The effect of environmental context on performance outcomes and movement coordination changes during the learning of complex motor skills

Four experiments presented here investigated the task demand relationship of intertrial variability (IV) and regulatory conditions (RC), on the outcome and movement changes that occurred with dart throwing practice. The four tasks included: (1) a stationary target with one location (closed w/no IV), (2) a stationary target with five possible locations (closed w/IV), (3) a moving target with one movement pattern (open w/no IV), (4) a moving target with five possible movement patterns (open w/IV). After each throw, the X, Y coordinates of the dart and the target were recorded to calculate radial error (RE). Kinematics was recorded using an eight-camera motion system with markers on the upper body, throwing arm, and dart. Novice participants performed 160 throws on each of 3 days. Results for all four tasks indicated that the RE decreased significantly (p\u3c 0.05) across trial blocks, at a different magnitude and rate for each task. The displacement patterns of the wrist, elbow, and shoulder indicated changes in movement coordination as novices practiced their respective tasks. During the three days of practice, learners became more consistent in the pattern used. The displacement at the elbow was significantly different from the shoulder and wrist for the two consistent tasks, while the variable tasks revealed the elbow and wrist to be similar. Analysis of the joint-linkage cross-correlations showed the elbow-wrist linkage to be significantly different from the elbow-shoulder and the shoulder-wrist linkages, for all four experiments. These observations suggested that the subject controlled the degrees of freedom at the shoulder, while the elbow and wrist remained linked throughout practice. Closer analysis of the magnitude of the changes indicated an inverse relationship between the movement coordination and outcome changes. Large changes in the movement pattern resulted in small changes in the outcomes and vice versa. The results of these experiments provide evidence that environmental context (EC) affects how one performs, and what changes occur in the outcome scores and movement coordination, but the magnitude of these changes presents differing information regarding skill acquisition. Overall, the results indicated the amount of IV in the EC had the greatest effect on the performance

A BIOMECHANICAL ANALYSIS OF COMPETITIVE AND RECREATIONAL PLAYERS IN RELATION TO THE DARTS THROWING TECHNIQUE

The aim of this study was to clarify the difference of the darts throwing motion (technique) between competitive (CG) and recreational (RG) groups. The darts throwing motions for each group were analyzed using an automatic motion capture system and force platforms. The performance (distance) of CG was statistically superior to RG. Shoulder and elbow joint movement indexes were smaller in CG than in RG. CG threw the dart with the static position that body weight was mostly distributed to the forward leg. However, RG started from the static position that distributed two thirds of body weight on the forward leg, and subsequently threw the dart while transmitting most of the remaining body weight from backward leg to forward leg. It is concluded that CG had the less movement of body segments involved in the darts throwing motion to achieve a high level of performance

Objective assessment of movement disabilities using wearable sensors

The research presents a series of comprehensive analyses based on inertial measurements obtained from wearable sensors to quantitatively describe and assess human kinematic performance in certain tasks that are most related to daily life activities. This is not only a direct application of human movement analysis but also very pivotal in assessing the progression of patients undergoing rehabilitation services. Moreover, the detailed analysis will provide clinicians with greater insights to capture movement disorders and unique ataxic features regarding axial abnormalities which are not directly observed by the clinicians

A multi-technology approach to identifying the reasons for lateral drift in professional and recreational darts

This work performs an extensive charterisation of precision targeted throwing in professional and recreational darts. The goal is to identify the contributing factors for lateral drift or throwing inaccuracy in the horizontal plane. A multitechnology approach is adopted whereby a custom built body area network of wireless inertial measurement devices monitor tilt, force and timing, an optical 3D motion capture system provides a complete kinematic model of the subject, electromyography sensors monitor muscle activation patterns and a force plate and pressure mat capture tactile pressure and force measurements. The study introduces the concept of constant throwing rhythm and highlights how landing errors in the horizontal plane can be attributable to a number of variations in arm force and speed, centre of gravity and the movements of some of the bodies non throw related extremities

In-vivo Measurement of Wrist Movements During the Dart-Throwing Motion Using Inertial Measurement Units

