Test-retest reliability of two-dimensional video analysis during running

Neuromuscular Control Deficits After Anterior Cruciate Ligament Reconstruction: A Pilot Study Using Single-Leg Functional Tests and Electromyography

Purpose: This study aimed to evaluate neuromuscular control and muscle activation patterns in individuals following anterior cruciate ligament (ACL) reconstruction, compared to healthy controls. Methods: A cross-sectional comparative study was conducted following STROBE guidelines, including 16 participants (ACL group: n = 9; control group: n = 7). Participants performed the single-leg squat (SLS) test and the single-leg drop landing (SLDL) test. Neuromuscular control was assessed using the Qualitative Analysis of Single-Leg Loading Score (QASLS), while gluteus medius and vastus medialis activation were recorded using surface electromyography. Results: The ACL group showed significantly higher QASLSs in the SLS test (p = 0.0113), indicating poorer movement quality, while no difference was found in the SLDL test (p = 0.5484). Gluteus medius activation was lower in the ACL group during the SLS test (p = 0.0564), and vastus medialis activation was higher but not significantly different (p = 0.095). Conclusions: These findings highlight persistent neuromuscular deficits post-ACL-reconstruction, particularly in SLS tasks, reinforcing the need for targeted rehabilitation strategies focusing on hip stabilization and quadriceps motor control to optimize movement quality and reduce reinjury risk.

Running Parameter Analysis in 400 m Sprint Using Real-Time Kinematic Global Navigation Satellite Systems

Accurate measurement of running parameters, including the step length (SL), step frequency (SF), and velocity, is essential for optimizing sprint performance. Traditional methods, such as 2D video analysis and inertial measurement units (IMUs), face limitations in precision and practicality. This study introduces and evaluates two methods for estimating running parameters using real-time kinematic global navigation satellite systems (RTK GNSS) with 100 Hz sampling. Method 1 identifies mid-stance phases via vertical position minima, while Method 2 aligns with the initial contact (IC) events through vertical velocity minima. Two collegiate sprinters completed a 400 m sprint under controlled conditions, with RTK GNSS measurements validated against 3D video analysis and IMU data. Both methods estimated the SF, SL, and velocity, but Method 2 demonstrated superior accuracy, achieving a lower RMSE (SF: 0.205 Hz versus 0.291 Hz; SL: 0.143 m versus 0.190 m) and higher correlation with the reference data. Method 2 also exhibited improved performance in curved sections and detected stride asymmetries with higher consistency than Method 1. These findings highlight RTK GNSS, particularly the velocity minima approach, as a robust, drift-free, single-sensor solution for detailed per-step sprint analysis in outdoor conditions. This approach offers a practical alternative to IMU-based methods and enables training optimization and performance evaluation.

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.

Instrumenting Parkrun: Usefulness and Validity of Inertial Sensors

The analysis of running gait has conventionally taken place within an expensive and restricted laboratory space, with wearable technology offering a practical, cost-effective, and unobtrusive way to examine running gait in more natural environments. This pilot study presents a wearable inertial measurement unit (IMU) setup for the continuous analysis of running gait during an outdoor parkrun (i.e., 5 km). The study aimed to (1) provide analytical validation of running gait measures compared to time- and age-graded performance and (2) explore performance validation. Ten healthy adults (7 females, 3 males, mean age 37.2 ± 11.7 years) participated. The participants wore Axivity AX6 IMUs on the talus joint of each foot, recording tri-axial accelerometer and gyroscope data at 200 Hz. Temporal gait characteristics-gait cycle, ground contact time, swing time, and duty factor-were extracted using zero-crossing algorithms. The data were analyzed for correlations between the running performance, foot strike type, and fatigue-induced changes in temporal gait characteristics. Strong correlations were found between the performance time and both the gait cycle and ground contact time, with weak correlations for foot strike types. The analysis of asymmetry and fatigue highlighted modest changes in gait as fatigue increased, but no significant gender differences were found. This setup demonstrates potential for in-field gait analysis for running, providing insights for performance and injury prevention strategies.

Validity and reliability of running gait measurement with the ViMove2 system

Running biomechanics have traditionally been analysed in laboratory settings, but this may not reflect natural running gait. Wearable technology has the potential to enable precise monitoring of running gait beyond the laboratory. This study aimed to evaluate the analytical validity and intra-session reliability of temporal running gait outcomes measured by the ViMove2 wearable system in healthy adults. Seventy-four healthy adults (43 males, 31 females, aged 18-55 years) wore the inertial device, ViMove2 on the tibia. Participants ran on a treadmill for one minute at various speeds (8, 10, 12, 14km/hr), completed in a standardised shoe (Saucony Guide Runner). Running gait was measured with the ViMove2 wearable and 3D motion capture (Vicon). Temporal running gait outcomes included ground contact time (GCT) and cadence (steps/min). GCT and cadence from the ViMove2 had face validity with expected changes in outcome with different running speeds, but ViMove2 tended to over-estimate GCT, and under-estimate cadence compared to the reference, especially at slower speeds. GCT demonstrated moderate to good agreement to the reference at speeds >10km/hr, but poor agreement at 8km/hr and within female runners. Cadence had moderate to excellent agreement across speeds compared to the reference. GCT and cadence had excellent reliability across speeds, but at 8km/hr GCT had good agreement between trials. Overall, temporal gait outcomes of GCT and cadence can be measured with the ViMove2, but accuracy and reliability are impacted at slow running speeds and within female runners. Future work is needed to clarify sex or speed-dependent corrections to algorithms / outcomes to aid interpretation and application.

Test-retest reliability and minimal detectable change in pelvis and lower limb coordination during running assessed with modified vector coding

The objective of this study was to evaluate the reliability of Modified Vector Coding in assessing the coordination and coordination variability of the lower limbs and pelvis during running and to determine the Minimal Detectable Change (MDC). Twenty-five healthy runners participated in a biomechanical analysis of treadmill running using a motion capture system. Modified vector coding was applied to assess the three-dimensional coordination among various pelvis and lower limb segmental couplings. Reliability was assessed using the Intraclass Correlation Coefficient (ICC), Standard Error of Measurement (SEM), MDC, and Bland-Altman analysis to ascertain measurement consistency, agreement, and the smallest clinically meaningful change that exceeds measurement error. The test-retest reliability for 33 of 42 segmental couplings analyzed was good to excellent, with ICC values ranging from 0.613 to 0.928 (p <0.05), which substantiates the robustness of modified vector coding in running biomechanics. However, nine couplings, particularly femur-tibia in the sagittal plane during midstance and foot in the frontal plane-tibia in the transverse plane during late stance, exhibited poor to moderate reliability. These findings underscore the need for cautious interpretation due to significant proportional bias (p <0.05). SEM and MDC provided insights into the precision and minimal clinically significant changes for each coupling. The findings confirm the reliability of modified vector coding for biomechanical analysis in running, with most couplings demonstrating consistent high reliability. Nevertheless, specific couplings should be interpreted with caution due to potential measurement errors. The application of MDC highlights the precision of modified vector coding in biomechanical analyses and emphasizes the importance of careful interpretation to improve clinical and research outcomes in running-related injuries.

