Process of dynamic balance recovery after voluntary perturbation: a time-series data analysis of young and older adults.

[Purpose] This study investigated differences in the convergence mode of post-step sway between young and older adults using a step-down task to identify fall causes in older adults and assess consecutive postural adjustments. [Participants and Methods] This study included 15 young and 15 older adults (nine females and six males in each group). The participants stepped down from a standing position to a force platform 10 cm lower and maintained a one-leg standing position. The center-of-pressure total trajectory length was assessed using a force plate and regression equations for time and sway were derived from the associated time-series data for both groups. [Results] An inversely proportional aspect was observed for both groups, with significantly different coefficients and constants. The center-of-pressure total trajectory length per second from foot contact was significantly different between 2-3 s and 4-5 s in the older group but not in the younger group. [Conclusion] The results suggest a difference in the convergence mode of dynamic balance between the two groups, with young adults exhibiting a more rapid balance-sway reduction than older adults. The novel computational approach used in this study may be useful for dynamic balance measurements.

Goal Orientation and Desire for Approval Were Associated With Sports Injuries Among Young Japanese Athletes.

Introduction: This study aimed to clarify the relationship between psychological factors (goal orientation and desire for approval from others) and the severity of sports injuries experienced by young Japanese athletes. Methods: A total of 560 young Japanese athletes (328 males and 232 females) aged 18-24 years completed an online survey in 2022-2023. A web questionnaire was used to investigate participants' task and ego orientations, desire for approval from others (e.g., coaches and friends/families), and history of injury. The samples were then split into 3 groups on the basis of the rest duration due to the injury: noninjury group (0 days), mild-to-moderate injury group (1-27 days), and severe injury group (>28 days). Spearman's test examined a correlation between task and ego orientation scores among all samples. The Mann-Whitney U test was used to compare the scores between the severe injury and noninjury groups. Result: A significant positive correlation was found between task and ego orientation scores from all samples (ρ=0.27, p<0.001). The severe injury group had significantly higher task orientation scores and desire for approval scores than the noninjury group (ρ=0.001, p<0.001). Conclusions: Japanese young athletes with high task orientation and approval desire may be at risk of severe sports injuries requiring >4 weeks to return to sports. The goal orientation profiles should be interpreted with caution. Future research should examine contextual effects such as the perceived motivational climate, in addition to the goal orientation profiles.

Body Part Pain Affects Subjective and Objective Handball Performance in Japanese Male National Athletes-Results of Short-Term Practical Monitoring of Athletes' Conditions.

This short-term survey examined the effect of body part pain on subjective and objective handball performance in Japanese male national handball athletes. Fourteen athletes participated in this study. Assessments of pain in 10 body parts and subjective performance (concentration and satisfaction with body movement) were performed using a visual analog scale from 0 to 10 over four consecutive training days. Monitoring of heart rate and body acceleration during training was also performed to quantify the objective performance. Path analysis and linear mixed modeling were employed to assess the relationship between body pain scores and subjective/objective handball performance. Over the four days of the study period, the body part in which most athletes reported pain was the dominant shoulder (6 of 14 athletes), followed by the dominant knee, the dominant elbow, the dominant ankle joint, and the non-dominant ankle joint (3 of 14 athletes). The path analysis revealed that pain in the dominant elbow negatively correlated with concentration (standardized path coefficient = -0.644, p = 0.00), which was associated with satisfaction with body movement (standardized path coefficient = 0.704, p = 0.00). No significant effect of body pain on objective performance (heart rate and body acceleration) was found among the athletes in this study. The results suggested that the elite athletes were practicing with pain. Even if pain does not physically affect athletes' objective performance, pain in the upper extremities, associated with the primary handball movement of throwing, may reduce the quality of practice by lowering athletes' subjective performance.

Decreased moment of inertia of the lower limb facilitates a rapid hip internal rotation in a simulated foot impact maneuver. A laboratory-controlled biomechanical study for a precursor mechanism of noncontact anterior cruciate ligament injury.

