Search

This study aimed to determine the acute effects of static stretching of the hamstrings on maximal sprint speed and its spatiotemporal variables and lower-limb kinematics during the late swing phase, as well as the relationship with Nordic hamstring strength. The study had a within-participant experimental design. Sixteen healthy male college sprinters were asked to sprint 80 m without static stretching and with static stretching of the hamstrings for 4 x 30 s per leg before the sprint: both conditions were counterbalanced. The knee ftexion peak torque was measured using the Nordic hamstring. The differences between no static stretching and static stretching as well as their relationship with Nordic hamstri ng strength were investigated. The results showed that the touchdown distance (p = .036) significantly increased following static stretching. Although not significant. maximal sprint speed decreased (p = .086), and the theoretical hamstring length (difference between knee angle and hip angle) at ipsilateral touchdown was greater (p =.069) following static stretching. In addition, a lower peak torque of the Nordic hamstring resulted in a more significant decrease in maximal sprint speed following static stretching. Therefore, static stretching of the hamstring just before sprinting may increase the theoretical hamstring length during the late swing phase at maximal sprint speed and induce kinematics that increases the hamstring strain injury risk. Moreover, it is suggested that improving the Nordic hamstring strength may help minimize the negative effects of static stretching on the hamstrings. [ABSTRACT FROM AUTHOR]

Postpartum mothers are susceptible to lumbopelvic pain which may be exacerbated by loading, like carrying their infant in arms and with baby carriers. Nulliparous women carrying infant mannequins may biomechanically mimic mother–infant dyad, but this has not been studied. The purpose of our study was to investigate biomechanical differences of 10 mothers carrying their infants and 10 nulliparous women carrying infant mannequins under 3 gait conditions: carrying nothing, carrying in arms, and carrying in a baby carrier (babywearing). Spatiotemporal gait parameters, peak ground reaction forces and impulses, and lower extremity and trunk kinematics were collected using motion capture and force plates and compared using a mixed 2 × 3 (parity × condition) analysis of variance (α ≤.05). The largest differences occurred between carrying conditions: carrying in arms or babywearing increased vertical and anteroposterior ground reaction forces, trunk extension, ankle dorsiflexion, and hip and knee flexion. Kinematic differences were identified between arms and babywearing conditions. Together this suggests alterations in joint loading for both groups. Our study also contributes a novel understanding of postpartum health by demonstrating alterations in step time, anterior forces, and ankle and knee mechanics, suggesting that during gait, mothers carrying their own infants choose different propulsive strategies than nulliparous women carrying mannequins. [ABSTRACT FROM AUTHOR]

As markerless motion capture is increasingly used to measure 3-dimensional human pose, it is important to understand how markerless results can be interpreted alongside historical marker-based data and how they are impacted by clothing. We compared concurrent running kinematics and kinetics between marker-based and markerless motion capture, and between 2 markerless clothing conditions. Thirty adults ran on an instrumented treadmill wearing motion capture clothing while concurrent marker-based and markerless data were recorded, and ran a second time wearing athletic clothing (shorts and t-shirt) while markerless data were recorded. Differences calculated between the concurrent signals from both systems, and also between each participant's mean signals from both asynchronous clothing conditions were summarized across all participants using root mean square differences. Most kinematic and kinetic signals were visually consistent between systems and markerless clothing conditions. Between systems, joint center positions differed by 3 cm or less, sagittal plane joint angles differed by 5° or less, and frontal and transverse plane angles differed by 5° to 10°. Joint moments differed by 0.3 N·m/kg or less between systems. Differences were sensitive to segment coordinate system definitions, highlighting the effects of these definitions when comparing against historical data or other motion capture modalities. [ABSTRACT FROM AUTHOR]

As markerless motion capture systems become more affordable than ever, it is becoming far easier to collect and analyze kinematic data on baseballers. To ensure this data can be used impactfully, coaches and practitioners should possess a good understanding of specific technique characteristics that are associated with enhanced performance in pitchers and hitters. This study used the open-source data provided by Driveline Baseball's OpenBiomechanics Project to evaluate the contribution of lower-body kinematics to pitch velocity and bat speed. In addition to correlational analyses to examine the association between discrete kinematic variables and performance, statistical nonparametric mapping was used to compare slow and fast velocity groups across the entirety of pitching and hitting motions from peak knee height to ball release/contact. It was found that rotation of the trail leg and extension of the lead knee were both associated with performance in pitchers and hitters. Consequently, coaches and practitioners should ensure that individuals possess an adequate level of strength and flexibility to facilitate optimal movement of the trail hip and lead knee during pitching and hitting movements. If deficiencies exist, then training programs should be designed to address these issues and eventually bring about an improvement in performance. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the preliminary effects of movement pattern training (MoveTrain) versus strengthening/flexibility (standard) treatment on hip and pelvic biomechanics in patients with chronic hip-related groin pain. This is a secondary analysis of data collected during a pilot randomized clinical trial. Thirty patients with hip pain, between the ages of 15 and 40 years, were randomized to MoveTrain or standard. Both groups completed 10 treatment sessions over 12 weeks along with a daily home exercise program. Three-dimensional motion analysis was used to collect kinematic and kinetic data of the pelvis and hip during a single-leg squat task at pretreatment and immediately posttreatment. Compared with the standard group, the MoveTrain group demonstrated smaller hip adduction angles (P =.006) and smaller hip external adduction moments (P =.008) at posttreatment. The desired changes to hip joint biomechanics, as found in this study, may require specificity in training that could allow health care professionals to better customize the rehabilitation of patients with hip pain. These findings can also be applied to the design and implementation of future clinical trials to strengthen our understanding of the long-term implications of different rehabilitation techniques for patients with hip pain. [ABSTRACT FROM AUTHOR]

More than 80% of adult manual wheelchair users with spinal cord injuries will experience shoulder pain. Females and those with decreased shoulder dynamics variability are more likely to experience pain in adulthood. Sex-related differences in shoulder dynamics variability during pediatric manual wheelchair propulsion may influence the lifetime risk of pain. We evaluated the influence of sex on 3-dimensional shoulder complex joint dynamics variability in 25 (12 females and 13 males) pediatric manual wheelchair users with spinal cord injury. Within-subject variability was quantified using the coefficient of variation. Permutation tests evaluated sex-related differences in variability using an adjusted critical alpha of P =.001. No sex-related differences in sternoclavicular or acromioclavicular joint kinematics or glenohumeral joint dynamics variability were observed (all P ≥.042). Variability in motion, forces, and moments are considered important components of healthy joint function, as reduced variability may increase the likelihood of repetitive strain injury and pain. While further work is needed to generalize our results to other manual wheelchair user populations across the life span, our findings suggest that sex does not influence joint dynamics variability in pediatric manual wheelchair users with spinal cord injury. [ABSTRACT FROM AUTHOR]

