Sagittal Plane Joint Research Articles

Development of An Anybody Musculoskeletal Model of The Thoroughbred Forelimb

Musculoskeletal injuries in horses are the main cause of retirement, rest, and death. To understand these injuries, it is necessary to study loads in muscles, tendons and ligaments. A musculoskeletal model makes it possible to consider all structures simultaneously and avoids invasive measurements. At present, most computational models of the equine limb described in the literature have been limited to the distal limb. The aim of this study was to create a preliminary musculoskeletal model of the whole equine forelimb and to run it with kinematic data collected during gait. The model was developed with the AnyBody Modelling System. It includes six limb segments, 11 muscle groups and 17 ligaments. Kinematic data were collected from the right forelimb of four Thoroughbreds at trot, right and left lead canter, and were then used in the model to compute sagittal plane joint excursions and ligament and tendon strains. The modelled joint excursions were in reasonable agreement with previous reports in the literature despite breed, gait and surface differences. Strain patterns of the tendons of the suspensory apparatus agreed with the literature, with maxima in mid-stance or at the end of stance. Strains in the distal palmar ligaments peaked in mid-stance, while strain in lacertus fibrosus peaked at the stance-swing transition. Tendon and ligament strains at canter were greatest when the measured forelimb was the trailing limb. Strain amplitudes varied against earlier models and these differences are discussed in relation to variations in methods, and especially in relation to attachment points of tendons and ligaments.

A 2D video-analysis scoring system of 90° change of direction technique identifies football players with high knee abduction moment

PurposeAbnormal joint biomechanics and poor neuromuscular control are modifiable risk factors for Anterior Cruciate Ligament (ACL) injury. Although 3D motion capture is the gold standard for the biomechanical evaluation of high-speed multidirectional movements, 2D video analysis is a growing-interest alternative because of its higher cost-effectiveness and interpretability. The aim of the present study was to explore the possible association between a 2D evaluation of a 90° change of direction (COD) and the KAM measured with gold standard 3D motion analysis.MethodsThirty-four competitive football (soccer) players (age 22.8 ± 4.1, 18 male and 16 females) were enrolled. Each athlete performed a series of pre-planned 90° COD at the maximum speed possible in a laboratory equipped with artificial turf. 3D motion analysis was recorded using 10 stereophotogrammetric cameras, a force platform, and three high-speed cameras. The 2D evaluation was performed through a scoring system based on the video analysis of frontal and sagittal plane joint kinematics. Five scoring criteria were adopted: limb stability (LS), pelvis stability (PS), trunk stability (TS), shock absorption (SA), and movement strategy (MS). For each criterion, a sub-score of 0/2 (non-adequate), 1/2 (partially adequate), or 2/2 (adequate) was attributed to the movement, based on objective measurements. The intra-rater and inter-rater reliability were calculated for each criterion and the total score. The Knee Abduction Moment (KAM) was extracted from the 3D motion analysis and grouped according to the results of the 2D evaluation.ResultsExcellent intra-rater reliability (ICC > 0.88) and good-to-excellent inter-rater reliability (ICC 0.68–0.92) were found. Significantly higher KAM was found for athletes obtaining a 0/2 score compared to those obtaining a 2/2 score in all the sub-criteria and the total score (20–47% higher, p < 0.05). The total score and the LS score showed the best discriminative power between the three groups.ConclusionThe 2D video-analysis scoring system here described was a simple and effective tool to discriminate athletes with high and low KAM in the assessment of a 90° COD and could be a potential method to identify athletes at high risk of non-contact ACL injury.Level of evidenceIV.

Effects of Overweight and Obesity on Running Mechanics in Children.

The purpose of this study is to determine differences in running mechanics between healthy weight (HW) children and children classified as OW/OB. Forty-two children (17 OW/OB, 25 HW) ran overground while kinematic and kinetic data were recorded using a motion capture system and force plate. Kinematic variables of interest included stance time, step length, and frontal and sagittal plane joint angles and excursions at the hip, knee, and ankle. Kinetic variables of interest included ground reaction forces and hip, knee, and ankle moments in the sagittal and frontal planes. The OW/OB group spent more time in stance, took shorter steps, displayed less hip flexion during the first half of stance, had greater ankle inversion at foot strike, had greater knee abduction throughout stance, and had smaller knee flexion, knee adduction, and hip adduction excursions. In comparing unscaled ground reaction forces, the OW/OB group displayed greater peak vertical force, vertical impact peaks, and vertical loading rates. The OW/OB group also displayed greater unscaled plantar and dorsiflexion moments, knee flexion and extension moments, ankle inversion moments, and knee and hip abduction moments. These data suggest that increased body weight in children is associated with changes in running mechanics. Higher joint moments and ground reaction forces may indicate increased injury risk or the development of joint degeneration among overweight/obese children.