BACKGROUND: Anterior cruciate ligament injury frequently occurs in the deceleration with the knee-extended position. In addition, a rapid hip internal rotation is concomitantly observed. However, how the extended knee position induces the hip internal rotation is unclear. METHODS: Sixteen healthy participants performed the simulated foot impact task on the experimental chair. To vary the knee flexion angle, the following four-foot placement positions relative to the pelvis segment, i.e.: 1) near; 2) middle; 3) far; and 4) far + heel strike, were tested. The reflective marker positions and the ground reaction force (GRF) data were collected. The moment of inertia of the entire lower limb around its long axis as well as the peak hip internal rotation angular velocity were calculated and compared among four conditions (Wilcoxon Signed-Rank Test with Bonferroni correction, P<0.0083). RESULTS: As the knee extended from the near to far + heel strike condition, the moment of inertia of the entire lower limb significantly decreased and hip internal rotation angular velocity significantly increased (P<0.001). CONCLUSIONS: The extended knee position with far foot placement from torso reduces the inertial resistance of the entire lower limb around its long axis and is vulnerable to the hip internal rotation.

Leaf spring exercise: A safe quadriceps strengthening exercise after anterior cruciate ligament reconstruction.

BACKGROUND: Leg extensions should be avoided in the early stages after anterior cruciate ligament reconstruction because the force exerted by the quadriceps muscle leads to anterior tibial displacement. To allow for safe quadriceps training in the knee extension range during this period, we devised the leaf spring exercise, which involves placing subjects in the prone position with their knee slightly flexed and instructing them to perform maximum isometric quadriceps contractions while supporting the proximal region of the lower leg's anterior surface and immobilizing the femur's posterior surface to prevent lifting. The current study aimed to examine the safety of Leaf spring exercise by determining the femur-tibia relationship using ultrasound imaging. METHODS: This controlled laboratory study included patients with unilateral anterior cruciate ligament-deficient knees (8 men and 8 women; age, 24.2 ± 8.3 years) who were instructed to perform Leaf spring exercise of both lower limbs. We measured the femur-tibia-step-off, which indicates the distance between the last point of the medial and lateral condyles of the femur and posterior margin of the tibial plateau, as a parameter to evaluate anterior tibial displacement via ultrasound diagnostic device. Further, peak torque of the quadriceps muscle was calculated using force measurement device. FINDINGS: No difference in anterior tibial displacement and peak torque was observed between the uninjured and injured sides during Leaf spring exercise. INTERPRETATION: Leaf spring exercise may add some strain on the reconstructed anterior cruciate ligament; hence, it can be considered a safe quadriceps exercise in the knee extension range.

Absorption function loss due to the history of previous ankle sprain explored by unsupervised machine learning.

BACKGROUND: Ankle sprains are common and cause persistent ankle function reduction. To biomechanically evaluate the ankle function after ankle sprains, the ground reaction force (GRF) measurement during the single-legged landing had been used. However, previous studies focused on discrete features of vertical GRF (vGRF), which largely ignored vGRF waveform features that could better identify the ankle function. PURPOSE: To identify how the history of ankle sprain affect the vGRF waveform during the single-legged landing with unsupervised machine learning considering the time-series information of vGRF. METHODS: Eighty-seven currently healthy basketball athletes (12 athletes without ankle sprain, 49 athletes with bilateral, and 26 athletes with unilateral ankle sprain more than 6 months before the test day) performed single-legged landings from a 20 centimeters (cm) high box onto the force platform. Totally 518 trials vGRF data were collected from 87 athletes of 174 ankles, including 259 ankle sprain trials (from previous sprain ankles) and 259 non-ankle sprain trials (from without sprain ankles). The first 100 milliseconds (ms) vGRF waveforms after landing were extracted. Principal component analysis (PCA) was applied to the vGRF data, selecting 8 principal components (PCs) representing 96% of the information. Based on these 8 PCs, k-means method (k = 3) clustered the 518 trials into three clusters. Chi-square test assessed significant differences (p < 0.01) in the distribution of ankle sprain and non-ankle sprain trials among clusters. FINDINGS: The ankle sprain trials accounted for a significantly larger percentage (63.9%) in Cluster 3, which exhibited rapidly increased impulse vGRF waveforms with larger peaks in a short time. SIGNIFICANCE: PCA and k-means method for vGRF waveforms during single-legged landing identified that the history of previous ankle sprains caused a loss of ankle absorption ability lasting at least 6 months from an ankle sprain.

