Technical note: sensitivity analysis of the SCoRE and SARA methods for determining rotational axes during tibiofemoral movements using optical motion capture.

PURPOSE:The first aim was to report the sensitivity of calculated tibiofemoral movements for the choice of placement of the set of femoral markers. The second aim was to report the influence of accuracy of the motion captured positions of the markers on the calculated tibiofemoral movements.METHODS:Tibiofemoral kinematics during single leg hops for distance were calculated. For the first aim, an experiment was conducted in which four different setups of the femoral markers were used to calculated tibiofemoral movements. For the second aim, an experiment was conducted in which all raw marker positions were mathematically moved independently with the known Vicon position error with a distance and in a random direction in each frame, repeated a hundred times. Each time, the tibiofemoral movements were calculated.RESULTS:The first experiment yields that the standard deviation of the calculated anterior tibia translation between marker setups was 0.88 mm and the standard deviation of the external tibia rotation between marker setups was 0.76 degrees. The second experiment yields that the standard deviation was 0.76 mm for anterior tibia translation and 0.38 degrees for external tibia rotation.CONCLUSION:A combined standard deviation of both experiments revealed that transients in anterior tibia translation less than 2.32 mm and external tibia rotations less than 1.70 degrees should be taken with caution. These results are 19.42% of the range of the anterior tibia translation and 13.51% of the rotation range during the jump task. The marker setup should be chosen carefully

TO DO OR NOT TO DO; INVESTIGATING THE EFFECTS OF POSITIVE AND NEGATIVE VIDEO INSTRUCTIONS ON SIDE-STEP CUTTING

The purpose of this study was to examine the effects of positive and negative instructions on knee joint loading. Eighteen basketball players performed sidestep cut exercises with positive (optimal knee joint loading) and negative (suboptimal knee joint loading) visual instructions given by videos of experts performing side-step cutting. The results showed that subjects performed not significantly different compared to experts in the positive condition.The reduced knee joint loading seemed to indicate that subjects were able to imitate the experts to some extent. However, there was a significant difference between the negative condition of subjects and experts. This finding suggest that subjects could not completely copy the negative movements of the experts. Therefore, this might implicate that coaches should use experienced athletes as experts when demonstrating exercises to promote the highest learning effect

A VALIDITY STUDY COMPARING XSENS WITH VICON

Conducting on-field measurements is warranted to investigate and reduce real-world anterior cruciate ligament (ACL) injury risk. However, validation is first warranted to ensure how Xsens relates to Vicon. The purpose of this study was therefore to compare lower extremity kinematics from Xsens with Vicon. Ten recreational ball team sport athletes (5 females, 5 males) were included, who performed isolated and dynamic movements. Strong correlations were found for movement patterns (\u3e0.7) for the isolated as well as the dynamics movements. However, absolute joint angles differ between both systems (ranging from 0.7º - 14.5º). This should be considered when using Xsens in an applied sport setting as drawing conclusions for being or not being at risk for ACL injury may depend on the system used. A major strength of this study is the inclusion of movements that are restricted to one plane and one joint as well as dynamic high-intensity movements resembling movements which occur in sports (e.g. change of direction). This analysis of methods of data collection leads to further advancement of knowledge the science of biomechanics in applied sports setting

Recovery of Motor Imagery Ability in Stroke Patients

Objective. To investigate whether motor imagery ability recovers in stroke patients and to see what the relationship is between different types of imagery and motor functioning after stroke. Methods. 12 unilateral stroke patients were measured at 3 and 6 weeks poststroke on 3 mental imagery tasks. Arm-hand function was evaluated using the Utrecht Arm-Hand task and the Brunnström Fugl-Meyer Scale. Age-matched healthy individuals (N = 10) were included as controls. Results. Implicit motor imagery ability and visual motor imagery ability improved significantly at 6 weeks compared to 3 weeks poststroke. Conclusion. Our study shows that motor imagery can recover in the first weeks after stroke. This indicates that a group of patients who might not be initially selected for mental practice can, still later in the rehabilitation process, participate in mental practice programs. Moreover, our study shows that mental imagery modalities can be differently affected in individual patients and over time

Explaining Deep Learning Models for Age-related Gait Classification based on time series acceleration

