Drop-jump Task Research Articles

Differences in Lower-Extremity Joint Coordination During Two Landing Phases of a Drop Jump Task.

The aim of the present study was to compare the differences in joint coordination patterns and variability in the lower extremity between the first and second landing phases of the drop jump. Eighteen resistance-trained men (age: 22.8 ± 1.8years) performed drop jumps from a height of 0.40m. An eight-camera motion capture system was utilized to record kinematic trajectories. Modified vector coding technique and circular statistics were used to determine the coordination pattern and variability of the following joint couples during the first and second landings: hip frontal-knee frontal (HfKf), hip sagittal-knee frontal (HsKf), hip sagittal-knee sagittal (HsKs), knee frontal-ankle frontal (KfAf), knee sagittal-ankle frontal (KsAf), and knee sagittal-ankle sagittal (KsAs). Statistical differences in the distribution frequencies of coupling angles and variability between the dominant and nondominant limbs across the two landing phases were compared using two-way repeated analysis of variance and Wilcoxon rank-sum tests. During the second landing phase, the proportion of HsKs, KfAf, and KsAs showing in-phase coordination was reduced but the proportion of KfAf and KsAs showing proximal joint (knee) coordination was increased (p < .05). Significant differences in bilateral asymmetry were observed only for the HfKf and KfAf patients (p < .05). HsKs, KfAf, and KsAf varied considerably during the second landing phase (p < .05). Joint coordination patterns during the second landing phase of the drop jump differed considerably from those during the first landing phase, thereby increasing the risk of knee and ankle injuries.

Reliability of Spatiotemporal Characteristics During Single-Legged Hop and Bilateral Drop Jump Tasks Using an Instrumented Pressure Walkway.

Single-legged hop tests have been widely used to assess performance-based outcomes after anterior cruciate ligament (ACL) reconstruction. Traditional single, triple, or 6-meter (6m) timed hop tests only measure distance or time as the principal variables, neglecting other variables, such as individual hop distances within a series of hops, flight time, and stance time. The development of portable instrumented pressure walkways has made it possible to collect parameters such as hop velocity, flight time, stance time, distance, and pressure outside of a laboratory setting. However, the reliability of instrumented pressure walkways in measuring spatial and temporal variables during single-legged hop tests is unknown. This study aimed to determine if the Zeno walkway can reliably measure spatiotemporal (ST) characteristics of hop tests. Cross-Sectional Study. Individuals (n=38) in this cross-sectional study performed single, triple, and 6m hop tests on a pressure-sensitive Zeno walkway. Twenty-one participants completed follow-up testing between one and 14 days later. Intraclass correlation coefficients (ICC(3,k)) were used to assess test-retest reliability of ST variables. The accuracy of vertical jump height and 6m hop timing were also measured. All ST variables demonstrated excellent test-retest reliability (ICC > 0.86) with small minimal detectable change (MDC) values during single-legged hop tests. Six-meter hop time and jump height during a bilateral drop jump were also accurately measured by the walkway. An instrumented pressure walkway is a novel tool to reliably assess non-traditional parameters of clinically relevant hop and jump tests such as flight time, stance time, and jump height after lower extremity injury, surgery, and rehabilitation. 3b.

Sex-Based Differences in Lower Extremity Kinematics During Dynamic Jump Landing Tasks After Neuromuscular Fatigue of the Hip Extensors and Knee Flexors.

