Plane Kinematics Research Articles

Impact of Running Clothes on Accuracy of Smartphone-Based 2D Joint Kinematic Assessment During Treadmill Running Using OpenPifPaf

The assessment of running kinematics is essential for injury prevention and rehabilitation, including anterior cruciate ligament sprains. Recent advances in computer vision have enabled the development of tools for quantifying kinematics in research and clinical settings. This study evaluated the accuracy of an OpenPifPaf-based markerless method for assessing sagittal plane kinematics of the ankle, knee, and hip during treadmill running using smartphone video footage and examined the impact of clothing on the results. Thirty healthy participants ran at 2.5 and 3.6 m/s under two conditions: (1) wearing minimal clothing with markers to record kinematics by using both a smartphone and a marker-based system, and (2) wearing usual running clothes and recording kinematics by only using a smartphone. Joint angles, averaged over 20 cycles, were analysed using SPM1D and RMSE. The markerless method produced kinematic waveforms closely matching the marker-based results, with RMSEs of 5.6° (hip), 3.5° (ankle), and 2.9° (knee), despite some significant differences identified by SPM1D. Clothing had minimal impact, with RMSEs under 2.8° for all joints. These findings highlight the potential of the OpenPifPaf-based markerless method as an accessible, simple, and reliable tool for assessing running kinematics, even in natural attire, for research and clinical applications.

A simple 2D multibody model to better quantify the movement quality of anterior cruciate ligament patients during single leg hop.

Patients with anterior cruciate ligament reconstruction frequently present asymmetries in the sagittal plane dynamics when performing single leg jumps but their assessment is inaccessible to health-care professionals as it requires a complex and expensive system. With the development of deep learning methods for human pose detection, kinematics can be quantified based on a video and this study aimed to investigate whether a relatively simple 2D multibody model could predict relevant dynamic biomarkers based on the kinematics using inverse dynamics. Six participants performed ten vertical and forward single leg hops while the kinematics and the ground reaction force "GRF" were captured using an optoelectronic system coupled with a force platform. The participants are modelled by a seven rigid bodies system and the sagittal plane kinematics was used as model input. Model outputs were compared to values measured by the force platform using intraclass correlation coefficients for seven outcomes: the peak vertical and antero-posterior GRFs and the impulses during the propulsion and landing phases and the loading ratio. The model reliability is either good or excellent for all outcomes (0,845 ≤ ICC ≤ 0.987). The study results are promising for deploying the developed model following a kinematics analysis based on a video. This could enable clinicians to assess their patients' jumps more effectively using video recordings made with widely available smartphones, even outside the laboratory.

Do bilateral deficits in hop for distance performance occur concomitantly with bilateral movement differences in people with patellofemoral pain? A cross-sectional investigation with between-group and -limb comparisons.

People with patellofemoral pain (PFP) may have bilateral deficits in hop for distance test (SLHD) performance, whereas the worsening performance of the pain-free or less painful limbs suggests that bilateral movement differences may occur. While clinicians may not be aware of bilateral movement differences that may be employed during the clinical assessment of SLHD performance (e.g., excessive trunk flexion, lower knee, hip and ankle angles), their suboptimal investigation may overestimate function and favor long-term sequelae. Do people with PFP exhibit bilateral differences in trunk and lower limb movements as well as bilateral deficits in SLHD performance compared to pain-free controls? We captured three-dimensional motion of 26 adults with PFP and 22 controls during testing and calculated trunk and lower limb sagittal plane kinematics, total concentric and eccentric work, and hip, knee, and ankle work contributions during the jumping and landing phases of the SLHD. We also calculated vertical ground reaction forces during the landing phase and compared between-group and -limb differences using independent and paired t-tests. People with PFP demonstrated bilateral deficits in SLHD performance (medium effects; p = .028-.050) and lower peak vertical ground reaction force values (medium-to-large effects; p = .006-.012) as compared to controls. No other between-group or -limb differences were identified. Bilateral deficits in SLHD performance seem to occur independently of movement differences in people with PFP, as they presented shorter distance but no differences in sagittal plane biomechanical patterns.

