Jump-landing Task Research Articles

Influence of Fatigue on Cognitive-Motor Function During Unanticipated Landings.

Physical fatigue and cognitive performance have been suggested as risk factors for an anterior cruciate ligament (ACL) injury, and fatigue has also been demonstrated to reduce cognitive processing. The combined effects of fatigue and lower cognitive function during cognitive-challenging movements may increase knee mechanics associated with the ACL injury risk. We hypothesized that (1) knee mechanics would be detrimentally affected by fatigue and associated with baseline cognitive function and (2) fatigue-induced deleterious changes in cognitive performance and knee mechanics would be correlated. Descriptive laboratory study. A total of 22 athletes completed baseline cognitive testing. After performing maximal vertical jumps, they performed a jump-land-jump task based on unanticipated visual cues. Then, they completed a fatigue protocol including countermovement jumps, among other tasks, until the jump height decreased below 90% of their assessed maximum. Immediately after reaching the first fatigue point, they performed another set of jump-landing tasks, followed by repeating the fatigue protocol until the jump height decreased below 85% of their assessed maximum. After reaching the second fatigue point, they performed a final set of jump-landing tasks and repeated the initial cognitive assessment battery. Mixed-effects models revealed that knee flexion decreased through the fatigue protocol (baseline: 61.8°; midpoint: 61.1°; final: 60.1°; P = .003). Stepwise regression showed that fatigue-worsened attentional control corresponded to smaller knee abduction angles (R2adjusted = 51.68%; βstandardized = 1.16; P = .001), and worse reaction time after fatigue correlated with increased knee abduction angles (βstandardized = 0.85; P = .006) after accounting for the role of attentional control. Fatigue induced incremental modifications in sagittal-plane knee mechanics during an unanticipated sports movement. In addition, fatigue induced changes in cognitive function related to ACL injury-relevant knee mechanics. The novel findings regarding fatigue-dependent changes in injury-relevant biomechanics during cognitively challenging movements represent an extension of recent developments in understanding the role of cognition in the ACL injury risk.

Dynamic postural control in injured collegiate cross-country runners is not associated with running-related injury

BackgroundBiomechanical factors have been associated with running-related injury, but associations are unclear. Dynamic postural stability may be a factor related to injury that has not been studied extensively. Research questionDoes dynamic postural control differ in those with a history of running-related injury or those who go on to sustain a running-related injury? MethodsSixty-five (45 injured; 20 uninjured) and fifty-eight (13 injured; 45 uninjured) collegiate cross-country runners were available for our retrospective and prospective analyses. Time to stabilization and dynamic postural stability index were collected during two separate jump landing tasks (forward and lateral direction) for each leg. Retrospective injury was tabulated by a running history survey. Prospective injuries were recorded by a licensed athletic trainer during the competitive season. Differences in postural stability were compared between injured and uninjured groups and between limbs using two-way ANOVA’s. An overall group by leg comparison was completed for each task. ResultsThe non-dominant limb demonstrated better postural stability indices regardless of injury history. An interaction was observed between limbs and history of injury for the anterior-posterior time to stabilization for the lateral task. The non-dominant limb demonstrated better medio-lateral postural stability indices and time to stabilization during the lateral task, regardless of prospective injury. SignificanceDynamic postural stability was reduced in the dominant limb, but no clear differences were seen between injured and uninjured runners. This suggests dynamic postural stability may be altered in individuals with a history of a running-related injury, but no relationship to subsequent injury was substantiated. Further work is needed to understand how dynamic postural stability may be related to running-related injury.

Prelanding Knee Kinematics and Landing Kinetics During Single-Leg and Double-Leg Landings in Male and Female Recreational Athletes.

Biomechanical behavior prior to landing likely contributes to anterior cruciate ligament (ACL) injuries during jump-landing tasks. This study examined prelanding knee kinematics and landing ground reaction forces (GRFs) during single-leg and double-leg landings in males and females. Participants performed landings with the dominant leg or both legs while kinematic and GRF data were collected. Single-leg landings demonstrated less time between prelanding minimal knee flexion and initial ground contact, decreased prelanding and early-landing knee flexion angles and velocities, and increased peak vertical and posterior GRFs compared with double-leg landings. Increased prelanding knee flexion velocities and knee flexion excursion correlated with decreased peak posterior GRFs during both double-leg and single-leg landings. No significant differences were observed between males and females. Prelanding knee kinematics may contribute to the increased risk of ACL injuries in single-leg landings compared with double-leg landings. Future studies are encouraged to incorporate prelanding knee mechanics to understand ACL injury mechanisms and predict future ACL injury risks. Studies of the feasibility of increasing prelanding knee flexion are needed to understand the potential role of prelanding kinematics in decreasing ACL injury risk.