Background: This study investigates the dart-throwing motion (DTM) by comparing an inertial measurement unit-based system previously validated for basic motion tasks with an optoelectronic motion capture system. The DTM is interesting as wrist movement during many activities of daily living occur in this movement plane, but the complex movement is difficult to assess clinically. Methods: Ten healthy subjects were recorded while performing the DTM with their right wrist using inertial sensors and skin markers. Maximum range of motion obtained by the different systems and the mean absolute difference were calculated. Results: In the flexion-extension plane, both systems calculated a range of motion of 100◦ with mean absolute differences of 8◦ , while in the radial-ulnar deviation plane, a mean absolute difference of 17◦ and range of motion values of 48◦ for the optoelectronic system and 59◦ for the inertial measurement units were found. Conclusions: This study shows the challenge of comparing results of different kinematic motion capture systems for complex movements while also highlighting inertial measurement units as promising for future clinical application in dynamic and coupled wrist movements. Possible sources of error and solutions are discusse

Capturing the overarm throw in darts employing wireless inertial measurement

This work employs a custom built body area network of wireless inertial measurement technology to conduct a biomechanical analysis of precision targeted throwing in competitive and recreational darts. The solution is shown to be capable of measuring key biomechanical factors including speed, acceleration and timing. These parameters are subsequently correlated with scoring performance to determine the affect each variable has on outcome. For validation purposes an optical 3D motion capture system provides a complete kinematic model of the subject and enables concurrent benchmarking of the 'gold standard' optical inertial measurement system with the more affordable and proactive wireless inertial measurement solution developed as part of this work

Clinical measurement of dart throwing motion of the wrist: variability, accuracy and correction

Despite being functionally important, dart throwing motion is difficult to assess accurately through goniometry. The objectives of this study were to describe a method for reliably quantifying the dart throwing motion using goniometric measurements within a healthy population. Wrist kinematics of 24 healthy participants were assessed using goniometry and optical motion tracking. Three wrist angles were measured at the starting and ending points of the motion: flexion-extension, radial-ulnar deviation and dart throwing motion angle. The orientation of the dart throwing motionplane relative to the flexion-extension axis ranged between 28° and 57° among the tested population. Plane orientations derived from optical motion capture differed from those calculated through goniometry by 25°. An equation to correct the estimation of the plane from goniometry measurements was derived. This was applied and differences in the orientation of the plane were reduced to non-significant levels, enabling dart throwing motion to be measured using goniometry alone

Evaluating the reliability of four-dimensional computed tomography scans of the wrist

Introduction: Four-dimensional CT (or 4D CT) scans are a novel approach to diagnosing musculoskeletal pathology. Although still in its infancy, there has been a surge of interest in identifying clinical applications for musculoskeletal 4D CT. The scapholunate joint has received the most attention thus far due to the complex articulations and challenges faced with prompt diagnosis of scapholunate injuries. The objective of this thesis is to review current literature on musculoskeletal 4D CT and to evaluate the inter- and intra-rater reliability of the assessment of scapholunate stability in 4D CT wrist scans. Methodology: 4D CT scans of thirteen healthy volunteers and four patients were prepared. Seven orthopaedic and plastic surgeons were recruited to qualitatively assess the stability of the scapholunate joint in the 4D CT scans. Statistical analysis included percent agreement, Fleiss’ kappa, and Gwet’s AC1 coefficient. Results: The percent agreement amongst all raters was 0.80392 (95% CI: 0.675 - 0.932). Fleiss’ Kappa was 0.54895 (95% CI: 0.252 - 0.846) and Gwet’s AC₁ was 0.54895 (95% CI: 0.391 - 0.915). The intraclass correlation coefficient (ICC) for intra-rater reliability was 0.71631 (95% CI: 0.5567 – 0.8423). Conclusion: Our pilot study suggests good inter- and intra-rater reliability for the qualitative assessment of scapholunate instability in 4D CT scans. Although further studies are required, this thesis highlights the vast potential of 4D CT as a non-invasive diagnostic technique of dynamic musculoskeletal injuries