Kinematic and Kinetic Predictors of Y-Balance Test Performance.

BackgroundThe Y-Balance Test (YBT) assesses dynamic stability and neuromuscular control of the lower extremity. Several authors have analyzed kinematic predictors of YBT performance with conflicting results, but the influence of kinetic factors is not well understood.PurposeTo examine kinematic predictors of YBT performance and determine the joint kinetics which predict YBT performance.Study DesignCross-sectional study.MethodsThirty-one physically active individuals performed YBT trials on a force plate while whole body kinematics were recorded using a motion capture system. Sagittal, frontal, and transverse plane joint kinematics and joint moments were calculated at maximum reach in each YBT reach direction. Variables correlated with reach distances at the p < 0.2 level were entered into a stepwise linear regression.ResultsIn the anterior direction, knee flexion and torso rotation (R2=0.458, p<0.001) and knee extensor and hip abductor moments (R2=0.461, p<0.001) were the best kinematic and kinetic predictors of reach distance. In the posterior medial direction, hip flexion, ankle dorsiflexion, and ankle rotation accounted for 45.8% of the variance in reach direction (p<0.001) while hip and knee extensor, and hip abductor moments explained 72.6% of the variance in reach distance (p<0.001). In the posterior lateral direction, hip flexion and pelvic rotation (R2=0.696, p<.001) and hip extensor moments (R2=0.433, p=0.001) were the best kinematic and kinetic predictors of reach distance.ConclusionThe ability to generate large hip and knee joint moments in the sagittal and frontal plane are critical for YBT performance.Level of Evidence3.

The Utility of Functional Data Analyses to Reveal Between-Limbs Asymmetries in Those With a History of Anterior Cruciate Ligament Reconstruction.

Researchers have traditionally used motion capture to quantify discrete data points (peak values) during hop testing. However, these analyses restrict the evaluation to a single time point (ie, certain percentage of stance) and provide only a narrow view of movement. Applying more comprehensive analyses may help investigators identify important characteristics that are masked by discrete analyses often used to screen patients for activity. To examine the utility of functional data analyses to reveal asymmetries that are undetectable using discrete (ie, single time point) evaluations in participants with a history of anterior cruciate ligament reconstruction (ACLR) who achieved clinical hop symmetry. Cross-sectional study. Laboratory. Fifteen participants with unilateral ACLR (age = 21 ± 3 years, time from surgery = 4 ± 3 years) and 15 control participants without ACLR (age = 23 ± 2 years). Lower extremity biomechanics during the triple-hop-for-distance task for the ACLR and contralateral limbs of patients and a representative limb of control participants were measured. Peak sagittal-plane joint power, joint work, and power profiles were determined. Using discrete analyses, we identified lower peak knee power and work in the ACLR limb compared with the contralateral and control limbs (P < .05) but were unable to demonstrate differences at the ankle or hip. Using functional data analyses, we observed asymmetries at the ankle, knee, and hip between the ACLR and contralateral or control limbs throughout stance (P < .05), and it was revealed that these asymmetries stemmed from knee power deficits that were prominent during early loading. Despite achieving hop-distance symmetry, the ACLR knees absorbed less power. Although this information was revealed using discrete analyses, underlying asymmetries at the ankle and hip were masked. Using functional data analyses, we found interlimb asymmetries at the ankle, knee, and hip. Importantly, we found that functional data analyses more fully elucidated the extent and source of asymmetries, which can be used by clinicians and researchers alike to aid in clinical decision making.