The Effect of Fatigue on Trunk and Pelvic Jump-Landing Biomechanics in View of Lower Extremity Loading: A Systematic Review.

Fatigue has often been considered a risk factor for developing sports injuries, modulating lower extremity jump-landing biomechanics. The impact of fatigue on proximal trunk and pelvic biomechanics has been suggested to play an important role in lower extremity loading and injury risk, yet the available evidence remains ambiguous as the trunk and pelvis were often not the primary focus of research. Therefore, the purpose of this systematic review was to determine how fatigue affects trunk and pelvic three-dimensional jump-landing biomechanics. PubMed (MEDLINE), Web of Science, Embase, CINAHL and SPORTDiscus were consulted up to and including April 2022 for potential studies investigating the effect of fatigue on trunk and pelvic kinematics, kinetics and/or muscular activity during jump-landing tasks in healthy, physically active populations. Methodological quality of the studies was assessed by the modified Downs and Black checklist. Twenty-one studies were included and methodological quality was moderate to high among these studies. The results indicate prevailing evidence for more trunk flexion during standardized jump-landing tasks after lower extremity muscle fatigue. Otherwise, lumbo-pelvic-hip muscle fatigue does not seem to elicit major detrimental changes to these jump-landing biomechanics. Although a wide variability of trunk and pelvic jump-landing strategies was observed, the results provide evidence for increased trunk flexion after lower extremity muscle fatigue. This proximal strategy is suggested to help unload fatigued lower extremity structures and lack of this compensation might increase knee injury risk.

Women's College Volleyball Players Exhibit Asymmetries During Double-Leg Jump Landing Tasks.

Women's volleyball requires frequent and repetitive jumping that when performed with altered biomechanics, including kinematic or kinetic asymmetry, may place the athlete at high risk for injury. This study identified and analyzed lower-extremity biomechanical asymmetries in college women's volleyball players during standard and sport-specific double-leg landing tasks. Cross-sectional laboratory study. Eighteen female college volleyball players were analyzed using standard 3D motion capture techniques during a drop vertical jump and an unanticipated lateral reactive jump task. Repeated-measures multivariate analysis of variance identified asymmetries in kinematic and kinetic variables of each task. Average symmetry indices ranged from 9.3% to 31.3% during the drop vertical jump and 11.9% to 25.6% during the reactive jump task. During the drop vertical jump, the dominant limb exhibited lower knee abduction moments (P = .03), ankle dorsiflexion moments (P = .02), ankle eversion moments (P = .003) and vertical ground reaction forces (P = .03), and greater ankle inversion moments (P = .001). Both kinematic (λ = 0.27, P = .03) and kinetic (λ = 0.12, P = .008) asymmetries were identified during the reactive jump task. The dominant limb exhibited greater peak knee flexion (P = .003) and ankle dorsiflexion (P = .02) angles, and greater ankle dorsiflexion (P = .005) and inversion (P = .03) moments than the nondominant limb. These asymmetries observed during double-leg landing tasks may predispose volleyball athletes to unilaterally higher ground reaction or muscle forces and ultimately a greater risk of injury during landing.

Dynamic Taping Improves Landing Biomechanics in Young Volleyball Athletes.

Poor landing biomechanics such as hip adduction, internal rotation, and knee valgus have been recognized as modifiable risk factors of anterior cruciate ligament (ACL) injury. Dynamic taping is a newly developed technique with better elasticity and extensibility, which could change the landing biomechanics. The purpose of this study was to identify whether dynamic taping could improve lower limb biomechanics in athletes. Forty-two high school volleyball athletes (21 males and 21 females) participated in the study. Biomechanical properties, including the landing error scoring system (LESS) and anterior–posterior knee laxity, were evaluated before and after the application of dynamic tape while athletes performed the jump-landing task. As a result, we found that dynamic tape significantly reduced the faulty landing strategy by an average of 0.64 errors in all volleyball athletes. The effect induced by dynamic tape was more prominent in female athletes and high-risk athletes (1.1 errors). Furthermore, the application of dynamic tape improved anterior–posterior knee laxity, especially in female athletes (p < 0.001). In conclusion, we found that dynamic tape provided a short-term, passive, and clinically significant means to normalize inadequate biomechanics during landing in athlete groups, which could have a protective effect and further alleviate the risk of ACL injury.

