Journal of Applied Biomechanics最新文献

Jones fracture is a common injury in soccer players, caused by overload on the fifth metatarsal (M5) that can occur during crossover cutting. This study aimed to investigate the effects of the hip internal rotation (HIR) range in passive and dynamic conditions and foot progression angle (FPA) on the forces applied to the M5 during crossover cutting. The study included 20 men with experience playing soccer. The passive HIR was measured in the prone position. A 3-dimensional motion analysis system, force plates, and Footscan were used to measure the angle of the lower limb, including dynamic HIR, FPA, and plantar pressure to the M5, during crossover cutting in the 45° direction. Pearson correlation coefficient was measured to examine the relationship between variables. Passive and dynamic HIR were not related to the plantar pressure on the M5 (P > .05). However, increased FPA in movement direction correlated with a reduction in plantar pressure on the M5 (r = -.56, P < .01). Minimizing the FPA with respect to the new direction during crossover cutting reduced plantar pressure on the M5 and thus could prevent Jones fracture.

This study investigates the specific influence of step frequency (SF) and speed on the coordination between pelvic and thigh movements. Eight recreational male runners ran at different SFs and speeds on an instrumented treadmill. The coordination between the pelvis and thigh segments was analyzed using modified vector coding in the sagittal and frontal planes (FPs). Our findings show that hip range of motion increases as a function of SF in the sagittal plane. Pelvic tilt plays a compensatory role in hip extension, particularly at lower SFs. In the FP, pelvic roll increased at lower SFs, whereas the thigh abduction angle was participant dependant. Coordination analysis showed that thigh movements dominated the sagittal plane motion, which was simplified at higher SF. At low SF, the pelvic movements were increased and anticipated, playing a more dominant role in explaining motion. In the FP, pelvic movements dominated the motion. The increase in pelvic motion at low SFs stretches the hip flexors further and for a longer period. The link between SF, pelvic motion, and the risks of running-related injuries in the sagittal and FP is considered. Understanding these could help athletes and sports professionals optimize performance and reduce injury risk.

Calibrating inertial measurement units (IMUs) involves converting orientation data from a local reference frame into a clinically meaningful reference system. Several solutions exist but little work has been done to compare different calibration methods with each other and an optical motion capture system. Thirteen healthy subjects with no signs of upper limb injury were recruited for this study and instrumented with IMU sensors and optical markers. Three IMU calibration methods were compared: N-pose calibration, functional calibration, and manual alignment. Subjects executed simple single-plane single-joint tasks for each upper limb joint as well as more complex multijoint tasks. We performed a 3-way analysis of variance on range of motion error, root mean squared error, and offset to assess differences between calibrations, tasks, and anatomical axes. Differences in the 3 IMU calibrations are minor and not statistically significant for most tasks and anatomical axes, with the exception of the offset interaction calibration × axes (P < .001, ηG2=.056). Specifically, manual alignment gives the best offset estimation on the abduction/adduction and internal/external rotation axes. Therefore, we recommend the use of a static N-pose calibration procedure as the preferred IMU calibration method to model the humerothoracic joint, as this setup is the simplest as it only requires accurate positioning of the trunk sensor.

Repeated-sprint ability is a significant factor in football performance. Notably, hamstring injuries in football players often occur during sprinting activities and fatigue-inducing conditions. Therefore, the aim of this study was to examine the impact of repeated-sprint training (RST) on repeated-sprint ability variables and sprint kinematics. Fourteen semiprofessional men's soccer players performed 8 weeks of RST, consisting of 1 to 2 sets of 5 to 8 × 30 m repeated sprints separated by 20 to 30 seconds of recovery. Sprint performance was computed from running speed data, and a high-frequency camera (240 Hz) was used to study kinematic data. Paired samples t test and repeated-measures analysis of variance were conducted for each performance and kinematic variable, respectively. After the RST period, moderate to large improvements were observed for 0 to 20 m time, 0 to 30 m time, and 20 to 30 m time. All the repeated-sprint ability-related variables were significantly improved (P < .05). In addition, during fatigue conditions, a decrease in trunk flexion and kick-back mechanism and a reduced overstriding pattern was found after RST. The findings of this study suggest that incorporating RST may lead to improved sprint performance and promote a "safer" sprint pattern, particularly during periods of fatigue.

The biomechanics of the rotational shot put technique have been demonstrated. However, the causal relationships among kinematics and kinetics for achieving higher release velocity remain poorly understood. This study investigated these causal relationships among biomechanical variables for achieving a higher release velocity in the rotational shot put technique. The study included 22 male shot putters whose 3-dimensional motion was captured during official competitions. Key kinematic and kinetic variables throughout the shot put motion were calculated, as suggested by previous studies. Path analysis was used to explore a hierarchical model that postulates both direct and indirect effects among variables. The findings revealed that the impulse of the shot, system angular momentum, and system linear momentum were critical kinetic variables contributing directly to release velocity. Additionally, 8 kinematic variables significantly affected the impulse of the shot, including shoulder rotation, shot path length, and trunk tilt, while movements such as swings and extensions of the lower extremities were related to system momentum. This model not only provides a detailed understanding of the mechanics involved in the rotational technique but also informs technical coaching strategies in the shot put.

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.

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.

Shoulder pain is a complex, prevalent problem that is multifactorial in nature. While there are many potential causes, one common suspect is the rotator cuff musculature. The purpose of the present study was to induce pain in the supraspinatus muscle of healthy subjects and observe the resulting changes in muscle activity. Eight muscles on 23 subjects were assessed using electromyography: anterior, middle, and posterior deltoid; pectoralis major; upper trapezius; latissimus dorsi; serratus anterior; supraspinatus; and infraspinatus. It was hypothesized that the rotator cuff muscles would display reduced activity during pain, and that reductions in activity would remain after the pain had dissipated. Both of the rotator cuff muscles measured did indeed display reduced activity in a majority of the dynamic, isometric, and maximal contractions. Many of those reductions remained after the pain had subsided.