Lead limb loading during a single-step descent in persons with and without a transtibial amputation in the trailing limb

BackgroundDecreased mechanical work done by the trailing limb when descending a single-step could affect load development and increase injury risk on the leading limb. This study assessed the effect of trailing limb mechanics on the development of lead limb load during a step descent by examining individuals with unilateral transtibial amputations who are known to exhibit reduced work in the prosthetic limb. MethodsEight amputees and 10 able-bodied controls walked 5 m along the length of a raised platform, descended a single-step of 14 cm height, and continued walking. The intact limb of amputees led during descent. Kinematic and kinetic data were recorded using integrated motion capture and force platform system. Lead limb loading was assessed through vertical ground reaction force, and knee moments and joint reaction forces. Sagittal-plane joint work was calculated for the ankle, knee, and hip in both limbs. FindingsNo differences were found in lead limb loading despite differences in trail limb mechanics evidenced by amputees performing 58% less total work by the trailing (prosthetic) limb to lower the centre of mass (P = 0.004) and 111% less for propulsion (P < 0.001). Amputees descended the step significantly slower (P = 0.003) and performed significantly greater lead limb ankle work (P = 0.017). After accounting for speed differences, initial loading at the knee was significantly higher in the lead limb of amputees versus controls. InterpretationIncreasing lead limb work and reducing forward velocity may be effective compensatory strategies to limit lead limb loading during a step descent, in response to reduced trailing limb work.

How Well Do Commonly Used Co-contraction Indices Approximate Lower Limb Joint Stiffness Trends During Gait for Individuals Post-stroke?

Muscle co-contraction generates joint stiffness to improve stability and accuracy during limb movement but at the expense of higher energetic cost. However, quantification of joint stiffness is difficult using either experimental or computational means. In contrast, quantification of muscle co-contraction using an EMG-based Co-Contraction Index (CCI) is easier and may offer an alternative for estimating joint stiffness. This study investigated the feasibility of using two common CCIs to approximate lower limb joint stiffness trends during gait. Calibrated EMG-driven lower extremity musculoskeletal models constructed for two individuals post-stroke were used to generate the quantities required for CCI calculations and model-based estimation of joint stiffness. CCIs were calculated for various combinations of antagonist muscle pairs based on two common CCI formulations: Rudolph et al. (2000) (CCI1) and Falconer and Winter (1985) (CCI2). CCI1 measures antagonist muscle activation relative to not only total activation of agonist plus antagonist muscles but also agonist muscle activation, while CCI2 measures antagonist muscle activation relative to only total muscle activation. We computed the correlation between these two CCIs and model-based estimates of sagittal plane joint stiffness for the hip, knee, and ankle of both legs. Although we observed moderate to strong correlations between some CCI formulations and corresponding joint stiffness, these associations were highly dependent on the methodological choices made for CCI computation. Specifically, we found that: (1) CCI1 was generally more correlated with joint stiffness than was CCI2, (2) CCI calculation using EMG signals with calibrated electromechanical delay generally yielded the best correlations with joint stiffness, and (3) choice of antagonist muscle pairs significantly influenced CCI correlation with joint stiffness. By providing guidance on how methodological choices influence CCI correlation with joint stiffness trends, this study may facilitate a simpler alternate approach for studying joint stiffness during human movement.

Duty Factor Reflects Lower Limb Kinematics of Running

The aim was to identify the differences in lower limb kinematics used by high (DFhigh) and low (DFlow) duty factor (DF) runners, particularly their sagittal plane (hip, knee, and ankle) joint angles and pelvis and foot segment angles during stance. Fifty-nine runners were divided in two DF groups based on their mean DF measured across a range of speeds. Temporal characteristics and whole-body three-dimensional kinematics of the running step were recorded from treadmill runs at 8, 10, 12, 14, 16, and 18 km/h. Across speeds, DFhigh runners, which limit vertical displacement of the COM and promote forward propulsion, exhibited more lower limb flexion than DFlow during the ground contact time and were rearfoot strikers. On the contrary, DFlow runners used a more extended lower limb than DFhigh due to a stiffer leg and were midfoot and forefoot strikers. Therefore, two different lower limb kinematic mechanisms are involved in running and the one of an individual is reflected by the DF.

Effect of gait retraining on segment coordination and joint variability in individuals with patellofemoral pain