Preventive Training Program Feedback Complexity, Movement Control, and Performance in Youth Athletes.

Preventive training programs (PTPs) reduce injury risk by improving movement control. Corrective feedback is important; however, many cues at once may be too complicated for athletes. To compare movement control and long-jump (LJ) changes in youth athletes participating in a season-long PTP, with simplified feedback, traditional feedback, or a warmup of the coaches' choosing. Cluster-randomized controlled trial. Soccer fields. A total of 420 athletes (simplified feedback = 173, traditional feedback = 118, and control = 129; age = 11 ± 3 years). Teams were randomized into the simplified PTP, traditional PTP, or control group. Simplified and traditional PTPs lasted 10 to 12 minutes and used the same exercises. The simplified PTP provided only sagittal-plane feedback (eg, "get low"), and the traditional PTP provided feedback targeting all motion planes (eg, "don't let your knees cave inward"). Research assistants administered the PTP warmups 2 to 3 times/week for the season. Control team coaches chose and ran their own warmup strategies. Participants completed 4 sessions (preseason [PRE], postseason [POST] at approximately 8 weeks after PRE, retention 1 [R1] at 6 weeks postseason, and retention 2 [R2] at 12 weeks postseason). They performed 3 trials of a jump-landing task, which was evaluated using the Landing Error Scoring System (LESS) and 2 recorded standing LJ trials at each test session. A time series panel was used to evaluate group differences across time points for the LESS and LJ. Change score analyses revealed improvements in the LESS score from PRE to POST for all groups. Improvements from PRE were retained at R1 and R2 for the intervention groups (simplified and traditional). The traditional group demonstrated better LJ performance at POST (P < .001) and R1 (P = .049) than the simplified or control group. Simplified cues were as effective as traditional cues in improving LESS scores from PRE to POST season. Participating in PTPs, regardless of their complexity, likely provides movement benefits.

Concurrent validation of the Noraxon MyoMotion wearable inertial sensors in change-of-direction and jump-landing tasks

ABSTRACT Wearable inertial sensors (WIS) facilitate the preservation of the athlete-environment relationship by allowing measurement outside the laboratory. WIS systems should be validated for team sports movements before they are used in sports performance and injury prevention research. The aim of the present study was to investigate the concurrent validity of a wearable inertial sensor system in quantifying joint kinematics during team sport movements. Ten recreationally active participants performed change-of-direction (single-leg deceleration and sidestep cut) and jump-landing (single-leg hop, single-leg crossover hop, and double-leg vertical jump) tasks while motion was recorded by nine inertial sensors (Noraxon MyoMotion, Noraxon USA Inc.) and eight motion capture cameras (Vicon Motion Systems Ltd). Validity of lower-extremity joint kinematics was assessed using measures of agreement (cross-correlation: XCORR) and error (root mean square deviation; and amplitude difference). Excellent agreement (XCORR >0.88) was found for sagittal plane kinematics in all joints and tasks. Highly variable agreement was found for frontal and transverse plane kinematics at the hip and ankle. Errors were relatively high in all planes. In conclusion, the WIS system provides valid estimates of sagittal plane joint kinematics in team sport movements. However, researchers should correct for offsets when comparing absolute joint angles between systems.

