Application of the joint coordinate system to three-dimensional joint attitude and movement representation: a standardization proposal

Residual kinematic deviations of the shoulder during humeral elevation after conservative treatment for mid-shaft clavicle fractures

Despite residual functional deficits clinically observed in conservatively treated mid-shaft clavicle fractures, no study has reported a quantitative assessment of the treatment effects on the kinematics of the shoulder complex during functional movement. Using computerised motion analysis, the current study quantified the 3D residual kinematic deviations or strategies of the shoulder complex bones during multi-plane elevations in fifteen patients with conservatively treated mid-shaft clavicle fractures and fifteen healthy controls. Despite residual clavicular malunion, the patients recovered normal shoulder kinematics for arm elevations up to 60° in all three tested planes. For elevations beyond 60°, normal clavicle kinematics but significantly increased scapular posterior tilt relative to the trunk was observed in the patient group, leading to significantly increased clavicular protraction and posterior tilt relative to the scapula (i.e., AC joint). Slightly different changes were found in the sagittal plane, showing additional changes of increased scapular upward rotations at 90° and 120° elevations. Similar kinematic changes were also found on the unaffected side, indicating a trend of symmetrical bilateral adaptation. The current results suggest that shoulder kinematics in multi-plane arm elevations should be monitored for any compromised integrated motions of the individual bones following conservative treatment. Rehabilitation strategies, including muscle strengthening and synergy stability training, should also consider compensatory kinematic changes on the unaffected side to improve the bilateral movement control of the shoulder complex during humeral elevation.

Hop Distance Symmetry Moderately Reflects Knee Biomechanics Symmetry During Landing But Not For Controlled Propulsions

Background

Landing with poor knee sagittal plane biomechanics has been identified as a risk factor for Anterior Cruciate Ligament (ACL) injury. However, it is unclear if the horizontal hop test battery reflects knee function and biomechanics.

Hypothesis/Purpose

To investigate the correlation between clinical limb symmetry index (LSI) and landing and propulsion knee biomechanics during the hop test battery using markerless motion capture.

Study Design

Cross-sectional biomechanics laboratory study.

Methods

Forty-two participants with and without knee surgery (age 28.0 ± 8.0 years) performed the hop test battery which consisted of a single hop for distance, crossover hop, triple hop, and 6-m timed hop in the order listed. Eight high speed cameras were used to collect simultaneous 3D motion data and Theia 3D (Theia Markerless Inc.) was used to generate 3D body model files. Lower limb joint kinematics were calculated in Visual3D. Correlation (Spearman's ρ) was computed between clinical LSI and symmetry in peak and initial contact (IC) knee flexion angle during propulsion and landing phases of each movement.

Results

In the single hop, clinical LSI showed positive correlation with kinematic LSI at peak landing (ρ= 0.39, p=0.011), but no correlation at peak propulsion (ρ= -0.03, p=0.851). In the crossover hop, non-significant correlations were found in both propulsion and landing. In the triple hop, positive correlation was found at peak propulsion (ρ= 0.38, p=0.027), peak landing (ρ= 0.48 - 0.66, p<0.001), and last landing IC (ρ= 0.45, p=0.009). In the timed hop, peak propulsion showed positive correlation (ρ= 0.51, p=0.003).

Conclusions

Single hop and triple hop distance symmetry reflected landing biomechanical symmetry better than propulsion symmetry. Poor scores on the hop test battery reflect asymmetrical knee landing biomechanics, emphasizing the importance of continuing to use the hop test battery as part of clinical decision making.

Level of Evidence

3b.

Females with hip pain walk with altered kinematics at peaks and throughout the gait cycle

BACKGROUND

Females with acetabular dysplasia and/or labral tears (hip pain) exhibit altered walking kinematics, with studies reporting mixed results in sagittal and frontal planes compared to pain-free controls, often conducting only discrete analyses and warranting further investigation. The objective of this study was to investigate discrete and continuous hip and pelvic kinematics between females with and without hip pain in two walking conditions.

METHODS

We collected kinematic walking data from 69 females (35 with hip pain, 34 controls) using motion capture and an instrumented treadmill in two conditions: preferred and fast (125% preferred). We used a general linear model and one-dimensional statistical parametric mapping to conduct discrete and continuous analyses comparing kinematics between groups, with and without adjustment for gait speed.

FINDINGS

The hip pain group walked with reduced peak hip extension (Preferred: P = .046, Cohen's d = 0.41; Fast: P = .028, d = 0.48) and greater peak anterior pelvic tilt (Preferred: P = .011, d = 0.57; Fast: P = .012, d = 0.58) compared to controls. From continuous analyses, the hip pain group walked with reduced hip extension during terminal stance (Fast: P = .040), greater anterior pelvic tilt throughout (Preferred: P = .007; Fast: P = .004), and greater contralateral pelvic drop (Preferred: P = .045) during midstance. Adjusting for speed slightly affected p-values, but significance was retained for all prior variables except pelvic drop.

INTERPRETATION

Kinematic differences between individuals with and without hip pain may provide insight into potential predisposing factors for hip pathology and/or compensations for pain or pathological processes. This work furthers understanding of altered movement patterns in individuals with hip pain and may inform physical therapy treatments.

Unraveling stroke gait deviations with movement analytics, more than meets the eye: a case control study

Background

This study aimed to identify and quantify the kinematic and kinetic gait deviations in post-stroke hemiplegic patients with matched healthy controls using Statistical Parametric Mapping (SPM).

Methods

Fifteen chronic stroke patients [4 females, 11 males; age 53.7 (standard deviation 12.2) years; body mass 65.4 (10.4) kg; standing height 168.5 (9.6) cm] and 15 matched healthy controls [4 females, 11 males; age 52.9 (11.7) years; body weight 66.5 (10.7) years; standing height 168.3 (8.8) cm] were recruited. In a 10-m walking task, joint angles, ground reaction forces (GRF), and joint moments were collected, analyzed, and compared using SPM for an entire gait cycle.

Results

Generally, when comparing the stroke patients' affected (hemiplegic) and less-affected (contralateral) limbs with the control group, SPM identified significant differences in the late stance phase and early swing phase in the joint angles and moments in bilateral limbs (all p < 0.005). In addition, the vertical and anteroposterior components of GRF were significantly different in various periods of the stance phase (all p < 0.005), while the mediolateral component showed no differences between the two groups.

Conclusion

SPM was able to detect abnormal gait patterns in both the affected and less-affected limbs of stroke patients with significant differences when compared with matched controls. The findings draw attention to significant quantifiable gait deviations in the less-affected post-stroke limb with the potential impact to inform gait retraining strategies for clinicians and physiotherapists.

Gait analysis of individuals with specific low back pain undergoing surgery: case series report with one and six-month follow-up

INTRODUCTION

In addition to pain, specific low back pain is frequently accompanied by restricted range of motion (ROM) during gait.

PURPOSE

To compare the behavior of kinematic and spatiotemporal gait parameters, pain, functional status, and self-efficacy, in patients with a diagnosis of herniated disk or lumbar stenosis undergoing surgery, in the pre- and postoperative periods of 1 and 6 months (PO6).

METHODS

Seven participants and 11 control subjects were assessed. A kinematics system comprising 10 optoelectronic cameras was used to assess gait. The Roland-Morris questionnaire, pain intensity, and self-efficacy, over three periods, were used.

RESULTS

The ROM of the pelvis, hip, and knee of the hernia group presented an increase after surgery and the stenosis group presented a reduction of values in the hip. During the stance phase, the pelvis and hip ROM of both groups remained smaller than the control group. There was improvement in pain in individuals with hernia and stenosis (effect size = 0.6 and 0.8, respectively) in the three analyzed moments; for functional status there was improvement in the first postoperative period (ES = 0.4) compared to the preoperative in those individuals with hernia; and those with stenosis had improvement at PO6 when compared to the time before the surgery (ES = 0.2).

CONCLUSION

Surgical intervention modifies the spatiotemporal parameters, the ROM of the pelvis, hip, and knee in the total gait cycle, primarily in the sagittal plane, and causes alterations, particularly in the hip joint, in these individuals during the support phase.

[Scientific methods for in-vitro investigations in the field of joint kinematics : Cluster experimental joint kinematics]

In vitro studies are an established method to determine joint kinematics for answering preclinical questions regarding the effects of new treatment options, surgical techniques or implant designs. The lack of standardized, interdisciplinary representation in the determination of joint kinematics poses a problem. In addition to representation forms such as the "neutral-zero method" or the description of movements within the three basic planes, there are other mathematical joint-specific representations of individual working groups. The International Society of Biomechanics (ISB) has already made recommendations for standardization, but most of these cannot be implemented in biomechanical in-vitro studies. The cluster has therefore set itself the goal of standardizing in-vitro test methods in order to achieve better comparability of scientific results from different working groups.

Strategies for knee stabilising and pivot-shift avoidance in a step-down and cross-over task observed sub-acutely after anterior cruciate ligament reconstruction

BACKGROUND

Individuals with a recent anterior cruciate ligament reconstruction may demonstrate an altered movement strategy for protecting the knee and maintaining stability. Altered knee movement might lead to abnormal intra-articular load, potentially contributing to early knee osteoarthritis onset. A protective strategy may be particularly evident during active tasks that induce a pivot-shift manoeuvre, such as a step-down and cross-over task. In this study, we investigated whether knee joint mechanics and muscle activity differed between participants early (∼3 months) following reconstruction (n = 35) to uninjured controls (n = 35) during a step-down and cross-over task with a 45° change-of-direction.