Context: Anterior cruciate ligament injuries are directly related to the control of dynamic knee valgus in the landing of a jump, and this is mainly due to the correct activation and neuromuscular function of the lower-extremity muscles. The aim of the study is to assess the relationship between lower limb muscle activity during a single-legged drop jump and knee frontal plane projection angle (FPPA). Design: A correlation study. Methods: Thirty healthy collegiate female athletes were included in the study. Main outcomes measures were peak knee FPPA and muscle activity (% of maximal voluntary isometric contraction). Peak knee FPPA during a single-legged drop jump test was identified using a 2-dimensional motion analysis system. Muscle activity was assessed using a surface electromyograph for gluteus maximus, gluteus medius, biceps femoris, semitendinosus, vastus medialis quadriceps, vastus lateralis quadriceps, medial gastrocnemius, and lateral gastrocnemius. All variables were assessed for both dominant and nondominant limbs. A correlation analysis between peak knee FPPA and muscle activity was performed. Statistical significance was set at P <.05. Results: A mean peak knee FPPA of 14.52° and 13.38° was identified for dominant and nondominant limb single-legged drop jump test, respectively. Muscle activity (% of maximal voluntary isometric contraction) for muscles assessed ranged from 43.97% to 195.71% during the single-legged drop jump test. The correlation analysis found no significant correlation between any of the muscles assessed and peak knee FPPA during the single-legged drop jump test (Pearson coefficient between −.3 and.1). Conclusions: There is no association between muscle activity from the lower limb muscles and the knee FPPA during a single-legged drop jump in female athletes. Thus, different muscle properties should be assessed in order to understand such an important movement as the knee FPPA during a jump. [ABSTRACT FROM AUTHOR]

ObjectiveTo evaluate the kinematics and stability of the temporomandibular joint (TMJ) of cats and dogs with and without a TMJ replacement (TMJR) prosthesis under simulated bite forces and mouth opening.AnimalsSixteen cadaver skulls from domestic cats (n = 8) and medium- to large-breed dogs (n = 8).MethodsIntact TMJs were tested. Following condylectomy and coronoidectomy, the skulls were fitted with a TMJR prosthesis unilaterally and retested. Prosthesis was similarly implanted in the contralateral TMJ in 4 cats and 4 dogs before retesting. Left and right bite motions were evaluated before bite contact to peak bite force (200 N in dogs, 63 N in cats). Mouth opening motion was recorded. Mandibular displacement under load was evaluated in 3 orthogonal planes. Maximal displacement was compared between TMJR groups and native TMJ. Prosthesis-bone motion of the temporal and mandibular components was evaluated during simulated bites and mouth opening.ResultsTMJR resulted in joint motion not demonstrably different from the native TMJ, with the ability to fully open and close the mouth and with minimal laterotrusion. The TMJR prosthesis demonstrated similar stability after unilateral and bilateral replacement during bite force and with an open mouth. Mean implant-bone motion during bite simulations for the temporal and mandibular TMJR components was ≤ 60 µm in cats and ≤ 30 µm in dogs.Clinical relevanceA novel TMJR can be implanted and allows normal jaw motion. Joint stability is maintained after TMJR implantation in the TMJ of dogs and cats TMJ that is devoid of muscular support.

Prior studies have explored the relationship between knee valgus and musculoskeletal variables to formulate injury prevention programs, primarily for females. Nonetheless, there is insufficient evidence pertaining to professional male soccer players. Here, the aim was to test the correlation of lateral trunk inclination, hip adduction, hip internal rotation, ankle dorsiflexion range of motion, and hip isometric strength with knee valgus during the single-leg vertical jump test. Twenty-four professional male soccer players performed a single-leg vertical hop test, hip strength assessments, and an ankle dorsiflexion range of motion test. A motion analysis system was employed for kinematic analysis. Maximal isometric hip strength and ankle dorsiflexion range of motion were tested using a handheld dynamometer and a digital inclinometer, respectively. The correlation of peak knee valgus with peak lateral trunk inclination was.43 during the landing phase (P =.04) and with peak hip internal rotation was −.68 (P <.001). For knee valgus angular displacement, only peak lateral trunk inclination presented a moderate positive correlation (r =.40, P =.05). This study showed that trunk and hip kinematics are associated with knee valgus, which could consequently lead to increased knee overload in male professional soccer players following a unilateral vertical landing test. [ABSTRACT FROM AUTHOR]

There is mixed evidence on the role that biological sex plays in shoulder biomechanics despite known differences in musculoskeletal disorder prevalence between males and females. Additionally, advancing age may contribute to shoulder kinematic changes. The purpose of this study was to determine if sex and age influenced scapular and thoracohumeral kinematics during a range of functional tasks. Sixty healthy participants aged 19–63 years (30 males; 30 females) completed a functional task protocol while their upper limb motion was recorded. Scapular and humeral angles were calculated and compared with multiple linear regressions to assess the interaction effects of sex and age. Shoulder kinematics were not different between sex and age groups for many of the functional tasks. However, females had lower humeral external rotation in the overhead lift task (15°, P <.001), and less scapular anterior tilt angles in the forward transfer task (6°, P <.001) than males. Age was positively associated with humeral elevation (R2 =.330, P <.001) and scapular rotation (R2 =.299, P <.001) in the Wash Axilla task. There exist some kinematic differences between sex and with advancing age for select functional tasks, which should be considered for musculoskeletal disorder development. [ABSTRACT FROM AUTHOR]

The present randomized study investigated the effect of acute supplementation of 800 mg/kg of ketone monoester ingestion (KE) or placebo (PL) and 210 mg/kg of NaHCO3 co-ingestion on cycling performance of WorldTour cyclists during a road cycling stage simulation. Twenty-eight cyclists participated in the study (27.46 ± 4.32 years; 1.80 ± 0.06 m; 69.74 ± 6.36 kg). Performance, physiological, biochemical, and metabolism outcomes, gut discomfort, and effort perceived were assessed during a road cycling simulation composed of an 8-min time-trial (TT) performance + 30-s TT + 4.5 hr of outdoor cycling + a second 8-min TT + a second 30-s TT. Greater absolute and relative mean power during the first 8-min TT (F = 5.067, p =.033, η p 2 =.163 , F = 5.339, p =.029, η p 2 =.170 , respectively) was observed after KE than after PL (KE: 389 ± 34, PL: 378 ± 44 W, p =.002, d = 0.294 and KE: 5.60 ± 0.42, PL: 5.41 ± 0.44 W/kg, p =.001, d = 0.442). Additionally, greater concentration of β-hydroxybutyrate blood concentration (F = 42.195, p <.001, η p 2 =.619) was observed after KE than after PL during the first steps of the stage (e.g., after warm-up KE: 1.223 ± 0.642, PL: 0.044 ± 0.058 mM, p <.001, d = 2.589), although the concentrations returned to near baseline after 4.5 hr of outdoor cycling. Moreover, higher values of anion gap were observed (F = 2.333, p =.026, η p 2 =.080) after KE than after PL ingestion, after the warm-up and after the first 8-min and 30-s TT. Additionally, lower concentrations of HCO 3 − were reported in the KE condition after warm-up and after the first 8-min and 30-s TT. During the initial phase of the stage simulation, acute supplementation with KE + NaHCO3 co-ingestion enhanced 8-min TT cycling performance (3.1%) in WorldTour cyclists with a concomitant hyperketonaemia. [ABSTRACT FROM AUTHOR]