Kinematic Changes of the Lower Limb in Individuals With Chronic Ankle Instability During Unilateral Landing Tasks: A Systematic Review

Purpose: Ankle sprain is one of the most common sports injuries and many people suffer from chronic ankle instability after ankle sprains. Changes in the function of the lower limbs following chronic ankle instability make a person susceptible to re-injury of ankle sprains. This is a systematic review of studies that investigated the kinematic changes of the lower limbs in people with chronic ankle instability during unilateral jump landing tasks. Methods: Articles in English were searched in Google Scholar, Science Direct, PubMed, Scopus, ProQuest, and Cochrane Library databases without a time limit until 2021 with keywords related to “chronic ankle instability,” “kinematics,” and “single-leg jump-landing.” The inclusion criteria included the subjects being male and female with ankle instability and the type of single-leg jump-landing task. The modified checklist of Downs and Black (1998) was used to evaluate the quality of the studies. Results: Based on the inclusion and exclusion criteria and the study quality review, 15 articles out of 762 studies, which investigated the kinematics of the lower limbs in the performance of unilateral jump landing, were comprehensively examined. Conclusion: According to the findings of this study, individuals with chronic ankle instability showed kinematic changes in the lower limbs during various unilateral jump landing tasks. These changes are possible factors for the recurrence of ankle sprain injury. The findings show the necessity of developing and creating a rehabilitation program that comprehensively considers the kinematic changes.

Acute effects of external visual feedback using cross-line laser on landing neuromechanics and postural control in chronic ankle instability

ABSTRACT Although neuromuscular training (NMT) programmes positively enhance clinical deficits in chronic ankle instability (CAI) patients, the effectiveness of NMTs in restoring movement patterns during jump landing is still questionable. Before developing new prolonged motor-learning interventions, it is important to determine the immediate effects of intervention on movement patterns during jump-landing in patients with CAI. Therefore, the purpose of this study was to determine whether real-time external feedback using a crossline laser device changes the movement patterns during jump-landing and balance tasks in patients with CAI. Eighteen patients with CAI completed three successful single-leg jump-landing tasks and single-leg balance tasks under the conditions of with and without external feedback. Lower-extremity joint angles, moments, and EMG activation of six muscles were collected during the single leg jump-landing task and centre of pressure data were collected during the single-leg balance test. Real-time external feedback allowed to change neuromechanical characteristics in the entire lower-extremity (i.e., ankle, knee, and hip joints) during jump-landing. However, there were no differences in static postural control between the two conditions. Clinicians should carefully consider incorporating a cost-effective laser device into an augmented NMT programme of longer duration to improve movement patterns during functional tasks in patients with CAI.

Association Between Landing Error Scoring System (LESS) Items and the Incidence Rate of Lower Extremity Stress Fracture.

Background:Lower extremity stress fracture injuries are a major cause of morbidity in physically active populations. The ability to screen for modifiable risk factors associated with injury is critical in developing injury-prevention programs.Purpose:To determine if baseline Landing Error Scoring System (LESS) scores are associated with the incidence rate of lower extremity stress fracture.Study Design:Cohort study; Level of evidence, 2.Methods:A total of 1772 participants with no history of lower extremity stress fracture were included. At preinjury baseline, the authors conducted a lower extremity movement assessment during a jump-landing task using the LESS. Incident lower extremity stress fractures were identified during a 4-year follow-up period. Potential incident cases were reviewed by 2 sports medicine fellowship–trained orthopaedic surgeons blinded to baseline LESS data. Univariate and multivariable Poisson regression models were used to estimate the association between baseline total LESS scores, individual LESS items, and the incidence rate ratio (IRR) of lower extremity stress fracture.Results:A total of 94 incident lower extremity stress fractures were documented, for a 5.3% (95% CI, 4.3%-6.5%) cumulative incidence. The overall LESS score was associated with the incidence rate of lower extremity stress fracture. For every additional movement error documented at baseline, there was a 15% increase in the incidence rate of lower extremity stress fracture (IRR, 1.15 [95% CI, 1.02-1.31]; P = .025). In univariate analyses, ankle flexion, stance width, asymmetrical landing, and trunk flexion at initial contact, in addition to overall impression, were associated with the incidence rate of stress fracture. After controlling for sex and year of entry into the study cohort, participants who consistently landed flat-footed or heel-to-toe were 2.33 times (95% CI, 1.36-3.97; P = .002) more likely to sustain a lower extremity stress fracture. Similarly, participants who consistently demonstrated asymmetric landing at initial contact were 2.53 times (95% CI, 1.34-4.74; P = .004) more likely to sustain a stress fracture.Conclusion:Components of the LESS may be associated with increased lower extremity stress fracture risk and may be helpful in efficiently assessing high-risk lower extremity biomechanics in large groups.