METHODS

We used motion capture, force plates and surface electromyography to compare time-normalised curves of sagittal and transverse-plane knee mechanics and muscle activity during the cross-over phase between groups using functional t-tests. We also compared knee mechanics between sides within the injured group and compared discrete outcomes describing the cross-over phase between groups.

FINDINGS

Compared to controls, the injured participants had greater knee flexion angle and moment, lower internal rotation moment, more preparatory foot rotation of the pivoting leg, a smaller cross-over angle, and a longer cross-over phase for both the injured and uninjured sides. The injured leg also had greater biceps femoris and vastus medialis muscle activity compared to controls and different knee mechanics than the uninjured leg.

INTERPRETATION

Individuals with anterior cruciate ligament reconstruction showed a knee-stabilising and pivot-shift avoidance strategy for both legs early in rehabilitation. These results may reflect an altered motor representation and motivate considerations early in rehabilitation.

Spatiotemporal lower-limb asymmetries during stair descent in athletes following anterior cruciate ligament reconstruction

PURPOSE

This study evaluated motor control recovery at different times following anterior cruciate ligament reconstruction (ACLR) by investigating lower-limb spatiotemporal symmetry during stair descent performances.

METHODS

We used a cross-sectional design to compare asymptomatic athletes (Controls, n = 18) with a group of people with ACLR (n = 49) divided into three time-from-ACLR subgroups (Early: <6 months, n = 17; Mid: 6-18 months, n = 16; Late: ≥18 months, n = 16). We evaluated: "temporal symmetry" during the stance subphases (single-support, first and second double-support) and "spatial symmetry" for hip-knee-ankle intra-joint angular displacements during the stance phase using a dissimilarity index applied on superimposed 3D phase plots.

RESULTS

We found significant between-group differences in temporal variables (p ≤ 0.001). Compared to Controls, both Early and Mid (p ≤ 0.05) showed asymmetry in the first double-support time (longer for their injured vs. non-injured leg), while Early generally also showed longer durations in all other phases, regardless of stepping leg. No statistically significant differences were found for spatial intra-joint symmetry between groups.

CONCLUSION

Temporal but not spatial asymmetry in stair descent is often present early after ACLR; it may remain for up to 18 months and may underlie subtle intra- and inter-joint compensations. Spatial asymmetry may need further exploration.

In-vitro external fixation pin-site model proof of concept: A novel approach to studying wound healing in transcutaneous implants

External fixation is an essential surgical technique for treating trauma, limb lengthening and deformity correction, however infection is common, with infection rates ranging from 4.5 to 100% of cases. Throughout the literature researchers and clinicians have highlighted a relationship between excessive movement of the pin and skin and an increase in the patient's risk of infection, however, currently no studies have addressed this role of pin-movement on pin-site wounds. This preliminary study describes a novel in vitro pin-site model, developed using a full-thickness human skin equivalent (HSE) model in conjunction with a bespoke mechanical system which simulates pin-movement. The effect of pin-movement on the wound healing response of the skin equivalents was assessed by measuring the expression of pro-inflammatory cytokines. Six human skin equivalent models were divided into three test groups: no pin as the control, static pin-site wound and dynamic pin-site wound (n = 3). On day 3 concentrations of IL-1α and IL-8 showed a significant increase compared to the control when a static fixation pin was implanted into the skin equivalent (p < 0.05) and (p < 0.005) respectively. Levels of IL-1α and IL-8 increased further in the dynamic sample compared to the static sample (p < 0.05) and (p < 0.0005). This study demonstrates for the first time the application of HSE model to study external-fixation pin-movement in vitro. The results of this study demonstrated pin-movement has a negative effect on soft-tissue wound-healing, supporting the anecdotal evidence reported in the literature, however further analysis of wound heading would be required to verify this hypothesis.

The Difference in the Assessment of Knee Extension/Flexion Angles during Gait between Two Calibration Methods for Wearable Goniometer Sensors

Frontal and axial knee motion can affect the accuracy of the knee extension/flexion motion measurement using a wearable goniometer. The purpose of this study was to test the hypothesis that calibrating the goniometer on an individual's body would reduce errors in knee flexion angle during gait, compared to bench calibration. Ten young adults (23.2 ± 1.3 years) were enrolled. Knee flexion angles during gait were simultaneously assessed using a wearable goniometer sensor and an optical three-dimensional motion analysis system, and the absolute error (AE) between the two methods was calculated. The mean AE across a gait cycle was 2.4° (0.5°) for the on-body calibration, and the AE was acceptable (<5°) throughout a gait cycle (range: 1.5-3.8°). The mean AE for the on-bench calibration was 4.9° (3.4°) (range: 1.9-13.6°). Statistical parametric mapping (SPM) analysis revealed that the AE of the on-body calibration was significantly smaller than that of the on-bench calibration during 67-82% of the gait cycle. The results indicated that the on-body calibration of a goniometer sensor had acceptable and better validity compared to the on-bench calibration, especially for the swing phase of gait.

Mobile Data Gathering and Preliminary Analysis for the Functional Reach Test

The functional reach test (FRT) is a clinical tool used to evaluate dynamic balance and fall risk in older adults and those with certain neurological diseases. It provides crucial information for developing rehabilitation programs to improve balance and reduce fall risk. This paper aims to describe a new tool to gather and analyze the data from inertial sensors to allow automation and increased reliability in the future by removing practitioner bias and facilitating the FRT procedure. A new tool for gathering and analyzing data from inertial sensors has been developed to remove practitioner bias and streamline the FRT procedure. The study involved 54 senior citizens using smartphones with sensors to execute FRT. The methods included using a mobile app to gather data, using sensor-fusion algorithms like the Madgwick algorithm to estimate orientation, and attempting to estimate location by twice integrating accelerometer data. However, accurate position estimation was difficult, highlighting the need for more research and development. The study highlights the benefits and drawbacks of automated balance assessment testing with mobile device sensors, highlighting the potential of technology to enhance conventional health evaluations.

Improving muscle capacity utilization with a 12-week strengthening program for females with symptomatic knee osteoarthritis

BACKGROUND

Strengthening exercise improves symptoms in knee osteoarthritis (OA), but it remains unclear if biomechanical mechanisms contribute to this improvement. Muscle capacity utilization, which reflects the proportion of maximum capacity required to complete tasks, may provide insight into how strengthening exercise improves clinical outcomes in painful knee OA.

PURPOSE

The purpose of this secondary analysis was to determine if a 12-week strengthening intervention reduced muscle capacity utilization during walking, squat and lunge tasks in females with painful knee OA.

METHODS

Data from 28 females (age 59.6 ± 6.2 years old; body mass index 29.1 ± 4.7 kg/m2) with clinical knee OA were included. Participants completed a strengthening intervention 3 times per week for 12 weeks. Knee extensor isometric torque was measured on a commercial dynamometer; peak values from three exertions were averaged. Peak KFM was extracted and averaged from five walking trials. Mean KFM was extracted and averaged from three trials for each of static lunges and squats. Muscle capacity utilization was the ratio of mean peak KFM to peak extensor torque for walking; and mean KFM to peak extensor torque for squats and lunges. Paired t-tests determined differences between peak extensor torque, peak KFM and muscle capacity utilization from pre to post intervention (p < 0.05).

RESULTS & SIGNIFICANCE

Peak extensor torque increased at follow up (p = 0.02). Peak KFM during walking decreased (p = 0.005). Muscle capacity utilization during walking (p = 0.008) and squat (p = 0.002) decreased. Mean KFM and muscle capacity utilization during lunge remained unchanged from pre to post intervention. The reduction in muscle capacity utilization at follow up indicates the strengthening intervention produced a decrease in proportion of the maximal capacity a participant used to complete walking and squat tasks. Strengthening both increases maximal muscle capacity and decreases the net moment required during daily tasks in knee OA.

Examining the joint coordination during dynamic balance learning using vector coding and statistical parametric mapping analyses

We aimed to examine the changes in balance performance, kinematic variables, and joint coordination of the lower extremities during the Y-balance learning task. Twenty female university students completed five consecutive blocks of Y-balance learning from days 3 to 7 (135 trials). Pre-tests and tests were performed on days 1 and 9. Maximum reach distance, peak joint angle, and joint coordination in the anterior (AL), posterolateral (PL), and posteromedial (PM) directions were measured to determine the efficacy of Y-balance performance. A repeated measures ANOVA was performed for the maximum reach distance across learning blocks to confirm whether learning had occurred. Our results indicated that the maximum reach distance on day 5 was longer than that on other learning days. The maximum reach distance significantly increased in the PL and PM directions after learning. The hip flexion (PL/PM), abduction (PM), internal rotation (PM), and external rotation (PL) angles increased after learning. The knee joint flexion angle increased in both AL and PL directions. Only the ankle dorsiflexion angle increased in the AL direction. Joint coordination indicated that the knee and hip joints performed simultaneously during internal rotation. Ankle-knee joint coordination was performed using dorsiflexion and flexion strategies. Statistical parametric mapping analysis indicated significant differences in the ankle sagittal plane in the AL direction, hip horizontal and hip/knee sagittal planes in the PL direction, and hip/knee sagittal and hip frontal/horizontal planes in the PM direction. These data suggest that the dynamic balance ability of the novice participants improved in relation to changes in coordination patterns after learning. The results of this study can be applied to other populations to improve their dynamic balance and prevent fall injuries.