BackgroundGait retraining is advocated for the management of patellofemoral pain. This case series examined changes in lower limb variability following 6-weeks of gait retraining in individuals with patellofemoral pain. MethodsSix runners with patellofemoral pain completed a 6-week physiotherapist-guided gait retraining program using minimalist footwear and increased cadence. Approximate entropy joint variability and segment coordination variability were calculated across the entire gait cycle during running at baseline, 6 and 12 weeks and compared using repeated measures analysis of variance and the standardised mean difference (SMD). FindingsCompared to baseline, there were large increases in hip joint transverse plane kinematic variability at 6 (SMD = 1.7) and 12 weeks (SMD = 1.3). Moderate increases in hip joint frontal plane and knee joint sagittal plane kinematic variability were also observed at 6 (SMD = 1.1 & 0.96) and 12 weeks (SMD = 1.1 & 0.89). Knee joint frontal plane and hip joint transverse plane kinetic variability demonstrated large increases from baseline at 6 (SMD = 1.3 & 0.9) and 12 weeks (SMD = 0.9 & 1.0). There was no main effect of time for segment coordination variability. All participants had clinically meaningful improvements in pain (visual analogue change score > 20 mm). InterpretationGait retraining increased joint kinematic and kinetic variability in those with patellofemoral pain and these changes persisted over 12 weeks. Increased variability was observed in joint kinematics and kinetics known to influence patellofemoral joint stress, which may vary patellofemoral joint loading patterns and partly explain the clinical effect.

Improved Ankle Mobility After a 4-Week Training Program Affects Landing Mechanics: A Randomized Controlled Trial.

Howe, LP, Bampouras, TM, North, JS, and Waldron, M. Improved ankle mobility after a 4-week training program affects landing mechanics: a randomized controlled trial. J Strength Cond Res 36(7): 1875-1883, 2022-This study examined the effects of a 4-week ankle mobility intervention on landing mechanics. Twenty subjects with restricted ankle dorsiflexion range of motion (DF ROM) were allocated to either a strength training only (n = 9) or a strength training and ankle mobility program (n = 11). Subjects performed a weight-bearing lunge test and bilateral drop-landings before and after the intervention. Normalized peak vertical ground reaction force (vGRF), time to peak vGRF, and loading rate were calculated, alongside sagittal-plane initial contact angles, peak angles, and sagittal-plane joint displacement for the ankle, knee, and hip. Frontal-plane projection angles were also calculated. After the intervention, only the strength and mobility group improved ankle DF ROM (mean difference = 4.1°, effect size [ES] = 1.00, p = 0.002). A one-way analysis of covariance found group effects for ankle joint angle at initial contact (p = 0.045), ankle (p < 0.001) and hip joint angle at peak flexion (p = 0.041), and sagittal-plane ankle (p < 0.001) and hip joint displacement (p = 0.024) during bilateral drop-landings. Post hoc analysis revealed that the strength and mobility group landed with greater ankle plantarflexion at initial contact (mean difference = 1.4 ± 2.0°, ES = 0.46) and ankle dorsiflexion at peak flexion (mean difference = 6.3 ± 2.9°, ES = 0.74) after the intervention, resulting in a greater ankle joint displacement (mean difference = 7.7 ± 4.0°, ES = 1.00). However, the strength training only group landed with increased peak hip flexion (mean difference = 14.4 ± 11.0°, ES = 0.70) and hip joint displacement (mean difference = 8.0 ± 6.6°, ES = 0.44) during post-testing. The findings suggest that changes in landing strategies following the performance of a strength training program are specific to whether restrictions in ankle mobility are considered as part of the intervention.

Lower Extremity Joint Stiffness And Energy Generation In Gait Transitions

Walk-to-run (WRT) or run-to-walk transitions (RWT) occur when walking at a constantly accelerated speed or running at a constantly decelerated speed. Lower extremity joint level kinetic patterns are related to gait transition mechanisms. Little is known about lower extremity joint stiffness, or mechanical work generation in the WRT and RWT processes. PURPOSE: To identify ankle, knee and hip joint stiffness and mechanical work generation patterns in WRT and RWT processes. METHODS: Ten middle age healthy subjects (50.7 ± 6.0 years, 173.4 ± 11.4 cm, 69.7 ± 14.9 kg) participated in treadmill WRT (1.8 m/s - 2.4 m/s) and RWT (2.4 m/s - 1.8 m/s) tests, with acceleration and deceleration set to 0.1 m/s2 and - 0.1 m/s2, respectively. Five steps were selected for data analysis: transition step (S0); two steps before transition (S-2, S-1); two steps after transition (S1, S2). Joint stiffness (Kjoint) was calculated as change in sagittal plane joint moment (∆Mjoint) divided by sagittal plane joint angular displacement (∆θjoint) in the braking phase of ground contact (Kjoint = ∆Mjoint/∆θjoint). Stance phase joint positive mechanical work (Wjoint+ ) was calculated as the sum of all positive net joint power integrated over time. RESULTS: In WRT, Kankle at S2 was higher than S-2 (p = 0.0004), S-1 (p = 0.0007) and S0 (p = 0.0001); Khip at S1 was higher than S-2 (p = 0.0002) and S-1 (p = 0.0001). In RWT, Kankle at S2 was lower than S-2 (p = 0.0009) and S-1 (p = 0.0006); Khip at S-1 was higher than S1 (p = 0.001) and S2 (p = 0.0003). In WRT stance phase, Wankle+ and Wknee+ were 34% and 60% higher, respectively at S0 compared with S-1; while for Whip+ there was a significant decrease (p = 0.0006) at S0 compared with S-1. In RWT stance phase, Wankle+ and Wknee+ at S0 were 28% and 42% lower than S-1, respectively; while Whip+ at S0 was 78% higher than S-1. CONCLUSIONS: Both WRT and RWT affected Kankle and Khip in the transition step and subsequent steps. Stance phase joint energy generation tended to transfer from proximal to distal during WRT, and vice versa during the RWT process. (Supported by Betty Foster McCue Scholarship.)