Comparison of Lower Limb Muscle Activation Patterns in Different Foot Structures using Voluntary Response Index: A Study Protocol

Background: Structural foot disorders can widely contribute to lower limb musculoskeletal conditions. Some researchers consider them the origin of overuse injuries in lower limbs. Although their effects on electrical activities of intrinsic and extrinsic foot muscles are well-established, their impact on other lower limb muscle groups are yet to be clarified.&#x0D; Objectives: This study aims to identify the activation patterns of lower limb muscle groups in various foot structures.&#x0D; Materials and Methods: In this case control study, 45 asymptomatic male and female subjects with different foot structures (pronated, supinated, and normal) will be selected using non-random sampling. The electrical activities of the gluteus medius, vastus lateralis and medialis, biceps femoris, semitendinosus, and lateral and medial gastrocnemius muscles will be examined during a jump-landing task. Voluntary response index, including magnitude and similarity index, will be subsequently calculated.&#x0D; Discussion: While several studies have evaluated the activation of lower limb muscles in different foot structures, they have solely focused on foot muscles. In contrast, the present study will assess activation patterns of the global lower limb muscles using the voluntary response index.

Plyometrics Did Not Improve Jump-Landing Biomechanics in Individuals With a History of Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial

Second anterior cruciate ligament (ACL) injury has similar biomechanical risk factors as primary injury. Standard of care rehabilitation does not adequately mitigate these biomechanical risks. This study examined the effectiveness of a 4-week plyometric intervention on biomechanical risk factors of second ACL injury versus no intervention in patients with a history of ACL reconstruction. Thirty adults post-ACL reconstruction received 12 sessions of plyometric (age: 19.9 ± 1.62 years; body mass index: 23.9 ± 2.6 kg/m2; months postoperative: 35.7 ± 24.2) or no (age: 21.3 ± 3.5 years; body mass index: 27.7 ± 4.8 kg/m2; months postoperative: 45.3 ± 25.4) exercise intervention. Hip and knee biomechanics were quantified during a jump-landing task before and after the intervention. Individual response to the intervention was evaluated via minimal detectable change. Hip flexion angle had the greatest response to plyometric training. Overall, focused plyometric intervention did not adequately mitigate biomechanical risk factors of second ACL injury; thus, development of interventions capable of modifying biomechanics known to contribute to ACL injury risk remains necessary.

Biomechanical features of drop vertical jump are different among various sporting activities

BackgroundRisk for non-contact anterior cruciate ligament (ACL) injury can be assessed based on drop vertical jump (DVJ). However, biomechanics of DVJ may differ with various sporting activities. The purpose of the present study was to clarify whether biomechanical features of DVJ are different among various sporting activities in female athletes.MethodsA total of 42 female athletes, including 25 basketball, 8 soccer and 9 volleyball players, participated in the current investigation. DVJ was done for each female athlete using a three-dimensional motion analysis system which consisted of six cameras, two force plates and 46 retro-reflective markers. Kinematic and kinetic data were recorded for both limbs in each athlete. Simultaneously, frontal and sagittal plane views of the DVJ were recorded using two different high-resolution video cameras to evaluate Landing Error Scoring System (LESS) score. Three-dimensional biomechanical parameters at the knee joint and LESS were compared among three different sporting activities using ANOVA or Kruskal–Wallis test after confirming normality assumption. Thereafter post hoc Tukey or Steel–Dwass was utilized for multiple comparison.ResultsSoccer players had better LESS score, and peak knee flexion angle was significantly larger in soccer players compared to the other sports. In addition, knee abduction angle at initial contact (IC), peak knee abduction angle, knee internal rotation angle, and knee abduction moment within 40 ms from IC were significantly smaller in soccer players, compared to basketball players. In terms of volleyball players, knee abduction angle at IC and knee internal rotation angle at IC were significantly larger than soccer players, whereas no significant biomechanical differences were found between basketball and volleyball players.ConclusionsFrom the present study, female basketball and volleyball players have worse LESS score, smaller peak knee flexion angle, greater knee abduction angle at IC and greater knee internal rotation angle at IC, compared to female soccer players. Thus, female basketball and volleyball players may have an increased risk of non-contact ACL injury during the jump-landing task, compared to soccer players. Biomechanics of DVJ depends on characteristics of the athlete's primary sport.