Neuromuscular fatigue can increase the activation of antagonist muscles, thereby reducing the moment produced by the agonist. During the deceleration phase of landing, hip extensor and knee flexor muscles contract eccentrically to counteract the external hip flexion moment. Decreased hip flexion is associated with greater knee extensor moments and risk of injury. To investigate sex-based differences in kinematics and muscle activity after neuromuscular fatigue of the hip extensors and knee flexors during dynamic single-leg tasks. Controlled laboratory study. In this study, 9 female (age, 22.3 ± 3.4 years) and 7 male participants (age, 21.3 ± 2.6 years) completed the triple hop (THop) for distance and single-leg drop-jump (SJump) tasks before and after a fatigue protocol consisting of eccentric hip extension and knee flexion. Motion capture and electromyography were used to compare lower extremity kinematics and muscular activation between the sexes. During the THop, neuromuscular fatigue resulted in significantly decreased maximum hip flexion angles (P = .01), maximum knee flexion angles (P = .039), and an effect of sex on all hip flexion angles, where both sexes saw decreased hip flexion postfatigue (P = .033). A significant interaction of fatigue and sex on hip flexion angular velocity was observed during the SJump, indicating that men experienced an increase while women experienced a decrease in hip flexion angular velocities due to fatigue (P = .03). Gluteus maximus activation was increased, and erector spinae activation was decreased postfatigue in women during the THop (P = .053 and P = .023, respectively). Results indicate that men and women compensated differently after fatigue of the hip extensors and knee flexors. Women more commonly assumed an erect landing posture associated with increased injury risk after fatigue of the hip extensors and knee flexors.

Association of clinically-measured and dynamic ankle dorsiflexion assessed by markerless motion capture during the drop-jump task on landing biomechanics and risk of ankle injury in military personnel undergoing 10 weeks of physical training.

Determine the influence of clinically-measured maximum dorsiflexion, dynamic peak dorsiflexion and percent of clinically-measured maximum dorsiflexion used during a drop-jump task on landing biomechanics and risk of ankle injury in military personnel. Prospective cohort study. 672 participants (122 women) enrolled. The weightbearing lunge test assessed clinically-measured maximum dorsiflexion averaged across limbs (degrees). Markerless motion capture and force plates collected lower extremity kinematic and kinetic data during a drop-jump task. Percent of clinically-measured maximum dorsiflexion used during landing was calculated as dynamic peak dorsiflexion divided by clinically-measured value, multiplied by 100 (%). De-identified injury data was derived from military physical therapists. Simple linear regression analysis determined the association between dorsiflexion measures and landing biomechanics. Simple binary logistic regression analyses identified predictors of ankle injuries. Statistical significance was set at α = 0.05. Eighteen participants sustained a traumatic ankle injury from a landing. All measures of dorsiflexion were associated with movement patterns that countered the stiff-legged landing strategy with dynamic measures showing a higher predictive value. Protective factors against ankle injury included height (odds ratio: 0.818, p = 0.006) and weight (odds ratio: 0.824, p = 0.023) for women. Relative braking impulse was a risk factor for men (odds ratio: 1.890, p = 0.001). Greater clinically-measured and dynamic measures of dorsiflexion were associated with movement patterns that countered the stiff-legged landing strategy but neither measure of dorsiflexion predicted ankle injury risk. Resultant biomechanics and anthropometrics influenced ankle injury risk to warrant recognition for injury prevention initiatives.

Differences In Lower-extremity Muscle Activation Patterns During Anticipated Or Unanticipated Single-leg Drop Jump Tasks