Validity and Test-Retest Reliability of Spatiotemporal Running Parameter Measurement Using Embedded Inertial Measurement Unit Insoles

Running is the basis of many sports and has highly beneficial effects on health. To increase the understanding of running, DSPro® insoles were developed to collect running parameters during tasks. However, no validation has been carried out for running gait analysis. The aims of this study were to assess the test-retest reliability and criterion validity of running gait parameters from DSPro® insoles compared to a motion-capture system. Equipped with DSPro® insoles, a running gait analysis was performed on 30 healthy participants during overground and treadmill running using a motion-capture system. Using an intraclass correlation coefficient (ICC), the criterion validity and test-retest reliability of spatiotemporal parameters were calculated. The test-retest reliability shows moderate to excellent ICC values (ICC > 0.50) except for propulsion time during overground running at a fast speed with the motion-capture system. The criterion validity highlights a validation of running parameters regardless of speeds (ICC > 0.70). This present study validates the good criterion validity and test-retest reliability of DSPro® insoles for measuring spatiotemporal running gait parameters. Without the constraints of a 3D motion-capture system, such insoles seem to be helpful and relevant for improving the care management of active patients or following running performance in sports contexts.

Running Biomechanics and Clinical Features Among Adolescent Athletes With Lower Leg Chronic Exertional Compartment Syndrome

OBJECTIVE

To compare clinical measures between patients with chronic exertional compartment syndrome (CECS) and healthy controls and evaluate running biomechanics, physical measurements, and exertional intracompartmental (ICP) changes in adolescent athletes with lower leg CECS.

DESIGN

Cross-sectional case-control study.

SETTING

Large tertiary care hospital and affiliated injury prevention center.

PARTICIPANTS

Forty-nine adolescents with CECS (39 F, 10 M; age: 16.9 ± 0.8 years; body mass index (BMI): 23.1 ± 2.9 kg/m 2 ; symptom duration: 8 ± 12 months) were compared with 49 healthy controls (39 F, 10 M; age: 6.9 ± 0.8 years; BMI: 20.4 ± 3.7 kg/m 2 ).

INTERVENTIONS

All participants underwent gait analyses on a force plate treadmill and clinical lower extremity strength and range of motion testing. Patients with chronic exertional compartment syndrome underwent Stryker monitor ICP testing.

MAIN OUTCOME MEASURES

Symptoms, menstrual history, and ICP pressures of the patients with CECS using descriptive statistics. Mann-Whitney U and χ 2 analyses were used to compare CECS with healthy patients for demographics, clinical measures, and gait biomechanics continuous and categorical outcomes, respectively. For patients with CECS, multiple linear regressions analyses were used to assess associations between gait biomechanics, lower extremity strength and range of motion, and with ICP measures.

RESULTS

The CECS group demonstrated higher mass-normalized peak ground reaction force measures (xBW) compared with controls (0.21 ± 0.05 xBW ( P < 0.001) and were more likely to have impact peak at initial contact ( P = 0.04). Menstrual dysfunction was independently associated with higher postexertion ICP (ß = 14.6; P = 0.02).

CONCLUSIONS

The CECS group demonstrated increased total force magnitude and vertical impact transient peaks. In women with CECS, menstrual dysfunction was independently associated with increased postexertion ICP. These biomechanical and physiological attributes may play a role in the development of CECS.

Identifying stress scores from gait biometrics captured using a camera: A cross-sectional study

BACKGROUND

Stress is a critical risk factor for various health issues, but an objective, non-intrusive and effective measurement approach for stress has not yet been established. Gait, the pattern of movements in human locomotion, has been proven to be a valid behavioral indicator for recognizing various mental states in a convenient manner.

RESEARCH QUESTION

This study aims to identify the severity of stress by assessing human gait recorded through an objective, non-intrusive measurement approach.

METHODS

One hundred and fifty-two participants with an average age of 23 years old (SD = 1.07) were recruited. The Chinese version of the Perceived Stress Scale with 10 items (PSS-10) was used to assess participants' stress levels. The participants were then required to walk naturally while being recorded with a regular camera. A total of 1320 time-domain and 1152 frequency-domain gait features were extracted from the videos. The top 40 contributing features, confirmed by dimensionality reduction, were input into models consisting of four machine-learning regression algorithms (i.e., Gaussian Process Regressor, Linear Regression, Random Forest Regressor, and Support Vector regression), to assess stress levels.

RESULTS

The models that combined time- and frequency-domain features performed best, with the lowest RMSE (4.972) and highest validation (r = 0.533). The Gaussian Process Regressor and Linear Regression outperformed the others. The greatest contribution to model performance was derived from gait features of the waist, hands, and legs.

SIGNIFICANCE

The severity of stress can be accurately detected by machine learning models using two-dimensional (2D) video-based gait data. The machine learning models used for assessing perceived stress were reliable. Waist, hand, and leg movements were found to be critical indicator in detecting stress.

Effects of two gait retraining programs on pain, function, and lower limb kinematics in runners with patellofemoral pain: A randomized controlled trial

BACKGROUND

Patellofemoral Pain (PFP) is one of the main injuries in runners. Consistent evidence support strengthening programs to modulate symptoms, however, few studies investigated the effects of gait retraining programs.

OBJECTIVE

To investigate the effects of two different two-week partially supervised gait retraining programs on pain, function, and lower limb kinematics of runners with PFP.

METHODS

Randomized controlled trial. Thirty runners were allocated to gait retraining groups focusing on impact (n = 10) or cadence (n = 10), or to a control group (n = 10). Impact group received guidance to reduce tibial acceleration by 50%, while cadence group was asked to increase cadence by 7.5-10%. The control group did not receive any intervention. Usual and running pain, knee function, and lower limb kinematics (contralateral pelvic drop, hip adduction, knee flexion, ankle dorsiflexion, tibia inclination, and foot inclination) were evaluated before (T0), immediately after the intervention (T2), and six months after the protocol (T24).

RESULTS

A significant group x time interaction was found for running pain (p = 0.010) and knee function (p = 0.019). Both programs had greater improvements in running pain compared to no intervention at T24 (Impact x Control-mean difference (MD) -3.2, 95% CI -5.1 to -1.3, p = 0.001; Cadence x Control-MD -2.9, 95% CI -4.8 to -1.0, p = 0.002). Participants of the impact group had greater improvements in knee function compared to no intervention at T2 (Impact x Control-MD 10.8, 95% CI 1.0 to 20.6, p = 0.027). No between-group differences in usual pain and lower limb kinematics were found (p>0.05).

CONCLUSION

Compared to no intervention, both programs were more effective in improving running pain six months after the protocol. The program focused on impact was more effective in improving knee function immediately after the intervention. Clinical trial registry number: RBR-8yb47v.

Novel Multi-View RGB Sensor for Continuous Motion Analysis in Kinetic Chain Exercises: A Pilot Study for Simultaneous Validity and Intra-Test Reliability

As the number of musculoskeletal disorders caused by smartphone usage, sedentary lifestyles, and active sports activities increases, there is a growing demand for precise and accurate measurement and evaluation of issues such as incorrect compensation patterns, asymmetrical posture, and limited joint operation range. Urgent development of new inspection equipment is necessary to address issues such as convenience, economic feasibility, and post-processing difficulties. Using 4DEYE®, a new multi-view red, green, and blue (RGB) sensor-based motion analysis equipment, and the VICON® ratio, which are infrared-based markers, we conducted a comparative analysis of the simultaneous validity of the joint angle (trajectory) and reliability. In this study, five healthy participants who could perform movements were selected for the pilot study and two movements (Y-balance and side dip) were analyzed. In addition, the ICC (Intraclass Correlation Coefficient) was analyzed using the SPSS (Statistical Package for the Social Sciences) V.18 while the number of data frames of each equipment was equalized using the MATLAB program. The results revealed that side dips, which are open kinetic chain exercises (intraclass correlation coefficient ICC(2.1), 0.895-0.996), showed very high concordance with the Y-balance test, a closed kinetic chain exercise (ICC(2.1), 0.678-0.990). The joint measurement results were similar regardless of the movement in the open or closed kinetic chain exercise, confirming the high reliability of the newly developed multiview RGB sensor. This is of great significance because we obtained important and fundamental results that can be used in various patterns of exercise movements in the future.