Gait analysis holds significant importance in monitoring daily health, particularly among older adults. Advancements in sensor technology enable the capture of movement in real-life environments and generate big data. Machine learning, notably deep learning (DL), shows promise to use these big data in gait analysis. However, the inherent black-box nature of these models poses challenges for their clinical application. This study aims to enhance transparency in DL-based gait classification for aged-related gait patterns using Explainable Artificial Intelligence, such as SHAP. A total of 244 subjects, comprising 129 adults and 115 older adults (age>65), were included. They performed a 3-minute walking task while accelerometers were affixed to the lumbar segment L3. DL models, convolutional neural network (CNN) and gated recurrent unit (GRU), were trained using 1-stride and 8-stride accelerations, respectively, to classify adult and older adult groups. SHAP was employed to explain the models' predictions. CNN achieved a satisfactory performance with an accuracy of 81.4% and an AUC of 0.89, and GRU demonstrated promising results with an accuracy of 84.5% and an AUC of 0.94. SHAP analysis revealed that both CNN and GRU assigned higher SHAP values to the data from vertical and walking directions, particularly emphasizing data around heel contact, spanning from the terminal swing to loading response phases. Furthermore, SHAP values indicated that GRU did not treat every stride equally. CNN accurately distinguished between adults and older adults based on the characteristics of a single stride's data. GRU achieved accurate classification by considering the relationships and subtle differences between strides. In both models, data around heel contact emerged as most critical, suggesting differences in acceleration and deceleration patterns during walking between different age groups

OPTIMAL MOVEMENT FOR LOWER EXTREMITY INJURY PREVENTION; HOW TO CREATE AN OPTIMAL LEARNING ENVIRONMENT FOR YOUTH SOCCER GIRLS

For lower extremity injury prevention, it is crucial to decrease external loads to the joints in sport-specific situations. The purpose of this study was to examine how landing kinetics and psychological factors (i.e., motivation) change during a four-week laboratory training program. Ten talented soccer girls practiced three sport-specific tasks and received expert video instruction. Increased fun and competence in week 3 compared to week 1 was observed. No significant changes of effort and joint load (a discrete number to describe combined external frontal and transverse plane knee and ankle moments) were found. Results are promising and innovative as this is the first study testing the entire OPTIMAL model including retention and linking biomechanics with perceived motivation. More research is planned on additional instructions and feedback that may enhance the motor learning curve

An investigation of motor learning during side-step cutting, design of a randomised controlled trial

BACKGROUND: Of all athletic knee injuries an anterior cruciate ligament (ACL) rupture results in the longest time loss from sport. Regardless of the therapy chosen, conservative or reconstructive, athletes are often forced to reduce their level of physical activity and their involvement in sport. Moreover, a recent review reported prevalences of osteoarthritis ranging from 0% to 13% for patients with isolated ACL-deficient (ACL-D) knees and respectively 21% to 48% in patients with combined injuries. The need for ACL injury prevention is clear. The identification of risk factors and the development of prevention strategies may therefore have widespread health and economic implications. The focus of this investigation is to assess the role of implicit and explicit motor learning in optimising the performance of a side-step-cutting task. METHODS/DESIGN: A randomized controlled laboratory study will be conducted. Healthy basketball players, females and males, 18 years and older, with no previous lower extremity injuries, playing at the highest recreational level will be included. Subjects will receive a dynamic feedback intervention. Kinematic and kinetic data of the hip, knee and ankle and EMG activity of the quadriceps, hamstrings and gastrocnemius will be recorded. DISCUSSION: Female athletes have a significantly higher risk of sustaining an ACL injury than male athletes. Poor biomechanical and neuromuscular control of the lower limb is suggested to be a primary risk factor of an ACL injury mechanism in females. This randomized controlled trial has been designed to investigate whether individual feedback on task performance appears to be an effective intervention method. Results and principles found in this study will be applied to future ACL injury prevention programs, which should maybe more focus on individual injury predisposition. TRIAL REGISTRATION: Trial registration number NTR2250

What is the true evidence for gender-related differences during plant and cut maneuvers? A systematic review

Purpose Female athletes have a significantly higher risk of sustaining an anterior cruciate ligament (ACL) injury than male athletes. Biomechanical and neuromuscular factors have been reported as the main cause. The purpose of this review was to critically review results of the published literature on gender differences regarding biomechanical and neuromuscular movement patterns during plant and cutting maneuvers. Methods MEDLINE (1966 to December 2008), EMBASE (1947 to December 2008) and CINAHL (1981 to December 2008) searches were performed. The seven studies meeting the inclusion criteria were analyzed. Results Biomechanical gender differences were of questionable clinical relevance. Quadriceps dominance was not found in women. Conclusion The question raises whether ACL injuries during plant and cutting maneuvers are purely gender related and whether women do have to move like men in order to reduce injury risk? Caution is warranted in making inferences as studies were heterogeneous in terms of subject and study characteristics and had low statistical power as a result of insufficient number of subjects. It is advised that future research moves beyond the isolated gender comparison and that larger sample sizes will be included. This review may aid in improving experiments to draw valid conclusions, in order to direct future ACL injury prevention programs, which might need to be more individualized