GGPSA: A GRAPHICS USER INTERFACE TO FILTER MOVEMENT ANALYSIS DATA

Data filtering is a challenging procedure for the biomechanics scientists. It is however a fundamental part of biomechanical analysis when higher derivatives are needed to examine the movement. We present graphics user interface software specially designed to help biomechanics lecturers and students. It is openly designed to provide a powerful tool that could also be used for research purposes. Manual and automatic filtering procedures are provided along with single or batch processing of files. The program can process exported ASCII data files but also can be linked with the well-known APAS movement analysis program and read its binary files. Future work includes processing of many other binary files from other motion analysis systems

The influence of acute variable resistance loading on subsequent free-weight maximal squat performance

Elastic bands attached to a loaded barbell during a squat exercise create a variable resistance (VR), thus changing the mechanical loading and stress placed through the musculoskeletal system. Preconditioning the neuromuscular system using near-maximal or maximal voluntary contractions (MVC) can induce a phenomenon known as post-activation potentiation (PAP) to enhance performance to ‘supramaximal’ levels. However, the potentiating effects of VR on subsequent free-weight resistance (FWR) squat performance have not been examined. Thus, the aim of the present study was to examine the influence of VR exercise using elastic bands on subsequent FWR squat performance. Sixteen recreationally active men (age = 26.0 ± 7.8 yr, height = 1.7 ± 0.2 m, mass 82.6 ± 12.7 kg) experienced in squatting (>3yr) volunteered for the study after giving written informed consent; ethical approval was granted from the University of Northampton. Subjects’ 1-RM were determined then on two subsequent days either a 3-RM FWR (control) or a 3-RM VR (experimental) squat exercise was performed at 85% 1-RM (35% of the load generated from band tension in the VR condition). Five minutes later, motion analysis recorded knee joint kinematics during a subsequent FWR 1-RM squat, with vastus medialis, vastus lateralis, rectus femoris and semitendinosus electromyograms (EMG) simultaneously recorded. Paired t-tests were used to determine significance, accepted at p0.05) or EMG amplitude (5.9%; p>0.05) occurred. No subjects increased 1-RM in the FWR condition, however 13 of 16 (81%) increased 1-RM by ~10% following VR. Preconditioning the neuromuscular system using VR significantly increased 1-RM without changes in knee extensor muscle activity or knee flexion angle, however eccentric and concentric velocities were reduced. Thus, VR can potentiate the neuromuscular system to enhance subsequent maximal lifting performance. The lack of change in EMG suggests that changes in muscle activity were small or non-existent, which may be explained by force-velocity effects (slower movement = larger forces). Alternatively a greater activation of hip musculature (not measured in the present study) may allow a greater total lower limb force to be developed. Regardless, as 1-RM increased greater lower-limb loading occurred, thus VR potentiated the neuromuscular system and could enhance training stimuli

ISOKINETIC PEAK POWER AND PREDICTION OF PERFORMANCE

The purpose of the present study was to examine the relationship between joint peak power during isokinetic concentric knee extension and during squat vertical jump performed on a Kistler force plate. Kjnematic data from both tests were colleded. Peak power was measured as the product of angular velocity and moment at the knee joint in both tests. Rank order correlations revealed that there is no relationship between the two tests concerning the peak power output at the knee joint. It was concluded that isolated joint isokinetic tests cannot be used to predict functional performance because of the differences in muscle and joint fundion characteristics during the different movements

Analysis of lower limb internal kinetics and electromyography in elite race walking.

The aim of this study was to analyse lower limb joint moments, powers and electromyography patterns in elite race walking. Twenty international male and female race walkers performed at their competitive pace in a laboratory setting. The collection of ground reaction forces (1000 Hz) was synchronised with two-dimensional high-speed videography (100 Hz) and electromyography of seven lower limb muscles (1000 Hz). As well as measuring key performance variables such as speed and stride length, normalised joint moments and powers were calculated. The rule in race walking which requires the knee to be extended from initial contact to midstance effectively made the knee redundant during stance with regard to energy generation. Instead, the leg functioned as a rigid lever which affected the role of the hip and ankle joints. The main contributors to energy generation were the hip extensors during late swing and early stance, and the ankle plantarflexors during late stance. The restricted functioning of the knee during stance meant that the importance of the swing leg in contributing to forward momentum was increased. The knee flexors underwent a phase of great energy absorption during the swing phase and this could increase the risk of injury to the hamstring muscles

The influence of chain-loaded resistance on subsequent 1-RM free-weight squat performance

Varying the load during a back squat exercise using chains in combination with free-weight resistance (FWR) will manipulate the loading characteristics of the lift. Consequently, this may alter neuromuscular demand and induce post-activation potentiation (PAP). Preconditioning the muscle using near maximal or maximal voluntary contractions can increase force production and improve subsequent strength performance, however the influence of chain-loaded resistance (CLR) on subsequent free-weight squat performance has not been examined. Thus, the aim of the present study was to determine the effects of a chain-loaded resistance warm-up routine on subsequent free-weight squat performance

Identifying Robust Risk Factors for Knee Osteoarthritis Progression: An Evolutionary Machine Learning Approach