Purpose: Advanced footwear technology is prevalent in distance running, with research focusing on these "super shoes" in competitive athletes, with less understanding of their value for slower runners. The aim of this study was to compare physiological and biomechanical variables between a model of super shoes (Saucony Endorphin Speed 2) and regular running shoes (Saucony Cohesion 13) in recreational athletes. Methods: We measured peak oxygen uptake (VO2peak) in 10 runners before testing each subject 4 times in a randomly ordered crossover design (ie, Endorphin shoe or Cohesion shoe, running at 65% or 80% of velocity at VO2peak [vVO2peak]). We recorded video data using a high-speed camera (300 Hz) to calculate vertical and leg stiffnesses. Results: 65% vVO2peak was equivalent to a speed of 9.4 km·h−1 (0.4), whereas 80% vVO2peak was equivalent to 11.5 km·h−1 (0.5). Two-way mixed-design analysis of variance showed that oxygen consumption in the Endorphin shoe was 3.9% lower than in the Cohesion shoe at 65% vVO2peak, with an interaction between shoes and speed (P =.020) meaning an increased difference of 5.0% at 80% vVO2peak. There were small increases in vertical and leg stiffnesses in the Endorphin shoes (P <.001); the Endorphin shoe condition also showed trivial to moderate differences in step length, step rate, contact time, and flight time (P <.001). Conclusions: There was a physiological benefit to running in the super shoes even at the slower speed. There were also spatiotemporal and global stiffness improvements indicating that recreational runners benefit from wearing super shoes. [ABSTRACT FROM AUTHOR]

Shoulder complex stability can be estimated in vivo through the analysis of helical axes (HAs) dispersion during upper limb movements. The study aimed at investigating test–retest reliability of shoulder HAs dispersion parameters during upper limb tasks. Twenty healthy volunteers performed 2 intransitive (shoulder flexion and rotation) and one transitive (combing) tasks with the dominant and nondominant upper limbs during 2 recording sessions at 1-week distance. Kinematics was detected through an optoelectronic system. Mean distance and mean angle (MA) were adopted as HAs dispersion indexes. Reliability was excellent for mean distance (intraclass correlation coefficient [ICC]:.91) and MA (ICC:.92) during dominant flexion, and good for MA (ICC:.90) during nondominant flexion. Moderate reliability was found for HAs parameters during rotation (ICCs from.70 to.59), except for MA during dominant rotation where reliability was poor. Reliability was good for mean distance (ICC:.83) and moderate for MA (ICC:.67) during the dominant combing task, whereas no reliability was found during the nondominant combing task. HAs dispersion parameters revealed high reliability during simple intransitive tasks with the dominant limb. Reliability decreased with the increase in task complexity due to the increase in movement variability. HAs dispersion technique could be used to assess shoulder complex stability in patients after rehabilitation or surgery. [ABSTRACT FROM AUTHOR]

Radiofrequency ablation of the medial branch is commonly used to treat chronic low back pain involving facet joints, which accounts for 12% to 37% of the total cases of chronic low back pain. An adverse effect of this procedure is the denervation of the multifidus muscle, which may lead to its atrophy which can affect the spine and possibly disc degeneration. This study aims to quantify changes in joint angles and loading caused by multifidus denervation after radiofrequency ablation. AnyBody model of the torso was used to evaluate intervertebral joints in flexion, lateral bending, and torsion. Force-dependent kinematics was used to calculate joint angles and forces. These dependent variables were investigated in intact multifidus, unilateral, and bilateral ablations of L3L4, L4L5, and L5S1 joints. The results showed pronounced angular joint changes, especially in bilateral ablations in flexion, when compared with other cases. The same changes' trend from intact to unilaterally then bilaterally ablated multifidus occurred in joint angles of lateral bending. Meanwhile, joint forces were not adversely affected. These results suggest that multifidus denervation after radiofrequency ablation affects spinal mechanics. Such changes may be associated with abnormal tissue deformations and stresses that can potentially alter their mechanobiology and homeostasis, thereby possibly affecting the health of the spine. [ABSTRACT FROM AUTHOR]

It is not currently possible to directly and noninvasively measure in vivo patellofemoral joint contact force during dynamic movement; therefore, indirect methods are required. Simple models may be inaccurate because patellofemoral contact forces vary for the same knee flexion angle, and the patellofemoral joint has substantial out-of-plane motion. More sophisticated models use 3-dimensional kinematics and kinetics coupled to a subject-specific anatomical model to predict contact forces; however, these models are time consuming and expensive. We applied a principal component analysis prediction and regression method to predict patellofemoral joint contact forces derived from a robust musculoskeletal model using exclusively optical motion capture kinematics (external approach), and with both patellofemoral and optical motion capture kinematics (internal approach). We tested this on a heterogeneous population of asymptomatic subjects (n = 8) during ground-level walking (n = 12). We developed equations that successfully capture subject-specific gait characteristics with the internal approach outperforming the external. These approaches were compared with a knee-flexion based model in literature (Brechter model). Both outperformed the Brechter model in interquartile range, limits of agreement, and the coefficient of determination. The equations generated by these approaches are less computationally demanding than a musculoskeletal model and may act as an effective tool in future rapid gait analysis and biofeedback applications. [ABSTRACT FROM AUTHOR]

Previous research has shown that there are differences in mechanical energy, kinematics, and muscle activation when comparing walking on level and incline surfaces, especially on inclines above 15%. Muscle activations are significantly different while walking on extreme inclines, suggesting a different coordination pattern. We utilized continuous relative phase to assess walking kinematic coordination with respect to increased incline angles. Twelve healthy, college-aged individuals walked for 7 inclines of 1 minute each on a motorized treadmill at 3 mph at 0%, 5%, 10%, 15%, 20%, 25%, and 30% inclines. Kinematic data were collected during the last 20 seconds of each stage (120 Hz). Segmental and joint angles and angular velocities in the sagittal plane were calculated, from which continuous relative phase was determined for 3 joint couples: hip–knee, hip–ankle, and knee–ankle. There were significant differences in the coordination patterns during the first part of the contact phase in the hip–knee and hip–ankle couplings between the 0% and 30% inclines, with all 3 joint couplings becoming more in-phase at inclines above 15%. Importantly, the hip–knee coupling changed significantly from more out-of-phase to more in-phase between 10% and 15% incline. Shifting lower-extremity joint coordination in response to extreme inclines identifies potential coordinative strategies to achieve steep walking. [ABSTRACT FROM AUTHOR]

Inertial measurement units (IMUs) provide exciting opportunities to collect large volumes of running biomechanics data in the real world. IMU signals may, however, be affected by variation in the initial IMU placement or movement of the IMU during use. To quantify the effect that changing an IMU's location has on running data, a reference IMU was 'correctly' placed on the shank, pelvis, or sacrum of 74 participants. A second IMU was 'misplaced' 0.05 m away, simulating a 'worst-case' misplacement or movement. Participants ran over-ground while data were simultaneously recorded from the reference and misplaced IMUs. Differences were captured as root mean square errors (RMSEs) and differences in the absolute peak magnitudes and timings. RMSEs were ≤1 g and ~1 rad/s for all axes and misplacement conditions while mean differences in the peak magnitude and timing reached up to 2.45 g, 2.48 rad/s, and 9.68 ms (depending on the axis and direction of misplacement). To quantify the downstream effects of these differences, initial and terminal contact times and vertical ground reaction forces were derived from both the reference and misplaced IMU. Mean differences reached up to -10.08 ms for contact times and 95.06 N for forces. Finally, the behavior in the frequency domain revealed high coherence between the reference and misplaced IMUs (particularly at frequencies ≤~10 Hz). All differences tended to be exaggerated when data were analyzed using a wearable coordinate system instead of a segment coordinate system. Overall, these results highlight the potential errors that IMU placement and movement can introduce to running biomechanics data.

