role in understanding noncontact anterior cruciate ligament injuries, but the research into how cognitive function influences sport-specific movements is underdeveloped. The purpose of this study was to determine how various cognitive tasks influenced dual-task jump-landing performance along with how individuals’ baseline cognitive ability mediated these relationships. Forty female recreational soccer and basketball players completed baseline cognitive function assessments and dual-task jump landings. The baseline cognitive assessments quantified individual processing speed, multitasking, attentional control, and primary memory ability. Dual-task conditions for the jump landing included unanticipated and anticipated jump performance, with and without concurrent working memory and captured visual attention tasks. Knee kinematics and kinetics were acquired through motion capture and ground reaction force data. Jumping conditions that directed visual attention away from the landing, whether anticipated or unanticipated, were associated with decreased peak knee flexion angle ( P < .001). No interactions between cognitive function measures and jump-landing conditions were observed for any of the biomechanical variables, suggesting that injury-relevant cognitive-motor relationships may be specific to secondary task demands and movement requirements. This work provides insight into group- and subject-specific effects of established anticipatory and novel working memory dual-task paradigms on the neuromuscular control of a sport-specific movement.

Biomechanical Symmetry During Drop Jump Landing and Takeoff in Adolescent Athletes Following Recent Anterior Cruciate Ligament Reconstruction

Article

Full-text available

Apr 2021

This study investigated asymmetry between lower extremities during the landing and takeoff phases of a vertical drop jump (VDJ) in adolescent athletes following anterior cruciate ligament reconstruction (ACLR) and examined if performance was affected by reducing jump height. Thirty-three athletes who underwent ACLR and were referred for 3D biomechanical assessment before returning to play (mean age 15.9, SD 1.3 years; 16/33 female; mean time since surgery 7.4, SD 1.2 months) completed the VDJ while kinematics and kinetics were collected using motion capture. Lower extremity symmetry was compared between phases using paired t-tests. Jump height was calculated to measure performance. Asymmetries in ankle inversion, ankle adduction, knee adduction, hip adduction, hip adduction moment, and hip rotation moment were observed in both phases. Asymmetry was also observed in both phases for sagittal moments and power integrals at the knee and ankle and total power integral, with the magnitude of asymmetry being smaller during takeoff for power absorption/generation. Jump height was related to power generation integrals during takeoff but not to the asymmetry of power generation. Since asymmetries are translated from landing through takeoff, rehabilitation should address both phases to decrease injury risk and maximize performance after return to play.

Effects of a 4-Week Plyometric Training on the Jumping Performance of Basketball Players

Conference Paper

Full-text available

Feb 2021

This study examined the effect of 4-week plyometric training programme on the jumping performance of undergraduate male basketball players. A total of 20 basketball players from the inter-faculty game at a public university were selected to participate in this study. The subjects were aged 20-23 years (mean = 21.3 + 1.12). Convenience sampling was used to select the students and subsequently randomly assigned to the control (n=10) and experimental (n=10) groups. Both groups were trained according to the compulsory training programme three times a week for four weeks. Additional plyometric training was provided to the experimental group, twice a week on non training days. The Vertec equipment (VER Vertec Jump Trainer) was used to measure the vertical jumping ability of the subjects. Control and experimental groups showed significant improvement in the mean vertical jump scores during the post-test as compared with the pre-test (t=-2.45; p < 0.05; and t=-21.00; p<0.05 respectively). Experimental group exhibited greater improvement (11.17%) as compared to the control group (2.12%). In short, plyometric training improved the jumping performance of basketball players and it is recommended to be used as a training strategy in improving jumping performance not only in basketball but in other sport as well.

THE INFLUENCE OF VISUAL FIXATION ON HOP TEST PERFORMANCE

Article

Aug 2020
Int J Sports Phys Ther

Background: It has been recognized that anterior cruciate ligament (ACL) injuries typically occur when athletes are attending to a secondary task or object, including teammates, opponents, and/or a goal. Commonly applied tests after ACL injury include a series of hop tests to determine functional status, yet do not control for visual fixation. Purpose: To examine the influence of visual fixation during two functional hop tests in healthy individuals. Study design: Repeated measures. Methods: Participants performed the crossover triple hop for distance (XHOP) on the left lower limb, and the medial triple hop for distance (MHOP) on the right. For the hop test only conditions, participants were not instructed where to fix their vision while performing the hop test. The visual fixation condition required participants to fix their vision on an alternating plus/minus sign at the center of a display monitor located in front of the participant while performing each hop test, respectively. A retest session occurred 48-72 hours after the initial test session in order to examine reliability. Results: Thirty-four healthy adults (age: 24.0 ± 3.9 years) completed testing procedures, performing the XHOP and MHOP under standard and visual fixation conditions. Of those participants, twelve completed a retest session for reliability analysis. Hop distance was not altered by the addition of visual fixation (p = 0.27), with trivial effect sizes found across conditions (d = 0.02 - 0.07); however, the addition of visual fixation slightly improved within- and between-session intrarater reliability, standard error of measurement, and minimal detectable change of the MHOP. Conclusion: Hop distance during the XHOP and MHOP was not influenced by visual fixation. Measurement of both the XHOP and MHOP was reliable, but lacked precision. Measurement properties for the MHOP including within- and between-session reliability, standard error of measurement, and minimal detectable change improved slightly with the addition of visual fixation compared to normal MHOP procedures. Level of evidence: 2b.

Evaluation of drop vertical jump kinematics and kinetics using 3D markerless motion capture in a large cohort

Article

Full-text available

Oct 2024

Introduction 3D Markerless motion capture technologies have advanced significantly over the last few decades to overcome limitations of marker-based systems, which require significant cost, time, and specialization. As markerless motion capture technologies develop and mature, there is increasing demand from the biomechanics community to provide kinematic and kinetic data with similar levels of reliability and accuracy as current reference standard marker-based 3D motion capture methods. The purpose of this study was to evaluate how a novel markerless system trained with both hand-labeled and synthetic data compares to lower extremity kinematic and kinetic measurements from a reference marker-based system during the drop vertical jump (DVJ) task. Methods Synchronized video data from multiple camera views and marker-based data were simultaneously collected from 127 participants performing three repetitions of the DVJ. Lower limb joint angles and joint moments were calculated and compared between the markerless and marker-based systems. Root mean squared error values and Pearson correlation coefficients were used to quantify agreement between the systems. Results Root mean squared error values of lower limb joint angles and joint moments were ≤ 9.61 degrees and ≤ 0.23 N×m/kg, respectively. Pearson correlation values between markered and markerless systems were 0.67-0.98 hip, 0.45-0.99 knee and 0.06-0.99 ankle for joint kinematics. Likewise, Pearson correlation values were 0.73-0.90 hip, 0.61-0.95 knee and 0.74-0.95 ankle for joint kinetics. Discussion These results highlight the promising potential of markerless motion capture, particularly for measures of hip, knee and ankle rotations. Further research is needed to evaluate the viability of markerless ankle measures in the frontal plane to determine if differences in joint solvers are inducing unanticipated error.

Posture and vision: How different distances of viewing target affect postural stability and plantar pressure parameters in healthy population

Article

Full-text available

Oct 2024

Background: Postural stability is maintained by the Postural Control System (PCS), consisting of anatomical structures of Central Nervous System and peripheral receptors, interacting with each other, in order to keep whole-body balance by modulating the myofascial chains against gravity. The vision is one of the most important peripheral receptors for postural control. Previous studies analyzed the changes of body sway during viewing nearby (VNT) and distant (VDT) targets in healthy population without considering the feet adaptations related to the body weight distribution. Aim of this study was to investigate how different distances of viewing target affect the variability of postural stability and plantar pressure parameters in healthy subjects. Methods: 31 stabilometric and plantar pressure parameters were acquired in 20 young healthy subjects by baropodometry performed in bipedal standing during VNT and VDT (0.70 m and 3 m from the heels, respectively). Variability and statistical differences between VDT and VNT were implemented. Results: Results showed the highest repeatability for plantar pressure parameters, a slightly high for CP speed and a lowest for CoPsa and Length Surface Function during both VNT and VDT. Moreover, a significant increase of load percentage on left-foot and right-Forefoot, of mean and maximum pressures on left-Forefoot, of CoPsa and CPspeed and a decrease of LSF were found during VDT. Discussion: This study revealed how a greater distance of viewing target affects body-weight distribution and increases body oscillations. These findings highlighted the importance of visual target distance for the correct interpretation of postural stability and plantar pressure parameters, and the need to standardize target distance during stabilometric exam. Keywords: Baropodometry; Postural control; Posture; Stabilometry; Visual target.

Validity and reliability of a new portable and cost-effective photoelectric cells device for measuring vertical jump performance: ''The ADR Jumping''

Article

May 2023

The vertical jump is one of the most used testing movements to assess athlete's physical performance and fatigue status in several sports. However, low-cost, portable, field-based, and reliable methods are needed to measure jumping performance. The aim of the current investigation was to assess the validity and reliability of a new photoelectric cells device (ADR) for measuring the vertical jump height. Twenty-three trained male participants (age: 24.8 6 5.2 years, body mass: 74.2 6 7.3 kg; height: 1.76 6 0.04 m) performed four maximal countermovement jumps (CMJ). Flight time-derived jump height was extracted simultaneously from three devices including a force plate (FP) (Kistler Quattro-Jump, criterion measurement) and two photoelectric cells (PC) devices (ADR and Optojump). The ADR mean CMJ height measurements demonstrated substantial validity compared to both FP and Optojump (r = 0.98 p \ 0.01). Intraclass correlation coefficients (ICCs) for reliability were classified as good to excellent for the three devices (0.986-0.994). All devices showed similar coefficients of variation (CV%), classified as very good (3.21-3.85), whereas observed standardized typical error values (STE) were small (1.29-1.39). The ADR Jumping device can be considered an affordable, reliable, and valid method to measure vertical jump height thereby making it a practical resource for coaches when monitoring the training process.

Ankle dorsiflexion range of motion and landing postures during a soccer-specific task

Article

Full-text available

Mar 2023
PLOS ONE

Introduction Ankle dorsiflexion range of motion (DF-ROM) has been shown to be associated with poor landing posture. However, previously used tasks have been controlled, and it is unclear whether clinical measurements of the ankle DF-ROM, are associated with landing positions during sport-specific task. This study sought to determine the relationship between ankle DF-ROM and landing positions. Methods Thirty male soccer players participated in this study. The ankle DF-ROM was measured by the weight bearing lunge test in degrees using a cell phone app (TiltMeter). Landing patterns were assessed during a soccer-specific task using landing error scoring system items using Kinovea software. Simple correlations were used to evaluate the relationships between ankle DF-ROM and landing error scores. Results Significant correlations were found between ankle DF-ROM and landing errors (r = -0.450, P = 0.006). A decreased ankle DF-ROM was associated with greater landing errors in a soccer specific situation. Conclusion These results suggest that ankle DF-ROM may serve a useful clinical measure for identifying poor landing posture in the real-world environment. Therefore, assessment of ankle DF-ROM could be included in the screening process, which could help identify the cause of the faulty motion.

Assessment of Physical Tests in 6–11 Years Old Children: Findings from the Play Lifestyle and Activity in Youth (PLAY) Study

Article

Full-text available

Jan 2023
Int J Environ Res Publ Health

The purpose was to evaluate selected physical tests in children and to compare the outcomes by sex. A cross-sectional study design was used to evaluate children 6–11 years who completed five physical tests: hand grip, vertical jump, sit and reach, Y-balance, and obstacle course (time and score). The outcome measures including test results were descriptively examined and compared by sex. The study participants consisted of 133 children (62 males and 71 females, with a median age of 7.8 years). Girls showed superior sit and reach performance (p = 0.002) compared with boys. Boys demonstrated better Y-balance scores (p = 0.007) and faster obstacle time (p = 0.042) than girls. Sex comparison within three age groups (6–<8 years, 8–<10 years, and 10–<12 years) showed that girls performed better on the sit and reach compared with boys in the in 6–<8 years (p = 0.009). Boys demonstrated higher Y-balance scores (p = 0.017) and faster obstacle time (p = 0.007) compared with girls in the 8–<10-year age group. These data will serve to guide future efforts to evaluate normative measures of physical literacy and guide targeted training interventions to promote sustained physical activity in children with deficits relative to their age and sex norms.

