The force-generating capacity of the ankle plantar flexor muscles is known to be influenced by both ankle and knee joint angles, but the metatarsophalangeal (MTP) joint may also affect these muscles. This effect may aris...The force-generating capacity of the ankle plantar flexor muscles is known to be influenced by both ankle and knee joint angles, but the metatarsophalangeal (MTP) joint may also affect these muscles. This effect may arise as 2 ankle plantar flexors, the flexor hallucis longus and the flexor digitorum longus, cross the MTP joint. It was the purpose of this study to determine the influence of the MTP joint on maximum voluntary isometric plantar flexor moments. Maximum isometric ankle plantar flexion moments were measured for 8 subjects with the MTP joint in either neutral or fully dorsiflexed position while the angles of the knee joint (90° flexion or fully extended) and ankle joint (4 angles) were systematically varied, giving 16 sets of joint configurations. There was no significant effect of the MTP joint angle on the maximum plantar flexion moment (P = .41), but both the ankle and knee joint angles had a significant effect (P < .001). During the stance phase of human gait, the MTP joint angle changes. The results of this study suggest that MTP orientation changes have no implications for the length-determined contributions of the flexor hallucis longus and flexor digitorum longus to the ankle plantar flexion moment.
Hip joint center (HJC) location estimation influences dependent angles and clinical interpretations. We examined the agreement between 6 HJC estimation methods; compared hip, thigh, and knee angles; and explored HJC loca...Hip joint center (HJC) location estimation influences dependent angles and clinical interpretations. We examined the agreement between 6 HJC estimation methods; compared hip, thigh, and knee angles; and explored HJC location and thigh angle associations. Pelvis markers were used to estimate HJC location via 6 popular methods using Harrington's method as the reference standard. HJC limits of agreement analysis and inferential angle comparisons during standing revealed that Bell's (HJC bias range = 0-11 mm, hip angle difference range = -0.2° to 0.1°) and Vaughan's (HJC bias range = -5 to 41 mm, hip angle difference range = -0.5° to -5.3°) methods were most and least like Harrington's but varied by dimension. Stepwise regression showed that anterior-posterior, medial-lateral, and anterior-posterior HJC coordinate differences best explained sagittal (R2 range = .95-.99, P < .001), frontal (R2 range = .83-.99, P < .001), and transverse (R2 range = .54-.72, P < .001) thigh angle differences, respectively. Different HJC methods caused several large sagittal but more minor frontal and transverse plane differences. We urge caution when using different HJC methods.
This study aimed to characterize differences in head kinematics across similar skills performed by women's (WAG) and men's artistic gymnastics (MAG). Twelve female and 8 male artistic gymnasts (ages 11-18) wore mouthpiec...This study aimed to characterize differences in head kinematics across similar skills performed by women's (WAG) and men's artistic gymnastics (MAG). Twelve female and 8 male artistic gymnasts (ages 11-18) wore mouthpieces with triaxial accelerometers and gyroscopes to perform a series of gymnastics skills from 5 common skill progression pathways: backward tumbling (floor), bar elements, forward tumbling, and vault-specific skills (Tsukahara and Yurchenko). Data were recorded at 100 Hz for 10-minute intervals and time-synchronized with video recordings. Peak linear acceleration (PLA), peak rotational acceleration (PRA), resultant change in rotational velocity during the maximum rotational acceleration (ΔRV), and peak rotational velocity (PRV) were compared using mixed-effects models. WAG experienced greater PRV during noncontact skills (eg, giant and clear hip). MAG experienced, on average, 1.7 times greater PRA during skills with significantly different PRA between MAG and WAG. MAG tended to have higher kinematic values for PLA, PRA, and ΔRV during contact phases compared with WAG. It is important to understand head kinematics in nonconcussive situations, as postconcussed gymnasts may have lower tolerance to head acceleration events during recovery. Understanding differences in head kinematics between WAG and MAG can help guide sport- and sex-specific injury prevention strategies.
The purpose of the present study was to clarify the dynamic factors that induce pelvic rotation when soccer players kick a ball toward angled directions using an instep kick. Nine experienced, right-footed, male soccer p...The purpose of the present study was to clarify the dynamic factors that induce pelvic rotation when soccer players kick a ball toward angled directions using an instep kick. Nine experienced, right-footed, male soccer players instep kicked a stationary ball in 3 different angled directions, 15°, 45°, and 75° relative to the run-up direction, and a motion capture system with a force plate recorded the kicking data. Kinematic and kinetic variables of the support leg, associated with pelvic rotation about the vertical axis, were compared among the kicking conditions. The pelvic rotation significantly increased in response to larger kicking angles, and it coincided with increase of the support leg hip joint and foot segment rotation about the vertical axis. The joint torque at the support leg hip joint significantly increased with the kicking angles. Additionally, the interaction torque due to the ground reaction force was the primary factor driving foot segment rotation relative to the force plate in angled kicking conditions, whereas no remarkable action of the free moment existed. Instep kicks toward angled directions involve a mechanism that increases the pelvic rotation about the support leg's hip joint and foot segment, which differs from the mechanism involved in straight kicks.