KeepRunning: A MoCap-Based Rapid Test to Prevent Musculoskeletal Running Injuries

The worldwide popularisation of running as a sport and recreational practice has led to a high rate of musculoskeletal injuries, usually caused by a lack of knowledge about the most suitable running technique for each runner. This running technique is determined by a runner's anthropometric body characteristics, dexterity and skill. Therefore, this study aims to develop a motion capture-based running analysis test on a treadmill called KeepRunning to obtain running patterns rapidly, which will aid coaches and clinicians in assessing changes in running technique considering changes in the study variables. Therefore, a review and proposal of the most representative events and variables of analysis in running was conducted to develop the KeepRunning test. Likewise, the minimal detectable change (MDC) in these variables was obtained using test-retest reliability to demonstrate the reproducibility and viability of the test, as well as the use of MDC as a threshold for future assessments. The test-retest consisted of 32 healthy volunteer athletes with a running training routine of at least 15 km per week repeating the test twice. In each test, clusters of markers were placed on the runners' body segments using elastic bands and the volunteers' movements were captured while running on a treadmill. In this study, reproducibility was defined by the intraclass correlation coefficient (ICC) and MDC, obtaining a mean value of ICC = 0.94 ± 0.05 for all variables and MDC = 2.73 ± 1.16° for the angular kinematic variables. The results obtained in the test-retest reveal that the reproducibility of the test was similar or better than that found in the literature. KeepRunning is a running analysis test that provides data from the involved body segments rapidly and easily interpretable. This data allows clinicians and coaches to objectively provide indications for runners to improve their running technique and avoid possible injury. The proposed test can be used in the future with inertial motion capture and other wearable technologies.

Validity and reliability of the DANU sports system for walking and running gait assessment

Objective. Gait assessments have traditionally been analysed in laboratory settings, but this may not reflect natural gait. Wearable technology may offer an alternative due to its versatility. The purpose of the study was to establish the validity and reliability of temporal gait outcomes calculated by the DANU sports system, against a 3D motion capture reference system.Approach. Forty-one healthy adults (26 M, 15 F, age 36.4 ± 11.8 years) completed a series of overground walking and jogging trials and 60 s treadmill walking and running trials at various speeds (8-14 km hr-1), participants returned for a second testing session to repeat the same testing.Main results. For validity, 1406 steps and 613 trials during overground and across all treadmill trials were analysed respectively. Temporal outcomes generated by the DANU sports system included ground contact time, swing time and stride time all demonstrated excellent agreement compared to the laboratory reference (intraclass correlation coefficient (ICC) > 0.900), aside from ground contact time during overground jogging which had good agreement (ICC = 0.778). For reliability, 666 overground and 511 treadmill trials across all speeds were examined. Test re-test agreement was excellent for all outcomes across treadmill trials (ICC > 0.900), except for swing time during treadmill walking which had good agreement (ICC = 0.886). Overground trials demonstrated moderate to good test re-test agreement (ICC = 0.672-0.750), which may be due to inherent variability of self-selected (rather than treadmill set) pacing between sessions.Significance. Overall, this study showed that temporal gait outcomes from the DANU Sports System had good to excellent validity and moderate to excellent reliability in healthy adults compared to an established laboratory reference.

Wearables for running gait analysis: A study protocol

Quantitative running gait analysis is an important tool that provides beneficial outcomes to injury risk/recovery or performance assessment. Wearable devices have allowed running gait to be evaluated in any environment (i.e., laboratory or real-world settings), yet there are a plethora of different grades of devices (i.e., research-grade, commercial, or novel multi-modal) available with little information to make informed decisions on selection. This paper outlines a protocol that will examine different grades of wearables for running gait analysis in healthy individuals. Specifically, this pilot study will: 1) examine analytical validity and reliability of wearables (research-grade, commercial, high-end multimodal) within a controlled laboratory setting; 2) examine analytical validation of different grades of wearables in a real-world setting, and 3) explore clinical validation and usability of wearables for running gait analysis (e.g., injury history (previously injured, never injured), performance level (novice, elite) and relationship to meaningful outcomes). The different grades of wearable include: (1) A research-grade device, the Ax6 consists of a configurable tri-axial accelerometer and tri-axial gyroscope with variable sampling capabilities; (2) attainable (low-grade) commercial with proprietary software, the DorsaVi ViMove2 consisting of two, non-configurable IMUs modules, with a fixed sampling rate and (3) novel multimodal high-end system, the DANU Sports System that is a pair of textile socks, that contain silicone based capacitive pressure sensors, and configurable IMU modules with variable sampling rates. Clinical trial registration: Trial registration: NCT05277181.

Reliability of 2D video analysis assessing running kinematic variables in patients with exercise-related leg pain in a primary care practice

BACKGROUND

Suboptimal lower limb and trunk positionings is known to influence exercise-related leg pain (ERLP). It is unknown whether simple 2D video analysis is useful for recording and interpreting running variables in a primary care practice.

RESEARCH QUESTION

Is 2D video analysis a reliable instrument to assess running variables in patients with ERLP in a primary care practice?

METHODS

Participants undergoing an evaluation for ERLP in two primary care practices were studied. In this reliability study, analysis of running variables was performed by 4 blinded raters on one-stride videos captured with non-high speed cameras (30 fps). Intraclass correlation coefficients (two-way random; ICC 2,1) were calculated to determine the inter-rater reliability. The intra-rater reliability was presented by ICC type two-way mixed (3,1). Footstrike pattern was analyzed by calculating the Fleiss' kappa for inter-rater agreement and Cohen's kappa for intra-rater agreement. Sample size calculation indicated that 16 participants would be required for answering the research question.

RESULTS

Data of all 16 participants (9 males, age 31 ± 10 yr) were of sufficient quality for analysis. The 2D video analysis demonstrated excellent inter-rater reliability with an overall ICC value of 0.999 (95 % CI = 0.998-0.999). The ICC value of the eversion was 0.384 (95 % CI = 0.148-0.66) and after correction of the systematic error, 0.817 (95 % CI = 0.664-0.922). The agreement on footstrike was substantial with a Fleiss kappa of 0.737. The overall intra-rater reliability was excellent with an ICC value of 0.997 (95 % CI = 0.996-0.997). The intra-rater agreement of the footstrike was excellent with a Cohen's kappa of 0.868.

SIGNIFICANCE

2D video analysis provides a highly reliable, relative inexpensive, feasible and suitable measuring instrument for determining running variables in patients ERLP in a primary care setting. This simple technique may identify possible running variables associated with different types of ERLP and may serve as an instrument for tailor-made gait retraining programs.

Validity and reliability of two-dimensional video-based assessment to measure joint angles during running: A systematic review and meta-analysis

Two-dimensional video analysis systems (2DVAS) are commonly used by clinicians and researchers to determine angles during running. The aim of this systematic review (PROSPERO: CRD42022322798) was to synthesize the literature on the criterion validity and reliability of 2DVAS for measuring angles during running compared to three-dimensional motion analysis systems (3DMAS). We searched for articles on MEDLINE/Pubmed, EMBASE, SciELO, and LILACS up to October/2022. We included studies that evaluated the validity of 2DVAS (when compared to 3DMAS) and/or the reliability of 2DVAS measurements of lower limb and trunk angles during running. Qualitative and quantitative analyses were performed. Seven hundred and five studies were found and 17 were included. Ten studies analysed criterion validity between 2DVAS and 3DMAS and the results ranged from poor to excellent, with most of the parameters assessed presenting poor or moderate validity. Inter-rater reliability of 2DVAS was assessed in nine studies and most of the parameters investigated had good to excellent reliability. Intra-rater reliability (between-day processing) of angular running parameters - investigated in ten studies - was considered excellent for most of the parameters analysed. Inter-session reliability was assessed in three studies and was defined as good or excellent for most of the variables assessed. 2DVAS is a reliable method for measuring joint angles during running. However, the validity of 2DVAS compared to 3DMAS ranges from low to moderate for most running parameters. Therefore, based on the available evidence, caution should be taken when applying 2DVAS, particularly for frontal and transverse plane angles.