Context: Single- and dual-task walking gait assessments have been used to identify persistent movement and cognitive dysfunction among athletes with concussions. However, it is unclear whether previous ankle sprain injuries confound these outcomes during baseline testing. The purpose of this study was to determine the effects of (1) ankle sprain history and (2) time since prior ankle sprain injury on single- and dual-task spatiotemporal gait outcomes and cognitive measures. Design: Cross- sectional study. Methods: We assessed 60 college Division-I athletes (31 with ankle sprain history; 13 females and 18 males, 19.3 [0.8] y; 29 with no ankle sprain history, 14 females and 15 males, 19.7 [0.9] y) who completed injury history forms and underwent concussion baseline testing. Athletes completed single- and dual-task gait assessments by walking back and forth along an 8-m walkway for 40 seconds. Athletes wore a smartphone with an associated mobile application on their lumbar spine to record spatiotemporal gait parameters and dual-task cognitive performance. Separate multivariate analyses of variance were used to assess the effects of ankle sprain injury history on spatiotemporal measures, gait variability, and cognitive performance. We performed a multivariate regression subanalysis on athletes who reported time since injury (n = 23) to assess temporal effects on gait and cognitive performance. Results: Athletes with and without a histoiy of ankle sprains had comparable spatiotemporal and gait variability outcomes during single- (P = .42; P = .13) and dual-task (P = .75; P = .55) conditions. Additionally, ankle sprain injury history did not significantly influence cognitive performance (P = .35). Finally, time since ankle sprain did not significantly affect single- (P = .75) and dual-task gait (P = .69), nor cognitive performance (P = 19). Conclusions: Ankle sprain injury history did not significantly alter spatiotemporal gait outcomes nor cognitive performance during this common clinical assessment. Future studies may consider including athletes with ankle sprain injury history during concussion assessments. [ABSTRACT FROM AUTHOR]

Context: To assess the reliability of a remote 2D markerless motion tracking method (Kinovea) to quantify knee and hip angles during dynamic tasks. Methods: Fourteen healthy adults performed body weight squats and lateral lunges while video recording themselves at home. Knee and hip angles were quantified in the sagittal plane for the squats and in the frontal plane for the lateral lunges. Two students each performed the video analysis procedure twice, 2 weeks apart. Intraclass correlation coefficients were used to calculate the intrarater and interrater reliability for angles at maximum depth. The intrarater and interrater agreement over the joint angle-time signals were quantified using a validation metric; an acceptable agreement threshold was set at a validation metric of 0.803 or higher. Standard error of measurement (SEM) was also calculated. Results: Reliability was good to excellent (intraclass correlation coefficients = .80-.98) for all angle comparisons at maximum depth. The agreement over the entire joint angle-time signal was acceptable for all squat variables except for the interrater hip angle comparison (validation metric = 0.797). None of the lateral lunge variables met the threshold of acceptable agreement. The mean SEM across participants for all joint angle-time signal and for maximum depth was acceptable (<5°) for all measurements (SEM = 1.2°-4.9°). Conclusions: Overall, the reliability, agreement, and SEM quantified in this study support the integration of remote methods to quantify lower-extremity kinematics into research and clinical practice. [ABSTRACT FROM AUTHOR]

Deficits in movement patterns during cutting while running might place soccer players at risk of injury. The objective was to compare joint angles and intersegment coordination between sexes and ages during an unanticipated side-step cutting task in soccer players. This cross-sectional study recruited 11 male (four adolescents and seven adults) and 10 female (six adolescents and four adults) soccer players. Three-dimensional motion capture was used to measure lower-extremity joint and segment angles as participants performed an unanticipated cutting task. Hierarchical linear models examined relationships between joint angle characteristics with age and sex. Continuous relative phase was used to quantify intersegment coordination amplitude and variability. These values were compared between age and sex groups using analysis of covariance. Adult males had greater hip flexion angle excursions than adolescent males, while adult females had smaller excursions than adolescent females (p = .011). Females had smaller changes in hip flexion angles (p = .045), greater hip adduction angles (p = .043). and greater ankle eversion angles (p =.009) than males. Adolescents had greater hip internal rotation (p = .044) and knee flexion (p = .033) angles than adults, but smaller changes in knee flexion angles at precontact compared with stance/foot off (p < .001). For intersegment coordination, females were more out-of-phase than males in the foot/shank segment in the sagittal plane. There were no differences in intersegment coordination variability between groups. Differences in joint motion during an unanticipated cutting task were present between age groups and sexes. Injury prevention programs or training programs may be able target specific deficits to lower injury risk and improve performance. [ABSTRACT FROM AUTHOR]

Context: Different resistance exercise determinants modulate the musculotendinous adaptations following eccentric hamstring training. The Nordic Hamstring Exercise (NHE) can be performed 2-fold: the movement velocity irreversibly increases toward the end of the range of motion or it is kept constant. Design: This cross-sectional study aimed to investigate if the downward acceleration angle (DWAangle) can be used as a classification parameter to distinguish between increasing and constant velocity NHE execution. Furthermore, the kinetic and kinematic differences of these 2 NHE execution conditions were examined by analyzing the DWAangle in relation to the angle of peak moment. Methods: A total of 613 unassisted NHE repetitions of 12 trained male sprinters (22 y, 181 cm, 76 kg) were analyzed. Results: The majority of analyzed parameters demonstrated large effects. NHEs with constant velocity (n = 285) revealed significantly higher impulses (P <.001; d = 2.34; + 61%) and fractional time under tension (P <.001; d = 1.29; +143%). Although the generated peak moments were significantly higher for constant velocity (P =.003; d = 0.29; +4%), they emerged at similar knee flexion angles (P =.167; d = 0.28) and revealed on average just low relationships to the DWAangle ( R mean 2 = 22.4 %). DWAangle highly correlated with the impulse ( R mean 2 = 60.8 %) and δ (DWAangle–angle of peak moment; R mean 2 = 83.6 %). Conclusions: Relating DWAangle to angle of peak moment assists to distinguish between significantly different NHE execution, which will potentially elicit different musculotendinous adaptations. These insights are essential for coaches and athletes to understand how to manipulate eccentric hamstring training to change its purpose. [ABSTRACT FROM AUTHOR]