Joint movement patterns differ among male recreational runners with different running style

The purpose of this study was to analyse the differences in joint kinematic patterns among runners with different spatiotemporal characteristics in the running cycle. Lower extremity kinematic data and spatiotemporal stride parameters were collected for ninety-two recreational runners during a treadmill run at a self-selected comfortable speed. A K-means clustering analysis was conducted on normalised stride cadence and Duty Factor to identify running style. Cluster 1 characterised by reduced stance times and low Duty Factor; Cluster 2, long stance times and low stride cadence; Cluster 3, high Duty Factor and stride cadence. Functional principal component analysis was used to identify patterns of variability between runners. Runners who used a combination of high cadence and Duty Factor showed differences in hip, knee and ankle sagittal kinematics compared to other runners. On the contrary, the joint kinematics was not altered when the Duty Factor was increased along with a decrease in the stride cadence. This study has demonstrated that the combination of several spatial-temporal parameters of the running cycle should be considered when analysing the movement pattern of the lower limb.

Frontal plane pelvic kinematics during high velocity running: Association with hamstring injury history

INTRODUCTION

Hamstring injuries are the most prevalent non-contact soft tissue injury in sports, with a larger portion of injuries being recurrent. The sagittal plane running kinematics correlated to hamstring injury history has been well documented. However, analysis of frontal plane kinematics allows for observation of stability and symmetry. This study aimed to examine the frontal plane running kinematics of elite collegiate level sprinters, with and without previous hamstring injury, compared to healthy counterparts.

METHODS

Thirty-nine participants performed three 50-m sprints, with three inertial measurement unit sensors placed on the pelvis: one on each iliac crest and one on the sacrum. Participants were classified based on sex, competitive status, and injury history. To investigate differences based on group classification, the data were used to analyze mediolateral motion (relative magnitude of mediolateral acceleration) and asymmetry (difference in acceleration between right and left iliac crests) during each stance phase throughout the run.

RESULTS

Injured sprinters displayed significantly greater mediolateral motion and asymmetry during stances than healthy counterparts.

CONCLUSIONS

This study demonstrates that frontal plane running stance dynamics are different in athletes with previous hamstring injury than healthy athletes. These athletes may benefit from rehabilitation strategies targeting postural control and stability during dynamic tasks.

Fatigue-induced Landing Alterations in ACL Reconstructed Athletes after Return-to-Sport

At the time of return-to-sport, anterior cruciate ligament reconstructed athletes still show altered neuromechanics in their injured leg during single leg hopping tasks. Part of these alterations can be magnified when these athletes are fatigued. So far, little is known whether fatigue-induced landing alterations persist after return-to-sport. Therefore, the aim of this study was to evaluate whether these alterations persist in the six months following return-to-sport. Sixteen anterior cruciate ligament reconstructed athletes performed five unilateral hop tasks before and after a fatigue protocol. The hop tasks were executed at three different time points (return-to-sport, 3 and 6 months post-return-to-sport). A 2-by-3 repeated measures ANOVA was performed to evaluate whether fatigue-induced landing alterations persisted 3 and 6 months following return-to-sport. At 6 months following return-to-sport, fatigue still induces a reduction in hamstring medialis activation and an increase in the knee abduction moment during a vertical hop with 90-degree inward rotation. Most fatigue-induced landing alterations present at the time of return-to-sport normalize after resumption of sports activities. However, a larger knee abduction moment in the injured leg after resumption of sports activities can still be observed.

The signed helical angle: A technique for characterizing midfoot motion during gait

Quantifying motion in the midfoot during gait and other movements is important for a variety of applications, but challenging due to the complexity of the multiple small articulations involved. The most common motion capture based techniques are limited in their ability to characterize the non-planar nature of the midfoot joint axes. In this study we developed a novel Signed Helical Angle (SHA) to quantify midfoot angular displacement. Motion capture data from 40 healthy subjects walking at a controlled speed were used to calculate finite helical axes and angles from a two-segment foot model. Axes were classified as either pronation or supination based on their orientation, and given a sign, thus either adding to or subtracting from the angular displacement. Analysis focused on insights from axis orientation and comparisons to other techniques. Results showed that when transitions were excluded, pronation and supination axes were fairly well clustered in the transverse plane. The resulting SHA midfoot angle waveform was comparable to sagittal plane Euler and helical component waveforms, but with 39% (approximately 3°) greater range of motion in pronation and 25% (approximately 4°) greater in supination, due to the direct measurement of the motion path and the influence of the other planes. The proposed SHA method may provide an intuitive and useful method to analyze midfoot motion for a variety of applications, particularly when interventions cause subtle changes that may be diluted in planar analyses.

Variations in Concurrent Validity of Two Independent Inertial Measurement Units Compared to Gold Standard for Upper Body Posture during Computerised Device Use

Inertial measurement units (IMUs) may provide an objective method for measuring posture during computer use, but research is needed to validate IMUs' accuracy. We examine the concurrent validity of two different IMU systems in measuring three-dimensional (3D) upper body posture relative to a motion capture system (Mocap) as a potential device to assess postures outside a laboratory environment. We used 3D Mocap and two IMU systems (Wi-Fi and Bluetooth) to capture the upper body posture of twenty-six individuals during three physical computer working conditions (monitor correct, monitor raised, and laptop). Coefficient of determination (R2) and root-mean-square error (RMSE) compared IMUs to Mocap. Head/neck segment [HN], upper trunk segment [UTS], and joint angle [HN-UTS] were the primary variables. Wi-Fi IMUs demonstrated high validity for HN and UTS (sagittal plane) and HN-UTS (frontal plane) for all conditions, and for HN rotation movements (both for the monitor correct and monitor raised conditions), others moderate to poor. Bluetooth IMUs for HN, and UTS (sagittal plane) for the monitor correct, laptop, and monitor raised conditions were moderate. Frontal plane movements except UTS (monitor correct and laptop) and all rotation had poor validity. Both IMU systems were affected by gyroscopic drift with sporadic data loss in Bluetooth IMUs. Wi-Fi IMUs had more acceptable accuracy when measuring upper body posture during computer use compared to Mocap, except for trunk rotations. Variation in IMU systems' performance suggests validation in the task-specific movement(s) is essential.

Development of a video camera-type kayak motion capture system to measure water kayaking

Background

In kayaking, trunk motion is one of the important factors that prevent injury and improve performance. Kinematic studies in kayaking have been reported in laboratory settings using paddling simulators and ergometers. However, such studies do not reflect kayaking on water, the actual competitive environment. Therefore, we developed a video camera-type kayak motion capture system (KMCS) wherein action cameras were fixed to a kayak to capture images of markers attached to an athlete's body. This study aimed to compare the kinematic data between KMCS and an optical motion capture system (OMCS) in kayaking and to determine the accuracy of the KMCS analysis.

Methods

In a competition, five elite junior female kayak athletes performed kayak paddling under the unloaded condition using a kayak. The kayak was secured using a tri-folding bench and a towel, and twenty strokes were recorded during maximal paddling. One stroke was defined as the period from right catch to left catch, and the first six strokes were used to evaluate the accuracy. Trunk angles (tilting, turning, and rotation) were examined with the simultaneous use of KMCS and OMCS, and the differences between these systems were evaluated. To ensure reliability, intraclass correlation coefficient (ICC; a two-way mixed model for absolute agreement) was calculated for each angle. Furthermore, Bland-Altman analysis was performed to understand the agreement between the two systems.

Results

Root mean square errors (RMSEs) were 1.42° and 3.94° for turning and rotation, respectively, and mean absolute errors (MAEs) were 1.08° and 3.00° for turning and rotation, respectively. The RMSE and MAE for tilting were 2.43° and 1.76°, respectively, which indicated that the validity was comparable to that of other angles. However, the range of motion in tilting was lower than that in turning and rotation. Bland-Altman analysis showed good agreement in the total range of motion, with mean bias values of -0.84°, -0.07°, and -0.41° for tilting, turning, and rotation, respectively. The ICCs for tilting, turning, and rotation were 0.966, 0.985, and 0.973, respectively, and showed excellent reliability.

Conclusions

The newly developed KMCS effectively measured the trunk motion with good accuracy in kayaking. In future studies, we intend to use KMCS to measure kayaking on water and collect data for performance improvement and injury prevention.