Crossover gait in running and measuring foot inversion angle at initial foot strike: a front-view video analysis approach

Introduction: Foot inversion angle at initial foot strike is associated with various running-related injuries. Traditionally, video analysis of foot inversion angle has been accomplished by positioning a camera to record from the back view, but complications arise when a crossover gait obscures the area of measurement. This study aims to investigate the viability of measuring foot inversion angles at initial foot strike of running from the front view as an alternative to using the back view in 2D video analysis. Methods: Forty-four healthy runners (20 females, 24 males) ran at their self-selected speeds on a treadmill with their gait recorded from front and back camera views. Foot inversion angles at initial foot strike were analyzed using Kinovea. A 2 × 2 (Camera × Foot) ANOVA with repeated measures was performed on the foot inversion angle data. Subsequently, correlation and linear regression were performed to determine the relationship between the back and front-view measurements. Results: Thirteen runners (29.5%) displayed crossover gait within 18 gait cycles. ANOVA revealed a significant main effect on Camera (p < .001) only, where foot inversion angle was greater from the front camera view. Correlation analysis showed a significant positive correlation between the front and back camera views (r = 0.388, p < .001). Regression analyses yielded an equation, y = 0.42 + 0.53 x, where y and x were the foot inversion angle measured from the back and front camera views, respectively. Discussion: With a linear regression conversion equation, front-view foot inversion angles at initial foot strike can be used to determine rearfoot inversion angles when crossover gait obstructs the back camera view.

Reliability and validity of two-dimensional motion capture to assess ankle dorsiflexion motion and heel raise work

OBJECTIVES

To determine the inter-rater reliability and criterion validity of two-dimensional (2D) measures of ankle function in the sagittal plane for participants with Achilles tendinopathy (AT).

DESIGN

Cohort study.

SETTING

University Laboratory, Participants, Adults with AT (N = 18, Women: 72.2%, Age = 43.4 ± 15.8 years, BMI = 28.7 ± 8.9 kg/m2) MAIN OUTCOME MEASURES: Reliability and validity were determined with intra-class correlation coefficients (ICC), standard error of the measurement (SEM), minimal detectable change (MDC), and Bland-Altman plots for ankle dorsiflexion and positive work during heel raises.

RESULTS

Inter-rater reliability between three raters for all 2D motion analysis tasks was good to excellent (ICC = 0.88 to 0.99). Criterion validity between 2D and 3D motion analyses for all tasks was good to excellent (ICC = 0.76 to 0.98). 2D motion analysis overestimated ankle dorsiflexion motion by 1.0-1.7° (3% of mean sample value) and positive ankle joint work by 76.8 J (9% of mean) compared to 3D motion analysis.

CONCLUSION

Although 2D and 3D measures are not interchangeable, the good to excellent reliability and validity of 2D measures in the sagittal plane support the use of video analysis to quantify ankle function for individuals with foot and ankle pain.

Wearables for Running Gait Analysis: A Systematic Review

BACKGROUND

Running gait assessment has traditionally been performed using subjective observation or expensive laboratory-based objective technologies, such as three-dimensional motion capture or force plates. However, recent developments in wearable devices allow for continuous monitoring and analysis of running mechanics in any environment. Objective measurement of running gait is an important (clinical) tool for injury assessment and provides measures that can be used to enhance performance.

OBJECTIVES

We aimed to systematically review the available literature investigating how wearable technology is being used for running gait analysis in adults.

METHODS

A systematic search of the literature was conducted in the following scientific databases: PubMed, Scopus, Web of Science and SPORTDiscus. Information was extracted from each included article regarding the type of study, participants, protocol, wearable device(s), main outcomes/measures, analysis and key findings.

RESULTS

A total of 131 articles were reviewed: 56 investigated the validity of wearable technology, 22 examined the reliability and 77 focused on applied use. Most studies used inertial measurement units (n = 62) [i.e. a combination of accelerometers, gyroscopes and magnetometers in a single unit] or solely accelerometers (n = 40), with one using gyroscopes alone and 31 using pressure sensors. On average, studies used one wearable device to examine running gait. Wearable locations were distributed among the shank, shoe and waist. The mean number of participants was 26 (± 27), with an average age of 28.3 (± 7.0) years. Most studies took place indoors (n = 93), using a treadmill (n = 62), with the main aims seeking to identify running gait outcomes or investigate the effects of injury, fatigue, intrinsic factors (e.g. age, sex, morphology) or footwear on running gait outcomes. Generally, wearables were found to be valid and reliable tools for assessing running gait compared to reference standards.

CONCLUSIONS

This comprehensive review highlighted that most studies that have examined running gait using wearable sensors have done so with young adult recreational runners, using one inertial measurement unit sensor, with participants running on a treadmill and reporting outcomes of ground contact time, stride length, stride frequency and tibial acceleration. Future studies are required to obtain consensus regarding terminology, protocols for testing validity and the reliability of devices and suitability of gait outcomes.

CLINICAL TRIAL REGISTRATION

CRD42021235527.

Effect of combining eight weeks of neuromuscular training with dual cognitive tasks on landing mechanics in futsal players with knee ligament dominance defect: a randomized controlled trial

BACKGROUND

The performing of jump and landing in futsal simultaneous with divided attention is one of the most common mechanisms of non-contact anterior cruciate ligament (ACL) injury. Neuromuscular training has effectively reduced the risk of ACL injury, but the effect of neurocognitive training has received less attention. This study investigated the effect of combining 8 weeks of neuromuscular training with dual cognitive tasks on the landing mechanics of futsal players with knee ligament dominance defects.

METHODS

Thirty male futsal players (mean ± SD: age: 21.86 ± 3.27 years) with knee ligament dominance defects were purposefully identified by the tuck jump test and were randomly divided into the intervention and the control group. The intervention group performed dual task (DT) training for three weekly sessions for 8 weeks and 60 min each, while the control group only did activities of daily living. During the drop vertical jump test, 2D landing kinematics in two moments of initial contact (IC) and full flexion (FF) were assessed. Data were analyzed by means of 2 × 2 repeated measures ANOVA followed by post hoc comparison (Bonferroni) at the significance level of (α ≤ 0.05).

RESULTS

A significant improvement was observed in the intervention group compared to the control group for the dynamic knee valgus at IC (F1,28 = 6.33; P = 0.02, ES = 0.31) and FF (F1,28 = 13.47; P = 0.003, ES = 0.49), knee flexion at IC (F1,28 = 20.08; P = 0.001, ES = 0.41) and FF (F1,28 = 13.67; P = 0.001, ES = 0.32), ankle dorsiflexion at IC (F1,28 = 37.17; P = 0.001, ES = 0.72) and FF (F1,28 = 14.52; P = 0.002, ES = 0.50), and trunk flexion at FF (F1,28 = 20.48; P = 0.001, ES = 0.59) angles. Changes in the trunk flexion at IC (F1,28 = 0.54; P = 0.47, ES = 0.03) and trunk lateral flexion at IC (F1,28 = 0.006; P = 0.93, ES = 0.00) and FF (F1,28 = 2.44; P = 0.141, ES = 0.148) angles were not statistically significant.

CONCLUSIONS

DT training compared to the control group improved landing mechanics in futsal players with knee ligament dominance defects.