Validity of an inertial measurement system to measure lower-limb kinematics in patients with hip and knee pathology

Gait analysis for patients with orthopedic joint diseases is crucial to understand their functional status. Inertial measurement unit (IMU) systems, as alternatives to optical motion capture (OMC) systems, enable gait analysis outside the laboratory. However, their accuracy requires validated before widespread clinical use. Therefore, this study evaluated the validity of the Xsens IMU system for lower-limb joint angle measurements during walking in patients with hip and knee pathology and compared the error metrics among patients with hip pathology, patients with knee pathology and healthy controls. We used OMC system and Xsens IMU systems to simultaneously collect lower-limb kinematic data of 130 patients with knee pathology, 110 patients with hip pathology and 25 healthy individuals during walking at self-selected speed. Validity was assessed using root mean square error (RMSE), amplitude difference and coefficient of determination (R2). The RMSEs for the patient groups ranged from 2.5° to 8.8°, with half of the joint angles showing acceptable accuracy and the rest tolerable accuracy. The joint angles measured by both systems were more consistent in the sagittal plane (R2: 0.62–0.96), with lower consistency in the frontal and transverse planes (R2: 0.44–0.63). Compared to the control group, both patient groups had higher RMSEs and lower R2 across most joint angles. Our results suggest that the Xsens IMU system offers highly comparable sagittal plane kinematic waveforms in patients with hip and knee pathology. Caution should be taken when interpreting the frontal and transverse plane kinematics and assessing patients with severe joint deformities.

Short-term selective dorsal rhizotomy responders among children with bilateral cerebral palsy.

To identify the short-term effects of selective dorsal rhizotomy (SDR) on gait and clinical impairments in children with bilateral spastic cerebral palsy (CP) and subgroups based on baseline gait patterns. Eighty-nine children with bilateral spastic CP (55 males, mean age [SD] before SDR: 9 years 5 months [2 years 3 months]; Gross Motor Function Classification System level I: 18; II: 54; III: 17) received three-dimensional gait analyses at two time points (baseline and 1 year after SDR); their baseline gait patterns were classified. The analysis included the comparisons of (1) sagittal plane kinematic waveforms, the Gait Profile Score, and non-dimensional spatiotemporal parameters between the two time points, (2) the kinematic waveforms of both time points to those of typically developing children, and (3) composite impairment scores of spasticity, weakness, and selectivity between the two time points. Overall, kinematics improved distally but deteriorated proximally in the entire sample, especially in genu recurvatum and crouch gait patterns. Jump gait showed the most improvements after SDR, followed by apparent equinus and crouch gait. Spasticity was reduced after SDR, but not at the expense of strength or selectivity. The potential merit of investigating short-term SDR effects on gait according to baseline gait patterns was shown, with an overview of changes after SDR that may facilitate patient-tailored treatment.

Ankle Taping Does Not Affect Running Kinematics During a Treadmill Protocol in Well-Trained Runners: A Secondary Analysis from a Randomized Cross-Over Controlled Trial.

Background: The purpose of this randomized cross-over controlled trial was to evaluate the biomechanical effects of ankle taping using rigid tape (RT) or kinesiotape (KT) compared to no taping during treadmill running in well-trained amateur runners. Methods: A total of 22 participants (15 men and 7 women) completed three running sessions on a treadmill, each lasting 30 min, under different conditions: no taping (CG), RT, and KT. Sagittal and frontal plane kinematics were analyzed using the Kinovea software to assess the ankle dorsiflexion, knee flexion, hip extension, tibial angle, foot strike pattern, heel eversion, and pelvic drop across three intervals (0-10, 10-20, and 20-30 min). Results: The results demonstrated no significant differences in sagittal plane variables (ankle dorsiflexion, knee flexion, hip extension, and cadence) or frontal plane variables (heel eversion and pelvic drop) between the CG, RT and KT groups at any time point. Although heel eversion significantly increased over time due to fatigue, the taping conditions did not affect running kinematics. Conclusions: These findings suggest that neither RT nor KT alters running biomechanics in well-trained runners over prolonged treadmill running. The study highlights that taping, commonly used to prevent ankle injuries, does not significantly modify lower limb kinematics in the absence of injury. Further research is needed to evaluate the effects of taping in novice or injured runners and under more demanding conditions, such as overground running.