PURPOSE: To examine the muscle activation patterns of the lower-extremity during an anticipated or unanticipated single-leg drop jump task. METHODS: Surface electromyography (EMG, 1,500 Hz) was collected from 17 healthy young male subjects (173 cm; 72 kg), including gluteus medius (GM), rectus femoris (RF), vastus medialis (VM), semitendinosus (ST), biceps femoris (BF), tibialis anterior (TA), and medial gastrocnemius (MG) on the dominant leg. Subjects were asked to drop down from a wooden box with a height of 40-cm with their dominant leg (landing), then immediately jump as high as possible (jumping). For the anticipated condition, subjects were informed of the drop jump task prior to the initial drop. For the unanticipated condition, the specific task was visually shown on the light-emitting diode screen (upwards or downwards arrow for jumping or landing, respectively), which triggered by the infrared sensor when a subject’s foot was sensed prior to initial contact (average time from sensor to initial contact: 48-ms). The data during unanticipated jumping were selectively compared to those during anticipated jumping. Time of muscle onset (time to reach 8% of peak amplitude) and time to peak amplitude were identified during the pre-contact phase (before initial contact: BIC) and the post-contact phase (after initial contact: AIC), and then analysed through t-tests (p < 0.05) and Cohen’s d effect size (d). RESULTS: Time of muscle onset of the BF (t = -2.21, p = 0.03) and TA (t = -2.76, p = 0.01) were different. Specifically, onset of the BF (116-ms BIC, d = 0.45) and TA (174-ms BIC, d = 0.56) was faster in the anticipated than the unanticipated condition (BF: 54-ms BIC; TA: 118-ms BIC). Time to peak amplitude of the GM (t = -2.51, p = 0.01), VM (t = -2.33, p = 0.02), ST (t = -2.01, p = 0.05), and BF (t = -2.69, p = 0.01) were different. Specifically, time to peak of the GM (350-ms AIC, d = 0.52), VM (365-ms AIC, d = 0.47), ST (374-ms AIC, d = 0.41), and BF (454-ms AIC, d = 0.54) was faster in the anticipated than unanticipated (GM: 439-ms AIC; VM: 451-ms AIC; ST: 472-ms AIC; BF: 646-ms AIC). CONCLUSIONS: When the task was unanticipated (between either landing or jumping after a drop landing from a 40-cm), the onset of the BF and TA were delayed during pre-contact while the GM, VM, ST, and BF were delayed reaching the peak amplitude during the post-contact phase.

The relationship between kinesiophobia and biomechanics in anterior cruciate ligament reconstructed females

ObjectiveKinesiophobia has been associated with deleterious biomechanical alterations during dual-limb landing tasks in anterior cruciate ligament (ACL) reconstructed females, however, no research has yet investigated single-limb tasks related to ACL injury. The aim of this investigation was to examine the relationship between kinesiophobia and biomechanics during a series of dual and single-limb functional tasks associated with ACL injury risk. DesignCross-sectional study. ParticipantsFifteen females (age = 22.67 ± 2.58yrs, height = 1.65 ±0 .05m, mass = 65.28 ± 10.36 kg) with a history of ACL reconstruction (time post surgery = 3.40 ±0 .74yrs) were recruited for this investigation. Main outcome measuresKinesiophobia, measured via the Tampa Scale of Kinesiophobia (TSK-11). Kinematics and muscle activation were measured during three functional tasks: the drop jump (DJ), single-limb hop (SLH), and single-limb landing (SLL). ResultsFor the DJ task, there was a strong negative correlation between kinesiophobia and knee flexion (r = −.592, p = .20) and between kinesiophobia and trunk flexion (r = −0.724, p = .002). For the SLH task, there was a strong positive correlation between kinesiophobia and hip flexion (r = 0.560, p = .03). ConclusionsThese findings indicate that kinesiophobia is associated with movement alterations years after completion of ACL reconstruction and rehabilitation.

Feedforward and Feedback Function of Selected Lower Limb Muscles Following Plyometric Exercises and Cryotherapy