The relationships between squat and countermovement jump heights and knee/ankle angles of 15-17 age swimmers conditions of the Creative Commons Attribution license (CC BY-NC-ND) (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Article

Full-text available

Jan 2022

The relationships between squat and countermovement jump heights and knee/ankle angles of 15-17 age swimmers

Article

Full-text available

Dec 2022

The aim of this study was to investigation of the relationship between knee and ankle angles and squat/countermovement jump heights at the age group of 15-17 swimmers. 10 girls (mean age 15.30±0.48yrs, mean height 165.00±5.33cm, mean mass 49.60±5.10kg) and 13 boys (mean age 16.00±1.00yrs, mean height 178.00±7.32cm, mean mass 64.31±7.35kg) were participated to this study as voluntarily. 10min dynamic dryland warming time were given and after that reflective markers were placed on the lower extremity joints. The wand calibration method was used for calibrated to the area. Fusion Sport Smart Jump matt was located in the area to calculated swimmers' jump heights. Swimmers performed three squat jump (SJ) and countermovement jump (CMJ) trials which were recorded at a frequency of 120Hz using seven high-speed cameras (Oqus 7+). The results were analyzed by Qualisys Track Manager program. Both knee and ankle angles and jump heights relations were calculated. Pearson Correlation and Mann Whitney-U was used in SPSS 21.0 program for analysed. There were no significant relations between SJ and CMJ performances and angles (p>0.05). There were significant differences between boys and girls in both jump heights (p<0.05). For correct jump performance, it is recommended to position the joints according to the recommended optimal angular values.

Peak Knee Moment and Extension Angle Changes During Simulated Soccer Match-Play

Conference Paper

Full-text available

Aug 2022

Previous biomechanical studies on non-contact anterior cruciate ligament (ACL) injuries have studied the influence of soccer-specific exertions on the lower limb joint kinematics and ACL loading using the treadmill or overground running simulations matching running activity profiles of actual match-play [1-6]. Generally, joint kinematics and ACL loading were assessed in these studies via a selection of unilateral or bilateral landing of dynamic tasks. However, very few studies have fully incorporated the ball-handling component into their investigations. Fine, coordinative tasks such as dribbling, passing, shooting and repeated jump-landing movements (i.e., during ball heading) in soccer are seldom recreated up to scale in simulated soccer match-play to improve ecological validity in the existing literature. The aim of this study was to investigate the lower limb biomechanical changes following a Ball Oriented Soccer Simulation (BOSS) during unilateral and bilateral landing tasks.

Assessment of Physical Literacy in 6-11 years old Children: Findings from the Play Lifestyle & Activity in Youth (PLAY) Study

Preprint

Full-text available

Jul 2022

Background: Physical illiteracy is often referred as a lack of movement competence and is a serious concern, especially among children. Physical tests to evaluate physical literacy are understudied, especially potential sex effects. To evaluate selected tests of physical literacy in children and to compare the outcomes by sex. Methods: A cross-sectional study design was used to evaluate children 6 -11 years who completed five physical tests: hand grip, vertical jump, sit and reach, Y-balance, and obstacle course (time and score). The obstacle course consisted of hopping, kicking a ball, catching a ball, throwing a ball, and sliding tasks. Outcome measures including test results were descriptively examined and compared by sex using the Wilcoxon rank sum test, with p<0.05 considered statistically significant. Results: The study cohort was comprised of 133 children (62 males and 71 females, with a median age of 7.8 years). The median values for the physical tests were 34.0 kg in hand grip, 22.3 cm in vertical jump, -4.2 cm in sit and reach, 165.3 composite score in Y-balance, 36.3 seconds in obstacle course time, and 29.0 points in obstacle course points. Girls showed superior sit and reach performance (p=0.002) compared to boys. Boys demonstrated better Y-balance scores (p=0.007) and faster obstacle time (p=0.042) than girls. Sex comparison within three age groups (6 - <8 years, 8 - <10 years, and 10 - <12 years) showed that girls performed better on the sit and reach compared to boys in the in 6 - <8 years (p=0.009). Boys demonstrated higher Y-balance scores (p=0.017) and faster obstacle time (p=0.007) compared to girls in the 8 - <10-year age group. Conclusions: Children 6-11 years showed notable sex differences in selected tests of physical literacy. Girls demonstrated better flexibility than boys in early childhood (6 - <8 years) while boys demonstrated superior balance and faster obstacle course time compared to girls, especially in 8 - <10 years. These data will serve to guide future efforts to evaluate normative measures physical literacy and guide targeted training interventions to promote sustained physical activity in children with deficits relative to their age and sex norms.

The role of attainability and external focus of attention on standing long jump performance

Article

Full-text available

Sep 2021

BACKGROUND: External focus of attention (FOA) promotes enhanced performance and learning in comparison to internal FOA; however, several dimensions associated with external FOA appear to have varying influence on motor skill performance. AIM: The purpose of this study was to investigate whether an attainability aspect of external FOA elicits enhanced standing long jump performance. METHOD: Fifteen healthy males performed standing long jumps in the following conditions: without a visual target (Tno), target placed at maximum distance (Tmax), and a target placed 10% beyond maximum distance (Tmax+10). Jump distances were measured, and kinetic data were recorded using a force platform. RESULTS: One-way ANOVA showed significantly greater jump distances for Tmax+10 compared to Tno and Tmax (p < 0.01). Additionally, the impulse of the ground reaction force (GRFimpulse) in the anterior-posterior direction was significantly greater for Tmax and Tmax+10 compared to Tno (p < 0.05). CONCLUSION: Thus, an external FOA tailored to individual ability benefits standing long jump performance. Overall, the findings support the approach of adopting an external FOA with an emphasis on targets that are specific to the individual and based on attainability.

The Relationship between Symmetrical and Asymmetrical Jumps and Their Influence on Speed Abilities: Gender Consideration

Article

Full-text available

Apr 2021

Purpose: Plyometric exercises, in the form of jumping, are extreme physical activities. The aim of the study was to determine how symmetrical-single versus asymmetrical-continued plyometric exercises differ between men and women and affect speed abilities. Methods: Twenty-two healthy females and forty-four males from different sports practices participated in the investigation. The countermovement jump (CMJ) and drop jump (DJ) of 40/60 cm box were performed on two independent and synchronized force platforms (Bilateral Tensiometric Platform S2P, Ljubljana, Slovenia). The measurement of a standing long jump (SLJ) and all continuous jumps: standing five jumps (SFJ), standing bounce triple jump (SBTJ), five double-leg jumps (FD-LJ), and a 10 m horizontal single leg jump (HSLJ-10mL/R) were performed using OptoJump–Next Microgate (OptoJump, Bolzano, Italy). Results: Statistically significant differences were noted in all jump kinematic and somatic parameters, in favor of the men. The correlations between values of height of symmetrical jumps (bilateral) and distance (SLJ) were stronger in women despite the shorter jumps than the men. When an alpha-level of 0.01 was set, this study demonstrated a stronger correlation between symmetrical-single and asymmetrical-continuous plyometrics exercises and sprints, both men and women. This relationship is due to their similar kinematic and dynamic structures with sprinting steps. Conclusions: The results showed a large dispersion of the relationship (p < 0.05) between jumps and sprints divided into 10, 20 and 30 m, both in men and women. Both types of exercises implemented as a plyometric training regime are an extremely important tool for sprint speed development.

Propensity for conscious control of movement is unrelated to asymptomatic hypermobility or injury-risk scores

Article

Full-text available

Feb 2021

The Movement Specific Reinvestment Scale (MSRS) measures the propensity for conscious monitoring and control of movement, which can inhibit automated movement processes, potentially causing movement disruption or injury. High injury risk individuals are more likely to make movement errors during jump-landing tasks, and hypermobile individuals present with poor movement control. The link between MSRS and these characteristics remains largely unexplored. Consequently, we examined propensity for movement specific reinvestment in high injury risk and asymptomatic hypermobile participants. Sixty volunteers (35 males, 25 females) were tested using the MSRS, Landing Error Scoring System (LESS), and Beighton hypermobility scale. Spearman rank correlation coefficients were computed between MSRS, LESS, and Beighton scores. Furthermore, MSRS scores were compared between low (LESS < 5 errors) and high (LESS ≥ 5 errors) injury risk, as well as non-hypermobile and hypermobile participants. MSRS scores were not significantly related to LESS (ρ = 0.06, p = 0.625) or Beighton (ρ = 0.09, p = 0.481) scores. MSRS scores of low and high injury risk (37.8 ± 7.8 vs 38.0 ± 8.6, p = 0.933), and non-hypermobile and hypermobile (37.5 ± 8.9 vs 39.0 ± 7.0, p = 0.524) participants were comparable. Based on our results, there is no evidence that movement specific reinvestment contributes to injury risk assessed by LESS, which might be due to the phylogenetic nature of the LESS jump-landing task and/or the low psychological pressure environment of laboratory testing. The propensity for movement specific reinvestment did not vary in asymptomatic hypermobile individuals compared to non-hypermobile individuals; however, examination of the MSRS in symptomatic hypermobile individuals and individuals with well-defined syndromes is needed to fully elucidate whether or not conscious monitoring and control of movement plays a role in injury risk or movement control across the hypermobility spectrum.

Jump and Landing Biomechanical Variables and Methods – A Literature Review

Article

Full-text available

Jan 2020
Crit Rev Biomed Eng

Noncontact lower extremity injuries are commonly related to jumping and landing activities. This review presents an overview of relevant biomechanical variables that can be modified in training to improve jumping performance, landing mechanics, and consequently, reduce injury risks. Relevant studies from the last 2 decades in the Compendex, Pubmed, and Scopus databases were considered for this review. Studies related to jumping and landing kinetics, kinematics, injuries, performance, and/or simulation were included. The use of experimental methods as the drop jump landing and jumping countermovement are widely used to measure biomechanical variables. At the same time, there has been a continuous development of simulation models that could present results without the need for testing on human subjects, with the final objective of exploring the limits of an athlete's performance without increasing the risk of any injury. The most common injuries occur in the knee and ankle ligaments and are directly related to joint angles and moments (i.e., torque or joint loading) at the hip, ankle, and knee joints. Jumping and landing biomechanics are considerably different between male and female subjects for different experimental methods and in both cases, these kinematics factors can be improved over shorter- or longer-time training to develop a better landing strategy.

Performance on sprint, agility and jump tests have moderate to strong correlations in youth football players but performance tests are weakly correlated to neuromuscular control tests

Article

Full-text available

Oct 2020
KNEE SURG SPORT TR A

Purpose: This study aimed at evaluating the correlation between seven different performance tests and two neuromuscular control tests in youth football players and to evaluate the influence of sex and age groups on test results. Methods: One-hundred and fifteen football players (66 boys, 49 girls) mean age 14 ± 0.7 (range 13-16) years from youth teams were tested at the start of the second half of the competitive season. A test battery including agility t-test, 505 agility test, single-leg hop for distance test, side-hop test, countermovement jump test, 10-m sprint test, 20-m sprint test, tuck jump assessment (TJA) and drop vertical jump (DVJ) was completed. Results: Correlations between the seven different performance tests of agility, jump and sprint ability were generally moderate to strong (r = 0.534-0.971). DVJ did not correlate with the performance tests (rho = 0.004 to - 0.101) or with TJA total score (rho = 0.127). There were weak to moderate correlations between TJA total score and the performance tests (r = - 0.323-0.523). Boys performed better than girls in all performance tests (p < 0.001) and in TJA total score (p = 0.002). In boys, older players performed better than younger players in the majority of the tests, while there was no clear age influence among girls. Conclusion: Sprint performance was moderately to strongly correlated with agility and jump performance, and performance tests were weakly to moderately correlated to TJA, while DVJ did not correlate with the other tests. Boys performed better than girls on performance tests and TJA. An age effect on performance was evident in boys but not in girls. Level of evidence: Level IV TRIAL REGISTRATION: Clinical Trials gov identifier: NCT03251404.

The Effects of Drop Vertical Jump Technique on Landing and Jumping Kinetics and Jump Performance

Article

Nov 2020
J ELECTROMYOGR KINES

The drop vertical jump is a popular plyometric exercise. Two distinct techniques are commonly used to initiate the drop vertical jump. With the ‘step-off’ technique, athletes step off a raised platform with their dominant limb, while their non-dominant limb remains on the platform. In contrast, with the ‘drop-off’ technique, athletes lean forward and drop off the platform, with both feet leaving the platform more simultaneously. The purpose of this study was to compare landing and jumping kinetics, inter-limb kinetic symmetry, and jump performance when individuals used the step-off and drop-off techniques, and to examine whether potential differences between these techniques are affected by platform height. Sixteen subjects completed drop vertical jumps with the drop-off and step-off techniques, from relatively low and high platform heights. Ground reactions forces were recorded for the dominant and non-dominant limbs during the land-and-jump phase of the drop vertical jump. Subjects demonstrated greater inter-limb asymmetry in peak impact forces when using the step-off technique, vs. the drop-off technique. This difference between the techniques was consistent across platform heights. The step-off technique appears to result in greater asymmetry in limb loading, which could contribute to the development of neuromuscular asymmetries between the limbs and/or asymmetric landing patterns.