Context: Early identification of incoming military personnel at elevated odds for bone stress injury (BSI) is important for the health and readiness of the US military. Design: Prospective cohort study. Methods: Knee kinematic data of the incoming US Military Academy cadets were collected while performing a jump-landing task (The Landing Error Scoring System) using a markerless motion capture system and depth camera. Data on incidence of lower-extremity injury, including BSI, were collected throughout the study period. Results: A total of 1905 participants (452 females, 23.7%) were examined for knee valgus and BSI status. A total of 50 BSI occurred during the study period (incidence proportion = 2.6%). The unadjusted odds ratio for BSI at initial contact was 1.03 (95% confidence interval [CI], 0.94–1.14; P =.49). Adjusted for sex, the odds ratio for BSI at initial contact was 0.97 (95% CI, 0.87–1.06; P =.47). At the instant of maximum knee-flexion angle, the unadjusted odds ratio was 1.06 (95% CI, 1.02–1.10; P =.01), and the odds ratio was 1.02 (95% CI, 0.98–1.07; P =.29) after adjusting for sex. This suggests that there was not a significant enough association for an increase in the odds of BSI based on either degree of knee valgus. Conclusions: Our results did not demonstrate an association between knee valgus angle data during a jump-landing task and future increased odds of BSI in a military training population. Further analysis is warranted, but the results suggests the association between kinematics and BSI cannot be effectively screened by knee valgus angle data in isolation. [ABSTRACT FROM AUTHOR]

Purpose: This study sought to quantify the within-individual relationships between spatiotemporal variables and initial acceleration sprint performance in elite rugby backs and to establish a normative data set of relevant strength-based measures. Methods: First, the spatiotemporal variables, ratios of step length to step rate and of contact time to flight time, and initial acceleration performance were obtained from 35 elite male rugby backs (mean [SD] age 25 [3] y) over the first 4 steps of 3 sprints. Angular and linear kinematic aspects of technique and strength-based qualities were collected from 25 of these participants. Second, the same spatiotemporal variables were collected from 19 of the participants on 3 further occasions (12 trials in total) to determine the within-individual associations of these variables and initial acceleration performance. Results: Moderate to very large meaningful within-individual relationships (|r| =.43–.88) were found between spatiotemporal variables and initial acceleration performance in 17 of the 19 participants. From these relationships, a theoretically "desirable" change in whole-body kinematic strategy was individually determined for each participant, and normative strength-based measures to contextualize these were established. Conclusions: Meaningful within-individual relationships are evident between sprint spatiotemporal variables and initial acceleration performance in elite rugby backs. Individualized approaches are therefore necessary to understand how aspects of technique relate to initial acceleration performance. This study provides an objective, evidence-based approach for applied practitioners to identify the initial acceleration technical needs of individual rugby backs. [ABSTRACT FROM AUTHOR]

A non-slip constraint between a particle and a wall is applied at the microscopic level of collision dynamics using the rough sphere model. We analyze the consequences of the translation–rotation coupling of a rough sphere confined between two parallel planar walls and establish that shearing the walls past each other (i) preferentially deposits energy into the rotational degree of freedom and (ii) results in a bounded oscillation of the energy of the confined particle. [ABSTRACT FROM AUTHOR]

Context: Laboratorial 3-dimensional kinematic analyses have shown changes in the single-leg squat's (SLS) pattern of patients with femoroacetabular impingement syndrome (FAIS). However, it is unknown whether clinicians are able to detect these changes using 2-dimensional kinematics. Objective: To compare the frontal plane 2-dimensional kinematics of patients with FAIS and asymptomatic individuals in the SLS test performed in a clinical setting. Design: Case-control study. Setting: Physical therapy clinic. Participants: Twenty men with bilateral FAIS and 20 asymptomatic men. Main Outcome Measures: Two-dimensional kinematic analysis was collected in the frontal plane during the execution of the SLS test. The outcomes were squat depth, pelvic drop (pelvis angle relative to the horizontal plane), hip adduction (femur angle relative to the pelvis), and knee valgus (femur angle relative to the tibia). Results: Most and least painful limbs of patients with FAIS had squat depth (9.8% [2.9%] and 9.5% [3.1%] of height), pelvic drop (4.2° [3.9°] and 3.7° [4.2°]), hip adduction (74.9° [5.8°] and 75.9° [5.7°]), and knee valgus (4.0° [11.0°] and 5.0° [9.9°]) similar to asymptomatic individuals (9.0% [2.3%], 4.8° [2.6°], 73.7° [4.9°], and −1.7° [8.5°]; P >.05 for all). Conclusion: The frontal plane 2-dimensional kinematic analysis of the SLS test in the clinical setting is not able to distinguish patients with FAIS from asymptomatic individuals. [ABSTRACT FROM AUTHOR]

Objectives: Although nonsurgical and surgical management of knee arthrofibrosis has been reported in the literature, there is little information on the effect of procedural treatment modalities of refractory arthrofibrosis on clinical outcomes. The purpose of this case report is to describe the intervention of refractory knee arthrofibrosis after anterior cruciate ligament reconstruction and investigate long-term clinical outcomes after procedural intervention. Methods: A 27-year-old male presented with decreased range of motion (ROM), patellar mobility, strength, and knee joint function following anterior cruciate ligament reconstruction of his left knee. After failed conservative management, the patient underwent manipulation under anesthesia (MUA) to release scar tissue. Following MUA, the emphasis of comprehensive physiotherapy was on decreasing inflammation, relieving pain, and maintaining patellar mobility while increasing knee joint ROM and strength. Knee ROM, patellofemoral motion, gait, and quadriceps recruitment were measured 3, 6, 12, and 24 months after MUA. Results: At 2-year follow-up after MUA, the patient continued to present with decreased ROM and quadriceps strength compared to the contralateral knee, but had returned to a running program and reported knee joint dysfunction no longer interfered with his daily activities. Conclusions: This case report demonstrates signs and symptoms that could indicate knee arthrofibrosis and introduces procedural intervention for refractory arthrofibrosis after anterior cruciate ligament reconstruction. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to assess the interaction of kinematic, kinetic, and energetic variables as speed predictors in adolescent swimmers in the front-crawl stroke. Design: Ten boys (mean age [SD] = 16.4 [0.7] y) and 13 girls (mean age [SD] = 14.9 [0.9] y) were assessed. Methods: The swimming performance indicator was a 25-m sprint. A set of kinematic, kinetic (hydrodynamic and propulsion), and energetic variables was established as a key predictor of swimming performance. Multilevel software was used to model the maximum swimming speed. Results: The final model identified time (estimate = −0.008, P =.044), stroke frequency (estimate = 0.718, P <.001), active drag coefficient (estimate = −0.330, P =.004), lactate concentration (estimate = 0.019, P <.001), and critical speed (estimate = −0.150, P =.035) as significant predictors. Therefore, the interaction of kinematic, hydrodynamic, and energetic variables seems to be the main predictor of speed in adolescent swimmers. Conclusions: Coaches and practitioners should be aware that improvements in isolated variables may not translate into faster swimming speed. A multilevel evaluation may be required for a more effective assessment of the prediction of swimming speed based on several key variables rather than a single analysis. [ABSTRACT FROM AUTHOR]