Purpose: Despite the widespread use of cryotherapy in sports, there is no specific evidence of its impact on muscle activation, especially following fatigue-induced exercises. This study aimed to assess the impact of cryotherapy alone and after plyometric exercises on knee muscle activation during the drop jump task. Methods: A total of 35 active female subjects (mean±SD age of 22.74±2.10 years, mean body mass index [BMI] of 20.02±2.55 kg/m2) participated in this quasi-experimental study with a pretest-Post-test design. There were three experimental groups (20-minute cryotherapy, plyometric, and plyometric-cryotherapy) and a control group. Electromyography (EMG) amplitudes of knee muscle activation (rectus femoris [RF], biceps femoris [BF], tibialis anterior [TA], medial gastrocnemius [MG]) were measured and compared in three phases of the drop-jump task (one feedforward preactivation and two feedback eccentric and concentric phases). Skin temperature was recorded before and after cooling intervention as well. For comparisons, repeated measure analysis of variance (ANOVA) was used at a significant level of 0.05. Results: The results showed that the skin temperature decreased significantly after cryotherapy and was maintained for 20 minutes. No significant changes were observed in the EMG of knee muscles in the feedforward and concentric phase of the drop jump task in any groups (P&gt;0.05). However, RF activation decreased following cryotherapy immediately and after 20 minutes as an eccentric phase (P=0.01) and had a significant difference from the control group (P=0.01); besides, EMG activation decreased in cryotherapy, plyometric, and plyometric-cryotherapy groups immediately (P=0.01). However, no significant differences were seen between them and the control group (P&gt;0.05). Conclusion: According to the present results, cryotherapy alone and after fatigue-induced plyometric training had a minor effect on the knee muscle activation during a functional jumping movement, but the impact of these changes on knee biomechanics is insignificant; hence, further studies are essential for a better conclusion.

The Landing Error Scoring System (LESS) and Lower Limb Power Profiles in Elite Rugby Union Players.

BackgroundThe Landing Error Scoring System (LESS) is a clinical test that assesses landing biomechanics during a drop-jump task. Performance measures such as jump height, power, contact time and reactive strength index are used commonly in athletic populations. Comparing results from the LESS against these performance measures has not been reported in elite rugby union.PurposeTo report i.) normative LESS scores for elite rugby union players ii.) correlations between LESS scores and performance measures and iii.) differences in performance measures between LESS scoring groups. A secondary purpose was to report the intra- and inter-rater reliability of the LESS test when used in elite rugby union players. # Study DesignCross-sectional design.MethodsThirty-six male, elite rugby union players participated. Each participant completed three trials of the LESS and performance measures were recorded concurrently using the OptojumpTM. LESS trials were scored independently by the authors. Statistical analyses were used to confirm reliability, data normality, and between group differences (p<0.05).ResultsThe LESS test is a reliable testing tool in elite rugby union players (excellent intra- (ICC=0.96) and inter-rater (ICC=0.94) reliability). One player demonstrated an excellent LESS score, six players had good scores, eight players moderate scores and the majority of the group, 21 players, scored poorly. LESS scores were correlated to contact time (r = -0.461, p = 0.005) only. Participants with moderate to poor LESS scores (a score ≤5) produced greater power (p=0.036, η2 = 0.139), contact time (p=0.002, η2 = 0.268) and reactive strength index (p=0.016, η2 = 0.180). There were no differences in jump height (p=0.842) between players scoring excellent to good and moderate to poor.ConclusionThe results of the current study demonstrate excellent intra- and inter-rater reliability for the LESS, supporting its use as a clinical assessment tool in elite rugby union players. The majority of players presented with moderate to poor LESS scores, indicating an area of concern in this population. Participants scoring moderate to poor in the LESS recorded significantly higher power and reactive strength index, increased contact time but not jump height. This suggests participants with high-risk landing biomechanics may also produce higher performance measures, but these do not necessarily result in an improved jump height.

Sex Disparity in Bilateral Asymmetry of Impact Forces during Height-Adjusted Drop Jumps.