The Effects of FIFA 11+ Kids Prevention Program on Kinematic Risk Factors for ACL Injury in Preadolescent Female Soccer Players: A Randomized Controlled Trial

This study aimed to investigate the effects of the 8-week FIFA 11+ Kids program on kinematic risk factors for ACL injury in preadolescent female soccer players during single-leg drop landing. For this, 36 preadolescent female soccer players (10-12 years old) were randomly allocated to the FIFA 11+ Kids program and control groups (18 players per group). The intervention group performed the FIFA 11+ Kids warm-up program twice per week for 8 weeks, while the control group continued with regular warm-up. Trunk, hip, and knee peak angles (from initial ground contact to peak knee flexion) were collected during the single-leg drop landing using a 3D motion capture system. A repeated measure ANOVA was used to analyze groups over time. Significant group × time interactions were found for the peak knee flexion, with a medium effect size (p = 0.05; effect size = 0.11), and peak hip internal rotation angles, with a large effect size (p < 0.01; effect size = 0.28). We found that the FIFA 11+ Kids program was effective in improving knee flexion and hip internal rotation, likely resulting in reducing ACL stress during single-leg drop landing in young soccer players.

The effect of trunk and shank position on the hip-to-knee moment ratio in a bilateral squat

OBJECTIVES

The effect of knee position on joint moments during squats has been studied; however, the effect of trunk angle has been less well investigated. This study evaluated the effect of both trunk and knee sagittal plane position on the distribution of moments between the hip and knee extensors during the bilateral squat.

DESIGN

Observational study.

SETTING

Biomechanics laboratory.

PARTICIPANTS

One hundred individuals performed bilateral squats.

MAIN OUTCOME MEASURES

Motion and force data were collected using motion capture and force plates. Trunk and shank angles and hip and knee moments were calculated. A linear regression was used to associate the ratio between the hip and knee moments (hip-to-knee moment ratio) with the sagittal plane trunk and shank angles, while accounting for six squat depths (between 60° and 110° of knee flexion) and side.

RESULTS

Trunk angle and shank angle each contributed to the hip-to-knee moment ratio (P < .001) with trunk accounting for a higher proportion of variance than the other variables. The hip-to-knee moment ratio increased with increasing trunk angle and with decreasing shank angle.

CONCLUSIONS

This large cohort study supports the use of trunk position to instruct squat technique with the goal of modifying hip and knee moments.

Increased hip adductor activation during sit-to-stand improves muscle activation timing and rising-up mechanics in individuals with hemiparesis

Long sit-to-stand (STS) time has been identified as a feature of impaired functional mobility. The changes in biomechanics of STS performance with simultaneous hip adductor contraction have not been studied, which may limit indications for use of hip adductor activation during STS training. Ten individuals with hemiplegia (mean age 61.8 years, injury time 29.8 ± 15.2 months) performed the STS with and without squeezing a ball between two legs. The joint moments, ground reaction force (GRF), chair reaction force and movement durations and temporal index of electromyography were calculated from the control condition for comparison with those from the ball squeezing condition. Under the squeeze condition, reduced peak vertical GRF during the ascension phase with increased loading rate was observed in the nonparetic limb, and the peak knee extensor moment occurred earlier in the paretic. Earlier activation of tibialis anterior and gluteus maximus, and gluteus medius were found in squeeze STS. Squeezing a ball between limbs during STS increased the contraction timing of tibialis anterior, gluteus maximus, gluteus medius, and soleus as well as a more symmetric rising mechanics encourage the use of squeezing a ball between limbs during STS for individuals with hemiparesis.

Changes in Walking Biomechanics after a 30-Min Exercise Bout in Sedentary Compared with Active Young Women

INTRODUCTION

Patellofemoral pain (PFP) is a common overuse injury associated with physical activity, including walking. The risk for PFP may increase if walking biomechanics change during a bout of walking. Because walking for exercise is often recommended to previously sedentary adults, this would be a cause for concern. The purpose of this study was to determine any differences in walking biomechanics associated with PFP between sedentary and active young women initially and after 30 min of walking for exercise.

METHODS

Fifteen sedentary and 15 active young women walked overground for five trials of three-dimensional gait analysis before and after a 30-min treadmill walk. Peak knee flexion angle and extensor moment were compared between groups and before and after the 30-min walk.

RESULTS

Comparing groups at baseline, peak knee flexion angle and peak knee extensor moment were not statistically significantly different between groups. After the 30-min walk, peak knee flexion angle and extensor moment increased slightly in both groups.

CONCLUSIONS

Smaller, not larger, peak knee flexion angle and extensor moment during walking have been associated with increased risk of PFP. Therefore, sedentary and active young women can walk for 30 min without further detrimental changes to walking biomechanics that may increase their risk of PFP.

Validity and Reliability of a Wearable Goniometer Sensor Controlled by a Mobile Application for Measuring Knee Flexion/Extension Angle during the Gait Cycle

Knee kinematics during gait is an important assessment tool in health-promotion and clinical fields. This study aimed to determine the validity and reliability of a wearable goniometer sensor for measuring knee flexion angles throughout the gait cycle. Twenty-two and seventeen participants were enrolled in the validation and reliability study, respectively. The knee flexion angle during gait was assessed using a wearable goniometer sensor and a standard optical motion analysis system. The coefficient of multiple correlation (CMC) between the two measurement systems was 0.992 ± 0.008. Absolute error (AE) was 3.3 ± 1.5° (range: 1.3-6.2°) for the entire gait cycle. An acceptable AE (<5°) was observed during 0-65% and 87-100% of the gait cycle. Discrete analysis revealed a significant correlation between the two systems (R = 0.608-0.904, p ≤ 0.001). The CMC between the two measurement days with a 1-week interval was 0.988 ± 0.024, and the AE was 2.5 ± 1.2° (range: 1.1-4.5°). A good-to-acceptable AE (<5°) was observed throughout the gait cycle. These results indicate that the wearable goniometer sensor is useful for assessing knee flexion angle during the stance phase of the gait cycle.

Lower extremity kinematics during running and hip abductor strength in iliotibial band syndrome: A systematic review and meta-analysis

BACKGROUND

Iliotibial band syndrome is a common overuse injury that is twice as likely to affect female runners compared to male runners. It is unclear if there is a consistent running pattern and strength profile exhibited by female and male runners with iliotibial band syndrome.

RESEARCH QUESTION

The purpose of this systematic review and meta-analysis was to determine if any differences existed in lower-extremity kinematics and hip strength between runners who retrospectively, currently, or prospectively had iliotibial band syndrome.

METHODS

Papers included must have reported three-dimensional kinematic running data and/or hip strength data that were statistically analyzed between runners that never developed iliotibial band syndrome and runners with iliotibial band syndrome. Meta-analysis was performed for each kinematic or strength variable reported in at least three studies. Female and male runners were analyzed separately and grouped into three cohorts (retrospective, current, prospective).

RESULTS

Seventeen articles were included in this systematic review. Data from 10 cross-sectional studies were included for meta-analysis. Female runners with current iliotibial band syndrome exhibited smaller peak hip internal rotation angles and lower isometric hip abductor strength compared to controls.

SIGNIFICANCE

Although limited biomechanical evidence exists, risk factors for ITBS are different between female and male runners and may vary according to injury status. Specifically, transverse plane hip motion and hip abductor strength weakness may be biomechanical risk factors in female runners with current iliotibial band syndrome only.

A Novel Procedure for Knee Flexion Angle Estimation Based on Functionally Defined Coordinate Systems and Independent of the Marker Landmarks

Knee angles are kinematic quantities that are commonly presented in gait analysis reports. They are typically calculated as the relative angles between the anatomical coordinate systems rigidly attached to the femur and the tibia. To give these angles a biomechanical meaning, the coordinate systems must be defined with respect to some anatomical landmarks. For example, if one axis of the joint coordinate systems is directed along the knee flexion/extension axis, then the relative angle assumes the meaning of flexion/extension angle. Defining accurate anatomical coordinate systems is not an easy task, because it requires skills in marker placement, landmark identification and definition of a biomechanical model. In this paper, we present a novel method to (i) functionally define two coordinate systems attached to femur and tibia and (ii) functionally calculate the knee angle based on the relative differential kinematics between the previously defined coordinate systems. As the main limitation, this method is unable to provide an absolute measurement of the knee flexion/extension angle; however, it is able to accurately capture and display the relative angular motion of the knee. We show that our method produced consistent results even when the measured coordinate systems were randomly modified, removing any anatomical referencing. The proposed method has the advantage of being independent/invariant of the choice of the original coordinate systems of the femur and tibia, removing the need for accurate marker placement. Some major consequences are that (i) the markers may be placed on optimal landmarks, for example, minimizing the soft tissue artifacts or improving the subject's comfort, and (ii) there is no need for anatomical calibration when technical marker clusters/triads are used.

Knee Movement Characteristics of Basketball Players in Landing Tasks Before Onset of Patellar Tendinopathy: A Prospective Study

Background

Patellar tendinopathy is one of the most common injuries for basketball players. Jumping and landing movement patterns are potential risk factors for patellar tendinopathy.

Hypothesis

Male college basketball players who developed patellar tendinopathy would demonstrate greater peak vertical ground reaction force and knee flexion angular velocity, and smaller knee flexion range of motion and knee flexion angles at initial contact compared to players who did not develop the injury when performing a stop-jump task within a year prior to the onset of the injury.

Study Design

Prospective study.