Anterior cruciate ligament (ACL) injuries commonly occur during unbalanced single-leg landings, where inadequate anticipation and response to ground contact might increase risk. Vision and knowledge of landing heights ma...Anterior cruciate ligament (ACL) injuries commonly occur during unbalanced single-leg landings, where inadequate anticipation and response to ground contact might increase risk. Vision and knowledge of landing heights may influence how athletes anticipate and respond to landings. This study examined the effects of the removal of visual input and knowledge of landing heights on knee biomechanics associated with ACL injury risk. Thirty-three recreational athletes performed single-leg landings from 3 different heights (11, 22, and 33 cm) under 3 conditions: with both vision and knowledge, with knowledge but without vision, and without both. The no vision and no knowledge condition resulted in an intermediate strategy that produced similar landing mechanics for 22 cm but significantly different kinematics and kinetics for 11 and 33 cm. Slower knee flexion angular velocities, increased peak vertical ground reaction forces, and greater knee internal rotation and abduction angles suggested increased ACL loading for 33 cm. Landing patterns with knowledge but without vision closely matched those with both. Removing both vision and knowledge significantly altered landing mechanics, emphasizing the need to train athletes to accurately anticipate initial contact of landings and adopt safe landing strategies under restricted visual and uncertain or perturbed conditions.
A higher risk of knee osteoarthritis (OA) has been identified in patients with slower walking speeds following anterior cruciate ligament reconstruction (ACLR). Given that altered loading of the surgical knee has been th...A higher risk of knee osteoarthritis (OA) has been identified in patients with slower walking speeds following anterior cruciate ligament reconstruction (ACLR). Given that altered loading of the surgical knee has been the most proposed mechanism for early knee OA post-ACLR, understanding how modulating walking speed may modify knee joint loading is essential for developing strategies to reduce the risk of knee OA in ACLR patients. The purpose of this study was to determine how modulation of walking speed affects knee joint loading during overground walking post-ACLR. Lower extremity kinematics and kinetics were recorded during overground walking at a self-selected, slower, and faster speed from 16 patients with unilateral ACLR. The results showed that ACLR patients demonstrated lesser peak knee flexion and adduction moments of the surgical knees when walking at slower speeds. However, modulating walking speed did not alter between-limb knee loading asymmetry. The ACLR limbs had lower peak knee flexion moments than the uninjured limbs across all 3 walking speeds. Although interventions that increase walking speed may deter the onset of knee OA by elevating the mechanical stimulation at the surgical knee, additional gait training strategies may be needed to restore the between-limb loading symmetry in ACLR patients.
The objective of this study was to examine the influence of relative hamstring flexibility and lumbar extensor strength on lumbar flexion during a stoop lift. Lumbar flexion during stoop lifting has been associated with...The objective of this study was to examine the influence of relative hamstring flexibility and lumbar extensor strength on lumbar flexion during a stoop lift. Lumbar flexion during stoop lifting has been associated with increased bending stress and load on the lumbar spine. The potential impairments that contribute to a flexed lumbar lifting posture during stoop lifting are unclear. Forty-nine healthy individuals (27 females and 22 males) between the ages of 18 and 40 participated. Strength of the lumbar extensors was measured with a motor-driven dynamometer, and relative hamstring flexibility was estimated with the passive knee extension test. Peak lumbar flexion and pelvis anterior rotation were quantified with 3D motion capture during a stoop lift. There was a positive correlation between relative hamstring flexibility and peak pelvis anterior rotation angle during the stoop lift (r = .544, P < .001). Meanwhile, there was a negative correlation between middle lumbar spine peak flexion and relative hamstring flexibility (r = -.538, P < .001) and a negative correlation between lumbar extensor strength and lower lumbar peak flexion (r = -.288, P = .045). Individuals with decreased strength and limited relative hamstring flexibility tended to exhibit increased lumbar flexion during stoop lifting.