Side-to-side asymmetry of lower extremities may influence the risk of injury associated with drop jump. Moreover, drop heights using relative height across individuals based on respective jumping abilities could better explain lower-extremity loading impact for different genders. The purpose of the current study was to evaluate the sex differences of impact forces and asymmetry during the landing phase of drop-jump tasks using drop heights, set according to participants’ maximum jumping height. Ten male and ten female athletes performed drop-jump tasks on two force plates, and ground reaction force data were collected. Both feet needed to land entirely on the dedicated force plates as simultaneously as possible. Ground reaction forces and asymmetry between legs were calculated for jumps from 100%, 130%, and 160% of each participant’s maximum jumping height. Females landed with greater asymmetry at time of contact initiation and time of peak impact force and had more asymmetrical peak impact force than males. Greater values and shorter time after ground contact of peak impact force were found when the drop height increased to 160% of maximum jumping ability as compared to 100% and 130%. Females exhibited greater asymmetry than males during drop jumps from relative heights, which may relate to the higher risk of anterior cruciate ligament injury among females. Greater sex disparity was evident in impact force asymmetry than in the magnitude of peak impact force; therefore, it may be a more appropriate field-screening test for risk of anterior cruciate ligament injury.

Improvements in Hip Extensor Rate of Torque Development Influence Hip and Knee Extensor Feed-Forward Control

Females have been reported to utilize a feedforward control strategy during landing in which they compensate for decreased rate of torque development (RTD) of the hip extensors through earlier pre-activation of the knee extensors. The purpose of this study was to determine the influence of a 4-week hip-focused training program on hip extensor RTD and feedforward control of the hip and knee extensors. Twenty-one females underwent hip extensor RTD evaluation and electromyographic assessment of the hip and knee extensors during a drop-jump task. Post-training, there was a significant improvement in hip extensor RTD (21.68 ± 5.44 to 23.33 ± 5.45 Nm/kg s, p = 0.009), and pre-activation of the hip extensors (87.1 ± 63.6 to 56.2 ± 60.9 ms, p < 0.001) and knee extensors (272.3 ± 113.8 to 124.0 ± 67.7 ms, p < 0.001) occurred closer to ground contact. A negative association was found between the change in hip extensor RTD and the change in knee extensor onset (r = −0.48, p = 0.03). We propose that the observed change in feedforward control is reflective of the decreased need for preparatory muscle activity owing to the improved capacity of the hip extensors to rapidly generate force.

Mechanical Differences Between Adolescents and Adults During Two Landing Phases of a Drop Jump Task.

Moir, GL, Munford, SN, Snyder, BW, and Davis, SE. Mechanical differences between adolescents and adults during two landing phases of a drop jump task. J Strength Cond Res XX(X): 000-000, 2020-The mechanical differences between the first and second landing phases of a drop jump (DJ) task performed by adolescent and adult male players were investigated. Eleven adolescent basketball players (age: 16.5 ± 0.7 years) and 11 resistance-trained adults (age: 22.3 ± 1.9 years) performed DJs from a height of 0.40 m. Force plates and a 3-dimensional motion analysis system were used to determine mechanical variables, including landing velocity, normalized vertical stiffness, normalized peak impact force, and work as well as mechanical characteristics of the hip, knee, and ankle joints during the absorption phase of each landing. The adolescents produced greater peak impact forces (mean difference [xDiff] = 42 N·kg; effect size [ES] = 1.15) and vertical stiffness (xDiff = 126 N·kg·m; ES = 1.28) during shorter absorption phases (xDiff = 0.09 seconds; ES = 2.67) compared with the adults, despite their lower landing velocities (xDiff = 0.21 m·s; ES = 1.37). Furthermore, the adolescents generated greater peak extensor joint moments at the lower-body joints compared with the adults (xDiff = 2.3 N·m·kg; ES = 1.17), but they did not effectively modulate the energy absorbed by the joint moments in response to the changing demands of the landing tasks. The assessment of the biomechanical characteristics of the 2 landing phases associated with a DJ task revealed that adolescent male basketball players adopt neuromuscular strategies that may increase the risk of incurring musculoskeletal injuries compared with resistance-trained adults.