Characteristics of physical activity during beginner-level group tennis lessons and the effect daily activity.

Tennis is a popular leisure sport, and studies have indicated that playing tennis regularly provides many health benefits. We aimed to clarify the characteristics of physical activity during beginner-level group tennis lessons and daily physical activity of the participants. Physical activity was measured using an accelerometer sensor device for four weeks, including the 80-min duration tennis lessons held twice a week. Valid data were categorized for tennis and non-tennis days. The mean physical activity intensity during the tennis lesson was 3.37 METs. The mean ratio of short-bout rest periods to the tennis lesson time in 90 and 120 s was 7% and 4%, respectively. The mean physical activity intensity was significantly higher (p < 0.0001) and the duration of vigorous-intensity physical activity (VPA) was increased in 76% of participants on days with tennis lessons compared to without tennis lessons. Beginner-level tennis lesson has characteristics of less short-bout rest physical activity than previously reported competitive tennis match and increased the duration of VPA in daily activity compared to without tennis lessons, suggesting that beginner-level tennis lessons contribute physical activity of health benefits.

The deterministic condition for the ground reaction force acting point on the combined knee valgus and tibial internal rotation moments in early phase of cutting maneuvers in female athletes.

BACKGROUND: Combined knee valgus and tibial internal rotation (VL + IR) moments have been shown to stress the anterior cruciate ligament (ACL) in several in vitro cadaveric studies. To utilize this knowledge for non-contact ACL injury prevention in sports, it is necessary to elucidate how the ground reaction force (GRF) acting point (center of pressure (CoP)) in the stance foot produces combined knee VL + IR moments in risky maneuvers, such as cuttings. However, the effects of the GRF acting point on the development of the combined knee VL + IR moment in cutting are still unknown. METHODS: We first established the deterministic mechanical condition that the CoP position relative to the tibial rotational axis differentiates the GRF vector's directional probability for developing the combined knee VL + IR moment, and theoretically predicted that when the CoP is posterior to the tibial rotational axis, the GRF vector is more likely to produce the combined knee VL + IR moment than when the CoP is anterior to the tibial rotational axis. Then, we tested a stochastic aspect of our theory in a lab-controlled in vivo experiment. Fourteen females performed 60° cutting under forefoot/rearfoot strike conditions (10 trials each). The positions of lower limb markers and GRF data were measured, and the knee moment due to GRF vector was calculated. The trials were divided into anterior- and posterior-CoP groups depending on the CoP position relative to the tibial rotational axis at each 10 ms interval from 0 to 100 ms after foot strike, and the occurrence rate of the combined knee VL + IR moment was compared between trial groups. RESULTS: The posterior-CoP group showed significantly higher occurrence rates of the combined knee VL + IR moment (maximum of 82.8%) at every time point than those of the anterior-CoP trials, as theoretically predicted by the deterministic mechanical condition. CONCLUSION: The rearfoot strikes inducing the posterior CoP should be avoided to reduce the risk of non-contact ACL injury associated with the combined knee VL + IR stress.

Individual Variation in Adaptive Ability of the Anticipated Postural Stability During a Dual-Task Single-Leg Landing in Female Athletes.