Methods

Freshmen college basketball male players (n = 181) were recruited for three consecutive years and followed to the end of the third year of the study. Three-dimensional kinematic and kinetic data during a stop-jump task were collected for all participants at the beginning of each school year. Peak vertical ground reaction force, knee flexion angle at initial foot contact with the ground, range of motion for knee flexion and maximal knee flexion angular velocity during the landing phases of the stop-jump task were collected and calculated. Development of patellar tendinopathy was monitored in follow-up. Independent t-tests and Cohen's d effect sizes (ES) were used to compare movement patterns between injury and no injury groups for each school year.

Results

A total of 60 knees developed patellar tendinopathy. The injury groups had a significantly greater peak vertical ground reaction force in freshmen and junior years (P = 0.020, ES = 0.13; P = 0.046, ES = 0.17), smaller knee flexion ROM in freshmen year (P = 0.002, ES = 0.10), and greater maximum knee flexion angular velocity in freshmen and junior year (P = 0.012, ES = 0.10; P = 0.001, ES = 0.35) during the horizontal landing phase before the takeoff of the jump compared to the no injury groups. The injury groups also had a significantly smaller knee flexion angle at initial contact during vertical landing phase after the takeoff of the jump in freshmen and junior years (P = 0.001, ES = 0.36; P = 0.001; ES = 0.37) during vertical landing phase.

Conclusion

Peak vertical ground reaction force, knee flexion angle at initial foot contact, knee flexion range of motion, and maximum knee flexion angular velocity are associated with patellar tendinopathy among male college basketball players in different school years.

Atypical Lower Limb Mechanics During Weight Acceptance of Stair Descent at Different Time Frames After Anterior Cruciate Ligament Reconstruction

BACKGROUND

An anterior cruciate ligament (ACL) rupture may result in poor sensorimotor knee control and, consequentially, adapted movement strategies to help maintain knee stability. Whether patients display atypical lower limb mechanics during weight acceptance of stair descent at different time frames after ACL reconstruction (ACLR) is unknown.

PURPOSE

To compare the presence of atypical lower limb mechanics during the weight acceptance phase of stair descent among athletes at early, middle, and late time frames after unilateral ACLR.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 49 athletes with ACLR were classified into 3 groups according to time after ACLR-early (<6 months; n = 17), middle (6-18 months; n = 16), and late (>18 months; n = 16)-and compared with asymptomatic athletes (control; n = 18). Sagittal plane hip, knee, and ankle angles; angular velocities; moments; and powers were compared between the ACLR groups' injured and noninjured legs and the control group as well as between legs within groups using functional data analysis methods.

RESULTS

All 3 ACLR groups showed greater knee flexion angles and moments than the control group for injured and noninjured legs. For the other outcomes, the early group had, compared with the control group, less hip power absorption, more knee power absorption, lower ankle plantarflexion angle, lower ankle dorsiflexion moment, and less ankle power absorption for the injured leg and more knee power absorption and higher vertical ground reaction force for the noninjured leg. In addition, the late group showed differences from the control group for the injured leg revealing more knee power absorption and lower ankle plantarflexion angle. Only the early group took a longer time than the control group to complete weight acceptance and demonstrated asymmetry for multiple outcomes.

CONCLUSION

Athletes with different time frames after ACLR revealed atypically large knee angles and moments during weight acceptance of stair descent for both the injured and the noninjured legs. These findings may express a chronically adapted strategy to increase knee control. In contrast, atypical hip and ankle mechanics seem restricted to an early time frame after ACLR.

CLINICAL RELEVANCE

Rehabilitation after ACLR should include early training in controlling weight acceptance. Including a control group is essential when evaluating movement patterns after ACLR because both legs may be affected.

The effects of foot orthosis and low-dye tape on lower limb joint angles and moments during running in individuals with pes planus

BACKGROUND

Pes Planus or Flat feet is one of the most common lower limb abnormalities. When runners with this abnormality participate in recreational running, interventional therapies could help in pain alleviation and enhance performance. To determine the most effective treatment, however, a biomechanical examination of the effects of each treatment modality is required.

RESEARCH QUESTION

The aim of the present study was to investigate the effects of Foot Orthoses (FOs) and Low-Dye Tape (LDT) on lower limb joint angles and moments during running in individuals with pes planus.

METHODS

kinematic and kinetic data of 20 young people with pes planus were measured during running in three conditions: (1) SHOD (2) with shoes and FOs (3) with shoes and LDT. One-way repeated measure ANOVA was used to investigate the impacts of the FOs and LDT on the lower limb joint angles and moments throughout the stance phase of the running cycle.

RESULTS

The results showed that FOs reduced ankle eversion compared to SHOD and LDT (P < 0.001) and decreased the dorsiflexion angle (P = 0.005) and the plantarflexor moment compared to the SHOD (P < 0.001). FOs increased knee adduction angle (P = 0.021) and knee external rotator moment (P < 0.001) compared to both conditions and increased knee extensor and abductor moments compared to SHOD (P < 0.001). At the hip joint, FOs only increased hip external rotation compared with the LDT condition (P = 0.031); and LDT increased hip extensor moment compared to SHOD and FOs (P = 0.037) and also increased hip adduction angle compared to SHOD (P = 0.037).

SIGNIFICANCE

FOs with a medial wedge appears to increase the external knee adduction moment and knee adduction angles, which are risk factors for the development and progression of knee osteoarthritis. Further, usage of FOs seems to reduce the ankle joint role in propulsion as it impacts the ankle sagittal angles and moments.

Female Athletes Exhibit Greater Trial-to-Trial Coordination Variability When Provided with Instructions Promoting an External Focus

The purpose of this study was to examine how instructions promoting different attentional foci influence joint coordination patterns and trial-to-trial coordination variability during landing. Sixteen females performed drop landings with their typical technique (baseline) and after receiving instructions promoting an internal focus and an external focus. The coordination patterns, and trial-to-trial coordination variability, of the sagittal plane hip-knee, hip-ankle, and knee-ankle angle pairings were compared across conditions. While there was no difference in the joint coordination patterns among the conditions, subjects exhibited greater hip-ankle and knee-ankle trial-to-trial coordination variability for the external focus condition, vs. the baseline and internal focus conditions, which may help to explain the improved motor learning outcomes for athletes who train with an external focus.

Non-South East Asians have a better running economy and different anthropometrics and biomechanics than South East Asians

Running biomechanics and ethnicity can influence running economy (RE), which is a critical factor of running performance. Our aim was to compare RE of South East Asian (SEA) and non-South East Asian (non-SEA) runners at several endurance running speeds (10-14 km/h) matched for on-road racing performance and sex. Secondly, we explored anthropometric characteristics and relationships between RE and anthropometric and biomechanical variables. SEA were 6% less economical (p = 0.04) than non-SEA. SEA were lighter and shorter than non-SEA, and had lower body mass indexes and leg lengths (p ≤ 0.01). In terms of biomechanics, a higher prevalence of forefoot strikers in SEA than non-SEA was seen at each speed tested (p ≤ 0.04). Furthermore, SEA had a significantly higher step frequency (p = 0.02), shorter contact time (p = 0.04), smaller footstrike angle (p < 0.001), and less knee extension at toe-off (p = 0.03) than non-SEA. Amongst these variables, only mass was positively correlated to RE for both SEA (12 km/h) and non-SEA (all speeds); step frequency, negatively correlated to RE for both SEA (10 km/h) and non-SEA (12 km/h); and contact time, positively correlated to RE for SEA (12 km/h). Despite the observed anthropometric and biomechanical differences between cohorts, these data were limited in underpinning the observed RE differences at a group level. This exploratory study provides preliminary indications of potential differences between SEA and non-SEA runners warranting further consideration. Altogether, these findings suggest caution when generalizing from non-SEA running studies to SEA runners.

Single leg vertical jump performance identifies knee function deficits at return to sport after ACL reconstruction in male athletes

Objectives

Vertical jump performance (height) is a more representative metric for knee function than horizontal hop performance (distance) in healthy individuals. It is not known what the biomechanical status of athletes after anterior cruciate ligament (ACL) reconstruction (ACLR) is at the time they are cleared to return to sport (RTS) or whether vertical performance metrics better evaluate knee function.

Methods

Standard marker-based motion capture and electromyography (EMG) were collected from 26 male athletes cleared to RTS after ACLR and 22 control healthy subjects during single leg vertical jumps (SLJ) and single leg drop jumps (SLDJ). Performance outcomes, jump height and the Reactive Strength Index, were calculated. Sagittal plane kinematics, joint moments and joint work were obtained using inverse dynamics and lower limb muscle forces were computed using an EMG-constrained musculoskeletal model. Muscle contribution was calculated as a percentage of the impulse of all muscle forces in the model. Between-limb and between-group differences were explored using mixed models analyses.

Results

Jump performance, assessed by jump height and Reactive Strength Index, was significantly lower in the involved than the uninvolved limb and controls, with large effect sizes. For the ACLR group, jump height limb symmetry index was 83% and 77% during the SLJ and SLDJ, respectively. Work generation was significantly less in the involved knee compared to uninvolved limb and controls during the SLJ (p<0.001; d=1.19; p=0.003, d=0.91, respectively) and during the SLDJ (p<0.001; d=1.54; p=0.002, d=1.05, respectively). Hamstrings muscle contribution was greater in the involved compared to the uninvolved limb and controls, whereas soleus contribution was lower in the involved limb compared to controls.