Kinetic Factors Influencing Y-Balance Test Performance Kinetic Factors Influencing Y-Balance Test Performance

The Y-Balance Test (YBT) is a movement screen which assesses dynamic stability and neuromuscular control of the lower extremity. Several studies have analyzed kinematic predictors of YBT performance, but kinetic factors determining YBT performance are not well understood. PURPOSE: To determine relationships between sagittal, frontal, and transverse plane joint kinetics and YBT performance. METHODS: 31 healthy individuals (15M, 16F; age 23.1 ± 7.3; height 172.3 ± 9.1 cm; mass 59.05 ± 9.8 kg) participated in this study. Whole body kinematics were recorded using a motion capture system while dominant limb YBT trials were performed on a single force plate. Joint moments were calculated using inverse dynamics. Maximum reach distances normalized to leg length in the anterior (A), posterior-medial (PM), and posterior-lateral (PL) directions were calculated. Joint moment values at maximum reach in each direction were determined. All joint kinetic variables which were correlated with max reach distances at the p < 0.1 level were entered into a stepwise linear regression. RESULTS: In the A direction, a model containing knee extensor moment explained 21% of the variance in reach distance (p = .01). In the PM direction, a model containing hip extensor and knee rotator moments explained 67% of the variance in reach distance (p < .001). In the PL direction, a model containing hip extensor moments explained 34% of the variance in reach distance (p=.001). CONCLUSIONS: Performance on the YBT is primarily influenced by the joint moments at the hip and knee. These results support previous claims that YBT performance is an indicator of neuromuscular control of the lower extremity, and at the hip and knee in particular. Further studies should evaluate the extent to which muscular strength influences both the moments generated during YBT and relationships between joint kinetics and YBT performance.Table 1:: Stepwise multivariable regression results for relationship between joint moments at peak reach direction and YBT performance.

Sagittal And Frontal Plane Joint Moments Of The Sumo Deadlift During Shod And Barefoot Conditions

Sumo style deadlifting has recently become more prevalent. Barefoot-style lifting has also become increasingly popular with claims such as increased force production and improved “grounding” of the foot. However, the biomechanics of sumo deadlifting while barefoot have not been examined. PURPOSE: To examine the effects on the hip, knee, and ankle joint moments during a sumo deadlift when comparing shod and barefoot conditions. METHODS: Ten subjects (27.3±3.5 yrs, 1.74±0.13m, 77.97±17.34kg) with minimum six months of deadlift experience (7.6±4.6 yrs), who were free from lower extremity injury, performed 1 repetition maximum (1RM; 137.7±43.0 kg) testing on day 1. This testing was performed in self-selected footwear. On day 2, a minimum of 72 hours later, subjects lifted 70% of their 1RM during a 3-dimensional analysis. Subjects performed one set of five continuous repetitions of a sumo deadlift in shod and barefoot conditions in randomized order. Five minutes of rest was given between sets. Marker data were collected using Qualisys Track Manager, sampling at 240Hz. Force data were collected using Bertec force plates, sampling at 1200Hz. Raw marker and force data were imported into Visual3D. Marker and force data were filtered using a fourth-order lowpass Butterworth filter at 8Hz. Peak internal sagittal and frontal plane joint moments of the hip, knee, and ankle were calculated during the concentric phase of each repetition. Peak vertical ground reaction force was measured during the concentric phase. RESULTS: No significant differences were detected in peak hip extension moment (p=0.855), hip abduction (p=0.288), knee extension (p=0.607), knee abduction (p=0.926), ankle plantarflexion (p=0.376), ankle eversion (p=0.739), or peak vertical ground reaction force (p=0.558). CONCLUSIONS: There is no evidence to suggest that the barefoot lifting style increases performance capabilities when lifting the same weight as in the shod condition. Additionally, there is no evidence to suggest that there is any increased risk in excess frontal plane joint moments during barefoot lifting. Future research should examine the 1RM capabilities in both shod and barefoot conditions to determine if differences exist during maximal compared to submaximal efforts.