The Effect of Height on Drop Jumps in Relation to Somatic Parameters and Landing Kinetics

Article

Full-text available

Aug 2020
Int J Environ Res Publ Health

The aim of this study was to assess the effect of drop height and selected somatic parameters on the landing kinetics of rebound jumps in force and power production, performed by male and female student athletes. Twenty female and forty male students with a sports background participated in the experiment (mean and standard deviation (± SD): age 20.28 ± 1.31 years, height 166.78 ± 5.29 cm, mass 62.23 ± 7.21 kg and 21.18 ± 1.29, 182.18 ± 6.43, 78.65 ± 7.09). Each participant performed three maximal jumps on two independent and synchronized force platforms (Bilateral Tensiometric Platform S2P) at each of the two assigned drop-jump heights (20-, and 40-, cm for female and 30-, and 60-, cm for the male special platform). Significant between-sex differences were observed in all variables of selected somatics, with men outperforming women. Statistically significant differences were noted in four parameters, between men and women, in both DJs from 20/40 and 30/60 cm. The height of the jump was 6 cm and 4 cm higher for men. A slightly higher statistical significance (p = 0.011) was demonstrated by the relative strength (% BW) generated by the left limb in both men and women. Only women showed a significant relationship between body mass, body height, and five parameters, dropping off of a 20 cm box. In men, only the left leg—relative maximal F (p =−0.45)—showed a relationship with body mass. There were no relationships between the above-mentioned dependencies in both groups, in jumps from a higher height: 40 cm and 60 cm. From a practical application, the DJ with lower 20/30 cm or higher 40/60 cm (women/men) respectively emphasizes either the force or power output via an increase in the velocity component of the rebound action or increased height of the DJ jump.

Increased visual distraction can impair landing biomechanics

Article

Full-text available

Jul 2020

Objective: Failed jump landings represent a key mechanism of musculoskeletal trauma. It has been speculated that cognitive dual-task loading during the flight phase may moderate the injury risk. This study aimed to explore whether increased visual distraction can compromise landing biomechanics. Method: Twenty-one healthy, physically active participants (15 females, 25.8±0.4 years) completed a series of 30 counter-movement jumps (CMJ) onto a capacitive pressure platform. In addition to safely landing on one leg, they were required to memorize either one, two or three jersey numbers shown during the flight phase (randomly selected and equally balanced over all jumps). Outcomes included the number of recall errors as well as landing errors and three variables of landing kinetics (time to stabilization/TTS, peak ground reaction force/pGRF, length of the centre of pressure trace/COPT). Differences between the conditions were calculated using Friedman tests and post hoc Bonferoni-Holm corrected Wilcoxon tests. Results: Regardless of the condition, landing errors remained unchanged (p=.46). In contrast, increased visual distraction resulted in a higher number of recall errors (Chi² = 13.3, p=.001). Higher cognitive loading, furthermore, appeared to negatively impact mediolateral COPT (p<.05). Time to stabilization (p=.84) and pGRF (p=.78) were unaffected. Conclusions: A simple visual distraction in a controlled experimental setting is sufficient to adversely affect landing stability and task-related short-term memory during CMJ. The ability to precisely perceive the environment during movement under time constraints may, hence, represent a new injury risk factor and should be investigated in a prospective trial.

Evaluation of Leg Joint Injury Risk Following Aerial Basketball Catching Movements

Article

Mar 2025
J APPL BIOMECH

The primary objective of the study was to evaluate the risk of lower-extremity injury during landing, after catching a basketball in the air for a rebound or a steal. A total of 32 (15 females and 17 males) recreational basketball players were asked to perform 4 different arm-reaching movements during the flight phase: no reaching, left (LAR), right (RAR), and bilateral (BAR) arm reaching. Knee and hip flexion and abduction angles at initial ground contact, peak ground reaction force within 100 milliseconds after contact, and peak moments for the hip and knee joints were analyzed. LAR, RAR, and BAR showed significantly smaller peak hip and knee flexion angles, while LAR demonstrated a significant increase in the knee’s peak abduction angle. Furthermore, the peak abduction moments of LAR were significantly increased in both males and females. Aerial basketball catching movements resulted in stiffer leg joints and larger knee abduction during landing, which was a potential factor in increasing the risk of lower-limb injury upon landing. It is recommended to include a softer landing technique and implement a training program for enhancing knee joint stabilization in the frontal plane.

Effects of Knee and Ankle Braces on Lower Limb Kinematics During Jump-Heading-Landing in Professional Soccer Players Following ACL Reconstruction

Article

Full-text available

Jan 2025

Neurophysiology of ACL Injury

Article

Full-text available

Feb 2025

The neurophysiology of ACL injury extends beyond the mechanical rupture of the ligament to encompass profound alterations in the central and peripheral nervous systems, impacting sensorimotor integration and neuromuscular control. The ACL, densely populated with mechanoreceptors, plays a critical role in joint proprioception, dynamically regulating knee stability through complex neural circuits that connect to the spinal cord and brain. When disrupted by injury, these neural pathways contribute to delayed muscular activation, altered motor planning, and compromised joint stability. Such neuromechanical deficits increase the likelihood of reinjury and highlight the need for comprehensive neuroplastic rehabilitation. Neuroplastic therapy, employing tools like external focus strategies, stroboscopic glasses, smartboards, and virtual reality, aims to restore and enhance neural connectivity, sensory integration, and motor coordination. These advanced tools target distinct phases of motor learning, promoting automaticity and resilience in movement patterns. By integrating visual-cognitive, proprioceptive, and reflexive controls, this therapeutic approach not only accelerates recovery but also optimizes performance and reduces the risk of re-injury, representing a paradigm shift in ACL rehabilitation.

Effects of attentional focus strategy on drop jump performance at various platform heights

Article

Nov 2024
Gazz Med Ital

Biophysics of ACL Injuries

Preprint

Full-text available

Aug 2024

Anterior Cruciate Ligament (ACL) injuries rank among the most prevalent and severe types of injuries, significantly impacting both athletes and non-athletes alike. These injuries not only result in immediate physical impairment, such as intense pain, substantial swelling, and a marked loss of mobility, but also carry long-term health consequences that can alter a person's quality of life. Chronic pain, persistent instability, and an increased risk of developing osteoarthritis are among the lasting effects that can follow an ACL injury. An in-depth understanding of the biophysics behind ACL injuries is paramount for devising effective prevention and treatment protocols. Biophysics, which combines principles from physics with biological systems, provides crucial insights into the mechanical and structural integrity of the ACL and its susceptibility to injury under various conditions. This systematic review aims to collate and synthesize the current knowledge surrounding the biophysical mechanisms that underlie ACL injuries. The review encompasses a range of factors, including the biomechanical forces that place stress on the ligament, anatomical structures that may predispose individuals to injury, and physiological conditions that affect ligament health and resilience. Each of these factors plays a crucial role in the incidence and severity of ACL injuries. Biomechanical forces, for example, can involve sudden changes in direction or impact during physical activity, leading to excessive stress on the ACL. Anatomical factors might include variations in bone structure or ligament alignment that inherently increase the risk of injury. Additionally, physiological conditions such as muscle strength, flexibility, and overall ligament health can influence the likelihood and extent of an ACL injury. The findings of this review underscore the necessity of adopting integrated approaches in both injury prevention and rehabilitation. Such approaches must consider the multifaceted nature of ACL injuries, involving not only mechanical and anatomical aspects but also physiological and possibly even genetic factors. By emphasizing a multi-faceted understanding, interventions can be more effectively tailored to address the complex interplay of elements that contribute to ACL injuries. This holistic approach can lead to better outcomes for those at risk of or recovering from ACL injuries, enhancing the efficacy of prevention strategies and rehabilitation protocols.

The effects of heading motion and sex on lower extremity biomechanics in soccer players

Article

Aug 2024

The Impact of Ball-Oriented Soccer Match Simulations on Anterior Cruciate Ligament Injury Risk and Implications for Multicomponent Injury Prevention Programs

Thesis

Full-text available

Jun 2023

Muhammad Hamdan

Anterior Cruciate Ligament (ACL) injury persists to be one of the dominant and dreaded injury in soccer. With costly implications to players, teams, and practitioners, injury prevention exercises and training programmes have been researched specifically with the intention to reduce the likelihood of ACL injury. However, the implementation, adherence, understanding of injury prevention training programmes in Malaysia have been underwhelming. Several factors to the issue include a lack of injury prevalence documentation and a lack of knowledge of injury risk and prevention, among coaches, practitioners, and the players themselves. In the first part of this study, injury rates and conditions were documented from several elite soccer teams in Malaysia across different age groups to get an illustration of the injury prevalence in elite soccer. It was found that most of the injuries that occur in Malaysian elite soccer occurs in the lower limb, specifically in the knee and ankle joints. Coaches, players, and practitioners from soccer teams across various soccer competition levels were then surveyed for their knowledge, attitude, and practices of injury prevention exercise programmes. It was generally agreed that injury prevention was very important, however, the practice of evidence-based injury prevention was reported by just over a third of respondents. Only half of the responding players admitted to being well informed about injury risk factors most players admitted practicing a combination of exercises both proven and unproven efficacy towards preventing injury. This finding suggests a better player education and maintenance of injury prevention programmes as irregular sessions and monotonous sessions were the most common barriers to proper implementation of such programmes. In the second and third part of the study, several selected overground soccer match simulations were reviewed in pursuit of developing an ecologically valid soccer match simulation with the incorporation of ball utility tasks, where similar physiological responses in the newly developed Ball-Oriented Soccer Simulation (BOSS) were similar to a previously existing overground soccer match-play simulation (OSMS; HR: BOSS = 156 ± 5 bpm, OSMS = 160 ± 7 bpm; RPE: BOSS = 14 ± 1, OSMS = 15 ± 2). Exertions in the BOSS revealed discrepancies between the left and right peak knee abduction moments during bipedal landings, as well as reductions in hamstrings eccentric peak torques, as well as functional hamstrings to quadriceps ratios, suggested a higher risk of injuries. Following a multicomponent injury prevention exercise program (IPEP), it was found that IPEP participants displayed improved tolerance to BOSS exertions. Biomechanical responses in the control group showed more extended knee and hip joint angles compared to the IPEP participants. The findings suggest that the BOSS may replicate similar responses to actual soccer match-play. The BOSS was then used as a fatigue protocol during the investigation towards the temporal efficacy of a multicomponent injury prevention training programme on biomechanical markers of ACL injury. It was found that a multicomponent injury prevention programme improved participants’ landing mechanics and allowed a sustained landing kinematic throughout the accumulation of fatigue from soccer-specific exertions.

Weighted Vest Load Arrangement and Data Normalization Effects on Lower Limb Biomechanics During Countermovement Jump Landings

Article

Full-text available

Apr 2024

This paper assessed the weighted vest load arrangement and data normalization method effects on ground reaction forces (GRF), joint kinematics, and joint kinetics during the landing portion of the countermovement jump. Vertical GRF and sagittal kinematic data were obtained from 12 males and 12 females during countermovement jump-landings in 4 different loading arrangements (unloaded, 10% body mass load placed anteriorly, posteriorly, and split anterior/posterior). Two methods (body mass vs. mass*landing height) were used to normalize joint torques to determine whether common mass-normalization (type A) yielded different results than a jump-landing specific mass*landing height normalization (type B) in statistical significance. Mixed-model analyses of variance (α=0.05) and effect sizes (ES) were used to assess differences between sexes and loading conditions for each normalization method. Results show that for normalization A, significant statistical differences were found between sexes for peak vertical GRF, hip moment, and knee moment. Pooled sex peak vertical GRF and hip moments showed significant differences when comparing the unloaded with the back and front-loaded conditions. For normalization B, the peak vertical GRF also showed significant differences between men and women but with smaller effect sizes. Only the hip moment showed significant differences for both normalization methods but changed the magnitude of its effect sizes. Results suggest that different normalization methods could be considered for joint moments or GRF depending on the nature of the statistical significance of jump height.