TRIAL REGISTRATION

Current Controlled Trials using the IRCT website with ID number IRCT20210602051477N1 prospectively registered on 20/06/2021.

Depth of single-leg squat influences the two-dimensional analysis of knee, hip, and pelvis frontal plane motion in pain-free women

BACKGROUND

The single-leg squat (SLS) is often used to measure two-dimensional frontal plane motion; however, there is a variability in the SLS depth across studies.

RESEARCH QUESTION

Are knee abduction (KABD), hip adduction (HADD), pelvic drop (PD), and lateral trunk flexion (LTF) angles different at greater knee flexion angles during a SLS?

METHODS

Twenty pain-free females (age=22.3 ± 1.1 years, height=1.68 ± 0.06 m, mass=63.1 ± 11.7 kg) participated in this cross-sectional study. Participants performed five SLSs to the lowest depth comfortable, keeping pace with a metronome, while being video recorded in the frontal and sagittal planes. The middle three SLSs were used for analysis. KABD, HADD, PD, and LTF angles were measured at 30º, 45º, 60º, 75º, and 90º of knee flexion using extracted images. Linear mixed model analyses were used to compare across knee flexion angles and clinical significance was determined by comparing angle changes to the standard error of measurement (SEM).

RESULTS

We observed significant differences for KABD (F=14.69, p < .001), HADD (F=46.29, p < .001), and PD (F=27.27, p < .001) among knee flexion angles. Post-hoc analyses revealed that KABD significantly increased at every increase of knee flexion angle (p ≤ .05, d=0.54-1.95), as did HADD (p ≤ .05, d=0.64-3.85) and PD (p ≤ .05, d=0.61-3.03). Changes in KABD, HADD, and PD often exceeded SEM for all changes in knee flexion angles.

SIGNIFICANCE

Knee, hip, and pelvic frontal plane motions are influenced by knee flexion angles during 2D analysis of a SLS task. Our results highlight the importance of standardizing SLS depth during research and clinical practice to ensure appropriate comparisons across measurements.

Agreement Between Sagittal Foot and Tibia Angles During Running Derived From an Open-Source Markerless Motion Capture Platform and Manual Digitization

Several open-source platforms for markerless motion capture offer the ability to track 2-dimensional (2D) kinematics using simple digital video cameras. We sought to establish the performance of one of these platforms, DeepLabCut. Eighty-four runners who had sagittal plane videos recorded of their left lower leg were included in the study. Data from 50 participants were used to train a deep neural network for 2D pose estimation of the foot and tibia segments. The trained model was used to process novel videos from 34 participants for continuous 2D coordinate data. Overall network accuracy was assessed using the train/test errors. Foot and tibia angles were calculated for 7 strides using manual digitization and markerless methods. Agreement was assessed with mean absolute differences and intraclass correlation coefficients. Bland-Altman plots and paired t tests were used to assess systematic bias. The train/test errors for the trained network were 2.87/7.79 pixels, respectively (0.5/1.2 cm). Compared to manual digitization, the markerless method was found to systematically overestimate foot angles and underestimate tibial angles (P < .01, d = 0.06-0.26). However, excellent agreement was found between the segment calculation methods, with mean differences ≤1° and intraclass correlation coefficients ≥.90. Overall, these results demonstrate that open-source, markerless methods are a promising new tool for analyzing human motion.

Novel biomechanical injury risk score demonstrates correlation with lower limb posterior chain injury in 50 elite-level rugby union athletes

Objectives

Lower limb posterior chain injury (PCI) is common among athletic populations, with multifactorial risk factors including age, previous injury, strength measurements, range of motion and training load. Biomechanics are commonly considered in the prevention and rehabilitation of PCI by performance staff. However, there is no documented testing method to assess for associations between biomechanics and PCI. The aim of this study was to investigate whether there is an association between an easily applicable, novel biomechanical assessment tool and PCI.

Methods

Fifty male elite-level rugby union athletes (age 22.83±5.08) participating in the highest tier of England were tested at the start of the 2019 preseason period and PCIs (N=48) were recorded over the 2019/2020 playing season. Participants’ biomechanics were analysed using two-dimensional video analysis against an injury risk score (IRS) system in the performance of the combined movement—prone hip extension and knee flexion. Participants’ biomechanics in carrying out this movement were scored against the 10-point IRS, where the more compensatory movement recorded sees an increase in an individual’s IRS. Participants’ IRS was then compared against the number of PCIs sustained and Spearman’s correlation coefficient was used for statistical analysis.

Results

There is a significant association between IRS and PCI (R=0.542, p<0.001). Linear regression demonstrated that an increase in 1 in IRS was associated with a 35% increase in PCI incidence (R²=0.346).

Conclusion

A significance between the IRS and PCI provides preliminary support for its use as an injury risk assessment tool.

Sex-Specific Hip Movement Is Correlated With Pelvis and Upper Body Rotation During Running

There is a sex bias for common overuse running injuries that are associated with sex-specific hip kinematics. Gait retraining programs aimed at altering hip kinematics may be more efficient if they incorporated an understanding of how hip kinematics are correlated with the movement of the remaining body segments. We applied a principal component analysis to structure the whole-body running kinematics of 23 runners (12 ♀) into k = 12 principal movements (PM_k), describing correlated patterns of upper and lower body movements. We compared the time-dependent movement amplitudes with respect to each PM_k between males and females using a waveform analysis and interpreted our findings according to stick figure animations. The movement amplitudes of two PMs (PM₆ and PM₈) showed statistically significant effects of "sex," which were independent of running speed. According to PM₈, females showed more hip adduction, which correlated with increased transverse rotation of the pelvis and upper body compared to men. We propose that increased hip adduction and upper body rotation in female runners may be a strategy to compensate for a less efficient arm and upper body swing compared to men. Gait interventions aimed at reducing hip adduction and running-related injuries in female runners should consider instructions for both upper and lower body to maximize training efficacy.

Effects of gait retraining with focus on impact versus gait retraining with focus on cadence on pain, function and lower limb kinematics in runners with patellofemoral pain: Protocol of a randomized, blinded, parallel group trial with 6-month follow-up

Patellofemoral pain (PFP) is one of the most prevalent injuries in runners. Unfortunately, a substantial part of injured athletes do not recover fully from PFP in the long-term. Although previous studies have shown positive effects of gait retraining in this condition, retraining protocols often lack clinical applicability because they are time-consuming, costly for patients and require a treadmill. The primary objective of this study will be to compare the effects of two different two-week partially supervised gait retraining programs, with a control intervention; on pain, function and lower limb kinematics of runners with PFP. It will be a single-blind randomized clinical trial with six-month follow-up. The study will be composed of three groups: a group focusing on impact (group A), a group focusing on cadence (group B), and a control group that will not perform any intervention (group C). The primary outcome measure will be pain assessed using the Visual Analog Pain scale during running. Secondary outcomes will include pain during daily activities (usual), symptoms assessed using the Patellofemoral Disorders Scale and lower limb running kinematics in the frontal (contralateral pelvic drop; hip adduction) and sagittal planes (foot inclination; tibia inclination; ankle dorsiflexion; knee flexion) assessed using the MyoResearch 3.14-MyoVideo (Noraxon U.S.A. Inc.). The study outcomes will be evaluated before (t0), immediately after (t2), and six months (t24) after starting the protocol. Our hypothesis is that both partially supervised gait retraining programs will be more effective in reducing pain, improving symptoms, and modifying lower limb kinematics during running compared with the control group, and that the positive effects from these programs will persist for six months. Also, we believe that one gait retraining group will not be superior to the other. Results from this study will help improve care in runners with PFP, while maximizing clinical applicability as well as time and cost-effectiveness.