Immediate Effect of Acupuncture on Performance in the Drop Jump Task: A Single-Group Pretest–Posttest Experimental Study

IntroductionAcupuncture is used in sports medicine to treat pain as well as improving athlete’s performance. Acupuncture stimulates the nerves and appears to affect the motor cortex. The drop jump (DJ) is a basic training method for enhancing lower extremity strength and jumping height in this study, acupuncture was used to stimulate nerve activation and observe the effect on individual’s performance in the DJ task. MethodsTwenty-two male sports students volunteered to participate in sessions consisting of 3 DJ trials, from heights of 30, 40 and 50 cm (DJH30, DJH40, and DJH50, respectively). Data was collected before (pretest) and 20 minutes after acupuncture (posttest); three testing sessions were performed at 7-day intervals. ResultsAfter acupuncture, the impact of the peak ground reaction force was decreased during the posttest at drop jump height of 50 cm (DJH50), and the peak joint moment in the right ankle was increased under the same conditions. Additionally, the angles of the knee and ankle joints in the right leg were increased in the DJH50 posttest. Therefore, acupuncture achieved high levels of improvement within a modest intervention period, reducing pain and increasing knee joint flexion amplitude. Acupuncture did not change the jump height. However, the ground reaction force was reduced in the DJH50 posttest. ConclusionsAcupuncture reduces the impact force during landing and could be used to reduce the risk of sports injury.

Effect of Sand on Landing Knee Valgus During Single-Leg Land and Drop Jump Tasks: Possible Implications for ACL Injury Prevention and Rehabilitation.

Despite significant emphasis on anterior cruciate ligament injury prevention, injury rates continue to rise and reinjury is common. Interventions to reduce injury have included resistance, balance, and jump training elements. The use of sand-based jump training has been postulated as an effective treatment. However, evidence on landing mechanics is limited. To determine potential differences in landing strategies and subsequent landing knee valgus when performing single-leg landing (SLL) and drop jump (DJ) tasks onto sand and land, and to compare between both male and female populations. A randomized repeated-measures crossover design. University laboratory. Thirty-one participants (20 males and 11 females) from a university population. All participants completed DJ and SLL tasks on both sand and land surfaces. Two-dimensional frontal plane projection angle (FPPA) of knee valgus was measured in both the DJ and SLL tasks (right and left) for both sand and land conditions. FPPA was lower (moderate to large effect) for SLL in sand compared with land in both legs (left: 4.3° [2.8°]; right: 4.1° [3.8°]) for females. However, effects were unclear (left: -0.7° [2.2°]) and trivial for males (right: -1.1° [1.9°]). FPPA differences for males and females performing DJ were unclear; thus, more data is required. Differences in FPPA (land vs sand) with respect to grouping (sex) for both SLL left (4.9° [3.0°]) and right (5.1° [4.0°]) were very likely higher (small)/possibly moderate for females compared with males. The effects of sand on FPPA during DJ tasks in males and females are unclear, and further data is required. However, the moderate to large reductions in FPPA in females during SLL tasks suggest that sand may provide a safer alternative to firm ground for female athletes in anterior cruciate ligament injury prevention and rehabilitation programs, which involve a SLL component.

Corticomotor Excitability of Gluteus Maximus Is Associated with Hip Biomechanics During a Single-Leg Drop-Jump

The purpose of this study was to determine the association between corticomotor excitability (CME) of gluteus maximus (GM) and hip biomechanics during a single-leg drop-jump task. Thirty-two healthy individuals participated. The slope of the input-output curve (IOC) obtained from transcranial magnetic stimulation was used to assess CME of GM. The average hip extensor moment and peak hip flexion angle during the stance phase of the drop jump task was calculated. The slope of the IOC of GM was found to be a predictor of the average hip extensor moment (r2 = 0.18, p = 0.016) and peak hip flexion angle (r2 = 0.20, p = 0.01). Our results demonstrate that greater functional use of the hip was associated with enhanced descending neural drive of GM.

An Examination of the Relationship Between the Functional Movement Screen, Landing Error Scoring System, and 3D Kinematic Data During a Drop Jump Task.