The upper body and trunk muscles are crucial to perform soccer kicks. Resistance training targeting these muscles may modify the pattern adopted during kicking. This study aimed to investigate the effect of resistance training of the arm and anterior trunk muscles on instep kicking kinematics. Twenty-six male participants were randomly allocated into a training group or control group. The training group underwent resistance training of arm and trunk muscles and practiced the instep kick for 8 weeks. The control group only practiced kicking during the same period. The trunk, hip, and knee kinematics were assessed during the instep kick before and after the intervention. Kinematics were analyzed according to their data distribution with statistical parametric or nonparametric mapping. The effect of the training on the 1-repetition maximum test was analyzed using a repeated-measures multivariate analysis of variance. The training group showed greater hip extension after the training during the backswing phase (Hedge g effect size of 0.316–0.321) and increased 1-repetition maximum for all exercises. There were no other differences. The present study documented the nonlocal effect of strengthening training in which arm and trunk muscle training resulted in changes in hip kinematics during the backswing phase of the instep kick. [ABSTRACT FROM AUTHOR]

Inertial sensors may help clinicians to assess patients' movement and potentially support clinical decision making. Our aim was to determine whether shoulder range of motion during movement tasks measured using inertial sensors is capable of accurately discriminating between patients with different shoulder problems. Inertial sensors were used to measure 3-dimensional shoulder motion during 6 tasks of 37 patients on the waiting list for shoulder surgery. Discriminant function analysis was used to identify whether the range of motion of different tasks could classify patients with different shoulder problems. The discriminant function analysis could correctly classify 91.9% of patients into one of the 3 diagnostic groups based. The tasks that associated a patient with a particular diagnostic group were the following: subacromial decompression: abduction, rotator cuff repair of tears ≤5 cm: flexion and rotator cuff repair of tears >5 cm: combing hair, abduction, and horizontal abduction–adduction. The discriminant function analysis showed that range of motion measured by inertial sensors can correctly classify patients and could be used as a screening tool to support surgery planning. [ABSTRACT FROM AUTHOR]

Single-leg landings with or without subsequent jumping are frequently used to evaluate landing biomechanics. The purpose of this study was to investigate the effects of subsequent jumping on the external knee abduction moment and trunk and hip biomechanics during single-leg landing. Thirty young adult female participants performed a single-leg drop vertical jumping (SDVJ; landing with subsequent jumping) and single-leg drop landing (SDL; landing without subsequent jumping). Trunk, hip, and knee biomechanics were evaluated using a 3-dimensional motion analysis system. The peak knee abduction moment was significantly larger during SDVJ than during SDL (SDVJ 0.08 [0.10] N·m·kg−1·m−1, SDL 0.05 [0.10] N·m·kg−1·m−1, P =.002). The trunk lateral tilt and rotation angles toward the support-leg side and external hip abduction moment were significantly larger during SDVJ than during SDL (P <.05). The difference in the peak hip abduction moment between SDVJ and SDL predicted the difference in the peak knee abduction moment (P =.003, R2 =.252). Landing tasks with subsequent jumping would have advantages for evaluating trunk and hip control as well as knee abduction moment. In particular, evaluating hip abduction moment may be important because of its association with the knee abduction moment. [ABSTRACT FROM AUTHOR]

Breast cancer affects one in 8 females with a 5-year survival rate of 89%. Up to 72% of breast cancer survivors have trouble with activities of daily living (ADL) following treatment. Increased time-from-treatment improves some measures of function, yet ADL limitations persist. Therefore, this study assessed the effect of time-from-treatment on upper extremity kinematics during ADLs in breast cancer survivors. Twenty-nine female breast cancer survivors were divided into 2 groups: <1 year (n = 12) and 1–2 years (n = 17) from treatment. Kinematics were collected during 6 ADL tasks, and humerothoracic joint angles were quantified. A 2-way mixed analysis of variance assessed the effects of time-from-treatment and arm on maximum angles for each ADL. Decreased maximum angle existed for breast cancer survivors with increased time-from-treatment during all ADLs. Breast cancer survivors in the 1–2 years group used ∼28° to 32° lower elevation, ∼14° to 28° lower axial rotation, and ∼10° to 14° lower plane of elevation range across tasks. Decreased ranges of arm movement during ADLs with increased time-from-treatment may reflect compensatory movement strategies. Recognizing this shift in strategies and accompanying underlying disease progression can help inform responses to functional performance limitations in breast cancer survivors as delayed effects are present posttreatment. [ABSTRACT FROM AUTHOR]

Soccer, one of the most popular sports in the world, has one of the highest rates of sports-related concussions. Additionally, soccer players are frequently exposed to nonconcussive impacts from intentionally heading the ball, a fundamental component of the sport. There have been many studies on head impact exposure in soccer, but few focus on soccer practices or practice activities. This study aimed to characterize the frequency and magnitude of head impacts in National Collegiate Athletic Association Division I female soccer practice activities using a custom-fit instrumented mouthpiece. Sixteen players were instrumented over the course of 54 practice sessions. Video analysis was performed to verify all mouthpiece-recorded events and classify practice activities. Category groupings of practice activities include technical training, team interaction, set pieces, position-specific, and other. Differences in head impact rates and peak resultant kinematics were observed across activity types and category groupings. Technical training had the highest impact rate compared to other category groupings. Impacts occurring during set piece activities had the highest mean kinematic values. Understanding drill exposure can help inform coaches on training plans aimed to reduce head impact exposure for their athletes. [ABSTRACT FROM AUTHOR]

Context: Excessive hip adduction and internal rotation are abnormal movements that may lead to the onset and progression of patellofemoral pain. Previous studies have reported that lower dynamic frontal plane hip joint stiffness in the gait of women is associated with the magnitude of hip adduction and internal rotation angles. However, the factors contributing to the lack of dynamic frontal plane hip joint stiffness in the gait of young women are unclear. This study aims to investigate the factors affecting dynamic frontal plane hip joint stiffness during the weight-acceptance phase of the gait of healthy young women. Design: Cross-sectional study. Methods: This study included 30 healthy women between the ages of 18 and 30 years. The pelvic width/femur length ratio was calculated by dividing the pelvic width by the femur length. Data on hip kinematics and kinetics and activation of the gluteus maximus and medius, tensor fasciae latae, and adductor longus muscles during gait were collected using a motion capture system, force plates, and surface electromyography. Stepwise multiple regression analysis was conducted to determine the extent to which each independent factor affected dynamic frontal plane hip joint stiffness. Results: In healthy young women, decreased dynamic frontal plane hip joint stiffness was associated with decreased muscle activity of the gluteus maximus during the gait, as well as greater pelvic width/femur length ratio. Conclusions: Women with a relatively great pelvic width relative to femur length may have more difficulty in producing dynamic frontal plane hip joint stiffness. However, increasing the muscle activity of the gluteus maximus may contribute to increased dynamic frontal plane hip joint stiffness. [ABSTRACT FROM AUTHOR]