Gelişim Çağı Erkek Voleybolcuların Reaktif Kuvvet İndekslerinde Bacak Sertliği, Zemin Temas Süresi ve Uyarım Değerlerinin İlişkinin İncelenmesi

Article

Oct 2023

Reaktif kuvvet indeksi, nöromüsküler kondisyonun derinlik sıçraması gibi standartlaştırılmış sıçrama testlerindeki genel performansını ifade eder. Özellikle voleybolda smaç ve blok uygulamalarında kritik yeri olan derinlik sıçramasının kinematik bileşenleri arasındaki ilişkiyi irdeleyen çalışma sayısının azlığı dikkat çekicidir. Bu çalışmanın amacı bacak sertliği, zemin temas zamanı ve uyarım değişkenleri arasındaki ilişkiyi araştırmaktır. Çalışmaya yaş ortalamaları 15-17 yıl arasında, 12 lisanslı erkek voleybol oyuncusu gönüllü olarak katılmıştır. Katılımcılar randomize bir şekilde seçilmiş ve çalışma tek oturumda gerçekleştirilmiştir. Katılımcılar 20 dakikalık standart bir ısınma protokolüne tabi tutulduktan sonra 15 cm lik bir platformdan tek adım önde olacak şekilde “drop sıçrama” gerçekleştirmiştir. Bacak sertliği, zemin temas zamanı ve uyarım değerleri ölçülmüştür. Elde edilen veriler IBM SPSS 26 paket programı ile analiz edilmiştir. Verilerin normallik testleri Kolmogorov-Smirnov ile Shapiro Wilk testi ile gerçekleştirilmiş ve uyarım verilerinin normal dağılım göstermediği tespit edilmiştir(p<0,05). İlişkinin test edilmesi için spearman rho korelasyon analizi uygulanmış ve anlamlılık düzeyi α =0,05 olarak kabul edilmiştir. Bulgular incelendiğinde bacak sertliği ile zemin temas zamanı arasında güçlü ve negatif yönlü bir ilişki olduğu görülmüştür ( r=-0,958, p<0.05). Çalışmanın bulguları ışığında bacak sertliği arttıkça zemin temas zamanının azaldığı, drop sıçrama performansı üzerinde olumlu bir etkisi olduğu görülmüştür. Bu çalışma, atlama ve sıçrama gerektiren spor branşlarında bacak sertliğinin dikkate alınması gereken güç aktarma rolünü göstermektedir. Bu bilginin erkek atletlerle çalışan spor çalışanları için yol gösterici olacağı düşünülmektedir. Anahtar Kelimeler: Bacak Sertliği, Drop Jump, Uyarım, Nöromusküler Performans, Zemin Temas Zamanı

Can Symmetry of Single-Leg Vertical Jump Height Represent Normal Lower Limb Biomechanics of Athletes After Anterior Cruciate Ligament Reconstruction?

Article

Aug 2023

Background: After anterior cruciate ligament reconstruction (ACLR), single-leg horizontal hop distance limb symmetry index (LSI) >90% is recommended as a cutoff point for safe return to sport (RTS). However, athletes after ACLR have abnormal lower limb biomechanics despite an adequate single-leg hop distance LSI, implying that athletes are at high risk of reinjury. Symmetry of single-leg vertical jump height appears to be more difficult to achieve and can be a better representation of knee function than single-leg horizontal hop distance. Hypothesis: Athletes after ACLR with single-leg jump height LSI >90% had similar biomechanical characteristics to healthy athletes. Study design: Controlled laboratory study. Level of evidence: Level 3. Methods: A total of 46 athletes after ACLR were divided into low jump height (LJH, jump height LSI <90%, n = 23) and high jump height (HJH, jump height LSI >90%, n = 23) groups according to symmetry of single-leg vertical jump height, while 24 healthy athletes acted as a control (CONT) group. One-way analysis of variance was used to compare the kinematic and kinetic characteristics of the LJH, HJH, and CONT groups during single-leg vertical jump. Results: Both the LJH and HJH groups demonstrated greater limb asymmetry (lower LSI) during landing compared with the CONT group in knee extension moment (P < 0.05), peak knee flexion angle (P < 0.05), and knee power (P < 0.05). Conclusion: Symmetry in single-leg vertical jump height does not represent normal lower limb biomechanics in athletes after ACLR. Clinical relevance: Symmetrical jump height may not signify ideal biomechanical or RTS readiness, but single-leg vertical jump test can be used as a supplement to horizontal hop test or other functional tests to reduce the likelihood of false-negative results in the absence of detailed biomechanical evaluation.

Sensorimotor function following anterior cruciate ligament injury: Movement control, proprioception and neuropsychological perspectives

Thesis

Full-text available

Jan 2023

Adam Grinberg

Background: The high incidence of anterior cruciate ligament (ACL) injuries in sports suggests an involvement of both biomechanical and neurocognitive risk factors. Athletes are constantly exposed to challenging sports scenarios, which are often characterised by high-intensity movements combined with a multi-stimuli environment and continuous psychological pressure. Post-injury loss of knee proprioception and long-term injury-associated neuroplasticity arguably place an athlete in a disadvantage when coping with such situations when returning to sports (RTS). This is postulated to contribute to a high rate of re-injuries, seen despite achieving RTS eligibility. Psychological factors such as re-injury fears and anxieties are also suggested to influence central sensorimotor processing and to therefore play a role in the generation and control of functional movements. Their assessment is however based on suboptimal tools, particularly when administered to the athletic population. In general, current clinical assessments focus primarily on coarse outcome measures while disregarding aspects such as multi-joint control and the influence of psychological aspects on motor performance. This thesis focuses on the role of proprioception and re-injury anxiety on functional movement control following ACL injury and reconstruction (ACLR), with implications for risks of re-injury. Methods: This thesis is comprised of four cross-sectional studies (Papers I-IV), that stem from two data collections performed in a motion analysis laboratory. Paper I introduces a novel obstacle clearance test aimed to functionally assess proprioception and sensorimotor control. The goal of the test was to cross an obstacle, downward vision occluded, aiming for minimal foot clearance. Individuals following ACLR and rehabilitation were compared to both mildly active uninjured persons (CTRL) and elite athletes (ATH). A kinematic analysis, using 3D motion capture, included estimates of lower limb movement accuracy, variability and symmetry. Paper II evaluates knee proprioception among the same individuals using a weight-bearing knee joint position sense (JPS) test, and outcomes were compared with associated outcomes from the obstacle clearance test. Paper III explores whether self-reported fear of re-injury is manifested in the biomechanics (kinematics and electromyography) of a standardised rebound side-hop test (SRSH). An ACLR group was stratified into high-fear and low-fear subgroups based on one discriminating question, and compared also to uninjured controls. In Paper IV, a threat-conditioning test paradigm is introduced, aiming to invoke and measure a neurophysiological arousal response to movement-related fear, among uninjured individuals. Conditioned auditory stimuli were occasionally followed by unexpected perturbations of the base of support, and compared with neutral stimuli. Electroencephalography was continuously registered and event-related potentials were explored as potential anxiety biomarkers. Results: Kinematic asymmetry was observed for the ACLR group during obstacle crossing, both for individual joints and for multi-joint movement and velocity curves. In addition, trailing leg trajectory variability during higher obstacle crossings was lower for ACLR compared to both control groups. The less physically-active CTRL group demonstrated less crossing accuracy (larger obstacle distances and JPS errors) compared to both ACLR and ATH. Moderate positive correlations were observed between knee JPS absolute errors and obstacle distances, for the injured leg of the ACLR group only. Individuals with ACLR, classified as having high fear, demonstrated higher biceps femoris amplitudes and anterior-posterior co-contraction index during landing. Side-hop performance was also distinguishable for ACLR (regardless of fear allocation) with greater hip and knee flexion, while high-fear individuals also had more trunk flexion. Perturbation-related fearful response was reflected as a high-amplitude contingent negative variation (CNV) wave in response to conditioned compared to neutral stimuli. The CNV wave was observed over all electrode cites but most significantly over frontal and central cortical areas. Conclusions: Even following rehabilitation, individuals with ACLR showed unique sensorimotor function, characterised by less trajectory variability and greater multi-joint asymmetry when proprioception was challenged (i.e., downward vision occluded). However, knee JPS did not seem to be deficient among these individuals, but instead more related to physical activity, than to the ACLR history. Correlations to JPS errors, seen exclusively for the ACLR leg might suggest a tendency to focus attention more internally when crossing an obstacle (generally an external focus task), though this should be investigated further. Higher levels of self-reported fear of re-injury were manifested in the biomechanics of side hops, with seemingly stiffer landings and protective neuromuscular strategy. This has potential implications for joint degeneration hastening as well as reduced motor adaptability, implying a risk for re-injury. Finally, the balance-perturbation test paradigm seemed to provoke threat-associated arousal in the form of a CNV wave among uninjured individuals. The CNV wave should further be explored as a potential biomarker for re-injury anxiety. Future research should implement this paradigm on individuals with different levels of self-reported movement-related fears and anxieties, striving for a more holistic approach in rehabilitation following ACLR.

Rehabilitation After ACL Reconstruction, Return to Sport and Prevention

Chapter

Jan 2023

Gernot Felmet

This chapter describes rehabilitation after ACL reconstruction, taking into account the all press-fit fixation: standard, after revision, osteoporotic bone fixation, and healing response reinsertion. Biomechanical knowledge is fundamental in early postoperative and subsequent follow-up treatment. Individual features have to be calculated. Proven and scientific backgrounds are made accessible. Exercises to be implemented without extensive technology are illustrated with examples. Coupled with the experience in athletes and occasional athletes, test options and special technical items are presented and discussed for qualification to return to sport or competition. Rehabilitation begins with exercises of basic sports and part of the prevention program. Prevention is a key issue today from many points of view such as the national economy, individual quality of life, and the cost unit or insurance. This once again underlines the demand for “prevention first.”

Effects of sex and weighted vest load arrangements on lower biomechanics and jump height during countermovement jump

Conference Paper

Aug 2022

Neuromuscular control and hop performance in youth and adult male and female football players

Article

Apr 2022
PHYS THER SPORT

Objectives to compare neuromuscular control and hop performance between youth and adult male and female football players. Design Cross-sectional study. Participants 119 youth players (13–16 years; 68 males) and 88 adult players (17–26 years; 44 males). Main outcome measures Neuromuscular control assessed with drop vertical jump (DVJ) and tuck jump assessment (TJA). Hop performance assessed with single-leg hop for distance and side hop. Results Adult females had smaller normalized knee separation distances (NKSD) during DVJ at initial contact (77.9 ± 18.5 vs. 86.1 ± 11.0, p = 0.010) and at maximum knee flexion (59.7 ± 23.4 vs.74.1 ± 18.1, p = 0.001) compared to youth females. TJA revealed more technique errors in youths compared to adults (males 10 (8–11) vs. 8 (7–10); females 11 (9–12) vs. 9 (8–11), p ˂0.05). Youths demonstrated inferior hop performance (males single-leg hop 142 ± 18 vs. 163 ± 17, side hop 41 ± 12 vs. 52 ± 12, p ˂0.001; females side hop 32 ± 10 vs. 38 ± 14, p ˂0.05). Conclusions Youth players demonstrated reduced neuromuscular control during TJA and inferior hop performance compared to adult players. Adult female players demonstrated greater knee valgus during DVJ compared to youth female players.

Hormonelle, neuromuskuläre und anatomische Ursachen für die erhöhte Inzidenz von Rupturen des vorderen Kreuzbands bei SportlerinnenCauses Hormonaux, Neuromusculaires et Anatomiques de l’Incidence Accrue des Ruptures du Ligament Croisé Antérieur chez les Sportives

Article

Mar 2022

Frauen haben ein erhöhtes relatives Risiko, eine vordere Kreuzbandruptur zu erleiden. Die Gründe hierfür sind multifaktoriell und beinhalten unter anderem anatomische, neuromuskuläre und hormonelle Faktoren. Dieses Risiko lässt sich durch dezidierte Präventionsprogramme, die insbesondere darauf abzielen, die neuromuskulären Voraussetzungen zu verbessern, reduzieren. Insgesamt ist die Datenlage sehr heterogen und lässt insofern nur bedingt Rückschlüsse auf die tägliche Praxis zu. Evidente Daten zu erhalten und sinnvoll aufgebaute Studien zu erstellen, erscheint aufgrund der vielschichtigen Einflussfaktoren schwierig. Eine Möglichkeit, eine höhere Qualität bezüglich der Literatur zu erhalten, sind nationale oder internationale Register, wie sie z. B. in manchen skandinavischen Ländern bereits implementiert sind.