The effect of gait speed on minimum toe clearance (MTC) amount may vary across the lifespan due to changes in joint relationships, potentially affecting trip-related fall risk in older adults. We evaluated whether age in...The effect of gait speed on minimum toe clearance (MTC) amount may vary across the lifespan due to changes in joint relationships, potentially affecting trip-related fall risk in older adults. We evaluated whether age influences the relationship between gait speed and MTC amount, as well as between joint movements and MTC amount. Optical motion capture data was collected on 62 participants between the ages of 20 and 83 years during 25 gait trials at self-selected normal, fast, and slow speeds. Multilevel models were used for data analysis. Gait speed was associated with a 0.13 cm increase in MTC amount for every meter per second increase in gait speed with other factors constant and was unaffected by age. Ankle dorsi-plantarflexion, knee and hip flexion-extension, and stance hip abduction-adduction changed the MTC amount by 0.05, 0.02, 0.04, and 0.04 cm, respectively, for each degree of joint movement, with other factors constant, and was unaffected by age. Age did not affect the relationship between gait speed and MTC amount, nor the relationship of joint moments with MTC, indicating that these factors may not be associated with trip-related fall risk with healthy aging.
Artificial neural networks (ANNs) are becoming a regular tool to support biomechanical methods, while physics-based models are widespread to understand the mechanics of body in motion. Thus, this study aimed to demonstra...Artificial neural networks (ANNs) are becoming a regular tool to support biomechanical methods, while physics-based models are widespread to understand the mechanics of body in motion. Thus, this study aimed to demonstrate the accuracy of recurrent ANN models compared with a physics-based approach in the task of predicting ground reaction forces and net lower limb joint moments during running. An inertial motion capture system and a force plate were used to collect running biomechanics data for training the ANN. Kinematic data from optical motion capture systems, sourced from publicly available databases, were used to evaluate the prediction performance and accuracy of the ANN. The linear and angular momentum theorems were applied to compute ground reaction forces and joint moments in the physics-based approach. The main finding indicates that the recurrent ANN tends to outperform the physics-based approach significantly (P < .05) at similar and higher running velocities for which the ANN was trained, specifically in the anteroposterior, vertical, and mediolateral ground reaction forces, as well as for the knee and ankle flexion moments, and hip abduction and rotation moments. Furthermore, this study demonstrates that the trained recurrent ANN can be used to predict running kinetic data from kinematics obtained with different experimental techniques and sources.
The aim of this study was to explore the association between pelvic floor dysfunction and running kinetics and pelvic acceleration in a cohort of postpartum women. The Australian Pelvic Floor Questionnaire was used to qu...The aim of this study was to explore the association between pelvic floor dysfunction and running kinetics and pelvic acceleration in a cohort of postpartum women. The Australian Pelvic Floor Questionnaire was used to quantify symptom severity (mean [SD]: 6 [ 4] out of 40; range: 1-14) in 25 postpartum women. Participants completed a pelvic floor muscle assessment to measure pelvic muscle strength and endurance, then completed a 7-minute treadmill running protocol at a speed of 10 km·h-1 to evaluate their running kinetics and pelvic acceleration. After the run, participants responded to a modified version of the symptom's component of the PFD-SENTINEL screening tool. Mean pelvic muscle strength and endurance were 3 (1) and 9 (2), respectively. We found no significant association between PFD symptom severity and running kinetic (P = .209-.410) or pelvic acceleration (P = .081-.947) outcome measures. Fifteen participants experienced at least one symptom during the treadmill protocol. Running kinetics and pelvic acceleration may not affect or be affected by symptoms of PFD. Given the relatively low symptom expression among study participants, further research in a cohort of women with higher levels of PFD is recommended.
Javelin throwers cannot safely throw with a long approach run often per training session. Therefore, implements of different shapes and masses are thrown from short run-ups to emulate the demands of achieving high throwi...Javelin throwers cannot safely throw with a long approach run often per training session. Therefore, implements of different shapes and masses are thrown from short run-ups to emulate the demands of achieving high throwing distances. This study examined the effects of different implements, thrown from various approaches, on the kinematics and kinetics of the throwing arm. The throwing motions of 6 athletes, each throwing 6 different implements were recorded using 12 infrared cameras. Kinematics and kinetics of the shoulder and elbow joints were calculated and statistically compared. The results show that lighter implement throws achieved higher release speeds, while heavier implements required greater work to be done on them. We identified significant differences for the shoulder external rotation angle (P < .001), the shoulder internal rotation (P = .040), and elbow extension (P = .003) angular velocities and the torques of the shoulder internal rotation (P = .006), horizontal flexion (P = .004), and the elbow varus (P = .008). It can be concluded that throws with balls of different masses have different angular velocities and joint torques, and therefore can be used to train speed and strength aspects of the javelin throw while using lower run-up speeds.