Comparison Of Shoe Vs No Shoe On Sagittal Plane Deadlift Biomechanics

Deadlifts are often an integral part of training programs to build posterior chain strength and power, but current research has not examined the performance outcomes when performed with and without shoes from a biomechanical perspective. PURPOSE: To examine the differences in lower extremity sagittal plane joint kinetics and peak vertical ground reaction force (vGRF) of a conventional barbell deadlift with and without shoes. METHODS: Ten subjects (age: 27.9 + 3.8 years) who deadlift twice a week for the past 6 months, were free from injury, and had no history of lower extremity surgery were recruited. Subjects first performed a one repetition max (1RM) test in self-selected footwear according to NSCA guidelines. At least 72 hours later subjects returned for a 3-dimensional analysis of their deadlift at 70% of their 1RM. Subjects performed 1 set of 5 continuous reps of a conventional deadlift in both shoe and barefoot conditions in a randomized order. A 5-minute rest was given between each condition. Visual3D was used to process raw marker and force data, calculate peak sagittal joint moments of the ankle, knee, and hip and to find peak vertical ground reaction force during the concentric phase. A one-way repeated measures MANOVA was performed to statistically test differences between shoe and no shoe conditions in the dependent variables. RESULTS: Average 1RM for males and females was 437.5 + 83.4 lbs. and 224.2 + 37.6 lbs., respectively. No significant differences were found in internal hip extension moments (p=0.444, S=2.99 Nm/kg, B=3.05 Nm/kg), knee extension moments (p=0.151, S=0.92 Nm/kg, B=0.81 Nm/kg), ankle plantar flexion moments (p=0.113, S=1.07 Nm/kg, B=1.01 Nm/kg), and peak vGRF (p=0.295, S=1044.9 N, B=1035.2 N) between shoe and barefoot conditions. CONCLUSION: Anecdotal claims suggest performing a deadlift barefoot enhances stability and increases connection to the ground which would lead to improvement in deadlift performance. The lack of difference seen in sagittal plane kinetics and peak vGRF suggest that deadlift performance is unaffected by footwear choice. Future research should investigate if similar results would be attained when subjects’ deadlift performance is tested at various percentages of the 1RM.

Lower Extremity Joint Work During Braking Phase Of The Triple Hop For Distance

The triple hop for distance (THD) involves three consecutive single leg hops for maximal horizontal displacement. This task imposes variable mechanical demands challenging balance, coordination and leg strength. While THD is common during late-stage rehabilitation, these demands may also qualify THD as appropriate for healthy athletes. While research shows that energy absorption strategies vary between landing styles, genders and heights, a limitation is the use of a single contact for analysis or training. As a result, changes in landing strategy over repeated landings are not well understood. PURPOSE: To determine changes in sagittal plane joint energetic landing strategy during each contact of THD. METHODS: Nine female college soccer players performed THD on the dominant limb. Ground reaction forces and lower extremity kinematics were measured using a force platform (1200Hz) and 9-camera motion capture system (240Hz). Three trials were collected of each contact in the THD sequence. Negative joint work was calculated as negative joint power integrated with respect to time. Total negative joint work (TJW) is the sum of eccentric work done on the hip, knee, and ankle, and the proportion of TJW done on each joint was defined as relative negative joint work (RJW). RESULTS: TJW increased from the first (-80.5 ± 26.3J) to the second (-95.5 ± 33.7J), and third (-145.2 ± 42.5J) landings. From the first to second contacts, RJW done on the ankle (33.5% vs 34.7%, d = 0.10), knee (53.9% vs 52.1%, d = 0.20), and hip (12.6% vs 13.1%, d = 0.08) was unchanged. From the second to third contacts, RJW done on the ankle was substantially decreased (34.7% vs 18.4%, d = 1.67), while RJW done on the hip was substantially increased (13.1% vs 25.4%, d = 1.68). RJW done on the knee was modestly greater (52.1% vs 56.3%, d = 0.54) in the second compared to third contacts in THD sequence. CONCLUSION: The serial nature of THD requires athletes to adapt to different demands in each ground contact. This includes progressively greater braking forces and landing strategy modulation during each contact. This represents a task which exposes athletes to variable demands of both ground reaction forces and joint work in a controlled manner. THD may therefore address multiple athletic performance qualities during performance enhancement and rehabilitation.