Is Motorized Treadmill Running Biomechanically Comparable to Overground Running? A Systematic Review and Meta-Analysis of Cross-Over Studies

BACKGROUND

Treadmills are often used in research, clinical practice, and training. Biomechanical investigations comparing treadmill and overground running report inconsistent findings.

OBJECTIVE

This study aimed at comparing biomechanical outcomes between motorized treadmill and overground running.

METHODS

Four databases were searched until June 2019. Crossover design studies comparing lower limb biomechanics during non-inclined, non-cushioned, quasi-constant-velocity motorized treadmill running with overground running in healthy humans (18-65 years) and written in English were included. Meta-analyses and meta-regressions were performed where possible.

RESULTS

33 studies (n = 494 participants) were included. Most outcomes did not differ between running conditions. However, during treadmill running, sagittal foot-ground angle at footstrike (mean difference (MD) - 9.8° [95% confidence interval: - 13.1 to - 6.6]; low GRADE evidence), knee flexion range of motion from footstrike to peak during stance (MD 6.3° [4.5 to 8.2]; low), vertical displacement center of mass/pelvis (MD - 1.5 cm [- 2.7 to - 0.8]; low), and peak propulsive force (MD - 0.04 body weights [- 0.06 to - 0.02]; very low) were lower, while contact time (MD 5.0 ms [0.5 to 9.5]; low), knee flexion at footstrike (MD - 2.3° [- 3.6 to - 1.1]; low), and ankle sagittal plane internal joint moment (MD - 0.4 Nm/kg [- 0.7 to - 0.2]; low) were longer/higher, when pooled across overground surfaces. Conflicting findings were reported for amplitude of muscle activity.

CONCLUSIONS

Spatiotemporal, kinematic, kinetic, muscle activity, and muscle-tendon outcome measures are largely comparable between motorized treadmill and overground running. Considerations should, however, particularly be given to sagittal plane kinematic differences at footstrike when extrapolating treadmill running biomechanics to overground running. Protocol registration CRD42018083906 (PROSPERO International Prospective Register of Systematic Reviews).

Internal and external focus show similar effect on the gait kinematics in patients with patellofemoral pain: A randomised controlled trial

PURPOSE

The purpose of this study was to examine how attentional focus during training influences the effects of a 6-week hip-knee strength training program on pain, function, strength, and kinematics in males and females with Patellofemoral pain (PFP).

METHODS

Seventy-five males and females with PFP were randomly allocated to a group that trained with an internal focus (n = 25), a group that trained with an external focus (n = 25), or a control group (n = 25). All patients completed testing before (baseline) and after (posttest) the 6-week period. The primary outcome was pain, assessed by Visual Analog Scale (VAS). The secondary outcomes were function, hip muscles strength and lower extremity kinematics, assessed by Kujala Questionnaire, handheld dynamometer and a 2-D motion capture, respectively. All outcomes were measured at the baseline and after the 6-week intervention. Analysis of covariance was used to compare posttest outcomes among the groups while accounting for group differences in baseline performance.

RESULTS

The hip-knee strengthening exercises resulted in improved knee valgus (ES(95 % CI) = 0.43(0.26 to 0.75), p = 0.03), and external rotator strength (ES(95 % CI) = 0.51(0.12 to 0.78), p = 0.03) for males and females who trained with an external compared to internal focus.

CONCLUSIONS

Our findings indicate that males and females with PFP may benefit from completing a hip-knee strengthening training program with an external focus vs. an internal focus. Physical therapists and clinicians should consider using instructions that promote an external focus when implementing hip-knee strengthening training programs with PFP patients. This result could be strengthened or re-enforced by larger studies with longer follow up.

A new method for assessing landing kinematics in non-laboratory settings

OBJECTIVES

1) Determine the concurrent validity of using automated 2D video analysis relative to 3D motion capture for assessing frontal and sagittal-plane knee kinematics during landing, 2) compare the accuracy of visually estimating joint center locations (2D Manual) with computing joint center locations using anatomical markers (2D Automatic), and 3) compare landing kinematics between a controlled laboratory setting and a non-laboratory setting.

DESIGN

Validity/repeatability study.

SETTINGS

Biomechanics research laboratory and non-laboratory athletic facility.

PARTICIPANTS

Thirty uninjured recreational athletes.

MAIN OUTCOME MEASURES

Peak knee flexion, knee flexion range of motion, peak knee frontal plane projection angle, and knee frontal plane projection angle range of motion during bilateral and unilateral landing were measured simultaneously in 3D using motion capture and in 2D using two low-cost video cameras during the first study session (biomechanics research laboratory), and in 2D only during the second study session (non-laboratory athletic facility).

RESULTS

There was good to excellent agreement between 3D motion capture and both 2D Manual (ICC = 0.86-0.99) and 2D Automatic (ICC = 0.89-0.99) video analysis methods. There was good to excellent agreement between data collected in a laboratory and non-laboratory setting (ICC = 0.75-0.95).

CONCLUSION

The methods introduced in this study are inexpensive, reliable, and feasible for use in non-laboratory settings.

INTER AND INTRA-RATER RELIABILITY OF THE DROP VERTICAL JUMP (DVJ) ASSESSMENT

Background

Non-contact injuries are common in sports as abnormal lower extremity joint mechanics can place athletes at risk for injury. It is important to have reliable, feasible, cost-effective assessment tools to determine lower limb control and injury risk.

Hypothesis/Purpose

The purpose of the study was to assess the intra- and inter-rater reliability of a three-tiered anterior cruciate ligament (ACL) injury risk rating assessment of the drop vertical jump using frontal plane, two-dimensional (2-D) motion capture.

Study Design

Repeated measures.

Methods

Twenty male elite basketball athletes performed the drop vertical jump during a 2-D video assessment at Mayo Clinic Sports Medicine Center in Minneapolis, Minnesota. DVJ scores indicated the following: 1 no visible knee valgus, 2 slight wobble, inward motion of the knees, and 3 knee collision or large frontal plane knee excursion. Score assessment from video of the drop vertical jump was obtained by four independent investigators. The four raters then re-examined the same videos 1 month later, blinded to their original scores.

Results

Intra-rater reliability Fleiss Kappa measure of agreement was substantial amongst all four raters at all scoring time points: initial contact (0.672), first landing (0.728), second landing (0.670), and peak valgus (0.662) (p < 0.001). The intra-rater ICC values were good at initial contact (0.809), second landing (0.874), and max valgus (0.885), however were excellent at first landing (0.914) (p < 0.001). Inter-rater reliability Fleiss Kappa measurement scores were slight at initial contact (0.173), fair at max valgus (0.343), and moderate at first landing (0.532) and second landing (0.514; p < 0.001). Inter-rater ICC values were moderate at initial contact (0.588), excellent at first landing (0.919), and good at second landing (0.883) and max valgus (0.882; p<0.001).

Conclusion

When comparing scores of the drop vertical jump between four independent raters across two sessions, the study demonstrated substantial Kappa and good to excellent ICC intra-rater reliability. Inter-rater reliability demonstrated slight to moderate Kappa measurements of agreement and moderate to excellent ICC's. Thus, for excellent reliability using this assessment, patients should be scored by one individual. For moderate reliability between multiple raters, the first landing of the DVJ should be scored. Findings indicate that the proposed drop vertical jump assessment may be used for reliable identification of abnormal landing mechanics.

Level of Evidence

Level 3.

Agreement Between Spatiotemporal Gait Parameters Measured by a Markerless Motion Capture System and Two Reference Systems-a Treadmill-Based Photoelectric Cell and High-Speed Video Analyses: Comparative Study

Background

Markerless systems to capture body motion require no markers to be attached to the body, thereby improving clinical feasibility and testing time. However, the lack of markers might affect the accuracy of measurements.

