Journal of Applied Biomechanics最新文献

Precise quantification of the lumbar flexion-relaxation phenomenon can provide a better understanding of the load transfer between active and passive tissues and its implications for spinal stability. This study aimed to compare the precision of instantaneous angles using 1 versus 2 inertial motion sensors to determine the deactivation (electromyography [EMG]-off) and reactivation (EMG-on) of left and right erector spinae muscles during trunk flexion and extension. Electromyography and kinematic data were collected from 12 participants who performed 20 slow, controlled trunk flexion-extension motions. The angle derived from 1 motion sensor was the pitch angle of the T12 sensor, and the angle derived from 2 sensors was the difference between the pitch angles of the T12 and S1 sensors. The EMG-off (or EMG-on) angle was defined as the angle at which unilateral erector spinae muscle activity dropped below (or exceeded) 3 times the muscle activity recorded at full trunk flexion during trunk flexion and extension. Results revealed that absolute and relative variability in 20 EMG-off and EMG-on angles were greater when measured with 1 inertial motion sensor than with 2 sensors (P ≤ .003), suggesting that using 2 sensors can improve the precision of flexion-relaxation phenomenon determination compared with using 1 sensor.

Trochanteric soft tissues have significant effects on fall-related hip fracture risk; however, little is known about their composition and spatial distribution. Accordingly, this study determined (1) the influence of sex and anatomical location on muscle thickness, adipose thickness, and total soft tissue thickness surrounding the proximal femur; and (2) the effects of sex- and location-specific soft tissue thickness on predicted fall-related hip impact forces. Ultrasound was used to measure muscle thickness, adipose thickness, and total soft tissue thickness at 12 locations surrounding the proximal femur in 25 young adult participants. Fall-related hip impact forces were predicted with a mass-spring model, accounting for force attenuation by soft tissues, at 2 common impact sites. The data demonstrated that tissue thickness and impact forces were significantly influenced by sex and anatomical location. Males had more muscle, less adipose, less total soft tissues, less force attenuation, and higher impact forces than females. Total soft tissue thickness and muscle thickness were lowest over the lateral femur, while adipose thickness was lowest over the anterolateral femur. Force attenuation was higher while impact forces were lower at the posterolateral impact site. The data support that the accuracy of hip impact models could be improved by incorporating sex-, location-, and composition-specific soft tissue thickness measures.

The objectives of this study were to examine youth football athletes' individual head acceleration event (HAEs) exposure, explore athletes' perspectives and experiences playing youth football, and investigate relationships between their perspectives and HAE exposure. Thirteen middle-school-aged football athletes wore instrumented mouthpieces to measure HAEs for 1 season and participated in a one-on-one interview, discussing motivations, mental focus, safety, and perceptions of contact. Kinematic data were integrated with qualitative data using triangulation to examine relationships between athlete perspectives and HAEs. Two thousand six hundred seventy-one true-positive HAEs were collected and analyzed. Topics discussed in interviews included aspirations, mental focus, potential for injury, and perceptions of contact. Athletes with the greatest HAE frequency discussed wanting to advance to higher levels of football (eg, college). Several athletes expressed an affinity for contact, many of whom had more HAEs per session than other athletes; however, some athletes disliked the risk of injury in football. Athletes reported that hits to the head felt the hardest, consistent with greater magnitudes measured among head impacts compared with body impacts. Athletes' perceptions of collisions and safety topics may inform our understanding of factors that influence HAE exposure in football and help guide identification of individual-level targets to reduce exposure and concussion risk.