Conclusions

During vertical jumps, male athletes after ACLR at RTS still exhibit knee biomechanical deficits, despite symmetry in horizontal functional performance and strength tests. Vertical performance metrics like jump height and RSI can better identify interlimb asymmetries than the more commonly used hop distance and should be included in the testing battery for the RTS.

Symmetry in Triple Hop Distance Hides Asymmetries in Knee Function After ACL Reconstruction in Athletes at Return to Sports

BACKGROUND

After anterior cruciate ligament reconstruction (ACLR), a battery of strength and hop tests is frequently used to determine the readiness of an athlete to successfully return to sports. However, the anterior cruciate ligament reinjury rate remains alarmingly high.

PURPOSE

To evaluate the lower limb function of athletes after ACLR at the time when they had been cleared to return to sports (RTS). We aimed to evaluate if passing discharge criteria ensures restoration of normal lower limb biomechanics in terms of kinematics, kinetics, work, and percentage work contribution during a triple hop for distance.

STUDY DESIGN

Controlled laboratory study.

METHODS

Integrated 3-dimensional motion analysis was performed in 24 male athletes after ACLR when cleared to RTS and 23 healthy male controls during the triple-hop test. The criteria for RTS were (1) clearance by the surgeon and the physical therapist, (2) completion of a sports-specific on-field rehabilitation program, and (3) limb symmetry index >90% after quadriceps strength and hop battery tests. Lower limb and trunk kinematics, as well as knee joint moments and work, were calculated. Between-limb differences (within athletes after ACLR) and between-group differences (between ACLR and control groups) were evaluated using mixed linear models.

RESULTS

Although achieving 97% limb symmetry in distance hopped and displaying almost 80% symmetry for knee work absorption in the second rebound and third landing, the ACLR cohorts demonstrated only 51% and 66% limb symmetry for knee work generation in the first and second rebound phases, respectively. During both work generation phases of the triple hop, the relative contribution of the involved knee was significantly smaller, with a prominent compensation from the hip joint (P < .001, for all phases) as compared with the uninvolved limb and the controls. In addition, patients deployed a whole body compensatory strategy to account for the between-limb differences in knee function, mainly at the hip, pelvis, and trunk.

CONCLUSION

Symmetry in the triple hop for distance masked important deficits in the knee joint work. These differences were more prominent during work generation (concentric-propulsive) than work absorption (eccentric-landing).

CLINICAL RELEVANCE

Symmetry in hop distance during the triple hop test masked significant asymmetries in knee function after ACLR and might not be the appropriate outcome to use as a discharge criterion. Differences between limbs in athletes after ACLR were more prominent during the power generation than the absorption phase.

Muscle Activation During Single-Legged Squat Is Affected by Position of the Nonstance Limb

CONTEXT

The single-legged squat (SLS) is appropriate for targeting activation, strengthening, and neuromuscular retraining of the gluteus maximus, gluteus medius, and quadriceps. However, the effects of different nonstance-limb positions on muscle activity have not been fully evaluated.

OBJECTIVE

To compare the muscle activity of selected stance-limb hip muscles during the SLS using 3 nonstance-limb positions: in front (SLS-Front), in the middle (SLS-Middle), and in back (SLS-Back).

DESIGN

Controlled laboratory study.

SETTING

Biomechanics laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 17 healthy adults (8 men, 9 women; age = 22.6 ± 3.6 years, height = 173.3 ± 10.7 cm, mass = 71.2 ± 11.0 kg) participated.

MAIN OUTCOME MEASURE(S)

Surface electromyographic data of the gluteus maximus, gluteus medius, lateral hamstrings, medial hamstrings, rectus femoris, and tensor fascia lata (TFL) as well as kinetic data of the hip and knee were collected while participants performed the 3 SLS tasks. Mean muscle-activation levels during the descent and ascent phases for the selected hip muscles and hip and knee kinetics in all 3 planes were compared for the 3 tasks. Each variable of interest was analyzed using a separate linear regression model with a generalized estimating equations correction.

RESULTS

Muscle-activation levels of the gluteus maximus, gluteus medius, medial hamstrings, rectus femoris, and TFL for the stance limb during descent (P ≤ .04) and the medial hamstrings and TFL during ascent (P ≤ .002) were different among the SLS tasks. The greatest number of differences occurred between SLS-Front and SLS-Back. During descent, gluteal muscle activity was greater in SLS-Front (P ≤ .03) and SLS-Middle (P = .03) than in SLS-Back. For both phases, TFL activity was greater during SLS-Front than during both SLS-Middle and SLS-Back (P ≤ .006). Kinetic differences at the hip and knee between SLS tasks were also observed (P values ≤ .02).

CONCLUSIONS

The 3 SLS tasks had different muscle-activation and kinetic profiles. Clinicians and researchers can vary nonstance-limb position during the SLS to manipulate muscle-activation levels and tailor the exercise to assist with goals at different stages of rehabilitation.

Effects of Tai-Chi Chuan Practice on Patterns and Stability of Lower Limb Inter-Joint Coordination During Obstructed Gait in the Elderly

Losing balance or tripping during obstacle-crossing is one of the most frequent causes of falls in the elderly. As a low speed, low impact exercise, Tai Chi Chuan (TCC) can be promising in helping the elderly develop strategies for improved balance, inter-joint coordination, and end-point control during obstacle-crossing. This study investigates the effects of TCC training on the patterns and variability of the lower-limb inter-joint coordination during obstacle-crossing in the elderly. Fifteen older TCC practitioners and 15 healthy controls crossed obstacles of three different heights, while sagittal angles (x) and angular velocities (x′) of the hips, knees and ankles were measured and their phase angles obtained. The continuous relative phases (CRP) of the hip-knee and knee-ankle coordination were also calculated. The standard deviations of the CRP curve points were averaged to obtain deviation phase (DP) values for the stance and swing phases. The TCC group was found to cross obstacles with increased leading and trailing toe-clearances with unaltered CRP values when the swing toe was above the obstacle. Long-term TCC training altered the patterns and magnitudes of the CRPs primarily over double-limb support and significantly reduced the variabilities of leading knee-ankle and trailing hip-knee and knee-ankle CRP curves over the crossing cycle, regardless of obstacle height. The current results suggest that long-term TCC practice was helpful for a crossing strategy with significantly increased foot-obstacle clearances and reduced variability of the way the motions of the lower limb joints are coordinated during obstacle-crossing. These benefits may be explained by the long-lasting effects of continuous practice of the slow movement patterns emphasizing between-limb transfer of body weight in TCC.

The Association Between Foot Structure and Foot Kinematics During Slow Running

BACKGROUND

Clinicians routinely assess foot posture as part of their assessment and management of foot pathologies. Flat or high-arched foot postures have been linked to kinematic deviations and increased risk of foot injuries. The Foot Posture Index (FPI) is a valid clinical tool used to classify feet into high-arched, normal-arched, and flat foot groups and predicts foot function during walking well. Walking and running are distinct locomotion styles, and studies have not been performed to correlate FPI to foot function during running. This study aims to investigate the association of FPI scores to foot kinematics during running. The results will further inform clinicians who perform static assessment of feet of individuals who are runners.

METHODS

Sixty-nine participants had their feet assessed using the FPI scoring system. Based on these scores, the feet were categorized as flat foot, normal-arched, and high-arched. Rearfoot eversion and forefoot dorsiflexion (arch flattening) of the foot were analysed during slow running between 1.4 and 2.2 m/sec. The Pearson correlation was used to analyse the FPI scores on an interval scale, with Cohen's d used to report effect size. One-way analysis of variance and a Bonferroni post hoc test was used to analyze data by category. Level of significance was set at P < .05.

RESULTS

Thirty-four flat feet, 26 normal-arched feet, and nine high-arched feet were analyzed. The FPI scores correlated significantly with rearfoot eversion (moderate effect size) and forefoot dorsiflexion (low effect size). Rearfoot eversion was greatest in the flat foot, followed by the normal-arched foot and the high-arched foot. Forefoot dorsiflexion was significantly higher in the flat foot compared with the high-arched group.

CONCLUSIONS

Foot Posture Index scores are positively correlated with rearfoot eversion and forefoot dorsiflexion during running. Clinicians can use this information to aid their foot assessment and management of individuals who are runners.