Asymmetry of the Trunk and Lower Extremity Joint Frontal Plane Kinematics During Single-Leg Standing and Squat in Paralympic Athletes With Upper Limb Deficiency Compared With Intact Athletes

OBJECTIVES: To compare trunk and lower extremity asymmetries in frontal and sagittal kinematics, between athletes with upper limb deficiency (ULD) and intact athletes, during bilateral-leg standing (BLST), single-leg standing (SLST), and single-leg squat (SLSQ). DESIGN: Cross-sectional study METHODS: Eleven elite Paralympic athletes with ULD, and eleven intact elite athletes performed BLST, SLST, and SLSQ. Angles of the trunk, pelvis, hip, knee, and ankle were recorded using fixed cameras in the frontal and sagittal planes. Kinematic asymmetries between groups, and the relationship between loss of mass relative to body mass (LM%) and ipsilateral trunk tilt were analyzed. RESULTS: Paralympic athletes exhibited greater ipsilateral trunk tilt during ULD side SLSQ (∆ = 7.1°, p = .02, d = 1.26) than intact athletes, but not during intact side SLSQ. No significant correlation was found between LM% and bilateral angle differences in the frontal plane among paralympic athletes ( p > .05, .06 ≤ | r| ≤ .27) CONCLUSION: Athletes with ULD compensated for missing body mass by tilting their trunk over their support leg when performing SLSQ only on the ULD side. The amount of trunk tilt did not seem to depend on the amount of missing mass.

Frontal Plane Kinematics And Kinetics Of Inexperienced Participants During Battle Rope Exercises

Frontal Plane Kinematics And Kinetics Of Inexperienced Participants During Battle Rope Exercises

What is the Gold Standard for Advanced Hallux Rigidus? Minimum 10 Year Follow-Up Comparison of Interposition Arthroplasty and Arthrodesis Shows Similar Outcomes

Category: Midfoot/Forefoot; Other Introduction/ Purpose: Hallux rigidus is characterized by arthritic changes of the first metatarsophalangeal joint (MTPJ) with joint space narrowing, osteophyte formation, and painful MTPJ motion. Although MTPJ arthrodesis is considered the “gold standard,” a Modified Oblique Keller Capsular Interposition Arthroplasty (MOKCIA) is an alternative treatment for hallux rigidus in patients who desire to retain MTPJ motion. The purpose of this study is to compare long-term outcomes (patient satisfaction, radiographic alignment, MTPJ walking kinematics, and plantar pressure) between the MOKCIA and 1st MTPJ arthrodesis. We hypothesized that patients undergoing MOKCIA will retain motion, but when compared to Arthrodesis at long-term follow-up, some MOKCIA patients may develop abnormal forefoot loading, toe malalignment and need revision. Methods: 26 patients who underwent a MOKCIA (n=14, 74±7 years old, 9 female, average 15 years from surgery) or an arthrodesis (n=12, 70±4 years old, 6 female, average 13 years from surgery) were recruited from a retrospective chart review (January 1, 2005, and December 31, 2018). Study measures included 11-point visual analog scale (VAS) Pain and satisfaction, Foot and Ankle Assessment Measure (FAAM) and PROMIS physical function scores, weight bearing radiographs (MTPJ valgus and 1st proximal phalanx to ground sagittal), walking MTPJ (first phalanx relative to forefoot) sagittal plane kinematics, forefoot and 1st toe peak plantar pressure during walking, MTPJ goniometer range of motion, and number of additional 1st MTPJ surgical interventions required. Two-sample t-tests or Chi-square were used to compare groups. Results: Groups did not differ on demographic characteristic or patient reported outcomes [VAS Pain (MOKCIA=0.1±0.3, Arthrodesis=1.2±1.8, p=0.06), satisfaction (MOKCIA=9.4±0.9, Arthrodesis=8.3±1.6, p=0.054), FAAM (MOKCIA=94±9, Arthrodesis=95±7, p=0.65), PROMIS (MOKCIA=50±6, Arthrodesis=48±6, p=0.41)]. MTPJ valgus was increased in the Arthrodesis group (MOKCIA=4±5°, Arthrodesis=7±4°, p=0.05). First phalanx to ground was more plantarflexed in the MOKCIA group (MOKCIA=9±7°, Arthrodesis=1±7°, p=0.01)]. Walking MTPJ excursion was greater in the MOKCIA group (MOKCIA=25±9°, Arthrodesis=13±8°, p< 0.001). There was no group difference in forefoot and 1st toe walking peak plantar pressure (Forefoot: MOKCIA=111±29 N/cm2, Arthrodesis=127±22 N/cm2, p=0.12 and Toe: MOKCIA=77±28 N/cm2, Arthrodesis=101±41 N/cm2, p=0.10). MTPJ extension range of motion was greater in the MOKCIA group (MOKCIA=48°±13, Arthrodesis=25°±8, p< 0.001). One person in the Arthrodesis group required hardware removal, but no MOKCIA patient required additional surgery. Conclusion: More than 10 years of follow-up after surgery, patients in both MOKCIA and Arthrodesis groups had little pain, were similarly satisfied, and reported high function with little limitation due to their toe surgery. Radiograph alignment showed no progressive deformity in the MOKCIA group and patients were able to retain MTPJ extension range of motion during walking. Plantar pressures were not impacted by surgical intervention. No MOKCIA patient required revision. These results suggest MOKCIA is a reasonable alternative option compared to first MTPJ arthrodesis for long term treatment of hallux rigidus in patients who desire to preserve toe range of motion.