Objective

This study aimed to determine the absolute reliability and concurrent validity of the Kinect system with MotionMetrix software for spatiotemporal variables during running at a comfortable velocity, by comparing data between the combination system and two widely used systems—OptoGait and high-speed video analysis at 1000 Hz.

Methods

In total, 25 runners followed a running protocol on a treadmill at a speed of 12 km/h. The Kinect+MotionMetrix combination measured spatiotemporal parameters during running (ie, contact time, flight time, step frequency, and step length), which were compared to those obtained from two reference systems.

Results

Regardless of the system, flight time had the highest coefficients of variation (OptoGait: 16.4%; video analysis: 17.3%; Kinect+MotionMetrix: 23.2%). The rest of the coefficients of variation reported were lower than 8.1%. Correlation analysis showed very high correlations (r>0.8; P<.001) and almost perfect associations (intraclass correlation coefficient>0.81) between systems for all the spatiotemporal parameters except contact time, which had lower values. Bland-Altman plots revealed smaller systematic biases and random errors for step frequency and step length and larger systematic biases and random errors for temporal parameters with the Kinect+MotionMetrix system as compared to OptoGait (difference: contact time +3.0%, flight time −7.9%) and high-speed video analysis at 1000 Hz (difference: contact time +4.2%, flight time −11.3%). Accordingly, heteroscedasticity was found between systems for temporal parameters (r²>0.1).

Conclusions

The results indicate that the Kinect+MotionMetrix combination slightly overestimates contact time and strongly underestimates flight time as compared to the OptoGait system and high-speed video analysis at 1000 Hz. However, it is a valid tool for measuring step frequency and step length when compared to reference systems. Future studies should determine the reliability of this system for determining temporal parameters.

Validity and reliability of 2-dimensional trunk, hip, and knee frontal plane kinematics during single-leg squat, drop jump, and single-leg hop in females with patellofemoral pain

OBJECTIVES

To investigate validity and between-session reliability of frontal plane trunk, hip, and knee kinematics during three functional tasks in females with patellofemoral pain (PFP).

DESIGN

Observational.

SETTING

Research Laboratory.

PARTICIPANTS

20 females with PFP (22.7 ± 3.2 years, 69.9 ± 9.2 kg, 167.7 ± 9.6 cm).

MAIN OUTCOME MEASURES

Trunk, hip, and knee frontal plane peak angles during the single leg squat (SLS), drop vertical jump (DVJ), and single leg hop (SLH) kinematics were evaluated using 2-dimensional (2D) and 3-dimensional (3D) motion capture. Participants returned to the lab one week later and competed a second 2D analysis of the functional tasks. Concurrent validity was assessed by evaluating relationship between 2D and 3D frontal plane kinematics with Pearson correlations. Between-session reliability was assessed by evaluating 2D kinematics with intraclass correlation coefficients by a single assessor.

RESULTS

Moderate to strong correlations (r = 0.55-0.76, p < .05) were found for frontal plane hip kinematics during all three tasks and the trunk during the SLH. Frontal plane kinematics demonstrated good to excellent test-retest reliability for each of the three tasks, (ICC _(2,1) = 0.70-0.90).

CONCLUSION

2D hip joint angles during the three functional tasks were the only valid frontal plane angles. Trunk, hip, and knee 2D frontal plane kinematics ranged between good-excellent reliability.

Two-dimensional video gait analysis: A systematic review of reliability, validity, and best practice considerations

BACKGROUND

Motion capture systems are widely used to quantify human gait. Two-dimensional (2D) video systems are simple to use, easily accessible, and affordable. However, their performance as compared to other systems (i.e. three-dimensional (3D) gait analysis) is not well established.

OBJECTIVES

This work provides a comprehensive review of design specifications and performance characteristics (validity and reliability) of two-dimensional motion capture systems.

STUDY DESIGN

Systematic review.

METHODS

A systematic literature search was conducted in three databases from 1990 to 2019 and identified 30 research articles that met the inclusion/exclusion criteria.

RESULTS

Reliability of measurements of two-dimensional video motion capture was found to vary greatly from poor to excellent. Results relating to validity were also highly variable. Comparisons between the studies were challenging due to differences in protocols, instrumentation, parameters assessed, and analyses performed.

CONCLUSIONS

Variability in performance could be attributed to study design, gait parameters being measured, and technical aspects. The latter includes camera specifications (i.e. resolution and frame rate), setup (i.e. camera position), and analysis software. Given the variability in performance, additional validation testing may be needed for specific applications involving clinical or research-based assessments, including specific patient populations, gait parameters, mobility tasks, and data collection protocols.

CLINICAL RELEVANCE

This review article provides guidance on the application of 2D video gait analysis in a clinical or research setting. While not suitable in all instances, 2D gait analysis has promise in specific applications. Recommendations are provided about the patient populations, gait parameters, mobility tasks, and data collection protocols.

Validity of Using Automated Two-Dimensional Video Analysis to Measure Continuous Sagittal Plane Running Kinematics

Two-dimensional video analysis is commonly used to assess kinematics when three-dimensional motion capture is unavailable. However, videos are often assessed using manual digitization, which limits the ability to extract outcomes that require continuous data. Here, we introduced a method to collect continuous kinematic data in 2D using an inexpensive camera and an open-source automated marker tracking program. We tested the validity of this method by comparing 2D video analysis to 3D motion capture for measuring sagittal-plane running kinematics. Twenty uninjured participants ran on a treadmill for 1-min while lower extremity kinematics were collected simultaneously in 3D using a motion capture system and in 2D using a single digital camera, both at 120 Hz. Knee, ankle, and foot angle at contact, peak knee flexion, knee flexion excursion, and knee-ankle flexion vector coding variability were computed using both the 3D and 2D kinematic data, and were compared using intraclass correlation coefficients and Bland-Altman plots. The agreement between collection methods was excellent for foot angle at contact and knee flexion excursion, good for ankle and knee angle at contact and knee-ankle vector coding variability, and moderate for peak knee flexion. However, Bland-Altman plots revealed significant differences between the 2D and 3D collection methods, which varied across study participants. These low-cost methods could be useful for collecting continuous sagittal plane running kinematics in non-laboratory settings.

Subclassification of recreational runners with a running-related injury based on running kinematics evaluated with marker-based two-dimensional video analysis

OBJECTIVES

To explore whether homogeneous subgroups could be discriminated within a population of recreational runners with a running-related injury based on running kinematics evaluated with marker-based two-dimensional video analysis.

DESIGN

Cross-sectional.

SETTING

Research laboratory.

PARTICIPANTS

Fifty-three recreational runners (15 males, 38 females) with a running-related injury.

MAIN OUTCOME MEASURES

Foot and tibia inclination at initial contact, and hip adduction and knee flexion at midstance were measured in the frontal and sagittal plane with marker-based two-dimensional video analysis during shod running on a treadmill at preferred speed. The four outcome measures were clustered using K-means cluster analysis (n = 2-10). Silhouette coefficients were used to detect optimal clustering.

RESULTS

The cluster analysis led to the classification of two distinct subgroups (mean silhouette coefficient = 0.53). Subgroup 1 (n = 39) was characterized by significantly greater foot inclination and tibia inclination at initial contact compared to subgroup 2 (n = 14).

CONCLUSION

The existence of different subgroups demonstrate that the same running-related injury can be represented by different kinematic presentations. A subclassification based on the kinematic presentation may help clinicians in their clinical reasoning process when evaluating runners with a running-related injury and could inform targeted intervention strategy development.

Validity and reliability of a smartphone motion analysis app for lower limb kinematics during treadmill running

OBJECTIVE

To investigate the validity and reliability of a smartphone application for selected lower-limb kinematics during treadmill running.

