Journal of Applied Biomechanics最新文献

Most injuries that dancers sustain are to the lower extremities, specifically the foot and ankle region. Numerous potential risk factors have been examined for dancer injuries such as technical mistakes and fatigue. The purpose of this study was to compare landing kinematics and kinetics during jumps that are common in dance pre and postfatigue. Ten adolescent advanced level dancers participated in this study. Subjects completed 3 split leaps and 3 center leaps before and after a fatigue protocol performed on a stationary bike. Live motion capture was used to record landing kinematic and kinetic data. Results of this study showed a significant increase in ankle eversion and external rotation angles for center leaps from pre- to postfatigue protocol (P = .020 and P = .020, respectively) as well as significant increases in ankle eversion and knee adduction moments for center leaps (P = .020 and P = .036, respectively). These results show that after a fatigue protocol, there are changes to the kinematics of dancers that may make them more susceptible to ankle injury.

Balance training paradigms have been shown to effectively reduce fall risk. Visual feedback is an important sensory mechanism for regulating postural control, promoting visual perturbations for balance training paradigms. Stroboscopic goggles, which oscillate from transparent to opaque, are a form of visual perturbation, but their effect on standing balance has not been assessed. In this study, 29 participants stood in bilateral and tandem stances as the center of pressure was recorded for 6 consecutive minutes wherein there were no stroboscopic perturbations in the first and last minutes. Spatial-temporal, frequency domain, and nonlinear standing balance parameters were calculated for each period. More differences in spatial-temporal parameters due to the strobe were found in the medial-lateral direction than the anterior-posterior direction. More differences in frequency domain parameters were observed in the anterior-posterior direction than the medial-lateral direction, but this did not occur for each variable. The nonlinear parameters were strongly affected by the strobe. Stroboscopic perturbations did not affect the bilateral and tandem stances equally. Spatial-temporal parameters for the tandem stance were greater in magnitude during the strobe period than the no strobe periods. This effect was not seen with the bilateral stance. This indicates that the efficacy of stroboscopic perturbations for challenging standing balance depends on task difficulty. Balance training paradigms that utilize stroboscopic perturbations will need to harmonize these perturbations with task difficulty.

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.