Background: Precise postural control helps prevent anterior cruciate ligament injury. However, it is unknown whether the anticipated postural stability can be improved during a physically uncertain and cognitively demanding task. Hypothesis: Anticipated postural stability will improve through unanticipated single-leg landing with a rapid foot placement target tracking. Study Design: Controlled laboratory study. Methods: A total of 22 healthy female university-level athletes performed a novel dual-task paradigm: an unanticipated single-leg landing with foot placement target tracking. In the normal condition (60 trials), the participants jumped from a 20 cm-high box onto the landing target with their dominant leg as softly as possible. In the subsequent perturbation condition (PC) (60 trials), the initially assigned landing target was abruptly switched randomly, requiring participants to modify their preplanned foot placement position to the newly assigned position. The center-of-pressure trajectory length within the first 100 ms after foot impact (CoP100) was calculated as a measure of anticipated postural stability for each trial. In addition, the peak vertical ground-reaction force (FzPeak) was quantified to assess landing load, and the degree of postural adaptation during PC was quantified by fitting an exponential function to trial-by-trial changes in CoP100. Participants were divided into 2 groups according to increase or decrease in CoP100, and results were compared between the groups. Results: The direction and magnitude of postural sway alterations of the 22 participants showed a spectrum-like variation during the repeated trials. Twelve participants (sway-decreased group) exhibited a gradual reduction in postural sway (CoP100) during the PC, while the remaining 10 participants (sway-increased group) showed a gradual increase in CoP100. The FzPeak during the PC was significantly less in the sway-decreased group compared with the sway-increased group (P < .05). Conclusion: Variation in the direction and magnitude of postural sway alteration among participants suggested that there was individual variation in an athlete's adaptive ability of the anticipated postural stability. Clinical Relevance: The novel dual-task paradigm described in this study may be useful for rating individual injury risk based on an athlete's postural adaptation ability and may aid in targeted prevention strategies.

Gaussian mixture modeling of acceleration-derived signal for monitoring external physical load of tennis player.

Introduction: With the widespread use of wearable sensors, various methods to evaluate external physical loads using acceleration signals measured by inertial sensors in sporting activities have been proposed. Acceleration-derived external physical loads have been evaluated as a simple indicator, such as the mean or cumulative values of the target interval. However, such a conventional simplified indicator may not adequately represent the features of the external physical load in sporting activities involving various movement intensities. Therefore, we propose a method to evaluate the external physical load of tennis player based on the histogram of acceleration-derived signal obtained from wearable inertial sensors. Methods: Twenty-eight matches of 14 male collegiate players and 55 matches of 55 male middle-aged players wore sportswear-type wearable sensors during official tennis matches. The norm of the three-dimensional acceleration signal measured using the wearable sensor was smoothed, and the rest period (less than 0.3 G of at least 5 s) was excluded. Because the histogram of the processed acceleration signal showed a bimodal distribution, for example, high- and low-intensity peaks, a Gaussian mixture model was fitted to the histogram, and the model parameters were obtained to characterize the bimodal distribution of the acceleration signal for each player. Results: Among the obtained Gaussian mixture model parameters, the linear discrimination analysis revealed that the mean and standard deviation of the high-intensity side acceleration value accurately classified collegiate and middle-aged players with 93% accuracy; however, the conventional method (only the overall mean) showed less accurate classification results (63%). Conclusion: The mean and standard deviation of the high-intensity side extracted by the Gaussian mixture modeling is found to be the effective parameter representing the external physical load of tennis players. The histogram-based feature extraction of the acceleration-derived signal that exhibit multimodal distribution may provide a novel insight into monitoring external physical load in other sporting activities.

Exploring pre-impact landing kinematics associated with increase and decrease in the anterior cruciate ligament injury risk.