The incidence of lower extremity injuries in collegiate distance runners is ∼20%. Identification of a runner sustaining a potential injury remains challenging. This exploratory, cross-institutional study sought to determ...The incidence of lower extremity injuries in collegiate distance runners is ∼20%. Identification of a runner sustaining a potential injury remains challenging. This exploratory, cross-institutional study sought to determine whether ground reaction force (GRF) characteristics during steady-state running could identify competitive collegiate distance runners who would later sustain lower extremity injuries. Normative boundaries for 10 GRF variables during braking and propulsion were established for noninjured runners using median ± scaled median absolute deviation. A subanalysis was conducted on runners with and without impact peaks in vertical GRF to mitigate the influence of impact peaks on GRF variables. We hypothesized that prior to injury, runners who later developed an injury would have more GRF variables outside of the normative boundaries than noninjured runners. Using Cliff's method, a rank-based, nonparametric method for comparing 2 independent groups, we found no statistically significant difference between the number of variables outside the boundaries for injured and noninjured runners overall (P = .17). However, injured runners without impact peaks had more variables outside the normative boundaries than noninjured runners (P < .001). This novel analytical approach demonstrates the potential for preidentifying collegiate distance runners without impact peaks who may be at risk for injury.
Historically, obstacle crossing has been studied in a laboratory setting using a dowel rod as a modality to understand how and why individuals trip and subsequently fall. The dowel features several characteristics that a...Historically, obstacle crossing has been studied in a laboratory setting using a dowel rod as a modality to understand how and why individuals trip and subsequently fall. The dowel features several characteristics that are optimal for research in a laboratory setting, however, it lacks applicability in real-life situations. The purpose of this study was to compare measures of obstacle crossing for the traditional laboratory obstacle (the dowel) to several real-world obstacles. Thirty healthy, young adults (23 [4] y, range: 19-35 y) completed 6 barefoot walking conditions over an 8-m instrumented walkway while motion was recorded in 3D. Participants performed unobstructed walking as familiarization trials and 5 obstructed walking conditions were presented in a randomized order: (1) dowel, (2) branch, (3) parking curb, (4) puddle, and (5) caution rope. Measures of vertical and horizontal obstacle clearance indicate that healthy young adults cross the dowel obstacle differently than they cross real-world obstacles, such as a curb, a puddle, and a caution rope but most similar to a branch. Since dowel rods have historically been used to assess obstacle crossing strategies, we encourage researchers and readers to exercise caution when extrapolating findings to real-world obstacles found in everyday life.
Greater knee adduction moment is associated with increased risk and progression of knee osteoarthritis, and this biomechanical risk factor is modulated through kinematic gait modifications. Emotions are known to influenc...Greater knee adduction moment is associated with increased risk and progression of knee osteoarthritis, and this biomechanical risk factor is modulated through kinematic gait modifications. Emotions are known to influence walking kinematics and speed, but the effect of different emotions on knee mechanics is unclear. To test this, 20 healthy participants walked while instrumented gait data was recorded. Participants initially walked naturally (baseline) and then acting 4 emotional walking conditions: Anger, Happy, Fear, and Sad, in randomized order. Statistical parametric mapping with an analysis of variance model determined the extent to which emotions influenced knee joint mechanics. Results indicated both the happy (P = .009) and sad (P < .001) condition resulted in lower knee adduction moment compared with baseline. Walking both happy and sad also resulted in walking speed changes from baseline (P < .001). A secondary analysis of covariance model with speed as the covariate indicated no significant effect of emotional condition on knee adduction moment (P > .05), which suggests that the changes from baseline can be attributed to the changes in walking speed. Decreased knee adduction is associated with reduced osteoarthritis progression and increased knee function, suggesting that walking while acting different emotions, specifically happy and sad, may moderate knee osteoarthritis risk.