APE-V: Athlete Performance Evaluation using Video

Conference Paper

Jan 2022

The challenge of regulating doping and non-doping ‘performance-enhancing strategies’ in elite sports

Article

Mar 2021

Chui Ling Goh

From the use of polyurethane swimsuits to carbon fibre-plated shoes for road racing, the term ‘techno-doping’ has been commonly used in categorising the use of technology as ‘strategies’ for performance enhancement in sports. There are various types of ‘strategies’ which are regularly (and increasingly) used by athletes to enhance their performance, especially in elite sports, such as the use of actual substances, methods of administering substances, and other modes of ‘strategies’ which have the effect of enhancing the performance of the athletes. However, it is curious that at present, only few ‘Performance-Enhancing Strategies’ (‘PESs’) are regulated, such as the use of Performance-Enhancing Drugs and methods (‘PEDs’) under the World Anti-Doping Agency (‘WADA’) Code. There are other PESs which are wholly unregulated, such as the use of nutrition and haematology, environmental factors, physiology testing opportunities, and sports equipment and technology [hereinafter known as Non-Doping Performance-Enhancing Strategies (‘NDPESs’)]. This paper discusses the unequal treatment between the regulation of PEDs and NDPESs in elite sports, and will conclude that steps ought to be taken in order to harmonise the treatment and regulation of all PESs in elite sports.

Biomechanics of Lower Extremity Movements and Injury in Basketball

Chapter

Oct 2020

Basketball is a multi-directional sport that has high lateral and vertical demands. Understanding the biomechanics of jumping, landing, and cutting can help coaches and clinicians better reduce the risk of injury in basketball athletes since abnormal movement strategies can lead to various lower extremity injuries especially to the foot, ankle, and knee. If injured, a rehabilitation and return-to-play plan should incorporate regional (hip-focused) and global (lateral and single-leg focused) interventions to elicit the athlete’s optimal performance and safety. This chapter will focus on the lower extremity movement demands characteristic to the sport of basketball as well as lower extremity joint biomechanics during basketball-specific movements, and biomechanical considerations of basketball-related lower extremity injuries.

Long-Term Follow-up of Skeletally Immature Patients With Physeal-Sparing Combined Extra-/Intra-articular Iliotibial Band Anterior Cruciate Ligament Reconstruction: A 3-Dimensional Motion Analysis

Article

Jun 2020
AM J SPORT MED

Background The physeal-sparing iliotibial band (ITB) anterior cruciate ligament (ACL) reconstruction (ACLR) is a well-established technique for treating skeletally immature patients with ACL rupture. However, the long-term implications of the procedure on the intricacies of kinetic and kinematic function of the knee have not been comprehensively investigated. Purpose To assess the short-, mid-, and long-term effects of ITB ACLR on kinetic and kinematic parameters of knee functions. Study Design Case series; Level of evidence, 4. Methods A total of 38 patients who had undergone an ITB ACLR as a skeletally immature child were recruited to participate in a 3-dimensional (3D) motion analysis testing protocol at an institutional injury prevention center between 1 and 20 years after reconstruction. Exclusion criteria were congenital ACL deficiency and any other major knee injury (defined as an injury requiring surgery or rehabilitation >3 months) on either knee. 3D and force plate parameters included in the analysis were knee moment, ground-reaction force, and vertical jump height measured during drop vertical jump and vertical single-limb hop. Paired t tests and equivalency analyses were used to compare the parameters between cases (ITB ACLR limb) and controls (contralateral/nonsurgical limbs). Results Paired t tests showed no statistically significant differences between limbs, and equivalency analyses confirmed equivalency between limbs for all tested outcome variables. Conclusion The ITB ACLR appears to restore normal, symmetric, physiologic kinetic and kinematic function in the growing knee by 1 year after reconstruction, with maintenance of normal parameters for up to 20 years.

RELIABILITY OF DYNAMIC KNEE MOTION IN FEMALE ATHLETES

Article

Full-text available

Aug 2003

INTRODUCTION The knee is one of the most commonly injured areas of the body in female athletes. Season ending knee injuries can occur at a rate as high as 1 in 10 athletes at the intercollegiate level, which can account for 15,000 female athletes lost each year to athletic participation (Hewett et al. 1999). Anterior cruciate ligament (ACL) ruptures are debilitating, often season-ending, knee injuries in female athletes that occur with a higher incidence than in male athletes. Numerous studies have found a 4-6 fold higher incidence of knee injuries in females compared to males participating in jumping and cutting sports (Hewett et al. 1999, Malone et al. 1993). This higher incidence of injury combined with the dramatic increase in female participation that has occurred since the inception of Title IX in 1972, has led to a gender gap in the number of ACL injuries over the last three decades. Screening tests are needed to identify athletes at high risk for ACL injuries. It is likely that a significant proportion of the female sports population may demonstrate decreased dynamic knee stability measured during landing. Measures of dynamic knee stability in this study include medial knee motion, knee joint varus-valgus angle and flexion-extension angle. The purposes of this study were to examine the efficacy of a drop vertical jump in assessing dynamic knee stability and to identify differences between three different methods to calculate dynamic knee motion. METHODS Subjects consisted of 77 female high school basketball, soccer and volleyball players. Each subject was instrumented with 19 retroreflective markers. The drop vertical jump (DVJ) consisted of the subject starting on top of a box (31 cm in height) with their feet positioned 35 cm apart (distance measured between toe markers). They were instructed to drop directly down off the box and immediately perform a maximum vertical jump. Two force platforms embedded into the floor were positioned 8 cm apart so that each foot contacted a different platform during the maneuver. The first contact on the platforms (i.e. the initial landing from the box drop) was used for analysis. Three successful trials were recorded for each subject. The motion analysis system consisted of eight digital cameras (Eagle cameras, Motion Analysis Corporation) and sampled at 300Hz. Two force platforms (AMTI) were sampled at 1000Hz and time synchronized to the motion analysis system. Data was imported into KinTrak (Version 6.2, Motion Analysis Corporation) for data reduction and analysis. Prior to each data collection session the motion analysis system was calibrated to manufacturer recommendations.

Building a Practically Useful Theory of Goal Setting and Task Motivation: A 35Year Odyssey

Article

Full-text available

Sep 2002

The authors summarize 35 years of empirical research on goal-setting theory. They describe the core findings of the theory, the mechanisms by which goals operate, moderators of goal effects, the relation of goals and satisfaction, and the role of goals as mediators of incentives. The external validity and practical significance of goal-setting theory are explained, and new directions in goal-setting research are discussed. The relationships of goal setting to other theories are described as are the theory’s limitations.

ON OPTIMAL FILTERING FOR INVERSE DYNAMICS ANALYSIS

Article

Full-text available

Jan 1996

Evaluation of Plyometric Exercise Training, Weight Training, and Their Combination on Vertical Jumping Performance and Leg Strength

Article

Full-text available

Nov 2000

The purpose of this study was to compare the effects of 3 different training protocols-plyometric training, weight training, and their combination-on selected parameters of vertical jump performance and leg strength. Forty-one men were randomly assigned to 1 of 4 groups: plyometric training (n = 11), weight training (n = 10), plyometric plus weight training (n = 10), and control (n = 10). Vertical jump, mechanical power, flight time, and maximal leg strength were measured before and after 12 weeks of training. Subjects in each training group trained 3 days per week, whereas control subjects did not participate in any training activity. Data were analyzed by a 2-way (4 [middle dot] 2) analysis of variance (repeated-measures design). Results showed that all training treatments elicited significant (p < 0.05) improvement in all tested variables. However, the combination training group produced improvements in vertical jump performance and leg strength that were significantly greater than improvements in the other 2 training groups (plyometric training and weight training). This study provides support for the use of a combination of traditional and Olympic-style weightlifting exercises and plyometric drills to improve vertical jumping ability and explosive performance in general. (C) 2000 National Strength and Conditioning Association

Effects of ballistic training on preseason preparation of elite volleyball players

Article

Full-text available

Feb 1999

The purpose of this study was to determine whether ballistic resistance training would increase the vertical jump (VJ) performance of already highly trained jump athletes. Sixteen male volleyball players from a NCAA Division I team participated in the study. A Vertec was used to measure standing vertical jump and reach (SJR) and jump and reach from a three-step approach (AJR). Several types of vertical jump tests were also performed on a Plyometric Power System and a forceplate to measure force, velocity, and power production during vertical jumping. The subjects completed the tests and were then randomly divided into two groups, control and treatment. All subjects completed the usual preseason volleyball on-court training combined with a resistance training program. In addition, the treatment group completed 8 wk of squat jump training while the control group completed squat and leg press exercises at a 6RM load. Both groups were retested at the completion of the training period. The treatment group produced a significant increase in both SJR and AJR of 5.9+/-3.1% and 6.3+/-5.1%. respectively. These increases were significantly greater than the pre- to postchanges produced by the control group, which were not significant for either jump. Analysis of the data from the various other jump tests suggested increased overall force output during jumping, and in particular increased rate of force development were the main contributors to the increased jump height. These results lend support to the effectiveness of ballistic resistance training for improving vertical jump performance in elite jump athletes.

A Joint Coordinate System for the Clinical Description of Three-Dimensional Motions: Application to the Knee

Article

Full-text available

Jun 1983

The experimental study of joint kinematics in three dimensions requires the description and measurement of six motion components. An important aspect of any method of description is the ease with which it is communicated to those who use the data. This paper presents a joint coordinate system that provides a simple geometric description of the three-dimensional rotational and translational motion between two rigid bodies. The coordinate system is applied to the knee and related to the commonly used clinical terms for knee joint motion. A convenient characteristic of the coordinate system shared by spatial linkages is that large joint displacements are independent of the order in which the component translations and rotations occur.

Muscle coordination of movement: A perspective

Article

Full-text available

Feb 1993
J BIOMECH

Felix E. Zajac

Multijoint movement requires the coordination of many muscles. Because multijoint movement is complex, kinesiological data must be analyzed and interpreted in the context of forward dynamical models rich enough to study coordination; otherwise, principles will remain elusive. The complexity arises because a muscle acts to accelerate all joints and segments, even joints it does not span and segments to which it does not attach. A biarticular muscle can even act to accelerate one of the joints it spans opposite to its anatomical classification. For example, gastrocnemius may act to accelerate the knee into extension during upright standing. One powerful forward dynamical modeling method to study muscle coordination is optimal control theory because simulations of movement can be produced. These simulations can either attempt to replicate experimental data, without hypothesizing the purpose of the motor task, or otherwise generate muscle and movement trajectories that best accomplish the hypothesized task. Application of the theory to the study of maximum-height jumping has provided insight into the biomechanical principles of jumping, such as: (i) jump height is more sensitive to muscle strength than to muscle speed, and insensitive to musculotendon compliance; (ii) uniarticular muscles generate the propulsive energy and biarticular muscles fine-tune the coordination; and (iii) countermovement is often desirable, even in squat jumps, because it seems both to prolong the duration of upwards propulsion, and to give muscles time to develop force so the body can move upwards initially with high acceleration. The effort necessary to develop forward dynamical models has been so high, however, that model-generated data of jumping or any other task are meager. An interactive computer workstation environment is proposed whereby users can develop neuromusculoskeletal control models, generate simulations of motor tasks, and display both kinesiological and modeling data more easily (e.g., animations). By studying a variety of motor tasks well, each within a theoretical framework, hopefully muscle coordination principles will soon emerge.

Plyometric Training in Female Athletes Decreased Impact Forces and Increased Hamstring Torques

Article

Full-text available

Dec 1996
AM J SPORT MED

The purpose of this study was to test the effect of a jump-training program on landing mechanics and lower extremity strength in female athletes involved in jumping sports. These parameters were compared before and after training with those of male athletes. The program was designed to decrease landing forces by teaching neuromuscular control of the lower limb during landing and to increase vertical jump height. After training, peak landing forces from a volleyball block jump decreased 22%, and knee adduction and abduction moments (medially and laterally directed torques) decreased approximately 50%. Multiple regression analysis revealed that these moments were significant predictors of peak landing forces. Female athletes demonstrated lower landing forces than male athletes and lower adduction and abduction moments after training. External knee extension moments (hamstring muscle-dominant) of male athletes were threefold higher than those of female athletes. Hamstring-to-quadriceps muscle peak torque ratios increased 26% on the nondominant side and 13% on the dominant side, correcting side-to-side imbalances. Hamstring muscle power increased 44% with training on the dominant side and 21% on the nondominant. Peak torque ratios of male athletes were significantly greater than those of untrained female athletes, but similar to those of trained females. Mean vertical jump height increased approximately 10%. This training may have a significant effect on knee stabilization and prevention of serious knee injury among female athletes.