This study aimed to explore the single-legged landing kinematics that could lead to increase or decrease in the risk of anterior cruciate ligament (ACL) injury. Immediate pre-impact kinematics at the single-legged landing from 33 healthy young female handball players were evaluated. Thereafter, two-year follow-up for ACL injury incidence was conducted, in which six new ACL injuries in non-dominant leg were registered. The evaluation of pre-impact kinematics across participants was performed first by the principal component analysis to decompose them into the kinematic components (KCs), and then by the linear discrimination analysis (LDA) for a set of KC-scores to obtain important KCs for discriminating injured and non-injured legs. The result of LDA showed that the combination of second major KC (knee flexion/extension angle and angular velocity) and some minor KCs such as torso medial/lateral leaning accurately discriminated the injured and non-injured legs with the error rate of 12.5%. To examine the mechanisms of this discriminative ability, we generated hypothetical pre-impact kinematics in the subspaces spanned by eigenvectors of multiple KCs, and examined relationships between pre-impact kinematics and the corresponding knee valgus torque predicted by the motion-equation-based model. The result showed that the second major KC and the minor KCs representing torso medial/lateral leaning and/or hip adduction/abduction angle, which contributed in LDA to discriminating injured legs, also significantly affected the frontal-plane knee loading patterns. These findings suggested that KC-based postural characterization of the pre-impact landing kinematics and the motion-equation-based knee stress quantification possibly explain the future ACL injury risks of female athletes.

The counteracting effect of the friction moment against the tibial rotational moment driven by the ground reaction force in an early stance phase of cutting maneuver among healthy male athletes.

The ground reaction force (GRF) is known to produce tibial internal rotation loading associated with the stress in the anterior cruciate ligament (ACL). However, it is unclear whether the friction moment (FM; the moment due to horizontal shoe-floor friction, acting around the vertical axis at the GRF acting point) facilitates or restrains the effect of GRF-driven tibial rotation loading during cutting. The 45° cutting motions with forefoot/rearfoot strikes were captured simultaneously with GRF and FM data from 23 healthy males. The FM- and GRF-driven tibial rotation moments were calculated. Time-series correlation between FM- and GRF-driven tibial rotation moments and the orientation relationship among those moment vectors was investigated. The FM-driven tibial rotation moment negatively correlated with the GRF-driven one within the first 10% of stance phase. The peak regression slope value was -0.34 [SD 0.33] for forefoot and -1.64 [SD 1.76] for rearfoot strikes, showing significant difference from zero (SPM one-sample t-test, p<0.05). The FM-driven tibial "external" rotation moment counteracted the GRF-driven tibial "internal" rotation moment within first 10% of the stance phase in most trials, suggesting that the FM-driven tibial rotation moment potentially diminishes the effect of GRF-driven one and may reduce ACL injury risk during cutting.

An Experimental Feasibility Study Evaluating the Adequacy of a Sportswear-Type Wearable for Recording Exercise Intensity.

Sportswear-type wearables with integrated inertial sensors and electrocardiogram (ECG) electrodes have been commercially developed. We evaluated the feasibility of using a sportswear-type wearable with integrated inertial sensors and electrocardiogram (ECG) electrodes for evaluating exercise intensity within a controlled laboratory setting. Six male college athletes were asked to wear a sportswear-type wearable while performing a treadmill test that reached up to 20 km/h. The magnitude of the filtered tri-axial acceleration signal, recorded by the inertial sensor, was used to calculate the acceleration index. The R-R intervals of the ECG were used to determine heart rate; the external validity of the heart rate was then evaluated according to oxygen uptake, which is the gold standard for physiological exercise intensity. Single regression analysis between treadmill speed and the acceleration index in each participant showed that the slope of the regression line was significantly greater than zero with a high coefficient of determination (walking, 0.95; jogging, 0.96; running, 0.90). Another single regression analysis between heart rate and oxygen uptake showed that the slope of the regression line was significantly greater than zero, with a high coefficient of determination (0.96). Together, these results indicate that the sportswear-type wearable evaluated in this study is a feasible technology for evaluating physical and physiological exercise intensity across a wide range of physical activities and sport performances.