Knee osteoarthritis (KOA) is a multifactorial disease which is responsible for more than 80% of the osteoarthritis disease’s total burden. KOA is heterogeneous in terms of rates of progression with several different phenotypes and a large number of risk factors, which often interact with each other. A number of modifiable and non-modifiable systemic and mechanical parameters along with comorbidities as well as pain-related factors contribute to the development of KOA. Although models exist to predict the onset of the disease or discriminate between asymptotic and OA patients, there are just a few studies in the recent literature that focused on the identification of risk factors associated with KOA progression. This paper contributes to the identification of risk factors for KOA progression via a robust feature selection (FS) methodology that overcomes two crucial challenges: (i) the observed high dimensionality and heterogeneity of the available data that are obtained from the Osteoarthritis Initiative (OAI) database and (ii) a severe class imbalance problem posed by the fact that the KOA progressors class is significantly smaller than the non-progressors’ class. The proposed feature selection methodology relies on a combination of evolutionary algorithms and machine learning (ML) models, leading to the selection of a relatively small feature subset of 35 risk factors that generalizes well on the whole dataset (mean accuracy of 71.25%). We investigated the effectiveness of the proposed approach in a comparative analysis with well-known FS techniques with respect to metrics related to both prediction accuracy and generalization capability. The impact of the selected risk factors on the prediction output was further investigated using SHapley Additive exPlanations (SHAP). The proposed FS methodology may contribute to the development of new, efficient risk stratification strategies and identification of risk phenotypes of each KOA patient to enable appropriate interventions

Influence of variable resistance loading on subsequent free weight maximal back squat performance

The purpose of the study was to determine the potentiating effects of variable resistance (VR) exercise during a warm-up on subsequent free-weight resistance (FWR) maximal squat performance. In the first session, 16 recreationally active men (age = 26.0 ± 7.8 years; height = 1.7 ± 0.2 m; mass = 82.6 ± 12.7 kg) were familiarized with the experimental protocols and tested for 1 repetition maximum (1RM) squat lift. The subjects then visited the laboratory on 2 further occasions under either control or experimental conditions. During these conditions, 2 sets of 3 repetitions of either FWR (control) or VR (experimental) squat lifts at 85% of 1RM were performed; during the experimental condition, 35% of the load was generated from band tension. After a 5-minute rest, 1RM, 3D knee joint kinematics, and vastus medialis, vastus lateralis, rectus femoris, and semitendinosus electromyogram (EMG) signals were recorded simultaneously. No subject increased 1RM after FWR, however, 13 of 16 (81%) subjects increased 1RM after VR (mean = 7.7%; p 0.05) or EMG amplitudes (mean = 5.9%; p > 0.05) occurred. Preconditioning using VR significantly increased 1RM without detectable changes in knee extensor muscle activity or knee flexion angle, although eccentric and concentric velocities were reduced. Thus, VR seems to potentiate the neuromuscular system to enhance subsequent maximal lifting performance. Athletes could thus use VR during warm-up routines to maximize squat performance

The acute effects of free-weight and elastic band back squat exercise on subsequent vertical jump performance

Introduction: The back squat exercise is a fundamental exercise for the development of lower limb strength and power. However, in successful attempts of one repetition maximum (1-RM), the upward barbell movement decelerates for a short period referred to as the “sticking point”. The inclusion of elastic bands (EB) minimises the loading during the early concentric phase, while maintaining average loading throughout the lift may limit the impact of the sticking point and enables the athlete to work more closely to maximal throughout a greater range of the lift. Objective: To examine the influence of free-weight resistance (FWR) and EB squat exercise following a comprehensive warm-up on subsequent vertical jump (VJ) performance. Hypothesis: The use of EB during squatting following a comprehensive warm-up would:- (a) enhance subsequent VJ performance; (b) alter VJ mechanics; and (c) increase the neuromuscular activity of the lower limb extensor muscles, when compared to FWR. Methods: Fifteen active men (n=15) visited the laboratory on two occasions under experimental conditions (FWR or EB). After completing a comprehensive warm-up procedure, three maximal VJs were performed and then three consecutive back squat repetitions were completed at 85% of 1-RM using either FWR or EB. Three VJs were then performed 30 s, 4 min, 8 min and 12 min later. During the VJs, knee joint kinematics, ground reaction force data and vastus medialis (VM), vastus (VL) lateralis and gluteus maximus (Glut) electromyograms (EMG) were recorded simultaneously using 3D motion, force platform, and EMG techniques, respectively. Results: No change in any variable was found after the FWR warm-up (p > 0.05). Significant increases (p < 0.05) were detected in CVJ height (5.3-6.5%), net impulse (2.7-3.3%), take-off velocity (2.7-3.8%), peak power (4.4-5.9%), kinetic (7.1-7.2%) and potential (5.4-6.7%) energy, peak (12.9-19.1%) and mean (33.2-35.8%) normalized rate of force development (RFD) following the EB warm-up. Significant increases (p < 0.05) in peak concentric knee angular velocities (3.1-4.1%) and mean concentric VL EMG activity (27.5-33.4%) following the EB warm-up. Discussion: The use of heavy squat lifts with EB increases vertical jump performance following a comprehensive warm-up. The use of EB manipulates the loading characteristics of the squat lift by reducing the effective load near the “sticking point”. This modification in loading allows the athlete to operate at near-maximal levels for a greater proportion of the movement to enhance muscle force output and elicit a greater dynamic muscle performance, which likely provides a greater loading stimulus and may be a more effective training tool even when comprehensive task-specific warm-up is performed