Hips Don't Lie: Analyzing Frontal Plane Kinematics In Adults Of Varying Ages During Step Tasks

Hips Don't Lie: Analyzing Frontal Plane Kinematics In Adults Of Varying Ages During Step Tasks

The Effects Of Incremental Loading On Center Of Pressure And Sagittal Plane Kinematics In Healthy Adults During Safety Bar Squat

The Effects Of Incremental Loading On Center Of Pressure And Sagittal Plane Kinematics In Healthy Adults During Safety Bar Squat

Drop Vertical Jump Landing Mechanics Are Similar Between Patients With Quadriceps Tendon and Patellar Tendon Autografts After Anterior Cruciate Ligament Reconstruction

To compare the biomechanics of a drop vertical jump (DVJ) landing task and functional outcomes among patients with anterior cruciate ligament reconstruction (ACLR) with quadriceps tendon (QT) and patellar tendon (PT) autografts. Physically active patients who underwent primary ACLR with either a QT or PT autograft were included in this study. All were within 6 months to 2 years after surgery and cleared for return to physical activity. Subjects completed DVJs in a biomechanics laboratory. Peak vertical ground reaction force (VGRF) and lower-extremity joint sagittal and frontal plane kinematics and kinetics were collected and analyzed. Mann-Whitney U tests were used to compare the surgical limbs of the QT and PT autograft groups for kinematic and kinetic variables. Wilcoxon rank-sum tests were used to compare the surgical and nonsurgical limbs for both the QT and PT autograft groups. Twenty-four physically active individuals who underwent primary ACLR with QT (n= 14) or PT (n= 10) autografts completed DVJs in a biomechanics laboratory. There were no statistically significant biomechanical differences between the QT and PT groups. Peak VGRF differed between the surgical and nonsurgical limbs for the QT (surgical and nonsurgical, 1.10 and 1.30 N) and PT (surgical and nonsurgical, 1.10 and 1.35 N) groups. Specifically, both groups demonstrated lower VGRFs in the surgical limb compared with the nonsurgical limb (P < .05). Additional medium and large effect sizes were found when comparing kinetic variables between limbs within both surgical groups. Regardless of the graft-specific surgical technique, patients who undergo ACLR are returning to activity with movements that resemble an offloading pattern of the surgical limb. Coupled with the finding of an absence of differences in kinematic and kinetic variables between the QT and PT autograft groups suggests that the QT graft may be a viable alternate graft source for ACLR. Level III, retrospective comparative study.