The Effect of Neuromuscular Training on the Incidence of Knee Injury in Female Athletes A Prospective Study

Article

Full-text available

Nov 1999
AM J SPORT MED

To prospectively evaluate the effect of neuromuscular training on the incidence of knee injury in female athletes, we monitored two groups of female athletes, one trained before sports participation and the other not trained, and a group of untrained male athletes throughout the high school soccer, volleyball, and basketball seasons. Weekly reports included the number of practice and competition exposures and mechanism of injury. There were 14 serious knee injuries in the 1263 athletes tracked through the study. Ten of 463 untrained female athletes sustained serious knee injuries (8 noncontact), 2 of 366 trained female athletes sustained serious knee injuries (0 noncontact), and 2 of 434 male athletes sustained serious knee injuries (1 noncontact). The knee injury incidence per 1000 athlete-exposures was 0.43 in untrained female athletes, 0.12 in trained female athletes, and 0.09 in male athletes (P = 0.02, chi-square analysis). Untrained female athletes had a 3.6 times higher incidence of knee injury than trained female athletes (P = 0.05) and 4.8 times higher than male athletes (P = 0.03). The incidence of knee injury in trained female athletes was not significantly different from that in untrained male athletes (P = 0.86). The difference in the incidence of noncontact injuries between the female groups was also significant (P = 0.01). This prospective study demonstrated a decreased incidence of knee injury in female athletes after a specific plyometric training program.

Building a practically useful theory of goal setting and task motivation - A 35-year odyssey

Article

Full-text available

Oct 2002

Interaction between pre-landing activities and stiffness regulation of the knee joint musculoskeletal system in the drop jump: Implications to performance

Article

Full-text available

Nov 2002

The purpose of the present study was to investigate the interaction between the pre-landing activities and the stiffness regulation of the knee joint musculoskeletal system and the takeoff speed during a drop jump (DJ). Nine healthy male subjects performed a DJ test from the height of 50 cm. The surface electromyographic (EMG) activity of the vastus lateralis (VL) muscle was recorded to evaluate both the pre-landing and post-landing muscle activation levels. Simultaneous recording of the jumping motion and ground reaction force was performed by a high-speed video camera (100 frames x s(-1)), and a force platform was employed to allow joint moment analysis. Joint stiffness was calculated by a linear regression of the knee joint moment/angle relationship. Elasticity of the knee extensor muscle during DJ was estimated by means of a four-element muscle model consisting of a parallel elastic component, a series elastic component (SEC), a viscous damper, and a contractile element. DJ performance correlated positively with the positive peak power of the knee joint (P < 0.01) and with the moment of the knee joint at the end of stretch (P < 0.01). However, there was no significant relationship between DJ performance and the positive peak power of the ankle joint. The knee joint moment at the end of stretch correlated with the SEC stiffness during the transmission phase from the end of the initial impact to the onset of the concentric action (P < 0.01) and with the maximum rate of isometric force development of the knee extensors (P < 0.01). Multiple regression analysis showed that the SEC stiffness during the transmission phase of the knee joint can be explained by a combination of the pre-activity of the VL muscle and the knee joint angular velocity at touchdown (F = 5.76, P < 0.05). These results seem to emphasize the functional significance of the pre-programmed activity for controlling the subsequent stiffness regulation and then contributing to the performance in DJ. Thus, it can be suggested that the centrally pre-programmed activity and the associated elastic behavior of the SEC in the knee extensor muscle in conjunction with the muscle contractile property play a major role in regulating the performance in DJ.

Gender differences in lower extremity kinematics, kinetics and energy absorption during landing

Article

Full-text available

Sep 2003
CLIN BIOMECH

To determine whether gender differences exist in lower extremity joint motions and energy absorption landing strategies between age and skill matched recreational athletes. Mixed factor, repeated measures design. Compared to males, females execute high demand activities in a more erect posture potentially predisposing the anterior cruciate ligament to greater loads and injury. The preferred energy absorption strategy may provide insight for this performance difference. Inverse dynamic solutions estimated lower extremity joint kinematics, kinetics and energetic profiles for twelve males and nine females performing a 60 cm drop landing. Females demonstrated a more erect landing posture and utilized greater hip and ankle joint range of motions and maximum joint angular velocities compared to males. Females also exhibited greater energy absorption and peak powers from the knee extensors and ankle plantar-flexors compared to the males. Examinations of the energy absorption contributions revealed that the knee was the primary shock absorber for both genders, whereas the ankle plantar-flexors muscles was the second largest contributor to energy absorption for the females and the hip extensors muscles for the males. Females may choose to land in a more erect posture to maximize the energy absorption from the joints most proximal to ground contact. Females may be at a greater risk to anterior cruciate ligament injury during landing due to their energy absorption strategy.

Biomechanics and Motor Control of Human Movement

Article

Jan 1990

D.A. Winter

The interpretation of relative momentum data to assess the contribution of the free limbs to the generation of vertical velocity in sports activities

Article

Nov 1996

Gabor Barton Adrian Lees

A Comparison of Plyometric Training Techniques for Improving Vertical Jump Ability and Energy Production

Article

May 1998

This study was done to determine which plyometric training technique is best for improving vertical jumping ability, positive energy production, and elastic energy utilization. Data were collected before and after 12 weeks of jump training and were analyzed by ANOVA. Subjects (N = 28) performed jumps under 3 testing conditions-squat jump, countermovement jump, and depth jump-and were randomly assigned to 1 of 3 groups: control, depth jump training, or countermovement jump training. The 12-week program resulted in significant increases in vertical jump height for both training groups. The depth jump group significantly improved their vertical jump height in all 3 jumps. None of the training methods improved utilization of elastic energy. In activities involving dynamic stretch-shorten cycles, drop jump training was superior to countermovement jump training due to neuromuscular specificity. This study provides support for the strength and conditioning professional to include plyometric depth jump training as part of the athlete's overall program for improving vertical jumping ability and concentric contractile performance.

Neuromuscular Control and Valgus Loading of the Knee Predict ACL Injury Risk in Female Athletes

Article

May 2004

Biomechanics and Motor Control of Human Movement, Fourth Edition

Article

Sep 2009

David A. Winter

Figure A.1 Walking Trial—Marker Locations and Mass and Frame Rate Information Table A.1 Raw Coordinate Data (cm) Table A.2(a) Filtered Marker Kinematics—Rib Cage and Greater Trochanter (Hip) Table A.2(b) Filtered Marker Kinematics—Femoral Lateral Epicondyle (Knee) and Head of Fibula Table A.2(c) Filtered Marker Kinematics—Lateral Malleolus (Ankle) and Heel Table A.2(d) Filtered Marker Kinematics—Fifth Metatarsal and Toe Table A.3(a) Linear and Angular Kinematics—Foot Table A.3(b) Linear and Angular Kinematics—Leg Table A.3(c) Linear and Angular Kinematics—Thigh Table A.3(d) Linear and Angular Kinematics—½ HAT Table A.4 Relative Joint Angular Kinematics—Ankle, Knee, and Hip Table A.5(a) Reaction Forces and Moments of Force—Ankle and Knee Table A.5(b) Reaction Forces and Moments of Force—Hip Table A.6 Segment Potential, Kinetic, and Total Energies—Foot, Leg, Thigh, and ½ HAT Table A.7 Power Generation/Absorption and Transfer—Ankle, Knee, and Hip

Assigned and self-selected goals as determinants of motor skill performance

Article

Jan 1984

93 5th graders in 3 classes were given a general goal on 3 simple motor tasks by the teacher, asked to set individual performance goals each day, or provided high but attainable specific goals each day by the teacher to investigate assigned and self-selected goals as determinants of Ss' motor-skill performance. Performance scores were collected prior to and following a 3-wk instructional period. Findings indicate that specific goals set either by the student or the teacher were effective in producing a higher level of performance. Results also suggest that the performance was influenced more favorably by goals set by the teacher: In 2 of the 3 motor tasks, teacher-set goals promoted greater achievement than student-set goals, a result that may reflect students' difficulties on establishing appropriate goals. (8 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)

The Effects of an Off-season Strength and Conditioning Program on Starters and Non-starters in Women's Intercollegiate Volleyball

Article

Nov 1991

Fourteen female NCAA Division I collegiate volleyball players were monitored during a 12-week off-season strength and conditioning program. Physical characteristics (mean +/- standard deviation) included: age, 19.6 +/- 0.6 years; height, 171.9 +/- 6.8 centimeters; weight, 64.3 +/- 7.0 kilograms. Training included resistance exercise, plyometrics, aerobic endurance exercise and on-court volleyball practice. At the beginning of the study, starters (ST, n = 6) were compared with non-starters (NST, n = 8), and were found to be faster, more flexible and stronger. ST were still stronger when one-repetition maximum (1 RM) values were corrected for fat-free mass (FFM). Ten subjects completed the 12-week strength and conditioning program and participated in the post-training tests. ST and NST responded similarly to the training program for all physical and performance tests. Significant improvements were observed for FFM, sport-specific peak and mean isometric force, vertical jump (VJ), shoulder flexibility, 1 RM strength and 1 RM/FFM for the bench press, military press, squat and hang power clean, and isokinetic leg extension torque at 1.05 and 3.14 rads*sec-1. Furthermore, two-mile run times and sit-up performance (in 60 seconds) also improved. Significant decreases were observed for VJ endurance. Over the course of the training program, the relationship between 1 RM strength and FFM decreased, while shoulder flexibility was increasingly related to sport-specific isometric strength. Isokinetic testing did not reflect the magnitude of changes in 1 RM tests. Thus, while differences appear to exist in physical characteristics between starters and non-starters, it was shown that most physical and performance variables for ST and NST can be improved with a comprehensive strength and conditioning program for female collegiate volleyball players. (C) 1991 National Strength and Conditioning Association

A Comparison of Medial Knee Motion in Basketball Players When Performing A Basketball Rebound

Article

May 2002

Physical Performance Characteristics of American Collegiate Football Players

Article

Aug 1991

Nineteen American collegiate football programs (NCAA Division I, n = 6; II, n = 7; III, n = 6) were surveyed for athlete (n = 981) performance on 1 RM bench press, 1 RM back squat, 1 RM power clean, vertical jump, and 36.6-meter (40-yard) sprint. Performances were evaluated with regard to NCAA division, position and plying ability (starter or non-starter). Performances (X +/- SD) for the entire sample included: bench press = 136.9 +/- 25.8 kilograms; back squat = 185.2 +/- 35.7 kilograms; power clean = 118.1 +/- 17.7 kilograms; vertical jump = 70.2 +/- 9.1 centimeters; 36.6-meter sprint = 4.92 +/- 0.27 seconds. Significant correlations were observed for most performance tests when compared to division of play (I, II and III) or playing ability. In general, bench press, power clean, 36.6-meter sprint, and vertical jump effectively differentiated between division of play as well as playing abilities, but the back squat was a relatively poor differentiator. The data provides helpful norms for strength and conditioning professionals. (C) 1991 National Strength and Conditioning Association

A Comparison of Plyometric Training Techniques for Improving Vertical Jump Ability and Energy Production

Article

May 1998
J STRENGTH COND RES

Increased Response Latency for Complicated Movements and A “Memory Drum” Theory of Neuromotor Reaction

Article

Nov 1959

The theory proposes a nonconscious mechanism that uses stored information (motor memory) to channel existing nervous impulses from brain waves and general afferent stimuli into the appropriate neuromotor coordination centers, subcenters, and efferent nerves, thus causing the desired movement. A consequent hypothesis requires that the simple reaction time will become longer when the response movement is required to be of greater complexity. Data obtained on college men and women, and 12- and 8-year-old boys, are in agreement with the hypothesis. Replacing a very simple finger movement with an arm movement of moderate complexity slows the reaction by about 20 percent; additional complexity produces a further slowing of 7 percent. The speed of the arm movement is considerably faster in college men than in younger boys or in college women. The correlation between reaction time and speed of movement averages approximately zero. Individual differences in ability to make a fast arm movement are about 70 percent specific to the particular movement being made; “general ability for arm speed” occurs only to the extent of 30 percent.