Context: Aberrant movement patterns among individuals with concussion history have been reported during sport-related movement. However, the acute postconcussion kinematic and kinetic biomechanical movement patterns during a rapid acceleration–deceleration task have not been profiled and leaves their progressive trajectory unknown. Our study aimed to examine single-leg hop stabilization kinematics and kinetics between concussed and healthy-matched controls acutely (≤7 d) and when asymptomatic (≤72 h of symptom resolution). Design: Prospective, cohort laboratory study. Methods: Ten concussed (60% male; 19.2 [0.9] y; 178.7 [14.0] cm; 71.3 [18.0] kg) and 10 matched controls (60% male; 19.5 [1.2] y; 176.1 [12.6] cm; 71.0 [17.0] kg) completed the single-leg hop stabilization task under single and dual task (subtracting by 6's or 7's) at both time points. Participants stood on a 30-cm tall box set 50% of their height behind force plates while in an athletic stance. A synchronized light was illuminated randomly, queuing participants to initiate the movement as rapidly as possible. Participants then jumped forward, landed on their nondominant leg, and were instructed to reach and maintain stabilization as fast as possible upon ground contact. We used 2 (group) × 2 (time) mixed-model analyses of variance to compare single-leg hop stabilization outcomes separately during single and dual task. Results: We observed a significant main group effect for single-task ankle plantarflexion moment, with greater normalized torque (mean difference = 0.03 N·m/body weight; P =.048, g = 1.18) for concussed individuals across time points. A significant interaction effect for single-task reaction time indicated that concussed individuals had slower performance acutely relative to asymptomatic (mean difference = 0.09 s; P =.015, g = 0.64), while control group performance was stable. No other main or interaction effects for single-leg hop stabilization task metrics were present during single and dual task (P ≥.051). Conclusions: Greater ankle plantarflexion torque coupled with slower reaction time may indicate stiff, conservative single-leg hop stabilization performance acutely following concussion. Our findings shed preliminary light on the recovery trajectories of biomechanical alterations following concussion and provide specific kinematic and kinetic focal points for future research. [ABSTRACT FROM AUTHOR]

Background: The development and influence of physical capabilities and game action performance over the course of the season are a big challenge for coaches and players. Purpose: The aims of the present study were to examine (1) the seasonal changes in the physical capabilities (mechanical and kinematic) and game-performance indicators in top-level men volleyball players and (2) the relationship between these physical capabilities and game-performance indicators in official matches. Methods: Eleven top-level players participated. Players were physically tested 3 times during the season. Before each test, players' match performance (11 sets) was analyzed according to the level of opposition and match location. The percentage of change, statistical differences over the season (Friedman and Wilcoxon tests), and associations between variables (Spearman r) were calculated (P <.05) among mechanical (force–velocity profile during vertical jump and bench press), kinematic (jump height and spike ball speed), and game action performance features (coefficient, efficacy, and percentage of errors in serve, attack, and block). Results: The theoretical maximal force and velocity during vertical jump and bench press, respectively; the peak spike ball speed; and the serve efficacy significantly increased over the season. Moreover, there was a significant reduction in serve errors as the jump height increased (r = −.44; P =.026), as well as a significant increase in serve errors as the peak spike ball speed increased (r = −.62; P =.001). Conclusion: These findings reveal how the physical and game action performance variables evolve and interact during the season. This may help coaches and trainers to monitor and analyze the most relevant volleyball performance factors. [ABSTRACT FROM AUTHOR]

Purpose: Change of direction while dribbling appears to be of interest for on-court performance in basketball. The study aim was to assess the validity and reliability of the V-cut dribbling test (VcutBk) in young basketball players. Methods: Ninety-two young basketball players from 8 to 21 years old (74% male) were classified in relation to peak height velocity (PHV) offset. To examine validity and test–retest reliability, VcutBk was performed in 2 identical sessions separated by 1 week. Participants also performed the V-cut test and linear sprint test with and without dribbling to analyze correlations between tests in different somatic maturity stages. Results: The relationships of the VcutBk with the other tests and skill-time-related deficits were interpreted from large (r >.51) to very large (r >.71). The comparisons between pre-PHV and post-PHV groups of basketball players showed significant and large effect in the VcutBk (d = 2.04; mean difference = 2.59; 95% CI, 1.86 to 3.32). Also, significant main effects when comparing PHV groups were reported in all skill-time-related deficits (P <.001, η p 2 =. 13 -.28 , moderate to large effect size). Test–retest reliability and signal-to-noise ratio analysis did not show substantial between-trials differences in VcutBk. Reliability scores showed high intraclass correlation coefficient (.95) and low coefficient of variation (0.23%). Conclusions: The VcutBk seems to be a valid and reliable test to assess change of direction while dribbling. VcutBk performance and skill-time-related deficits seem to be sensitive to somatic maturity. Basketball coaches should consider the VcutBk to assess young basketball players. [ABSTRACT FROM AUTHOR]

Purpose: To examine the effects of 6 weeks of training cessation on young swimmers' anthropometrics, in-water force, performance, and kinematics according to biological maturation. Methods: Eighteen swimmers (7 girls: 12.43 [0.73] y old; 11 boys: 13.27 [0.79] y old) were assessed pretest and posttest 6 weeks apart. Body mass, stature, arm span, and hand surface area were measured as anthropometric parameters, and biological maturation was estimated (ie, peak height velocity [PHV]). The in-water force was retrieved during 2 bouts of 25-m front crawl, allowing the estimation of the symmetry index. The time to complete the 25-m was considered the performance outcome, whereas velocity, stroke rate, stroke length, stroke index, and arm stroke efficiency were used as kinematic parameters. Results: All anthropometric parameters increased during the detraining period. Although the in-water force remained unchanged, the magnitude of the effects was large for the symmetry index (P =.021; d = 0.87). For the pooled sample, neither performance nor kinematics changed after detraining, but the stroke index increased (P =.054; d = 0.27). Pre-PHV swimmers showed unchanged values in all parameters, despite natural growth. Mid-PHV swimmers showed a similar trend in addition to reductions in stroke rate (P =.040; d = 0.60) and increases in stroke length (P =.043; d = 1.00). Conclusions: In-water force, performance, and kinematics (25-m front crawl) were not impaired after 6 weeks of training cessation in a group of young swimmers. Given interindividual and intraindividual differences according to maturity status, coaches should be aware that distinct trends within the group can be found. [ABSTRACT FROM AUTHOR]