Minimum toe clearance (MTC) location relative to the stance-phase foot, as well as how this location changes with walking speed, helps in better understanding the circumstances when MTC is most relevant. This study helps define where MTC occurs for the swing-phase foot in relation to the stance-phase foot. Gait speed was assessed also to determine its effect on this relative positioning. 3D lower body gait data were collected from 14 barefoot participants (age: 8-14 y). Participants ambulated at slow, self-selected, and fast gait speeds. At all speeds, MTC was found to occur closer to the tip of the hallux rather than to the heel of the stance-phase foot. At slow gait speeds, the MTC was 70.2% from the heel. For the self-selected and fast speeds, the MTC was 113.6% and 98.8% from the heel, respectively. Though the location changed, the vertical height of the swing-phase foot at MTC did not change significantly as a function of gait speed. These results indicate that the location of MTC is significantly impacted by the placement of the stance-phase foot as well as walking speed. These factors can play a role in assessing the risk of tripping when an unexpected trip hazard is present.

Knee pain in patients with knee osteoarthritis leads to decreased physical activity. The knee adduction moment impulse is closely related to pain, multiplied by the number of steps per day, reflecting the cumulative knee adductor load (CKAL). The intervention of lateral wedge insole (LWI) can relieve pain by reducing the CKAL, but changes in physical activity have not been investigated. This study aimed to determine the effect of the LWI on the CKAL and changes in physical activity. Twenty-one patients with knee osteoarthritis were enrolled in our study. The knee adduction moment impulse was estimated by a VICON system without LWI (baseline) and with LWI immediately (T0) at the initial visit and 3 months after intervention (T1). An accelerometer was worn for 8 days to monitor daily steps and activity. The physical activity was performed at baseline and T1. Pain was evaluated at baseline, T0, and T1. Pain and CKAL were reduced significantly after the intervention of the LWI. The knee adduction moment impulse at T0 and T1 was reduced compared with the baseline. There was no significant change in daily steps. However, physical activity significantly decreased in terms of the total duration of activity, standing, and periods of standing and walking.

Interlimb asymmetries may influence contralateral knee osteoarthritis (OA) progression, yet research remains unclear. This study examined whether patient-reported outcomes and knee biomechanics differ between individuals with knee OA exhibiting symmetrical versus asymmetrical knee loading. Forty-three individuals with knee OA were dichotomized into symmetrical (≤14% asymmetry; n = 19) and asymmetrical (>14% asymmetry; n = 24) groups based on total joint moment symmetry indices. Participants completed the Knee Injury and Osteoarthritis Outcome Score and Intermittent and Constant Osteoarthritis Pain questionnaires. Three-dimensional kinematics and kinetics were collected during walking at a self-selected speed. Independent t tests and statistical parametric mapping examined between-group differences in patient-reported outcomes and biomechanical measures. Individuals with symmetrical knee loading had worse Knee Injury and Osteoarthritis Outcome Score activities of daily living scores (P = .041) than those with asymmetrical loading. Individuals with symmetrical knee loading exhibited less knee extension moment during late stance (P = .031) and lower knee adduction moment range in their affected knee compared with asymmetrical loaders. Individuals with symmetrical knee loading walked with lower knee flexion angles (P = .011), less midstance unloading (P = .011), and lower peak knee flexion moment (P < .001) in their contralateral knee compared with asymmetrical loaders. Symmetrical knee loading was associated with affected and contralateral knee biomechanics that were consistent with more severe knee OA and worse functional outcomes.

Marker-based motion analysis is the standard for evaluating human movement, yet it is time-intensive and requires extensive technical knowledge. Markerless-based motion analysis can simplify and expedite clinical biomechanics research, but its utility with unique populations, like manual wheelchair users, remains understudied. The purpose of this study was to compare 3-dimensional thorax and bilateral upper-extremity joint kinematics during manual wheelchair propulsion between criterion-standard marker-based and novel markerless-based biomechanical models. Fifteen young adult, manual wheelchair users propelled on a stationary roller while synchronized optical motion analysis cameras recorded 3-dimensional marker trajectory and 2-dimensional video data simultaneously. Statistical parametric mapping was used to evaluate kinematic differences between models. Pearson correlation and average root mean square were also used to explore the relationships and the magnitudes of observed differences between models. Significant differences in thorax and upper-extremity joint kinematics were observed between the models (P < .05). Joint angle differences varied in magnitude from 3.6° to 36.6° and joint center differences varied in magnitude from 0.4 to 2.4 cm. Differences were dependent upon the joint and anatomical plane/axis. Despite some observed limitations, markerless-based motion analysis may be a useful clinical research tool to evaluate thorax and upper-extremity kinematics during wheelchair mobility.