Everard, E, Lyons, M, and Harrison, AJ. An examination of the relationship between the functional movement screen, landing error scoring system and 3D kinematic data during a drop jump task. J Strength Cond Res 35(11): 3012-3020, 2021-Tests such as the Functional Movement Screen (FMS) and Landing Error Scoring System (LESS) have become an established component of preparticipation screening. Despite their practical use, there is a lack of empirical evidence examining their relationship to established assessments of movement, such as 3D kinematics of a drop jump. Fifty-two male collegiate athletes undertook the LESS, FMS, and a drop jump where 3D lower-limb kinematic variables were assessed. Spearman correlations were conducted to examine the relationship between LESS, FMS, and drop-jump 3D kinematic variables. A series of independent t-tests examined differences in hip and knee kinematic variables in acceptable and poor FMS and LESS groups as determined by established cut-off scores. Landing Error Scoring System scores had significant moderate correlations with most kinematic variables (r = 0.35-0.64; p < 0.01). Subjects with poor LESS scores displayed significantly worse lower-limb kinematics compared with their high-scoring counterparts (effect size = 1.99-2.76, large effect). There were significant moderate correlations with maximal hip and knee flexion (r = 0.46 and 0.39 respectively; p < 0.01) and small or nonsignificant correlations between all other kinematic variables and FMS scores. Hip flexion and knee valgus at maximal displacement were the only kinematic variables significantly different between FMS groups (ES = 0.70-0.72, small-to-moderate effect). The results confirm limitations in the ability of the FMS to distinguish between groups for landing biomechanics.

Sub-elite Football Players With Hip-Related Groin Pain and a Positive Flexion, Adduction, and Internal Rotation Test Exhibit Distinct Biomechanical Differences Compared With the Asymptomatic Side.

Background Hip-related groin pain is common in sub-elite football players and may be associated with altered hip biomechanics. Objectives To compare the hip biomechanics, bony hip morphology associated with femoroacetabular impingement (FAI) syndrome, and hip strength and range of motion (ROM) between the symptomatic and asymptomatic limbs of sub-elite football players with unilateral hip-related groin pain and a positive flexion, adduction, and internal rotation (FADIR) test. Methods Fifteen sub-elite football (soccer) players with unilateral hip-related groin pain and a positive FADIR test were recruited for this observational cross-sectional study. Three-dimensional motion analysis and ground reaction force data were recorded for walking and a single-leg drop-jump (SLDJ) task. Participants also underwent a standard anterior-posterior hip radiograph and hip strength and ROM assessment. Between-limb differences were assessed using paired t tests or Wilcoxon signed-rank tests. Results The symptomatic limb displayed a smaller peak hip extension angle (P = .01) and a lower peak hip adduction moment (P = .03) compared with the asymptomatic limb during the stance phase of walking. Additionally, during the SLDJ, the symptomatic limb demonstrated less total sagittal plane ROM (P = .04). The symptomatic limb also demonstrated less external rotation ROM (P = .03). However, no differences were found between limbs for bony hip morphology associated with FAI syndrome or hip strength. Conclusion This study found between-limb asymmetries in low- and high-impact functional tasks, such as walking and an SLDJ, in football players with unilateral hip-related groin pain. Despite unilateral pain, bony morphology associated with FAI syndrome did not differ between limbs. J Orthop Sports Phys Ther 2018;48(7):584-593. Epub 8 May 2018. doi:10.2519/jospt.2018.7910.