Are Elite Collegiate Female Athletes PRIME for a Safe Return to Sport after ACLR? An Investigation of Physical Readiness and Integrated Movement Efficiency (PRIME).

BackgroundElite female athletes who successfully return to sport after anterior cruciate ligament reconstruction (ACLR) represent a high-risk group for secondary injury. Little is known about how the functional profile of these athletes compares to their teammates who have not sustained ACL injuries.PurposeTo compare elite collegiate female athletes who were able to successfully return to sport for at least one season following ACLR to their teammates with no history of ACLR with regard to self-reported knee function, kinetics, and kinematics during a double limb jump-landing task.Study DesignCross-Sectional StudyLevel of EvidenceLevel 3MethodsEighty-two female collegiate athletes (17 ACLR, 65 control) completed the knee-specific SANE (single assessment numeric evaluation) and three trials of a jump-landing task prior to their competitive season. vGRF data on each limb and the LESS (Landing Error Scoring System) score were collected from the jump-landing task. Knee-SANE, vGRF data, and LESS scores were compared between groups. All athletes were monitored for the duration of their competitive season for ACL injuries.ResultsAthletes after ACLR reported worse knee-specific function. Based on vGRF data, they unloaded their involved limb during the impact phase of the landing, and they were more asymmetrical between limbs during the propulsion phase as compared to the control group. The ACLR group, however, had lower LESS scores, indicative of better movement quality. No athletes in either group sustained ACL injuries during the following season.ConclusionDespite reporting worse knee function and demonstrating worse kinetics, the ACLR group demonstrated better movement quality relative to their uninjured teammates. This functional profile may correspond to short-term successful outcomes following ACLR, given that no athletes sustained ACL injuries in the competition season following assessment.

Does insole hardness affect the dynamic postural stability of basketball athletes during jump landing?

This study aimed to examine the effects of shoe insole hardness on the dynamic postural stability of basketball athletes during jump landing manoeuvres. Twenty college basketball athletes were recruited to complete a single-leg jump landing task on a force plate in three insole conditions (soft-, rigid- and no-insole). Kistler force plate and Pedar-X insole system were used to collect the ground reaction force (GRF) and plantar pressure data. Dynamic Postural Stability Index (DPSI), Anterior-Posterior Stability Index (APSI), Medial-Lateral Stability Index (MLSI), and Vertical Stability Index (VSI) were then calculated from GRF data. DPSI, APSI, MLSI, and VSI were statistically conducted among the three insole conditions by a one-way ANOVA with repeated measures. MLSI were decreased when wearing soft- and rigid insoles compared with no-insole condition (p &lt; 0.05). However, there were no significant differences in APSI and VSI among the three insole conditions. In the midfoot region, contact areas were increased in the soft- and rigid insole than the no-insole condition (p &lt; 0.0001). Dynamic balance of basketball athletes in the medial-lateral direction could be enhanced by wearing insoles during jump landings tasks. However, the postural stability of basketball athletes did not increase with insole hardness increasing.

Effects of Dual Task Interference on Biomechanics of The Entire Lower Extremity During the Drop Vertical Jump.

The dual task is an important factor affecting knee biomechanics during jump-landing tasks. Athletes often have trouble in performing two tasks concurrently and a dual task can deteriorate landing performance. However, it is still unknown whether a dual task will affect the entire lower extremity. The purpose of this study was to clarify the effects of cognitive task interference on biomechanics of hip and ankle joints as well as the knee joint during the drop vertical jump (DVJ). A total of 20 female collegiate athletes participated in the study. Athletes performed a DVJ with or without a cognitive task. The DVJ was captured using a motion analysis system. Mental arithmetic of 2-digit addition was used as a cognitive task. Maximum vertical ground reaction force (vGRF), joint angles at initial contact (IC), joint moments within 40 milliseconds (ms) after IC, and joint angles and moments at peak vGRF were assessed. The data were statistically compared between with and without a cognitive task condition using a two-tailed paired t-test or the Wilcoxon singed rank test. The peak external knee abduction moment on both limbs within 40 ms after IC during the DVJ was significantly larger in the dual task than in the single task with less knee and hip flexion at initial contact. In addition, all moments of hip and ankle joints within 40 ms after IC were significantly larger in the dual task than in the single task accompanied with greater vGRF, except for the hip internal rotation moment. Cognitive tasks during a DVJ will result in biomechanical changes of the entire lower extremity in female athletes.