Effect of the foot-strike pattern on the sagittal plane knee kinetics and kinematics during the early phase of cutting movements.

Anterior cruciate ligament (ACL) injury occurs soon after foot-strike. Cutting with a shallow flexed knee is considered a risk factor for ACL injury; however, how foot-strike patterns (forefoot strike [FFS] vs. rearfoot strike [RFS]) affect sagittal plane knee kinetics and kinematics after a foot-strike, is unknown. This study aimed to investigate the effect of foot-strike patterns on the sagittal plane knee kinetics and kinematics during cutting. Twenty-three males performed 45° cutting under RFS and FFS conditions. The marker position data on the lower limb, and the ground reaction force (GRF) data were collected and time-normalized (0-100%) during the stance phase. The knee flexion angle, shank and GRF vector inclination angle relative to the global vertical axis, knee flexion/extension moment, and anterior/posterior component of GRF relative to the shank segment were calculated and compared between foot-strike patterns using statistical parametric mapping paired t-test (p < 0.0071). The knee flexion angle was smaller in RFS than in FFS in the initial 40% of the stance phase. In the RFS condition, the GRF vector was directed anteriorly to the shank segment, and the knee extension moment was produced by GRF in 0-7% of the stance phase, while these results were not observed in the FFS condition. These results suggest that compared to FFS, RFS induces a shallow flexed knee with an anterior-directed GRF component in the early stance phase and might potentially provoke a risk of ACL injury.

Meniscal Displacement and Loss of Load-Transmission Function After Radial Tear of the Lateral Meniscus in a Porcine Model: New Insights Into the Functional Dynamics of the Injured Meniscus.

BACKGROUND: Meniscal extrusion/translation has been used as an index for meniscal treatment. However, the relationship between meniscal displacement and the degree of meniscal tear or load-transmission function of the lateral meniscus (LM) remains unclear. PURPOSE: To clarify the relationship between the width of the radial tear of the LM and (1) meniscal displacement or (2) resultant force through the meniscus under axial compressive load in the porcine model. STUDY DESIGN: Controlled laboratory study. METHODS: Eight intact porcine knees with or without a partial radial tear at the midbody of the LM (involving 30%, 60%, or 90% of its width) were investigated. Reflective markers were attached to the outer wall of the anterior, anteromiddle, posteromiddle, and posterior segments of the LM. A 300-N axial load was applied at 2 flexion angles (30° and 60°), and the 3-dimensional forces and trajectories of the knees were recorded. Marker movements were simultaneously tracked using a motion capture camera system. After total meniscectomy of the LM, the recorded knee trajectories were reproduced, and the resultant force through the LM was calculated (a force carried only by the meniscus in response to a load applied to the whole knee joint). RESULTS: At both flexion angles, the change in distance (mean ± SD) between the anterior and posterior markers under load increased significantly more in the anteroposterior direction in LMs with a 90% tear than in intact LMs (30°, 0.4 ± 0.3 vs 1.4 ± 0.8 mm, P = .004; 60°, 0.1 ± 0.7 vs 1.4 ± 1.0 mm, P < .001 [intact vs 90% tear]). The change in distance between the anteromiddle and posteromiddle markers at 30° also significantly increased in LMs with a 90% tear (0.2 ± 0.2 vs 1.3 ± 1.2 mm, P = .02 [intact vs 90% tear]). The resultant force was significantly lower in LMs with a 90% tear than in intact LMs (30°, 125 ± 47 vs 48 ± 20 N, P < .001; 60°, 93 ± 46 vs 43 ± 11 N, P = .002 [intact vs 90% tear]). We found no significant differences in either meniscal displacements or resultant forces between intact LMs and those with 30% or 60% tears. CONCLUSION: LMs with a 90%-width midbody radial tear lost load-transmission function with their displacement relative to the tibia primarily in the anteroposterior direction in the porcine model. CLINICAL RELEVANCE: Even 1 mm of displacement after meniscal injury is evidence that the load-transmission function of the meniscus is greatly impaired. When a displaced torn LM is diagnosed in preoperative imaging, meniscal repair surgery should be considered.