Identifying Goalkeeper Movement Timing from Single-Camera Broadcast Footage through Pose Estimation: A Pilot Study

This study explores how open-source pose estimation can be utilized to identify goalkeeper dive initiation during soccer penalty kicks. The purpose of this study is to provide an accessible, low-cost heuristic methodology for identifying goalkeeper dive initiation. This study uses single-camera broadcast footage (1080 p resolution, 50 frames per second) of all 41 penalty shootout kicks attempted during the 2022 FIFA Men’s World Cup. We isolated each penalty kick and recorded the frames of goalkeeper dive initiation and flight. We then identified goalposts to create a homography matrix to account for camera movement and identified the goalkeeper’s skeletal keypoints through pose estimation. From these keypoints, we derived frontal plane kinematics for the torso and legs. We identified local extrema for each kinematic variable and isolated the last observed extrema prior to goalkeeper flight for each variable. Using OLS regression, we found that the last local extremum of the goalkeeper centroid’s y-value was the strongest predictor of labeled commitment to the dive side, with an R2 of 0.998 and a p-value of 0.00. The results of this research are preliminary but demonstrate the promise of pose estimation in identifying sport-specific action timing during live game play using a single camera.

Ex vivo biomechanical investigations of combined extra- and intracapsular stabilization in canines with cranial cruciate ligament deficiency.

Intracapsular reconstruction (ICR) has long been recommended as a treatment for cranial cruciate ligament deficiency (CCLD) in dogs, but it has fallen out of favor due to its inferior long-term functional outcomes. These outcomes may be attributed to the poor stiffness and strength of the graft in the early period before ligamentization is completed. Additional placement of extracapsular sutures to mechanically protect the graft during the ligamentization process may be a viable method to address this problem. However, the biomechanical effect of this combined surgical approach remains unknown. This study aimed to evaluate the 3D kinematics of the CCLD stifle in dogs in response to ICR and combined extra- and intracapsular reconstruction (CEICR). Twelve hindlimbs were collected from nine cadavers of mature dogs. The limbs were tested using a custom-made testing apparatus that reproduces their sagittal plane kinematics during the stance phase. Four statuses of stifle joints were tested, namely, (a) cranial cruciate ligament (CCL) intact; (b) CCLD; (c) CCLD stifle stabilized by CEICR; and (d) CCLD stifle stabilized by ICR only. Three-dimensional stifle kinematics at the 5 instances of the stance phase were measured with an optoelectronic system. The results showed that ICR marginally corrects the increased adduction, internal rotation, and caudodistal stifle joint center displacement that occur as a result of CCLD. CEICR led to better restoration of the stifle kinematics, especially with respect to the internal rotation and cranial translation stabilities. Furthermore, CEICR only resulted in minor excessive restraints on other motion components. The findings indicated that the additional lateral fabellotibial suture offers immediate stability to the stifle, consequently lowering the risk of graft over-elongation in the short term postoperatively. Considering the propensity for the extracapsular suture to degrade over time, further in vivo studies are warranted to explore the long-term effects of the CEICR procedure.

Short-term results of soft tissue balance obtained with 'manual gap balancing' in varus knees; a prospective study supported by gait analysis

Aim: The aim of this study was to investigate the contribution of medial ligament release using the manual gap balance method in patients with varus deformity to alignment and functional outcomes. Materials and Methods: The study included 14 female and 8 male patients who underwent total knee arthroplasty. Telemetric radiographs of the lower extremities and valgus stress radiographs of the knees to be operated on were taken for each patient one day before and 1.5 months after the operation. The functional evaluation of patients was conducted using the HSS (Hospital for Special Surgery, 1970) scoring system. Simultaneously, gait analyses were conducted. The patients were divided into groups based on their stress radiographs. Results: The mean valgus angle in postoperative static radiographs was 2.5 degrees. A statistically significant change in rotational deformity was observed in both swing and stance phases after surgery compared to preoperative values. Improvement in coronal plane varus knees was statistically significant. No significant change was found in the flexion-extension angles of sagittal plane kinematics. It was found that there was a statistically significant difference in the data for single support, double support, and stance percentage (p