The Effect Of Treadmill Speed And Grade On Ice Hockey Skating Biomechanics

Skating treadmills are used by ice hockey players to develop stride efficiency, power, and endurance. PURPOSE: Evaluate the effect of treadmill speed and grade on biomechanics. It was hypothesized that greater speeds and grades would elicit larger ranges of motion (ROM) and decrease stride time. METHODS: Seven competitive male ice hockey players (22.0 ± 0.6 y, 86.5 ± 4.4 kg, 1.82 ± 0.06 m) skated at five speed and grade conditions including 4.47 m·s-1 at 4% grade (10/4), 5.36 m·s-1 at 0% grade (12/0), 5.36 m·s-1 at 4% grade (12/4), 5.36 m·s-1 at 8% grade (12/8), and 6.26 m·s-1 at 4% grade (14/4). Left leg biomechanics were assessed using three-dimensional motion capture. Stride time was determined as the mean time between successive initial contacts of the left skate blade with the treadmill. Kinematics were normalized to percent of gait cycle. ROM was calculated as the difference between the maximum and minimum left hip and knee angles during the stance phase of the normalized kinematics. Separate repeated measures ANOVA and corrected, paired t-tests were used to assess the effect of condition. Significance was set to p < .05. RESULTS: A significant effect of condition on stride time (p < .001) was identified. Pairwise comparisons revealed that stride time was different for each condition (10/4 = .87 ± .07 s, 12/0 = 1.18 ± .13 s, 12/4 = .83 ± .06 s, 12/8 = .68 ± .05 s, 14/4 = .77 ±. 06 s). A significant effect of condition on hip sagittal plane ROM (p < .001) was identified. 12/0 (57.4 ± 4.4°) had smaller ROM than 12/4 (65.4 ± 6.6°), 12/8 (70.8 ± 7.0°), and 14/4 (66.6 ± 7.3°), 10/4 (63.0 ± 5.5°) had smaller ROM than 12/8, and 12/4 had smaller ROM than 12/8. A significant effect of condition on hip frontal plane ROM (p = .007) was also revealed, although no significant pairwise comparisons were identified (10/4 = 27.6 ± 4.4°, 12/0 = 31.3 ± 4.8°, 12/4 = 26.6 ± 4.6°, 12/8 = 23.3 ± 5.3°, 14/4 = 26.7 ± 4.0°). No effect of condition on knee sagittal plane ROM was revealed (p = .271; 10/4 = 44.6 ± 4.7°, 12/0 = 44.6 ± 4.9°, 12/4 = 44.8 ± 2.6°, 12/8 = 41.9 ± 3.0°, 14/4 = 42.3 ± 2.6°). CONCLUSIONS: In this small sample, increasing skating treadmill speed, grade, or both appears to decrease stride time, increase hip joint sagittal plane ROM, and have no effect on knee joint sagittal plane ROM. Results may aid in training program design and future ice hockey biomechanics research.

CNN-Based Estimation of Sagittal Plane Walking and Running Biomechanics From Measured and Simulated Inertial Sensor Data.

Machine learning is a promising approach to evaluate human movement based on wearable sensor data. A representative dataset for training data-driven models is crucial to ensure that the model generalizes well to unseen data. However, the acquisition of sufficient data is time-consuming and often infeasible. We present a method to create realistic inertial sensor data with corresponding biomechanical variables by 2D walking and running simulations. We augmented a measured inertial sensor dataset with simulated data for the training of convolutional neural networks to estimate sagittal plane joint angles, joint moments, and ground reaction forces (GRFs) of walking and running. When adding simulated data, the root mean square error (RMSE) of the test set of hip, knee, and ankle joint angles decreased up to 17%, 27% and 23%, the RMSE of knee and ankle joint moments up to 6% and the RMSE of anterior-posterior and vertical GRF up to 2 and 6%. Simulation-aided estimation of joint moments and GRFs was limited by inaccuracies of the biomechanical model. Improving the physics-based model and domain adaptation learning may further increase the benefit of simulated data. Future work can exploit biomechanical simulations to connect different data sources in order to create representative datasets of human movement. In conclusion, machine learning can benefit from available domain knowledge on biomechanical simulations to supplement cumbersome data collections.