Developing Explosive Muscular Power: Implications for a Mixed Methods Training Strategy

Article

Oct 1994

Utilization of stored elastic energy in leg extensor muscles by men and women

Article

Feb 1978
Med Sci Sports

An alternating cycle of eccentric-concentric contractions in locomotion represents a sequence when storage and utilization of elastic energy takes place. It is possible that this storage capacity and its utilization depends on the imposed stretch loads in activated muscles, and that sex differences may be present in these phenomena. To investigate these assumed differences, subjects from both sexes and of good physical condition performed vertical jumps on the force-platform from the following experimental conditions: squatting jump (SJ) from a static starting position; counter-movement jump (CMJ) from a free standing position and with a preparatory counter-movement; drop jumps (DJ) from the various heights (20 to 100 cm) on to the platform followed immediately by a vertical jump. In all subjects the SJ, in which condition no appreciable storage of elastic energy takes place, produced the lowest height of rise of the whole body center of gravity (C.G.). The stretch load (drop height) influenced the performance so that height of rise of C. of G. increased when the drop height increased from 26 up to 62 cm (males) and from 20 to 50 cm (females). In all jumping conditions the men jumped higher than the women. However, examination of the utilization of elastic energy indicated that in CMJ the female subjects were able to utilize most (congruent to 90%) of the energy produced in the prestretching phase. Similarly, in DJ the overall change in positive energy over SJ condition was higher in women as compared to men. Thus the results suggest that although the leg extensor muscles of the men subjects could sustain much higher stretch loads, the females may be able to utilize a greater portion of the stored elastic energy in jumping activities.

Preseason strength and flexibility imbalances associated with athletic injuries in female collegiate athletes

Article

Jan 1991
AM J SPORT MED

One hundred thirty-eight female collegiate athletes, participating in eight weightbearing varsity sports, were administered preseason strength and flexibility tests and followed for injuries during their sports seasons. Strength was measured as the maximal isokinetic torque of the right and left knee flexors and knee extensors at 30 and 180 deg/sec. Flexibility was measured as the active range of motion of several lower body joints. An athletic trainer evaluated and recorded injuries occurring to the athletes in practice or competition. Forty percent of the women suffered one or more injuries. Athletes experienced more lower extremity injuries if they had: 1) a right knee flexor 15% stronger than the left knee flexor at 180 deg/sec; 2) a right hip extensor 15% more flexible than the left hip extensor; 3) a knee flexor/knee extensor ratio of less than 0.75 at 180 deg/sec. There was a trend for higher injury rates to be associated with knee flexor or hip extensor imbalances of 15% or more on either side of the body. These data demonstrate that specific strength and flexibility imbalances are associated with lower extremity injuries in female collegiate athletes.

Drop jumping. II. The influence of dropping height on the biomechanics of drop jumping

Article

Sep 1987

In the literature, athletes preparing for explosive activities are recommended to include drop jumping in their training programs. For the execution of drop jumps, different techniques and different dropping heights can be used. This study was designed to investigate for the performance of bounce drop jumps the influence of dropping height on the biomechanics of the jumps. Six subjects executed bounce drop jumps from heights of 20 cm (designated here as DJ20), 40 cm (designated here as DJ40), and 60 cm (designated here as DJ60). During jumping, they were filmed, and ground reaction forces were recorded. The results of a biomechanical analysis show no difference between DJ20 and DJ40 in mechanical output about the joints during the push-off phase. Peak values of moment and power output about the ankles during the push-off phase were found to be smaller in DJ60 than in DJ40 (DJ20 = DJ60). The amplitude of joint reaction forces increased with dropping height. During DJ60, the net joint reaction forces showed a sharp peak on the instant that the heels came down on the ground. Based on the results, researchers are advised to limit dropping height to 20 or 40 cm when investigating training effects of the execution of bounce drop jumps.

Drop jumping. I. The influence of jumping technique on the biomechanics of jumping

Article

Sep 1987

In the literature, drop jumping is advocated as an effective exercise for athletes who prepare themselves for explosive activities. When executing drop jumps, different jumping techniques can be used. In this study, the influence of jumping technique on the biomechanics of jumping is investigated. Ten subjects executed drop jumps from a height of 20 cm and counter-movement jumps. For the execution of the drop jumps, two different techniques were adopted. The first technique, referred to as bounce drop jump, required the subjects to reverse the downward velocity into an upward one as soon as possible after landing. The second technique, referred to as counter-movement drop jump, required them to do this more gradually by making a larger downward movement. During jumping, the subjects were filmed, ground reaction forces were registered, and electromyograms were recorded. The results of a biomechanical analysis show that moments and power output about knee and ankle joints reach larger values during the drop jumps than during counter-movement jumps. The largest values were attained during bounce drop jumps. Based on this finding, it was hypothesized that bounce drop jump is better suited than counter-movement drop jump for athletes who seek to improve the mechanical output of knee extensors and plantar flexors. Researchers are, therefore, advised to control jumping technique when investigating training effects of executing drop jumps.

The validity of the stretch shortening cycle in selected jumping events

Article

Apr 1981

Junior high school students (N-160) were administered pretests in the high, triple, and long jumps, and randomly subdivided into depth jump, box drill, flexibility-agility exercise, and control groups, the first three exercises being specific for the high, triple, and long jumps, respectively. After training ten minutes per day, five days per week for seven weeks, the posttest was administered. Results of the 4 x 2 x 2 x 2 repeat measures ANOVAs indicate that training with any of the drills, or the warmup of the control, resulted in gains, with the greatest registered by those who trained with the drills specific for the event. Significant test x sex interactions found for the high and triple jumps were a normal physiological phenomenon. Several second order interactions were significant and may involve complex patterns of growth, development, and motivation. The results and examination of the literature confirm the concepts of specificity of exercise and training, reinforces the physiological principle of the return of elastic energy from active muscle, and establishes the 'plyometric' principle as an elastic phenomena of the stretch shortening cycle of active muscle.

The interpretation of relative momentum data to assess the contribution of the free limbs to the generation of vertical velocity in sports activities

Article

Jan 1997

The contribution that the free limbs (the arms and lead leg) make to vertical velocity at take-off during jumping activities was determined by using a relative momentum approach. This requires the momentum of each free limb to be quantified relative to the joint at which the limb is attached to the body between the touchdown (or start of movement) and the take-off. The contribution that each makes to the vertical velocity at take-off requires interpretation of the momentum data. It has been shown that two interpretations cited in the literature pose difficulties, and a third is offered. This interpretation is that: (1) the contribution of a single limb to vertical velocity at take-off is determined by the increase in the positive relative momentum value between the beginning (touchdown) and end (take-off) of the action; (2) when considering a single limb, the negative relative momentum can be ignored as it makes no direct contribution to upward movement; and (3) the contribution of relative momentum for a number of limbs together is the increase in the positive value of the sum of the relative momentum for all limbs between the start and end of the action. This interpretation was applied to a counter-movement vertical jump and a running stride. In the counter-movement jump, the arms were found to produce a relative momentum of 30.9 N s, which was 12.7% of the peak total body vertical momentum. In running, the arms produced a relative momentum of 3.75 N s, which corresponded to 6.4% of the peak total body vertical momentum, while the arms and lead leg combined produced a peak value of 2.45 N s, which corresponds to a contribution of 4.2%. We conclude that the proposed interpretation enabled sensible estimations to be made of the contribution of the arms to jumping performance.

Gait biomechanics are not normal after anterior cruciate reconstruction and accelerated rehabilitation

Article

Oct 1998

Accelerated rehabilitation for anterior cruciate ligament (ACL) injury and reconstruction surgery is designed to return injured people to athletic activities in approximately 6 months. The small amount of empirical data on this population suggests, however, that the torque at the knee joint may not return until 22 months after surgery during walking and even longer during running. Although the rehabilitation has ended and individuals have returned to preinjury activities, gait mechanics appear to be abnormal at the end of accelerated programs. The purpose of this study was to compare lower extremity joint kinematics, kinetics, and energetics between individuals having undergone ACL reconstruction and accelerated rehabilitation and healthy individuals. Eight ACL-injured and 22 healthy subjects were tested. Injured subjects were tested 3 wk and 6 months (the end of rehabilitation) after surgery. Ground reaction force and kinematic data were combined with inverse dynamics to predict sagittal plane joint torques and powers from which angular impulse and work were derived. The difference in all kinematic variables between the two tests for the ACL group averaged 38% (all P < 0.05). The kinematics were not different between the ACL group after rehabilitation and healthy subjects. Angular impulses and work averaged 100% difference for all joints (all P < 0.05) between tests for the ACL group. After rehabilitation, the differences between injured and healthy groups in angular impulse and work at both the hip and knee remained large and averaged 52% (all P < 0.05). Results indicated that after reconstruction surgery and accelerated rehabilitation for ACL injury, humans walk with normal kinematic patterns but continue to use altered joint torque and power patterns.

Neuromuscular functioning of athletes and non-athletes in the drop jump

Article

Nov 1998
Eur J Appl Physiol Occup Physiol

In many sports vertical jumping is important. This study compared neuromuscular functioning of the lower extremity muscles together with some kinetic and kinematic parameters before and during ground contact in drop jumps from two heights [0.4 m (DJ40) and 0.8 m (DJ80)] in 7 highly trained triple-jumpers and 11 physically active controls. The triple-jumpers jumped 32% higher in DJ40 and 34% higher in DJ80, had shorter braking and total contact times, and greater average and peak vertical ground reaction forces than the controls. In both drop jumps in the electromyogram pre-activity of the vastus lateralis and gastrocnemius muscles started earlier in the jumpers than in the controls. For the control group the increase in dropping height was associated with a decrease in the propulsion force, and resulted in more extended knee and ankle angles at touch down and more flexed angles at the deepest position than for the jumpers. All angular displacements for DJ80 were larger than for DJ40 in the control group. The triple jumpers and control subjects differed with respect to their neuromuscular functioning in the drop jump exercise and they responded in a different way to the increase in dropping height.

Upper extremity augmentation of lower extremity kinetics during countermovement vertical jumps

Article

Jul 1999

Twenty-five volleyball players (14 males, 11 females) were videotaped (60 Hz) performing countermovement vertical jumps with and without an arm swing. Ground reaction force and video-based coordinate data were collected simultaneously. The resultant joint force and torque at the hip, knee, ankle and shoulder for two trials per subject per condition were computed and normalized. Average kinematic, resultant joint force and torque data were compared using repeated-measures analysis of variance. Larger values were recorded for the vertical velocity of the centre of mass at take-off in the jumps with (mean 2.75, s = 0.3 m.s-1) versus without (mean 2.44, s = 0.23 m.s-1) an arm swing. The jumps with no arm swing produced larger torques at the hip during the first third of the propulsive phase (from zero to maximum vertical velocity of the centre of mass). During the final two-thirds of the propulsive phase, the arm swing augmented hip extensor torques by slowing the rate of trunk extension and placing the hip extensor muscles in slower concentric conditions that favoured the generation of larger forces and resultant joint torques. During the first two-thirds of the propulsive phase, knee extensor torque increased by 28% in the jumps with an arm swing, but maintained a relatively constant magnitude in the jumps with no arm swing.

The Effect of Upper-Limb Motion on Lower-Limb Muscle Synchrony: Implications for Anterior Cruciate Ligament Injury

Article

Jan 2001

A high prevalence of rupture of the anterior cruciate ligament is associated with activities that incorporate both abrupt deceleration and catching a ball. In the present study, we examined whether the upper-limb motion involved in catching a ball affected the synchrony of the lower-limb muscles during tasks known to stress the anterior cruciate ligament-namely, abrupt decelerative landings. Seven male and eleven female subjects decelerated abruptly to land in single-limb stance after catching a chest-height pass and after no catching. Ground-reaction force and electromyographic data for six lower-limb muscles were sampled while the subjects' landing technique was filmed. The joint-reaction forces and the sagittal planar net moments for the knee then were calculated to derive the tibiofemoral shear forces. The muscle onsets and peak muscle activities were temporally analyzed with respect to the time of initial foot-ground contact, the peak resultant ground-reaction force, and the peak tibiofemoral shear force. When catching a pass, the subjects demonstrated significantly (p < 0.05) earlier rectus femoris onset relative to the timing of the initial foot-ground contact and of the peak tibiofemoral shear force, and they showed delayed biceps femoris onset relative to the timing of the peak tibiofemoral shear force compared with the findings in the trials without catching. We concluded that catching a ball during an abrupt landing could increase the potential for an anterior cruciate ligament injury by limiting the time available for the hamstring muscles to generate posterior tibial-drawer force before the onset of the quadriceps-induced anterior tibial translation. Clinical Relevance: The integrity of the anterior cruciate ligament during landing relies on the proper coordination of the lower-limb muscles, particularly the quadriceps and the hamstrings. The present study demonstrated that motion of the upper-limbs may interfere with recruitment of these muscles, thereby predisposing the anterior cruciate ligament to injury.