Due to inadequate commercial availability of sports bras designed with adequate breast support for full-busted women (cup size D and above), breast discomfort can be a significant barrier to exercise. In this study, post...Due to inadequate commercial availability of sports bras designed with adequate breast support for full-busted women (cup size D and above), breast discomfort can be a significant barrier to exercise. In this study, postural characteristics during dynamic physical activities were evaluated for 20 full-busted women in 3 different sports bra conditions, 2 of which were bras designed specifically for full-busted women. Participants performed quiet standing, walking, jumping jacks, high knees, and running tasks on a force plate treadmill in each condition to collect postural measures associated with center of pressure (COP). COP measures were also evaluated with respect to body composition, metabolic health markers, and sex hormone profiles. COP measures were larger in high knees and jumping tasks with respect to quiet standing. Across running speeds, conventional bras were associated with the largest COP metrics. Analysis of covariance analysis indicated increased anthropometry measures such as mass and body fat percentage resulted in decreased COP area and favored mediolateral orientation. Luteinizing hormone, estradiol, progesterone, testosterone, and sex hormone-binding globulin were all found to impact statistical models, indicating the importance of incorporating a comprehensive hormone panel when considering the impact subject-level variations have on motor function.
The primary objective of the study was to evaluate the risk of lower-extremity injury during landing, after catching a basketball in the air for a rebound or a steal. A total of 32 (15 females and 17 males) recreational...The primary objective of the study was to evaluate the risk of lower-extremity injury during landing, after catching a basketball in the air for a rebound or a steal. A total of 32 (15 females and 17 males) recreational basketball players were asked to perform 4 different arm-reaching movements during the flight phase: no reaching, left (LAR), right (RAR), and bilateral (BAR) arm reaching. Knee and hip flexion and abduction angles at initial ground contact, peak ground reaction force within 100 milliseconds after contact, and peak moments for the hip and knee joints were analyzed. LAR, RAR, and BAR showed significantly smaller peak hip and knee flexion angles, while LAR demonstrated a significant increase in the knee's peak abduction angle. Furthermore, the peak abduction moments of LAR were significantly increased in both males and females. Aerial basketball catching movements resulted in stiffer leg joints and larger knee abduction during landing, which was a potential factor in increasing the risk of lower-limb injury upon landing. It is recommended to include a softer landing technique and implement a training program for enhancing knee joint stabilization in the frontal plane.
Patients with peripheral artery disease (PAD) often experience leg muscle damage, leading to noticeable walking difficulties. Using ankle foot orthosis (AFO) may enhance gait by supporting weak muscles. This study examin...Patients with peripheral artery disease (PAD) often experience leg muscle damage, leading to noticeable walking difficulties. Using ankle foot orthosis (AFO) may enhance gait by supporting weak muscles. This study examined whether wearing AFOs improved the spatiotemporal gait characteristics of patients with PAD to be closer to those of healthy individuals, both from its first use and after a 3-month intervention. Spatiotemporal parameters were calculated from the kinematics of 26 patients with PAD captured in a biomechanics lab. Subjects walked with and without AFOs before and following a 3-month AFO intervention on a crossover basis. The immediate intervention group wore AFOs for 3 months (intervention) before switching to their control shoes (control), while the delayed intervention group followed the reverse sequence. Means and standard deviations (variability) for step width, length, time, and velocity were compared using separate linear repeated measures models. The models included group (immediate vs delayed intervention), time (before vs after intervention or baseline vs 3 mo), and condition (non-AFO vs AFO) as factors of comparison, in addition to interactions, if significant. A 3-month AFO intervention enhanced the temporal gait parameters and reduced gait variability. The mean and variability of temporal gait parameters were sensitive enough to determine whether patients walked more like healthy individuals after a 3-month AFO intervention. This may decrease fall risk and promote more efficient walking patterns in patients with PAD. The long-term benefits and adherence to AFOs and other assistive devices need further study.
When carrying out a motor task, the direction of the performer's attentional focus can affect mechanical output and muscle activation. Cortical excitability increases with the observation of motor skills. However, it is...When carrying out a motor task, the direction of the performer's attentional focus can affect mechanical output and muscle activation. Cortical excitability increases with the observation of motor skills. However, it is unknown if this effect can be additive to that resulting from an internal attentional focus during resistance exercise. A crossover-study design was employed to examine the acute effects of combining mirror self-motor observation (MO) and internally focused verbal instructions on mechanical output and muscle activation during isokinetic concentric knee-extension exercise. Ten participants were tested in 2 different conditions: verbal alone and verbal + MO-mirror. The combination of verbal + MO-mirror attenuated the decrease in torque output in response to 6 sets of 10 isokinetic contractions (P = .043). Interestingly, this effect was paired by a lower-level antagonist/agonist coactivation with the verbal + MO-mirror condition (P = .031). No other differences between conditions were noted. Taken together, these results suggest that the combination of both cueing modalities elicits a more effective contraction strategy during knee-extension exercise. Ultimately, this provides preliminary evidence of better motor performance and heightened fatigue resistance in response to isokinetic exercise.