DESIGN

Validity and reliability study.

SETTING

Biomechanics laboratory.

PARTICIPANTS

Twenty healthy female runners.

MAIN OUTCOME MEASURE(S)

Sagittal-plane hip, knee, and ankle angle and rearfoot eversion were assessed using the Coach's Eye Smartphone application and a 3D motion capture system. Paired t-test and intraclass correlation coefficients (ICC) established criterion validity of Coach's Eye; ICC determined test-retest and intrarater/interrater reliability. Standard error of measurement (SEM) and minimal detectable change (MDC) were also reported.

RESULTS

Significant differences were found between Coach's Eye and 3D measurements for ankle angle at touchdown and knee angle at toe-off (p < 0.05). ICCs for validity of Coach's Eye were excellent for rearfoot eversion at touchdown (ICC = 0.79) and fair-to-good for the other kinematics (range 0.51-0.74), except for hip at touchdown, which was poor (ICC = 0.36). Test-retest (range 0.80-0.92), intrarater (range 0.95-0.99) and interrater (range 0.87-0.94) ICC results were excellent for all selected kinematics.

CONCLUSION

Coach's Eye can be used as a surrogate for 3D measures of knee and rearfoot in/eversion at touchdown, and hip, ankle, and rearfoot in/eversion at toe-off, but not for hip and ankle at touchdown or knee at toe-off. Reliable running kinematics were obtained using Coach's Eye, making it suitable for repeated measures.

Test-retest reliability and minimum detectable change for various frontal plane projection angles during dynamic tasks

OBJECTIVE

Establish between-day test-retest reliability metrics for 2-dimensional frontal plane projection angles (FPPAs) during the lateral step-down (LSD), single-limb squat (SLS), single-limb landing (SLL), and drop vertical jump (DVJ).

DESIGN

Test-retest reliability study.

SETTING

University laboratory.

PARTICIPANTS

20 healthy adults (12 female, age = 23.60 ± 1.93 years old, body mass index = 24.26 ± 2.54 kg/m²) were tested on 2 separate occasions 7-14 days apart.

MAIN OUTCOME MEASURES

Intraclass correlation coefficients (ICC), standard errors of the measurement (SEM), and minimal detectable change (MDC) values across the LSD, SLS, SLL, and DVJ for the following body region variables: trunk, trunk on pelvis, pelvis, hip, thigh to vertical, knee, and shank to vertical.

RESULTS

There was moderate-to-substantial between-day test-retest reliability for nearly all body regions across all tasks (ICC = 0.65-0.96). SEM values varied across body regions and tasks (0.9-3.5°). MDCs were variable (2.3-9.8°). Of the body regions, MDCs were largest for the knee and hip. By task, MDCs were lowest for the LSD.

CONCLUSIONS

This study identified between-day test-retest reliability metrics for 2-dimensional FPPAs across a variety of body regions during commonly assessed clinical tasks. These data allow clinicians and researchers to more confidently assess true change between assessments or over time.

Agreement between the spatiotemporal gait parameters from two different wearable devices and high-speed video analysis

This study aimed to evaluate the concurrent validity of two different inertial measurement units for measuring spatiotemporal parameters during running on a treadmill, by comparing data with a high-speed video analysis (VA) at 1,000 Hz. Forty-nine endurance runners performed a running protocol on a treadmill at comfortable velocity (i.e., 3.25 ± 0.36 m.s^-1). Those wearable devices (i.e., Stryd™ and RunScribe™ systems) were compared to a high-speed VA, as a reference system for measuring spatiotemporal parameters (i.e. contact time [CT], flight time [FT], step frequency [SF] and step length [SL]) during running at comfortable velocity. The pairwise comparison revealed that the Stryd™ system underestimated CT (5.2%, p < 0.001) and overestimated FT (15.1%, p < 0.001) compared to the VA; whereas the RunScribe™ system underestimated CT (2.3%, p = 0.009). No significant differences were observed in SF and SL between the wearable devices and VA. The intra class correlation coefficient (ICC) revealed an almost perfect association between both systems and high-speed VA (ICC > 0.81). The Bland-Altman plots revealed heteroscedasticity of error (r² = 0.166) for the CT from the Stryd™ system, whereas no heteroscedasticity of error (r² < 0.1) was revealed in the rest of parameters. In conclusion, the results obtained suggest that both foot pods are valid tools for measuring spatiotemporal parameters during running on a treadmill at comfortable velocity. If the limits of agreement of both systems are considered in respect to high-speed VA, the RunScribe™ seems to be a more accurate system for measuring temporal parameters and SL than the Stryd™ system.

Agreement between spatiotemporal parameters from a photoelectric system with different filter settings and high-speed video analysis during running on a treadmill at comfortable velocity

The aim of this study was to determine the level of agreement between spatiotemporal gait characteristics from a photoelectric system with different filter settings and high-speed video analysis during running on a treadmill at comfortable velocity. Forty-nine runners performed a running protocol on a treadmill at comfortable velocity. Two systems were used to determine spatiotemporal parameters (i.e. contact time [CT], flight time [FT], step frequency [SF] and step length [SL]) during running: OptoGait system and high-speed video analysis at 1000 Hz. The collected data was re-filtered in the OptoGait software by using nine different settings (i.e. 0_0, 1_1, 2_2, 3_3, 3_4, 4_4, 4_5, 5_4 and 5_5), and compared to those obtained through video analysis. The Pearson correlation analysis revealed very large correlations (r > 0.9, p < 0.001) in CT, FT, SF and SL between both systems, regardless of the OptoGait's filter settings. The ICC reported an almost perfect association (ICC > 0.9) for both SL and SF regardless of the filter setting. However, large variations between filter settings according to the data from video analysis were reported in CT and FT (0_0, 1_1 and 2_2 filter settings obtained an association ICC > 0.9, whereas other filters obtained lower ICCs). Bland-Altman plots revealed small bias and error and no presence of heteroscedasticity of error for 1_1 setting. In conclusion, the filter setting for the OptoGait system should be considered to minimize the bias and error of spatiotemporal parameters measurement. For running on a treadmill, the 1_1 filter setting is recommended if gait parameters are to be compared to a high-speed video analysis (1000 Hz).

Quantitative and qualitative assessment of frontal plane knee motion in males and females: A reliability and validity study

BACKGROUND

The aim was to determine reliability and validity of frontal plane projection angle (FPPA) and visual assessments (VA) in both males and females.

METHODS

Fifty-four participants (30 females) performed lateral step-downs while kinematics were recorded by two-dimensional and three-dimensional analyses. Two raters viewed the videos, extracted images, and measured the FPPA (quantitative). Using the videos, the raters also categorized (qualitative VA) each participant's motion as demonstrating dynamic valgus (>10° valgus), dynamic varus (>10° varus), or no change. Reliability was assessed for FPPA and VA using intraclass correlation coefficients and Kappa, respectively. Validity was determined by comparing the FPPA to three-dimensional measures (Pearson correlations) and comparing the VA to both FPPA and standard reference 3D kinematics (Kappa).

RESULTS

FPPA showed good-excellent reliability (ICC = 0.850-0.998). VA showed minimal-moderate reliability (κ = 0.370-0.766). The FPPA showed large correlations (r = -0.514-0.531) with hip adduction in both sexes but only a moderate relationship with knee abduction in males (r = 0.427-0.445). VA showed no-weak (κ = 0.153-0.475) and weak-moderate (κ = 0.455-0.698) agreement compared to FPPA and no-weak (κ = -0.300-0.183) and no-minimal (κ = -0.078-0.027) disagreement compared to the reference standard 3D kinematics in males and females, respectively.

CONCLUSION

The quantitative FPPA is more reliable and valid than qualitative VA of frontal knee plane motion.