Variability in Physical Inactivity Responses of University Students during COVID-19 Pandemic: A Monitoring of Daily Step Counts Using a Smartphone Application.

This study investigated the changes in physical inactivity of university students during the COVID-19 pandemic, with reference to their academic calendar. We used the daily step counts recorded by a smartphone application (iPhone Health App) from April 2020 to January 2021 (287 days) for 603 participants. The data for 287 days were divided into five periods based on their academic calendar. The median value of daily step counts across each period was calculated. A k-means clustering analysis was performed to classify the 603 participants into subgroups to demonstrate the variability in the physical inactivity responses. The median daily step counts, with a 7-day moving average, dramatically decreased from 5000 to 2000 steps/day in early April. It remained at a lower level (less than 2000 steps/day) during the first semester, then increased to more than 5000 steps/day at the start of summer vacation. The clustering analysis demonstrated the variability in physical inactivity responses. The inactive students did not recover daily step counts throughout the year. Consequently, promoting physical activity is recommended for inactive university students over the course of the whole semester.

Validity of Spatio-Temporal Gait Parameters in Healthy Young Adults Using a Motion-Sensor-Based Gait Analysis System (ORPHE ANALYTICS) during Walking and Running.

Motion sensors are widely used for gait analysis. The validity of commercial gait analysis systems is of great interest because calculating position/angle-level gait parameters potentially produces an error in the integration process of the motion sensor data; moreover, the validity of ORPHE ANALYTICS, a motion-sensor-based gait analysis system, has not yet been examined. We examined the validity of the gait parameters calculated using ORPHE ANALYTICS relative to those calculated using conventional optical motion capture. Nine young adults performed gait tasks on a treadmill at speeds of 2−12 km/h. The three-dimensional position data and acceleration and angular velocity data of the feet were collected. The gait parameters were calculated from motion sensor data using ORPHE ANALYTICS, and optical motion capture data. Intraclass correlation coefficients [ICC(2,1)] were calculated for relative validities. Eight items, namely, stride duration, stride length, stride frequency, stride speed, vertical height, stance phase duration, swing phase duration, and sagittal angleIC exhibited excellent relative validities [ICC(2,1) > 0.9]. In contrast, sagittal angleTO and frontal angleIC demonstrated good [ICC(2,1) = 0.892−0.833] and moderate relative validity [ICC(2,1) = 0.566−0.627], respectively. ORPHE ANALYTICS was found to exhibit excellent relative validities for most gait parameters. These results suggest its feasibility for gait analysis outside the laboratory setting.

Measurement of various intensities of physical activities and categorization of "Locomotive" and "Household" activities provide a subject-specific detailed assessment.

This study aimed to compare the physical activity (PA) measured by a wearable sensor device (WSD) and the step count measurement, and to investigate the association between PAs and lifestyle. Data of 301 participants were collected from March 2019 to March 2021. Step counts, sedentary behavior, performance time of light/moderate/vigorous PA, METs × hour of "Locomotive" and "Household" categorized activities, and energy expenditure (EE) were measured by the WSD, respectively. Furthermore, the participants were classified into student, standing worker, and sitting worker groups. Data were analyzed using the Steel-Dwass and Pearson correlation coefficient tests. The correlation between the performance time of each PA and step count was weak, except for moderate PA. "Household" EE and step count also had a weak correlation. In the comparison of lifestyle, there was a significant difference in the mean performance time of each type of PA between the groups. Additionally, the standing worker and sitting worker groups had a significant difference in METs × hour of "Household" activities, indicating that the difference between the occupations is reflected in "Household" activities. The WSD measurement can be used to evaluate detailed individual PA, whereas the step count measurement showed weakness in the PA estimation.