Patellar Tendon Force Differs Depending on Jump-Landing Tasks and Estimation Methods

Patellar tendinopathy is a chronic overuse injury of the patellar tendon which is prevalent in jump-landing activities. Sports activities can require jumping not only with a vertical component but also in a forward direction. It is yet unknown how jumping in the forward direction may affect patellar tendon forces. The main purpose of this study was to compare PTF between landings preceded by a vertical jump and a forward jump in volleyball players. The second purpose was to compare two different estimation methods of the patellar tendon force. Fifteen male volleyball players performed vertical and forward jump-landing tasks at a controlled jump height, while kinetics and kinematics were recorded. Patellar tendon forces were calculated through two estimation methods based on inverse dynamic and static optimization procedures, using a musculoskeletal model. Results showed that forward jump-landing generated higher patellar tendon forces compared to vertical jump-landing for both estimation methods. Surprisingly, although the static optimization method considered muscle co-contraction, the inverse kinematic method provided statistically significant higher patellar tendon force values. These findings highlight that limiting the forward velocity component of the aerial phase appears to reduce the load on the patellar tendon during landing and may help to prevent patellar tendinopathy.

The effects of intrinsic foot muscles strengthening exercises on foot kinetic parameters in pronated foot subjects during forward jump landing.

Pronated foot is one of the most important factors that may lead to musculoskeletal injuries of the lower extremities. Among all treatments for this disorder, intrinsic foot muscles strengthening exercises (IFMSE) have an important role in management of the individuals with pronated foot. Although the effect of the IFMSE is well accepted in this population; however, their impacts on foot kinetic are yet to be clarified. The present study aims to identify the effects of the IFMSE on foot kinetic parameters in pronated foot individuals during forward jump landing. In this quasi-experimental study, 20 asymptomatic male and female subjects (mean age of 22.65 ± 2.51 years) with pronated foot structures were selected by using a simple non-random sampling method. The ground reaction force (GRF), rate of loading (ROL), and the resultant vector of time to stabilization (RVTTS) were examined during a forward jump landing task by using a force plate before and after six weeks of the IFMSE. The findings showed that the following parameters were not significantly change before and after of the IFMSE: GRF (1.97 ± 0.49 vs. 2.03 ± 0.54, P =0.667), ROL (.09 ±0.12 vs. 08 ±.12, P =.632), and RVTTS (2836.60 ± 1144.62 vs. 2644.35 ± 704.71, P =.479). In the pronated feet subjects, the IFMSE alone was not capable of changing the kinetic parameters of the foot, or the duration of using these exercises. In this study, six weeks may not be enough to make changes the foot kinetic parameters and therefore these exercises should be used for a longer period of time.

The effects of intrinsic foot muscles strengthening exercises on knee kinematic in pronated foot subjects during forward jump landing

The foot and ankle are a complex set of multiple joints with multiple degrees of freedom that play an important role in static and dynamic activities. The intrinsic and extrinsic muscles of this complex play a role in controlling the deformity of the arch; thus, the aim of this study was to investigate the effect of the intrinsic foot muscle-strengthening exercises on knee kinematic parameters in pronated foot subjects during forward jump landing. This interventional study was performed on students aged 20-30-years old with foot pronation in the School of Rehabilitation. In this study, the kinematic changes of the knee in the frontal, sagittal and transverse plane before and after 6 weeks of strengthening exercises of the intrinsic foot muscles during the forward jump-landing task were examined using a motion analyser. All data analysis was performed offline using a special software program in the MATLAB software environment. Knee angle variables have a normal distribution before and after exercise. The ICC coefficient of all variables was calculated as between 0.44 and 0.71; therefore, the reproducibility of the variables under study in this study was considered moderate to good. The knee angle on the frontal plate was 2.54 ± 2.4 before the exercises and 2.49 ± 2.14 after the exercises, and there was no significant difference between them (P = 0.21). Plantar intrinsic foot muscle-strengthening exercises alone have no effect on the kinematic changes of the knee in people with foot pronation, or the duration of strengthening exercises should be increased during the day to see the effect of strengthening the intrinsic muscles among pronated foot subjects.