Postural Balance in Individuals With Knee Osteoarthritis During Stand-to-Sit Task

Objective: Stand-to-sit task is an important daily function, but there is a lack of research evidence on whether knee osteoarthritis (knee OA) affects the postural balance during the task. This study aimed to compare individuals with knee OA and asymptomatic controls in postural balance and identify kinematic and lower extremity muscle activity characteristics in individuals with knee OA during the stand-to-sit task. Methods: In total, 30 individuals with knee OA and 30 age-matched asymptomatic controls performed the 30-s Chair Stand Test (30sCST) at self-selected speeds. Motion analysis data and surface electromyography (sEMG) were collected while participants performed the 30sCST. To quantify postural balance, the displacement of the center of mass (CoM) and the peak instantaneous velocity of the CoM were calculated. The kinematic data included forward lean angles of the trunk and pelvic, range of motion (RoM) of the hip, knee, and ankle joints in the sagittal plane. The averaged activation levels of gluteus maximus, vastus lateralis, vastus medialis, rectus femoris, biceps femoris (BF), tibialis anterior (TA), and medial head of gastrocnemius muscles were indicated by the normalized root mean square amplitudes. Results: Compared with the asymptomatic control group, the knee OA group prolonged the duration of the stand-to-sit task, demonstrated significantly larger CoM displacement and peak instantaneous CoM velocity in the anterior-posterior direction, reduced ankle dorsiflexion RoM, greater anterior pelvic tilt RoM, and lower quadriceps femoris and muscles activation level coupled with higher BF muscle activation level during the stand-to-sit task. Conclusion: This study indicates that individuals with knee OA adopt greater pelvic forward lean RoM and higher BF muscle activation level during the stand-to-sit task. However, these individuals exist greater CoM excursion in the anterior-posterior direction and take more time to complete the task. This daily functional activity should be added to the rehabilitation goals for individuals with knee OA. The knee OA group performs reduced ankle dorsiflexion RoM, quadriceps femoris, and TA activation deficit. In the future, the rehabilitation programs targeting these impairments could be beneficial for restoring the functional transfer in individuals with knee OA.

Comparing shallow, deep, and transfer learning in predicting joint moments in running

Joint moments are commonly calculated in biomechanics research and provide an indirect measure of muscular behaviors and joint loads. However, joint moments cannot be easily quantified clinically or in the field, primarily due to challenges measuring ground reaction forces outside the laboratory. The present study aimed to compare the accuracy of three different machine learning (ML) techniques - functional regression [ ML_fregress ], a deep neural network (DNN) built from scratch [ ML_DNN ], and transfer learning [ ML_TL ], in predicting joint moments during running. Data for this study came from an open-source dataset and two studies on running with and without external loads. Three-dimensional (3D) joint moments of the hip, knee, and ankle, were derived using inverse dynamics. 3D joint angle, velocity, and acceleration of the three joints served as predictors for each of the three ML techniques. Prediction performance was generally the best using ML_DNN, and the worse using ML_fregress. Absolute predictive performance was the best for sagittal plane moments, which ranged from a RMSE of 0.16 Nm/kg at the ankle using ML_DNN, to a RMSE of 0.49Nm/kg at the knee using ML_fregress. ML_DNN resulted in the greatest improvement in relative prediction performance (relRMSE) by 20% compared to ML_fregress for the ankle adduction-abduction moment. DNN with or without transfer learning was superior in predicting joint moments using kinematic inputs compared to functional regression. Synergizing ML with kinematic inputs has the potential to solve the constraints of obtaining high fidelity biomechanics data normally only possible during laboratory studies.

Fear of Reinjury Following Anterior Cruciate Ligament Reconstruction Is Manifested in Muscle Activation Patterns of Single-Leg Side-Hop Landings

OBJECTIVE

The purpose of this study was to determine whether fear of re-injury is manifested in joint kinematics and muscle activation patterns during landings of a standardized rebound side-hop (SRSH), or in patient-reported outcome measures (PROMs), among individuals with anterior cruciate ligament reconstruction (ACLR).

METHODS

In this cross-sectional observational study, 38 individuals within 2 years post-ACLR were grouped into HIGH-FEAR (n = 21, median 11.2 months post-surgery) or LOW-FEAR (n = 17, median 10.1 months post-surgery) based on a discriminating question (Q9; Tampa Scale of Kinesiophobia-17). These individuals and 39 asymptomatic controls performed the SRSH. Three-dimensional motion recordings were used to calculate trunk, hip, and knee joint angles at initial contact and range of respective joint motion during landing. Surface electromyography registered mean amplitudes and co-contraction indexes for thigh muscles during pre-activation (50 ms) and landing phases. PROMs of knee function, knee health, and physical activity were also analyzed.

RESULTS

The HIGH-FEAR and LOW-FEAR classification was corroborated by distinct Tampa Scale of Kinesiophobia-17 total and subscale scores and revealed distinguishable muscle activation patterns. HIGH-FEAR demonstrated higher biceps femoris electromyography amplitude and higher anterior-posterior co-contraction index during landing than both LOW-FEAR and controls. However, there were no fear-related differences for kinematics or PROMs. Instead, both ACLR subgroups showed different kinematics at initial contact to controls; HIGH-FEAR with more trunk, hip, and knee flexion, and LOW-FEAR with more hip and knee flexion.

CONCLUSION

Individuals with ACLR who had high fear of re-injury seem to have adopted a protective strategy with higher muscular activation patterns, presumably to stabilize the knee joint, compared with individuals with low fear of re-injury and controls. SRSH landing kinematics or knee-related PROMs may not be as sensitive to fear of re-injury.

IMPACT

Fear of reinjury following anterior cruciate ligament injury should be evaluated as an independent psychological outcome throughout rehabilitation after ACLR for improved return to sport transition.

LAY SUMMARY

If you have an anterior cruciate ligament injury treated with reconstructive surgery, you might have a high fear of reinjury, and that can change how you activate the muscles around your knee. Your physical therapist can do a simple screening test in addition to functional tests to help reduce your fear and improve your treatment outcomes.

Functional calibration does not improve the concurrent validity of magneto-inertial wearable sensor-based thorax and lumbar angle measurements when compared with retro-reflective motion capture

 Magneto-inertial measurement unit (MIMU) systems allow calculation of simple sensor-to-sensor Euler angles, though this process does not address sensor-to-segment alignment, which is important for deriving meaningful MIMU-based kinematics. Functional sensor-to-segment calibrations have improved concurrent validity for elbow and knee angle measurements but have not yet been comprehensively investigated for trunk or sport-specific movements. This study aimed to determine the influence of MIMU functional calibration on thorax and lumbar joint angles during uni-planar and multi-planar, sport-specific tasks. It was hypothesised that functionally calibrating segment axes prior to angle decomposition would produce smaller differences than a non-functional method when both approaches were compared with concurrently collected 3D retro-reflective derived angles. Movements of 10 fast-medium cricket bowlers were simultaneously recorded by MIMUs and retro-reflective motion capture. Joint angles derived from four different segment definitions were compared, with three incorporating functionally defined axes. Statistical parametric mapping and root mean squared differences (RMSD) quantified measurement differences one-dimensionally and zero-dimensionally, respectively. Statistical parametric mapping found no significant differences between MIMU and retro-reflective data for any method across bowling and uni-planar trunk movements. The RMSDs for the functionally calibrated methods and non-functional method were not significantly different. Functional segment calibration may be unnecessary for MIMU-based measurement of thorax and lumbar joint angles.

Three-dimensional joint kinematic and two-dimensional quality of movement comparison between lateral and forward step-downs

OBJECTIVES

While lateral and forward step-down tasks are commonly used, they may have different kinematic and performance demands that could influence clinical assessment and rehabilitation. Therefore, the purpose of this study was to compare 3D lower extremity kinematics and 2D quality of movement between the tasks.

DESIGN

Cross-sectional comparative study.

SETTING

Research laboratory.

PARTICIPANTS

Thirty healthy adults (18 females, age = 23.2 ± 1.4 years, BMI = 23.9 ± 2.2 kg/m²).

MAIN OUTCOME MEASURES

Participants underwent 3D and 2D motion analysis. 3D variables were peak hip, knee, and ankle angles. Dichotomous clinical criteria were used for 2D assessment. An alpha level of 0.05 was used for statistical analyses.

RESULTS

In the sagittal plane, the forward step-down averaged 7° more knee flexion (p < 0.001, d = 2.30) and 4° more ankle dorsiflexion (p < 0.001, d = 1.72), but 2° less hip flexion (p = 0.001, d = 0.64). In the frontal plane, forward step-downs averaged 1° more hip adduction (p = 0.006, d = 0.54) and 1° more ankle eversion (p < 0.001, d = 1.04). The forward step-down elicited 2D movement faults more often (p = 0.003).

CONCLUSIONS

The increased knee flexion and ankle dorsiflexion demands of the forward step-down were accompanied by increases in frontal plane aberrations. The forward step-down may be more challenging for individuals with reduced tolerance to loaded knee flexion and/or limited ankle mobility.

Individuals With Pre-arthritic Hip Pain Walk With Hip Motion Alterations Common in Individuals With Hip OA

Background: Individuals with hip osteoarthritis (OA) commonly walk with less hip extension compared to individuals without hip OA. This alteration is often attributed to walking speed, structural limitation, and/or hip pain. It is unclear if individuals who are at increased risk for future OA (i.e., individuals with pre-arthritic hip disease [PAHD]) also walk with decreased hip extension.

Objectives: (1) Determine if individuals with PAHD exhibit less hip extension compared to individuals without hip pain during walking, and (2) investigate potential reasons for these motion alterations.

Methods: Adolescent and adult individuals with PAHD and healthy controls without hip pain were recruited for the study. Kinematic data were collected while walking on a treadmill at three walking speeds: preferred, fast (25% faster than preferred), and prescribed (1.25 m/s). Peak hip extension, peak hip flexion, and hip excursion were calculated for each speed. Linear regression analyses were used to examine the effects of group, sex, side, and their interactions.