In-lab, marker-based gait analyses may not represent real-world gait. Real-world gait analyses may be feasible using inertial measurement units (IMUs) in combination with open-source data processing pipelines (OpenSense). Before using OpenSense to study real-world gait, we must determine whether these methods estimate joint kinematics similarly to traditional marker-based motion capture (MoCap) and differentiate groups with clinically different gait mechanics. Healthy young and older adults and older adults with knee osteoarthritis completed this study. We captured MoCap and IMU data during overground walking at 2 speeds. MoCap and IMU kinematics were computed with OpenSim workflows. We tested whether sagittal kinematics differed between MoCap and IMU, whether tools detected between-group differences similarly, and whether kinematics differed between tools by speed. MoCap showed more anterior pelvic tilt (0%–100% stride) and joint flexion than IMU (hip: 0%–38% and 61%–100% stride; knee: 0%–38%, 58%–89%, and 95%–99% stride; and ankle: 6%–99% stride). There were no significant tool-by-group interactions. We found significant tool-by-speed interactions for all angles. While MoCap- and IMU-derived kinematics differed, the lack of tool-by-group interactions suggests consistent tracking across clinical cohorts. Results of the current study suggest that IMU-derived kinematics with OpenSense may enable reliable evaluation of gait in real-world settings. [ABSTRACT FROM AUTHOR]

Although the ability to recover balance in the lateral direction has important implications with regard to fall risk in older adults, the effect of visual input on balance recovery in response to lateral perturbation and the effect of age are not well studied. We investigated the effect of visual input on balance recovery response to unpredictable lateral surface perturbations and its age-related changes. Ten younger and 10 older healthy adults were compared during balance recovery trials performed with the eyes open and eyes closed (EC). Compared with younger adults, older adults showed increased electromyography (EMG) peak amplitude of the soleus and gluteus medius, reduced EMG burst duration of the gluteus maximus and medius, and increased body sway (SD of the body's center of mass acceleration) in EC. In addition, older adults exhibited a smaller % increase (EC—eyes open) of the ankle eversion angle, hip abduction torque, EMG burst duration of the fibularis longus, and a greater % increase of body sway. All kinematics, kinetics, and EMG variables were greater in EC compared with eyes open in both groups. In conclusion, the absence of visual input negatively affects the balance recovery mechanism more in older adults compared with younger adults. [ABSTRACT FROM AUTHOR]

Inertial measurement units (IMUs) attached to the distal tibia are a validated method of measuring lower-extremity impact accelerations, called tibial accelerations (TAs), in runners. However, no studies have investigated the effects of small errors in IMU placement, which would be expected in real-world, autonomous use of IMUs. The purpose of this study was to evaluate the effect of a small proximal shift in IMU location on mean TAs and relationships between TAs and ground reaction force loading rates. IMUs were strapped to 18 injury-free runners at a specified standard location (∼1 cm proximal to medial malleolus) and 2 cm proximal to the standard location. TAs and ground reaction forces were measured while participants ran at self-selected and 10% slower/faster speeds. Mean TA was lower at the standard versus proximal IMU location in the faster running condition (P =.026), but similar in the slower (P =.643) and self-selected conditions (P =.654). Mean TAs measured at the standard IMU explained more variation in ground reaction force loading rates (r2 =.79−.90; P <.001) compared with those measured at the proximal IMU (r2 =.65−.72; P <.001). These results suggest that careful attention should be given to IMU placement when measuring TAs during running. [ABSTRACT FROM AUTHOR]

Spatiotemporal gait kinematics and their variability are commonly assessed in clinical and laboratory settings to quantify fall risk. Although the Hawthorne effect, or modifications in participant behavior due to knowledge of being observed, has the potential to impact such assessments, it has received minimal attention in the study of gait—particularly gait variability. The purpose of this study was to quantify the Hawthorne effect on variability and central tendency measures of fall-related spatiotemporal gait parameters. Seventeen healthy young adults walked on a treadmill at a self-selected velocity for 2 minutes under covert evaluation (ie, without awareness of being evaluated) and 2 minutes under overt evaluation. The movement was recorded using motion capture technology, from which we calculated mean value and step-to-step variability (using standard deviation and mean absolute deviation) of step length, step width, percent double support, percent stance phase, and stride time. Although central tendencies were unaffected by evaluation type, four-of-five measures of variability were significantly lower during overt evaluation for at least one-of-two metrics. Our results suggest a Hawthorne effect on locomotor control. Researchers should be aware of this phenomenon when designing research studies and interpreting gait assessments. [ABSTRACT FROM AUTHOR]

In sports situations, players may be required to throw at different speeds. The question of how skilled players throw the ball accurately to the desired location under different speed conditions is of interest to biomechanics researchers. Previous research suggested that throwers use different types of joint coordination. However, joint coordination with a change in throwing speed has not been studied. Here, we show the effects of changes in throwing speed on joint coordination during accurate overhead throwing. Participants were seated on a low chair with their trunk fixed and threw a baseball aimed at a target under 2 different speed conditions (slow and fast). In the slow condition, the elbow flexion/extension angle coordinated with other joint angles and angular velocities to reduce the variability of the vertical hand velocity. In the fast condition, the shoulder internal/external rotation angle and the shoulder horizontal flexion/extension angular velocity coordinated with other joint angles and angular velocities to reduce the variability of the vertical hand velocity. These results showed that joint coordination differed with changes in throwing speed, indicating that joint coordination is not always fixed, but may differ depending on the task constraints, such as throwing speed. [ABSTRACT FROM AUTHOR]

Many head acceleration events (HAEs) observed in youth football emanate from a practice environment. This study aimed to evaluate HAEs in youth football practice drills using a mouthpiece-based sensor, differentiating between inertial and direct HAEs. Head acceleration data were collected from athletes participating on 2 youth football teams (ages 11–13 y) using an instrumented mouthpiece-based sensor during all practice sessions in a single season. Video was recorded and analyzed to verify and assign HAEs to specific practice drill characteristics, including drill intensity, drill classification, and drill type. HAEs were quantified in terms of HAEs per athlete per minute and peak linear and rotational acceleration and rotational velocity. Mixed-effects models were used to evaluate the differences in kinematics, and generalized linear models were used to assess differences in HAE frequency between drill categories. A total of 3237 HAEs were verified and evaluated from 29 football athletes enrolled in this study. Head kinematics varied significantly between drill categorizations. HAEs collected at higher intensities resulted in significantly greater kinematics than lower-intensity drills. The results of this study add to the growing body of evidence informing evidence-based strategies to reduce head impact exposure and concussion risk in youth football practices. [ABSTRACT FROM AUTHOR]

A systematic search was performed of online databases for any anterior cruciate ligament (ACL) injuries within the NBA. Video was obtained of injuries occurring during competition and downloaded for 2-dimensional video analysis. Thirty-five in-game videos were obtained for analysis. Of the reviewed cases, 19% were noncontact ACL injuries where there was no player-to-player contact from an opposing player. Three injury mechanism categories were found based on the events at the point of initial ground contact of the foot of the injured limb: single-leg casting (mean dorsiflexion angle 18.9° (14.4°); mean knee flexion angle 15.6° (7.8°); and mean trunk lateral flexion 18.2° (8.4°)); bilateral hop (mean dorsiflexion angle 18.2° (15.2°), mean knee flexion angle 21° (14.5°), mean trunk extension angle 6.9° (11.4°), and landing angle from the athlete's center of mass 47.9° (10.1°)); and single-leg landing after contact (mean abduction angle of the swing leg 105.4° (18.1°), mean knee flexion angle of the injured limb 34.2° (8.0°), and mean trunk ipsilateral flexion angle 22.2° (7.0°)). [ABSTRACT FROM AUTHOR]