A hinge-free, non-restrictive, lightweight tethered exosuit for knee extension assistance during walking.

In individuals with motor impairments such as those post-stroke or with cerebral palsy, the function of the knee extensors may be affected during walking, resulting in decreased mobility. We have designed a lightweight, hinge-free wearable robot combining soft textile exosuit components with integrated rigid components, which assists knee extension when needed but is otherwise highly transparent to the wearer. The exosuit can apply a wide range of assistance profiles using a flexible multi-point reference trajectory generator. Additionally, we implemented a controller safety limit to address the risk of hyperextension stemming from the hinge-free design. The exosuit was evaluated on six healthy participants walking uphill and downhill on a treadmill at a 10° slope with a set of joint power-inspired assistance profiles. A comparison of sagittal plane joint angles between no exosuit and exosuit unpowered conditions validated the device transparency. With positive power assistance, we observed reduction in average positive knee biological power during uphill walking (left: 17.5 ± 3.21%, p = 0.005; right: 23.2 ± 3.54%, p = 0.008). These initial findings show promise for the assistive capability of the device and its potential to improve the quality of gait and increase mobility in clinical populations.

Distance running stride-to-stride variability for sagittal plane joint angles

ABSTRACT Recent research indicates that distance running stride-to-stride variability (SSV) is related to performance and injury. Previous studies have primarily focused on stride characteristics (stride length and time). We assessed SSV for sagittal plane joint angles with the primary purpose of testing for significant differences among the lower body joints. The secondary purpose was to determine if strong correlations exist among joint SSV measures. Thirty recreational adult runners participated in the study (8 females, 22 males, 39 ± 10 years; 53.1 ± 25.7 km/week). A 6-camera motion capture system (200 Hz) collected kinematic data during treadmill running at a preferred pace. A 2 by 3 repeated measures factorial ANOVA (phase—stance, swing; joint—hip, knee, ankle) was run (p = 0.05). There was a significant interaction effect (p < 0.001) and post hoc analysis revealed knee swing to be the most variable condition by far. For all three joints, there were strong correlations between stance and swing SSV (r = 0.80 to r = 0.88) and correlations among the joints were moderate to strong (r = 0.55 to 0.86). This study helps to better understand the joints/phases that contribute most to variability in the overall stride. Also, the strong correlations suggest that runners appear to have an overall SSV pattern that is similar across joints/phases.

Effects of Inertial Load on Sagittal Plane Kinematics of the Lower Extremity During Flywheel-Based Squats.

Worcester, KS, Baker, PA, and Bollinger, LM. Effects of inertial load on sagittal plane kinematics of the lower extremity during flywheel-based squats. J Strength Cond Res 36(1): 63-69, 2022-Increasing load increases flexion of lower extremity joints during weighted squats; however, the effects of inertial load on lower extremity kinematics during flywheel-based resistance training (FRT) squats remain unclear. The purpose of this study was to evaluate sagittal plane kinematics of lower extremity joints during FRT squats at various inertial loads. Nine recreationally resistance-trained subjects (3M, 6F) completed a bout of FRT squats with inertial loads of 0.050, 0.075, and 0.100 kg·m2. Two-dimensional sagittal plane kinematics were monitored with retroreflective markers at a rate of 60 Hz. Joint angles and angular velocities of the knee, trunk + hip, trunk inclination, and ankle were quantified throughout concentric and eccentric actions. Effects of inertial load were determined by repeated-measures analysis of variance with α = 0.05. Average power and average vertical velocity decreased with increasing inertial load, whereas average force increased. Minimal and maximal sagittal plane joint angles of the knee, trunk + hip, trunk inclination, and ankle were not significantly different among inertial loads. However, peak joint angular velocities of the knee and trunk + hip tended to decrease with increasing inertial load. Conversely trunk inclination and ankle dorsiflexion velocities were not significantly different among inertial loads. Increasing inertial load from 0.050 to 0.100 kg·m2 significantly reduces average power during FRT squats primarily by decreasing movement velocity, which seems to be specific to the knee and hip joints. It is possible that lower concentric energy input at high inertial loads prevents increased joint flexion during FRT squats.