Results: Individuals with PAHD had 2.9° less peak hip extension compared to individuals in the Control group (p = 0.014) when walking at their preferred speed. At the prescribed speed, the PAHD group walked with 2.7° less hip extension than the Control group (p = 0.022). Given the persistence of the finding despite walking at the same speed, differences in preferred speed are unlikely the reason for the reduced hip extension. At the fast speed, both groups increased their hip extension, hip flexion, and hip excursion by similar amounts. Hip extension was less in the PAHD group compared to the Control group (p = 0.008) with no significant group-by-task interaction (p = 0.206). Within the PAHD group, hip angles and excursions were similar between individuals reporting pain and individuals reporting no pain.

Conclusions: The results of this study indicate that kinematic alterations common in individuals with hip OA exist early in the continuum of hip disease and are present in individuals with PAHD. The reduced hip extension during walking is not explained by speed, structural limitation, or current pain.

Within-Session Reliability and Minimum Detectable Differences for Discrete Lower-Extremity Angles and Moments During Walking

Differences in walking biomechanics between groups or conditions should be greater than the measurement error to be considered meaningful. Reliability and minimum detectable differences (MDDs) have not been determined for lower-extremity angles and moments during walking within a session, as needed for interpreting differences in cross-sectional studies. Thus, the purpose of this study was to determine within-session reliability and MDDs for peak ankle, knee, and hip angles and moments during walking. Three-dimensional gait analysis was used to record walking at 1.25 m/s (±5%) in 18 men, 18-50 years of age. Peak angles and moments were calculated for 2 sets of 3 trials. Intraclass correlation coefficients (3, 3) were used to determine within-session reliability. In addition, MDDs were calculated. Within-session reliability was good to excellent for all variables. The MDDs ranged from 0.9° to 3.6° for joint angles and 0.06 to 0.15 N·m/kg for joint moments. Within-session reliability for peak ankle, knee, and hip angles and moments was better than the between-session reliability reported previously. Overall, our MDDs were similar or smaller than those previously reported for between-session reliability. The authors recommend using these MDDs to aid in the interpretation of cross-sectional comparisons of lower-extremity biomechanics during walking in healthy men.

Chronic plantar fasciitis reduces rearfoot to medial-forefoot anti-phase coordination

BACKGROUND

It is commonly assumed that abnormal foot biomechanics cause plantar fasciitis; however, this assumption is not well supported. In this study, we investigated rearfoot to medial-forefoot coordination of healthy and plantar fasciitis individuals. We hypothesized that chronic plantar fasciitis individuals would exhibit greater intersegmental rearfoot to medial-forefoot anti-phase coordination and greater coordinative variability than a healthy cohort.

METHODS

Twenty-two individuals with chronic plantar fasciitis (symptomatic mean 4.5 years) and 22 healthy individuals participated. Three-dimensional kinematics of the rearfoot and medial forefoot segments were captured using reflective markers for walking trials. After resolving rearfoot and medial-forefoot segment angle data, a modified vector coding method was used to compute coupling angles, anti-phase movements, and coordinative variability.

FINDINGS

Compared to healthy individuals, individuals with plantar fasciitis exhibited fewer anti-phase movements (frontal plane: P = 0.003, effect size = 0.38). No group differences were detected in coordinative variability magnitude (sagittal, frontal, transverse, respectively: P = 0.99, 0.72, 0.86; effect sizes = 0.00, 0.12, 0.04). There were significant main effect differences in coupling variability between stance periods (P < 0.0001).

INTERPRETATION

Contrary to our hypothesis, these data suggest that a relative reduction of rearfoot to medial-forefoot anti-phase movements with a chronic plantar fasciitis injury indicates a coordinative deficit, and that a greater frequency of anti-phase movements is associated with healthy foot function. Pain, guarding, and/or the state of chronic injury may be impairing fluid inter-segmental motion. Although no group differences were found in coordinative variability, this variability increased around transitions between loading, weight acceptance, and propulsive phases of gait.

Stable Coordination Variability in Overground Walking and Running at Preferred and Fixed Speeds

Coordination variability (CV) is commonly analyzed to understand dynamical qualities of human locomotion. The purpose of this study was to develop guidelines for the number of trials required to inform the calculation of a stable mean lower limb CV during overground locomotion. Three-dimensional lower limb kinematics were captured for 10 recreational runners performing 20 trials each of preferred and fixed speed walking and running. Stance phase CV was calculated for 9 segment and joint couplings using a modified vector coding technique. The number of trials required to achieve a CV mean within 10% of 20 strides average was determined for each coupling and individual. The statistical outputs of mode (walking vs running) and speed (preferred vs fixed) were compared when informed by differing numbers of trials. A minimum of 11 trials were required for stable mean stance phase CV. With fewer than 11 trials, CV was underestimated and led to an oversight of significant differences between mode and speed. Future overground locomotion CV research in healthy populations using a vector coding approach should use 11 trials as a standard minimum. Researchers should be aware of the notable consequences of an insufficient number of trials for overall study findings.

Test-retest reliability of entire time-series data from hip, knee and ankle kinematics and kinetics during one-leg hops for distance: Analyses using integrated pointwise indices

Motion capture systems enable in-depth interpretations of human movements based on data from three-dimensional joint angles and moments. Such analyses carry important bearings for evaluation of movement control during for instance hop landings among sports-active individuals from a performance perspective but also in rehabilitation. Recent statistical development allows analysis of entire time-series of angle and moment during hops using functional data analysis, but the reliability of such multifaceted data is not established. We used integrated pointwise indices (intra-class correlation, ICC; standard error of measurement, SEM) to establish the test-retest reliability of three-dimensional hip, knee and ankle angle and moment curves during landings of one-leg hop for distance (OLHD) in 23 asymptomatic individuals aged 18-28. We contrasted these findings to reliability of discrete variables extracted at specific events (initial contact, peak value). We extended the calculations of ICC and SEM to handle unbalanced situations (varying number of repetitions) to include all available data. Hip and knee angle curves proved reliable with stable ICC curves throughout the landing, with integrated ICCs ≥ 0.71 for all planes except for knee internal/external rotation (ICC = 0.57). Hip and knee moment curves and ankle angle and moments were less reliable and less stable, particularly in the first ~ 10-25% of the landing (integrated ICCs 0.44-0.57). Curve data were generally not in agreement with the results for discrete event data, thus advocating analysis of curve data which contains more information. To conclude, hip and knee angle curve data during OLHD landings can reliably be evaluated, while moment curves necessitate careful consideration.

Hip and Trunk Muscle Activity and Mechanics During Walking With and Without Unilateral Weight

Pelvic drop is caused by decreased hip abductor muscle activity and is associated with lower-extremity injury. Hip abductor strengthening exercises are well established; however, no standard method exists to increase hip abductor activity during functional activities. The purpose of this research was to study the effects of walking with a unilateral weight. A total of 26 healthy adults walked on an instrumented treadmill with and without handheld weight (15%-20% body weight). Muscle activity, kinematic, and kinetic data were collected using surface electromyography, motion capture, and force plates, respectively. Average hip and trunk muscle activity, hip, pelvic, and trunk angles, and peak internal hip moments during stance were compared for each side (contralateral/ipsilateral to the weight) between conditions (unweighted/weighted) using a generalized linear model with generalized estimating equation correction. Interactions between condition and side were observed for muscle activity, frontal plane pelvic and trunk angles, and frontal plane hip moments (P ≤ .003). Compared with the unweighted condition, the weighted condition had higher hip abductor activity contralateral to the weight (P < .001), while no change was found ipsilateral to the weight (P ≥ .790). Similar changes were found for kinematic and kinetic variables. Walking with a unilateral weight may be a therapeutic option to increase functional hip abductor activity.

Relationship between passive ankle dorsiflexion range, dynamic ankle dorsiflexion range and lower limb and trunk kinematics during the single-leg squat

BACKGROUND

Limited passive ankle dorsiflexion range has been associated with increased knee valgus during functional tasks. Increased knee valgus is considered a contributing factor for musculoskeletal disorders in the lower limb. There is conflicting evidence supporting this association. The extent of passive ankle dorsiflexion range is associated with dynamic ankle dorsiflexion range and the way how these variables are related to lower limb or trunk kinematics is unclear.

RESEARCH QUESTION

What is the association between passive ankle dorsiflexion range or dynamic ankle dorsiflexion range with shank, thigh, pelvis or trunk movements during the single-leg squat?

METHODS

This is a cross-sectional study with a convenience sample. Thirty uninjured participants performed the single-leg squat with their dominant limb. Ankle, shank, thigh, pelvis and trunk 3D kinematics were recorded. Passive ankle dorsiflexion range was assessed through the weight-bearing lunge test and the dynamic ankle dorsiflexion range was defined as the ankle dorsiflexion range of motion in the sagittal plane during the single-leg squat.

RESULTS

Greater passive ankle dorsiflexion range was associated with smaller thigh internal rotation (r= -0.38). Greater dynamic ankle dorsiflexion range was associated with smaller trunk flexion (r = 0.59) and pelvis anteversion (r= -0.47). Passive ankle dorsiflexion range and dynamic ankle dorsiflexion range were not associated.

SIGNIFICANCE

Greater passive ankle dorsiflexion range seems to be associated with a better lower limb alignment during the single-leg squat, while dynamic ankle dorsiflexion range seems to reflect different lower limb and trunk kinematic strategies.