Augmented Feedback Reduces Jump Landing Forces

Article

Oct 2001

Randomized, experimental design using a 1-way ANCOVA to determine the influence of various forms of feedback on jump landing forces. To investigate the effects of augmented feedback versus sensory feedback on the reduction of jump landing forces. Several investigators have reported an increased risk of lower extremity injury associated with landing from a jump. Nonimpaired college students (N=63) were randomly assigned to 1 of 4 feedback groups. Subjects were instructed to perform maximal vertical jumps onto a force plate for 3 testing sessions (baseline, 2-minute post-test, and 1-week post-test). Three feedback groups (augmented, sensory, and control I) were tested during all 3 testing sessions, while a fourth feedback group (control II) was evaluated at only 2 sessions (baseline and 1-week post-test). Subjects in the augmented feedback condition were provided information via video and verbal analysis of how to land softer. Subjects in the sensory feedback condition were asked to use the experience of their baseline jumps to document how they could land softer. Subjects in each of the control groups were not provided any extraneous feedback. Peak vertical ground reaction force data were collected for analysis. The subjects in the augmented feedback group significantly reduced their peak vertical ground reaction force in both post-test conditions (2-minute post-test reduction, 0.85+/-0.62; 1-week post-test reduction, 0.74+/-0.58) as compared to the sensory, control I, and control II feedback groups. High impact landing forces may be reduced by the implementation of augmented feedback information instructing individuals about how to land properly. The reduction of jump landing forces with the use of augmented feedback may prove beneficial in the creation of instructional landing programs.

The female ACL: Why is it more prone to injury?

Article

Nov 2002
ORTHOP CLIN N AM

Mary Lloyd Ireland

Multiple factors are responsible for ACL tears. The key factor in the gender discrepancy appears to be dynamic, not static, and proximal, not distal. The factors involved in evaluating the female ACL are multiple. However, it is the dynamic movement patterns ot hip and knee position with increased flexion and a coordinated proximal muscle firing pattern to keep the body in a safe landing position that are the most critical factors. An ACL injury at an early age is a life-changing event. We can very successfully reconstruct and rehabilitate an ACL, but we cannot stop there. We must now go into the prevention arena. In the United States there is tremendous variation in the exposure and acquisition of skills of physical activities in our youth. Today, children are often playing inside, using computers and watching television-missing out on the opportunity to learn safe movement patterns. Therefore, physical movement classes should occur very early in life, teaching children to land safely and in control, similar to the cry of "get down, stay down" routinely heard during youth soccer. Similarly, specific strength training programs can address landing as well as foot movements during cutting in basketball. Coaches should issue stern warnings when athletes demonstrate a high-risk movement patterns such as one-leg landings, out-of-control baseline landings, or straight-leg landings. The warnings may serve to keep the athlete from "touching the hot stove again" for fear of getting burned. No athlete feels she will be the one to get injured. Therefore, prospective analysis is likely to be received more warmly by the athletes if the program is presented with an emphasis on performance improvement rather than injury prevention. With increased participation in these programs, multiple-center analysis will have the power necessary to determine which factors significantly predispose athletes to ACL injury. The future for injury prevention is bright. We must rise to the challenge.

Prevention of Anterior Cruciate Ligament Injuries in Female Team Handball Players: A Prospective Intervention Study Over Three Seasons

Article

Apr 2003
CLIN J SPORT MED

To assess the effect of a neuromuscular training program on the incidence of anterior cruciate ligament injuries in female team handball players. Prospective intervention study. Female team handball: Division I-III in Norway. Players from the three top divisions: control season (1998-1999), 60 teams (942 players); first intervention season (1999-2000), 58 teams (855 players); second intervention season (2000-2001), 52 teams (850 players). A five-phase program (duration, 15 min) with three different balance exercises focusing on neuromuscular control and planting/landing skills was developed and introduced to the players in the autumn of 1999 and revised before the start of the season in 2000. The teams were instructed in the program and supplied with an instructional video, poster, six balance mats, and six wobble boards. Additionally, a physical therapist was attached to each team to follow up with the intervention program during the second intervention period. The number of anterior cruciate ligament injuries during the three seasons and compliance with the program. There were 29 anterior cruciate ligament injuries during the control season, 23 injuries during the first intervention season (OR, 0.87; CI, 0.50-1.52; p = 0.62), and 17 injuries during the second intervention season (OR, 0.64; CI, 0.35-1.18; p = 0.15). In the elite division, there were 13 injuries during the control season, six injuries during the first intervention season (OR, 0.51; CI, 0.19-1.35; p = 0.17), and five injuries in the second intervention season (OR, 0.37; CI, 0.13-1.05; p = 0.06). For the entire cohort, there was no difference in injury rates during the second intervention season between those who complied and those who did not comply (OR, 0.52; CI, 0.15-1.82; p = 0.31). In the elite division, the risk of injury was reduced among those who completed the anterior cruciate ligament injury prevention program (OR, 0.06; CI, 0.01-0.54; p = 0.01) compared with those who did not. This study shows that it is possible to prevent anterior cruciate ligament injuries with specific neuromuscular training.

Effect of Negative Work on the Amount of Positive Work Performed by an Isolated Muscle

Article

Feb 1965
J Appl Physiol

An isolated frog gastrocnemius tetanically stimulated performs a greater amount of positive work, during shortening at a given speed, if it has been stretched immediately before it was allowed to shorten. The increase of work performed is greater, the shorter the interval between stretching and shortening. A substantial amount of the work done on the contracted muscle during the stretching appears to be available during the shortening phase, as in elastic bodies. Note: (With the Technical Assistance of G. Orlando) tension-length diagram of isolated contracted muscle; elasticity of contracted muscle; efficiency of muscular contraction Submitted on May 4, 1964

Valgus Knee Motion during Landing in High School Female and Male Basketball Players

Article

Nov 2003

The purpose of this study was to utilize three-dimensional kinematic (motion) analysis to determine whether gender differences existed in knee valgus kinematics in high school basketball athletes when performing a landing maneuver. The hypothesis of this study was that female athletes would demonstrate greater valgus knee motion (ligament dominance) and greater side-to-side (leg dominance) differences in valgus knee angle at landing. These differences in valgus knee motion may be indicative of decreased dynamic knee joint control in female athletes. Eighty-one high school basketball players, 47 female and 34 male, volunteered to participate in this study. Valgus knee motion and varus-valgus angles during a drop vertical jump (DVJ) were calculated for each subject. The DVJ maneuver consisted of dropping off of a box, landing and immediately performing a maximum vertical jump. The first landing phase was used for the analysis. Female athletes landed with greater total valgus knee motion and a greater maximum valgus knee angle than male athletes. Female athletes had significant differences between their dominant and nondominant side in maximum valgus knee angle. The absence of dynamic knee joint stability may be responsible for increased rates of knee injury in females but is not normally measured in athletes before participation. No method for accurate and practical screening and identification of athletes at increased risk of ACL injury is currently available to target those individuals that would benefit from neuromuscular training before sports participation. Prevention of female ACL injury from five times to equal the rate of males would allow tens of thousands of young females to avoid the potentially devastating effects of ACL injury on their athletic careers.

Decrease in Neuromuscular Control About the Knee with Maturation in Female Athletes

Article

Sep 2004

Compared with male athletes, female athletes demonstrate increased dynamic valgus angulation of the knee during landing from a jump, although prior to maturation male and female athletes have similar forces and motions about the knee when they land from a jump. Our hypothesis was that musculoskeletal changes that accompany maturation result in poor neuromuscular control of the knee joint in female athletes. One hundred and eighty-one middle-school and high-school soccer and basketball players-100 girls and eighty-one boys-participated in the study. Dynamic control of the knee joint was measured kinematically by assessing medial knee motion and the lower-extremity valgus angle and was measured kinetically by assessing knee joint torques; the values were then compared between female and male athletes according to maturational stage. Lower-extremity bone length was measured with three-dimensional kinematic analysis. Following the onset of maturation, the female athletes landed with greater total medial motion of the knees and a greater maximum lower-extremity valgus angle than did the male athletes. The girls also demonstrated decreased flexor torques compared with the boys as well as a significant difference between the maximum valgus angles of their dominant and nondominant lower extremities after maturation. After girls mature, they land from a jump differently than do boys, as measured kinematically and kinetically.

Neuromuscular Training Improved Performance and Lower-Extremity Biomechanics in Female Athletes

Article

Mar 2005

The purpose of this study was to examine the effects of a comprehensive neuromuscular training program on measures of performance and lower-extremity movement biomechanics in female athletes. The hypothesis was that significant improvements in measures of performance would be demonstrated concomitant with improved biomechanical measures related to anterior cruciate ligament injury risk. Forty-one female basketball, soccer, and volleyball players (age, 15.3 +/- 0.9 years; weight, 64.8 +/- 9.96 kg; height, 171.2 +/- 7.21 cm) underwent 6 weeks of training that included 4 main components (plyometric and movement, core strengthening and balance, resistance training, and speed training). Twelve age-, height-, and weight-matched controls underwent the same testing protocol twice 6 weeks apart. Trained athletes demonstrated increased predicted 1 repetition maximum squat (92%) and bench press (20%). Right and left single-leg hop distance increased 10.39 cm and 8.53 cm, respectively, and vertical jump also increased from 39.9 +/- 0.9 cm to 43.2 +/- 1.1 cm with training. Speed in a 9.1-m sprint improved from 1.80 +/- 0.02 seconds to 1.73 +/- 0.01 seconds. Pre- and posttest 3-dimensional motion analysis demonstrated increased knee flexion-extension range of motion during the landing phase of a vertical jump (right, 71.9 +/- 1.4 degrees to 76.9 +/- 1.4 degrees ; left, 71.3 +/- 1.5 degrees to 77.3 +/- 1.4 degrees ). Training decreased knee valgus (28%) and varus (38%) torques. Control subjects did not demonstrate significant alterations during the 6-week interval. The results of this study support the hypothesis that the combination of multiple-injury prevention-training components into a comprehensive program improves measures of performance and movement biomechanics.

The effect of upper-limb motion on lower-limb muscle synchrony Implications for anterior cruciate ligament injury 83-A:35–41 Gender differences in lower extremity kinematics, kinetics and energy absorption during landing

Jan 2001
662-669

E J Cowling
J R Steele Decker
M R Torry
D J Wyland
W I Sterett
And J Richard

COWLING, E.J., AND J.R. STEELE. The effect of upper-limb motion on lower-limb muscle synchrony. Implications for anterior cruciate ligament injury. J. Bone Joint Surg. Am. 83-A:35–41. 2001. 5. DECKER, M.J., M.R. TORRY, D.J. WYLAND, W.I. STERETT, AND J. RICHARD STEADMAN. Gender differences in lower extremity kinematics, kinetics and energy absorption during landing. Clin. Biomech. (Bristol, Avon) 18:662–669. 2003.

Assigned and self-selected goals as determinants of motor skill performance Education EFFECTS OF AN OVERHEAD GOAL ON VERTICAL JUMP 399 25 The interpretation of relative momentum data to assess the contribution of the free limbs to the generation of vertical velocity in sports activities

Jan 1984
87-91503

A M Lee

LEE, A.M. Assigned and self-selected goals as determinants of motor skill performance. Education 105:87–91. 1984. EFFECTS OF AN OVERHEAD GOAL ON VERTICAL JUMP 399 25. LEES, A., AND G. BARTON. The interpretation of relative momentum data to assess the contribution of the free limbs to the generation of vertical velocity in sports activities. J. Sports Sci. 14:503–511. 1996.

Effects of ballistic training on preseason preparation of elite volleyball players Augmented feedback reduces jump landing forces

Jan 1999
323-330511

W J Kraemer
K Onate
K M Guskiewicz

NEWTON, R.U., W.J. KRAEMER, AND K. HAKKINEN. Effects of ballistic training on preseason preparation of elite volleyball players. Med. Sci. Sports Exerc. 31:323–330. 1999. 32. ONATE, J.A., K.M. GUSKIEWICZ, AND R.J. SULLIVAN. Augmented feedback reduces jump landing forces. J. Orthop. Sports Phys. Ther. 31:511–517. 2001.

The influence of dropping height on the bio-mechanics of drop jumping

339-346

Jumping Drop

Drop jumping. II. The influence of dropping height on the bio-mechanics of drop jumping. Med. Sci. Sports Exerc. 19:339–346

Athletic Injuries and Rehabilitation

Jan 1996

J E Zachazewski
D J Magee
W S Quillen

ZACHAZEWSKI, J.E., D.J. MAGEE, AND W.S. QUILLEN. Athletic Injuries and Rehabilitation. W.B. Saunders, 1996.

Use of an Overhead Goal Alters Vertical Jump Performance and Biomechanics

Abstract

No full-text available

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