Differences in Joint Mechanics Between Adolescent and Adult Males Performing Countermovement and Drop Jump Tasks

PURPOSE: To investigate the differences in joint mechanics between adolescent and adult males performing countermovement and drop jump tasks. METHODS: Eleven adolescent basketball players (age: 16.5 ± 0.7 years; height: 1.78 ± 0.07 m; mass: 68.9 ± 8.8 kg) and eleven resistance-trained adults (age: 22.3 ± 1.9 years; height: 1.80 ± 0.10 m; mass: 84.3 ± 9.3 kg) performed two trials of a countermovement jump (CMJ) and a drop jump from a height of 0.40 m (DJ). Force plates (1000 Hz) and an 8-camera 3-D motion analysis system (200 Hz) were used to determine the following kinetic variables for the hip, knee, and ankle joints during the propulsive phase of each jump: normalized work performed by the moment (JWNORM), normalized power output of the moment (JPONORM), and normalized joint stiffness (JSNORM). RESULTS: The adults produced significantly greater JWNORM across the two jumps (mean difference [MD]: 0.32 J/kg, p=0.014). JWNORM at the knee was greater than that at the hip (MD: 2.09 J/kg, p<0.001) and the ankle (MD: 2.61 J/kg, p<0.001), while JWNORM was greater at the hip compared to the ankle (MD: 0.52 J/kg, p=0.001). The adults performed greater JWNORM at the hip compared to the adolescents (MD: 0.75 J/kg, p=0.005). JPONORM at the knee was greater than that at the hip (MD: 4.49 W/kg, p<0.001) and ankle (MD: 4.32 W/kg, p<0.001) across the two jumps while JPONORM was significantly greater in DJ compared to CMJ (MD: 0.49 W/kg, p=0.10). The adolescents produced significantly greater JPONORM at the ankle compared to the adults (MD: 1.35 W/k, p=0.002). The adolescents produced significantly greater JSNORM compared to the adults (MD: 0.021 Nm/kg/deg, p<0.001). Both groups produced significantly greater JSNORM in DJ compared to CMJ (MD: 0.015 Nm/kg/deg, p=0.001) with significant increases in JSNORM at the knee joint from CMJ to DJ (MD: 0.02 Nm/kg/deg, p<0.001). The increase in JSNORM at the hip (MD: 0.025 Nm/kg/deg, p=0.033) and knee (MD: 0.023 Nm/kg/deg, p=0.046) between CMJ and DJ was significantly greater in adolescents compared to adults. CONCLUSION: Adolescent males produce different joint mechanics compared to adults during jumping tasks and rely on a strategy of increasing joint stiffness at the hip and knee joints when performing DJ. These differences may have implications for musculoskeletal injuries in adolescent males.

Mechanical Differences between Adolescents and Adults during Two Landing Phases of a Drop Jump Task

Mechanical Differences between Adolescents and Adults during Two Landing Phases of a Drop Jump Task

Mechanics of Countermovement and Drop Jump Tasks Performed by Adolescent and Adult Males

Mechanics of Countermovement and Drop Jump Tasks Performed by Adolescent and Adult Males

Rate of Torque Development and Feedforward Control of the Hip and Knee Extensors: Gender Differences

ABSTRACTThe purpose of this study was to determine whether women demonstrate decreased rate of torque development (RTD) of the hip and knee extensors and altered onset timing of the vastus lateralis and gluteus maximus during a drop-jump task when compared with men. On average, women demonstrated significantly lower normalized RTD of the hip extensors (women: 11.6 ± 1.3 MVT.s−1, men: 13.1 ± 0.9 MVT.s−1; p ≤ .01); however, there was no significant difference in knee extensor RTD. Women also demonstrated significantly earlier activation of their vastus lateralis (women: 206.0 ± 130.6 ms, men: 80.9 ± 69.6 ms; p ≤ .01) and gluteus maximus (women: 85.7 ± 58.6 ms, men: 54.5 ± 35.4 ms; p = .02). In both men and women, there was a significant negative correlation between the hip extensor RTD and the vastus lateralis electromyographic onset time (men: r = –.386, p = .046; women: r = –.531, p = .008). The study findings suggest that women may utilize a feedforward control strategy in which they activate their knee extensors earlier than men to compensate for deficits in hip extensor RTD. The impaired capacity to rapidly stabilize the hip and knee joints during dynamic maneuvers may contribute to the increased risk of anterior cruciate ligament injury observed in women.