Placement of sutures for inside-out meniscal repair: both sutures through meniscal tissue reduces displacement on cyclical loading.

PURPOSE: The inside-out meniscal repair is widely performed to preserve the function of meniscus. In this technique, the outer suture is passed through the capsule as well as the outer meniscus, while the inner suture is inserted into the meniscus. The aim of this study was to biomechanically compare the suture stability between meniscus-meniscus and meniscus-capsule suture methods for the longitudinal meniscal tear with inside-out technique. METHODS: Twenty-seven porcine knees were dissected to maintain the femur-medial capsule/meniscus-tibia complex, and the inner meniscus was cut off along the meniscus circumferential fiber with 3 mm width of the peripheral meniscus preserved. After one needle with a 2-0 polyester suture was inserted into the inner portion of the meniscus, the other needle was inserted through 1) the peripheral meniscus (Group A), 2) capsule just above the meniscus (Group B), and 3) capsule at 10 mm apart from the meniscus-capsule junction (Group C) in the inside-out manner. Then, the suture was manually tied on the capsule. The suture gap at the repair site during 300 times of cyclic loading and the ultimate failure load in the load-to-failure test were measured. The statistical significance of the data between two groups in each combination was considered by Bonferroni correction, following a one-way analysis of variance. RESULTS: In the cyclic loading test, the suture gap was 0.68 ± 0.26 mm in Group A, 1.08 ± 0.36 mm in Group B, and 1.94 ± 0.57 mm in Group C with a significant difference. In the load-to-failure test, the ultimate failure load was 59.1 ± 13.6 N in Group A, 60.0 ± 7.9 N in Group B, and 57.4 ± 4.7 N in Group C, and there was no significant difference. CONCLUSION: The stitching region in the inside-out technique for longitudinal meniscal tear affected the stability of the tear site, and stitching the mid-substance region of the meniscus provides good stability in response to cyclic tensile loading. In addition, the stitching region did not affect the ultimate failure load. CLINICAL RELEVANCE: In the inside-out meniscal repair, the outer suture should be inserted into the remaining peripheral meniscus or the capsule near the meniscus.

Effect of Rearfoot Strikes on the Hip and Knee Rotational Kinetic Chain During the Early Phase of Cutting in Female Athletes.

BACKGROUND: Biomechanical factors affecting horizontal-plane hip and knee kinetic chain and anterior cruciate ligament (ACL) injury risk during cutting maneuvers remain unclear. This study aimed to examine whether different foot strike patterns alter horizontal-plane hip and knee kinetics and kinematics during a cutting maneuver in female athletes and clarify the individual force contribution for producing high-risk hip and knee loadings. Twenty-five healthy female athletes performed a 60° cutting task with forefoot and rearfoot first strike conditions. Horizontal-plane hip and knee moment components, angles, and angular velocities were calculated using synchronized data of the marker positions on the body landmarks and ground reaction forces (GRFs) during the task. The one-dimensional statistical parametric mapping paired t test was used to identify the significant difference in kinetic and kinematic time-series data between foot strike conditions. RESULTS: In the rearfoot strike condition, large hip and knee internal rotation loadings were produced during the first 5% of stance due to the application of GRFs, causing a significantly larger hip internal rotation excursion than that of the forefoot strike condition. Dissimilarly, neither initial hip internal rotation displacement nor knee internal rotation GRF loadings were observed in the forefoot strike condition. CONCLUSIONS: Rearfoot strike during cutting appears to increase noncontact ACL injury risk as the GRF tends to produce combined hip and knee internal rotation moments and the high-risk lower limb configuration. Conversely, forefoot strike during cutting appears to be an ACL-protective strategy that does not tend to produce the ACL-harmful joint loadings and lower extremity configurations. Thus, improving foot strike patterns during cutting should be incorporated in ACL injury prevention programs.