Statistical Parametric Mapping to detect the effects of the secondary jump direction on landing kinematics

ABSTRACT Anterior cruciate ligament (ACL) injuries in sports often occur with non-contact mechanisms, such as landing and cutting. Previous studies explored the ACL injury biomechanical risk factors through drop-jumps combined with secondary jumps. This study aimed to investigate the effect of the secondary jump direction on first landing kinematic temporal series. Fifty-seven participants (29 males, 28 females) performed three single-leg drop-jumps followed by secondary jumps in vertical (single-planar), 45°-medial and 45°-lateral direction (multi-planar). Lower limb and trunk landing kinematics was recorded using a 9-camera motion capture system and analysed with a One-way ANOVA through Statistical Parametric Mapping (SPM), from initial contact to maximum knee flexion. All variables were affected by the secondary jump direction, except trunk rotation. In sagittal plane, kinematic main differences were found between single- and multi-planar tasks. The latter elicited higher trunk, hip, and knee flexion. Frontal plane kinematics was more influenced by medio-lateral components of secondary jumps. Our results could underline how a single task may be insufficient for ACL injury risk assessment. Single- and multi-planar tasks including a secondary jump should be considered for more comprehensive evaluations in prevention and rehabilitation programs, but caution should be used when comparing results of studies adopting different tasks.

Quantifying lumbar sagittal plane kinematics using a wrist-worn inertial measurement unit.

Wearable sensors like inertial measurement units (IMUs), and those available as smartphone or smartwatch applications, are increasingly used to quantify lumbar mobility. Currently, wearable sensors have to be placed on the back to measure lumbar mobility, meaning it cannot be used in unsupervised environments. This study aims to compare lumbar sagittal plane angles quantified from a wrist-worn against that of a lumbar-worn sensor. Twenty healthy participants were recruited. An IMU was placed on the right wrist and the L3 spinal level. Participants had to position their right forearm on their abdomen, parallel to the floor. Three sets of three consecutive repetitions of flexion, and extension were formed. Linear mixed models were performed to quantify the effect of region (lumbar vs. wrist) on six outcomes [minimum, maximum, range of motion (ROM) of flexion and extension]. Only flexion ROM was significantly different between the wrist and lumbar sensors, with a mean of 4.54° (95% CI = 1.82°-7.27°). Across all outcomes, the maximal difference between a wrist-worn and lumbar-worn sensor was <8°. A wrist-worn IMU sensor could be used to measure gross lumbar sagittal plane mobility in place of a lumbar-worn IMU. This may be useful for remote monitoring during rehabilitation.

Females Present Different Single-Leg Squat Kinematics and Muscle Activation Strategies than Males Even after Hip Abductor Fatigue

Background: Despite the potential connection between hip and knee muscle control, there is limited research on the effects of hip abductor fatigue on the hip and knee neuromuscular responses in both males and females. This study aimed to investigate the influence of sex on the hip and knee frontal plane kinematics and the EMG responses of the hip abductors and knee extensor muscles during the single-leg squat before and after hip abductor fatigue. Methods: A total of 30 participants (males, n = 15; females, n = 15) performed single-leg squats before and immediately after a hip abductor fatigue protocol (10° hip abduction position while bearing a 20% load of their estimated 1RM until exhaustion). The frontal plane kinematics (hip adduction and knee frontal plane projection angle) and EMG parameters (amplitude and median frequency) of the gluteus medius (GMed), tensor fascia latae (TFL), vastus lateralis (VL) and vastus medialis (VM) were measured during the single-leg squat. Results: We did not find any effects of hip abductor fatigue or interaction between fatigue and sex on the evaluated parameters (p &gt; 0.05). However, compared to males, females had greater values for the hip and knee frontal plane kinematics (p = 0.030), GMed EMG amplitude (+10.2%, p = 0.012) and median frequency (+10.3%; p = 0.042) and lower VL median frequency (−9.80%; p = 0.007). Conclusions: These findings establish sex-related differences in the kinematics and hip and knee EMG parameters during the single-leg squat, which were not influenced by the hip abductor fatigue protocol.