It is unknown how pitching biomechanics in college baseball pitchers differ between windup and stretch pitching deliveries from a dirt surface mound. The purpose was to assess differences in shoulder and elbow kinetics and pitching kinematics in college pitchers between windup and stretch pitching deliveries from a dirt surface mound. Eighteen college pitchers pitched from a dirt surface mound using windup and stretch pitching deliveries. All pitchers were tested using a 240-Hz, 12-camera motion analysis system, and 28 kinematic and 7 kinetic parameters were calculated. Paired within-subjects t tests (P < .05) were used to assess biomechanical differences between windup and stretch deliveries. Maximum shoulder horizontal adduction torque, maximum shoulder anterior force, maximum lead knee height, ball velocity at ball release, forward trunk tilt at ball release, maximum upper trunk angular velocity, maximum elbow extension angular velocity, and maximum shoulder internal rotation angular velocity were all significantly greater using a windup delivery compared with a stretch delivery. Pelvic drift at maximum lead knee height was the only parameter that was significantly greater in a stretch delivery compared with a windup delivery. Nine of the 35 (26%) biomechanical parameters were significantly different between windup and stretch deliveries. Shoulder injury risk may be slightly lower using a stretch delivery compared with a windup delivery due to overall lower shoulder kinetics during the stretch delivery.

This study investigated the relationship between neuromuscular (motor unit action potential amplitude [MUAP], firing rate, recruitment threshold), biomechanical (force loss), physiological (skin temperature), and perceptual (delayed onset of muscle soreness) markers following an intense knee exercise protocol. Eleven participants performed 2 maximal isometric and 5 concentric-eccentric knee contractions. Assessments were made immediately postexercise (0 h), at 24 hours and 48 hours after intense knee exercise protocol. Electromyography signal decomposition and skin temperature were measured during the protocol, while delayed onset of muscle soreness was evaluated at 24 and 48 hours. A reduction in force production (isometric, dynamic, and Work) was observed at all postexercise time points. Delayed onset of muscle soreness increased at 24- and 48-hour postexercise compared to Pre-exercise. At 0 hours, a positive, moderate correlation was observed between dynamic force loss and MUAP of the vastus lateralis (VL). Two moderate positive correlations were observed between firing rate of rectus femoris and minimum temperature, and between the recruitment threshold of VL and mean temperature. At 24-hour postexercise, a positive moderate correlation was observed between dynamic peak torque and MUAP of VL. These findings suggest that full recovery of force is not achieved at 48-hour postexercise, with MUAP of VL playing a key role in muscle recovery.

Gait analysis is a valuable approach for understanding human movement, but the space and setup requirements of traditional marker-based systems can limit their use outside specialized laboratories. Markerless motion capture may provide a more flexible option, though its agreement in constrained environments compared with traditional spaces is not well established. This study compared a 10-camera markerless system deployed in a hallway with a traditional 8-camera laboratory setup. Twenty-five healthy adults (15 females, 10 males; age 34 [16] y) completed quiet standing, 60 seconds of self-selected walking, and 5-repetition sit-to-stand tasks at both sites on the same day. Three-dimensional pose estimates were processed to calculate alignment during standing, lower-limb joint kinematics during walking, and trunk flexion during sit-to-stand. Agreement within and between sites was assessed using Pearson correlations, root mean square error, Bland Altman limits of agreement, and intraclass correlation coefficients. Standing and walking outcomes showed excellent agreement (intraclass correlation coefficients ≥ .97; root mean square error < 2.3°; mean differences < 1.1°). Sit-to-stand was more variable (limits of agreement 12°-20°) but remained highly reliable (intraclass correlation coefficients > .96). These findings indicate that a constrained markerless setup can yield kinematic data comparable to a laboratory arrangement, suggesting potential for broader use of markerless approaches in diverse environments.