How reliable are femoropelvic kinematics during deep squats? The influence of subject-specific skeletal modelling on measurement variability

BackgroundBiplanar radiography displays promising results in the production of subject-specific (S.specific) biomechanical models. However, the focus has predominantly centred on methodological investigations in gait analysis. Exploring the influence of such models on the analysis of high range of motion tasks linked to hip pathologies is warranted. The aim of this study is to investigate the effect of S.Specific modelling techniques on the reliability of deep squats kinematics in comparison to generic modelling. Methods8 able-bodied male participants attended 5 motion capture sessions conducted by 3 observers and performed 5 deep squats in each. Prior to each session a biplanar scan was acquired with the reflective-markers attached. Inverse kinematics of pelvis and thigh segments were calculated based on S.specific and Generic model definition. Agreement between the two models femoropelvic orientation in standing was assessed with Bland-Altman plots and paired t- tests. Inter-trial, inter-session, inter-observer variability and observer/trial difference and ratio were calculated for squat kinematic data derived from the two modelling approaches. ResultsCompared to the Generic model, the S.Specific model produced a calibration trial that is significantly offset into more posterior pelvis tilt (–2.8±2.7), hip extension (–2.2±3.8), hip abduction (–1.2±3.6) and external rotation (–13.8±11.4). The S.specific model produced significantly different squat kinematics in the sagittal plane of the pelvis (entire squat cycle) and hip (between 40 % and 60 % of the squat cycle). Variability analysis indicated that the error magnitude between the two models was comparable (difference<2°). The S.specific model exhibited a lower variability in the observer/trial ratio in the sagittal pelvis and hip, the frontal hip, but showed a higher variability in the transverse hip. SignificanceS.specific modelling appears to introduce a calibration offset that primarily translates into an effect in the sagittal plane kinematics. However, the clinical added value of S.specific modelling in terms of reducing experimental sources of kinematic variability was limited.

Lower Extremity Kinematic and Kinetic Characteristics as Effects on Running Economy of Recreational Runners.

This study aimed to determine associations between running economy (RE) and running sagittal plane kinematic and kinetic parameters. A total of 30 male recreational runners (age: 21.21 ± 1.22 yr, V̇O 2max : 54.61 ± 5.42 mL·kg -1 ·min -1 ) participated in two separate test sessions. In the first session, the participant's body composition and RE at 10 and 12 km·h -1 were measured. In the second session, measurements were taken for the sagittal plane of hip, knee, and ankle angles and range of motion (ROM), as well as ground reaction force. Moderate correlations were found between lower energy costs at 12 km·h -1 and smaller hip flexion at toe-off ( r = 0.373) as well as smaller peak hip flexion during stance ( r = 0.397). During the swing phase, lower energy costs at 10 km·h -1 were moderately correlated with smaller peak knee flexion and smaller knee flexion and extension ROM ( r = 0.366-0.443). Lower energy costs at 12 km·h -1 were moderately correlated with smaller peak hip and knee flexion as well as knee extension ROM ( r = 0.369-0.427). In terms of kinetics, there was a moderate correlation between higher energy costs at 10 km·h -1 and larger peak active force, as well as larger peak braking and propulsion force ( r = -0.470-0.488). Lower energy costs at 12 km·h -1 were moderately to largely correlated with smaller peak impact and braking force ( r = 0.486 and -0.500, respectively). Regarding the statistical parametric mapping analysis, most outcomes showed associations with RE at 10 km·h -1 , including knee flexion (42.5%-65.5% of the gait cycle), ankle plantarflexion (32.5%-36% of the gait cycle), active force (30.5%-35% of the stance phase), and propulsion force (68%-72.5% of the stance phase). Lower energy costs at 12 km·h -1 were correlated with smaller hip flexion (5.5%-12% and 66.5%-74%) and smaller knee flexion (57%-57.5%) during the running gait cycle. This study indicates that biomechanical factors are associated with RE in recreational runners. To design effective training methods to improve RE, coaches and runners should focus on the sagittal plane kinematics of the hip, knee, and ankle, as well as lower vertical and horizontal kinetic parameters.