The scaphoid : from fracture to fusion

In paper I, the incidence, treatment approaches, and rates of nonunion in scaphoid fractures were examined using data from 34,377 patients recorded in the Swedish National Patient Register (NPR) between 2006-2015. The accuracy of NPR data was confirmed through validation involving 300 patients, revealing that approximately 41% of diagnosed scaphoid fractures were false positives. The overall incidence rate was found to be around 22 per 105 person-years. Median age was 26 years and 69% of the patients were men. 5% of the patients were operated and 2% developed scaphoid nonunion. Paper II evaluated the outcomes of scaphoid nonunion surgery in 63 patients in a retrospective study with a mean follow-up of 7 years. Patients were divided into two groups: those with residual deformity and those without. The calculation of scaphoid deformity was based on computed tomography (CT) scans, comparing the heightlength (H/L) ratio of the operated scaphoid to that of the uninjured one. There were no significant differences between the two groups in Disabilities of the Arm, Shoulder and Hand score (DASH), Patient-Rated Wrist Evaluation score (PRWE), wrist range of motion (ROM), and grip strength. Wrist extension was slightly worse in the deformity group. In paper III, we analyzed the direct motion between the scaphoid and lunate during the dart-throwing motion (DTM) in vivo with a volume registration technique (computed tomography based micromotion analysis, CTMA). We found motion between the scaphoid and lunate, including translation and rotation and that scapholunate ligament injury leads to increased motion. Paper IV was a pragmatic randomized controlled trial (RCT) which compared lunocapitate fusion (LCF) and four-corner fusion (4CF) as surgical treatments for scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC). There was only a small improvement in grip strength with no clinically significant difference between the two treatment groups. No differences between groups were found in DASH, PRWE, European quality of life-5 dimensions-3 level (EuroQol-5D-3L), wrist ROM, key pinch strength, and complications at 12 months postoperatively. In paper V we examined seven patients who had undergone LCF at least one year before. CT scans were performed in maximal radial extension and maximal ulnar flexion. Using CTMA, motion of the triquetrum was analyzed compared to the contralateral side. Triquetral movement was observed in all patients but significantly less than in the nonsurgical wrist. There also was minor motion between the hamate and fused lunocapitate bones. In conclusion, Scaphoid fractures primarily occur in young males, and the risk of developing a nonunion after such a fracture is relatively low. Residual scaphoid deformity has no relevant negative impact on mid-term wrist function. There is scapholunate motion during DTM and caution should be taken when implementing dart-throwing exercises during early rehabilitation after scapholunate repair surgery. LCF is not inferior to 4CF in terms of strength, range of motion or patient-reported outcome measures. Triquetral motion is limited after lunocapitate arthrodesis

Development of an inverse musculoskeletal model of the wrist

The wrist is a complex mechanical system that plays a crucial role in many activities of daily living. Some pathologies that affect the wrist are mechanically instigated or propagated, like osteoarthritis, and can have significant effects on quality of life. The small size of the joint complex precludes some of the investigative techniques that are employed in investigating lower-limb pathology. One way to gain understanding of the biomechanics of the system is to create a computational model to perform investigations that cannot be carried out in vivo. The ambition is to apply an inverse musculoskeletal model of the wrist, previously developed at Imperial College London and implemented using a novel anatomical data set, to answer clinical questions by using biomechanical research to inform intervention. As a key input to the model is joint kinematics, the formation of the joint coordinate system (JCS) used to collect upper limb kinematics was a primary focus of this thesis. The recommendations for building the coordinate system commonly used, published by the International Society of Biomechanics (ISB), are difficult to implement in vivo as they depend on observations only feasible with cadavers. Likewise, the model uses the natural anatomical axes identified by calculating screw displacement axes of passive motions of a cadaveric wrist and thus the axes may differ from axes defined in vivo. Inconsistencies in the relative position and orientation of these axes in the literature raised the question of whether their in vitro definition would match the in vivo definition. A study was conducted to investigate the relative position and orientation of the natural axes of the wrist and to create an alternate joint coordinate system for the wrist using readily palpable anatomical landmarks of the hand and forearm. Participants performed flexion-extension (FE) and radial-ulnar deviation (RUD) motions with their dominant limb, both unrestricted and with a single-plane constraint, as well as pronation- supination (PS) and dart throwing motion. The muscle activities for the flexor digitorum superficialis, flexor carpi ulnaris, flexor carpi radialis, pronator teres, extensor digitorum communis, extensor carpi ulnaris, and extensor carpi radialis were recorded using surface electromyography (EMG). It was determined that defining the axes of the wrist with a prescribed motion pathway produces different results to unconstrained in vivo motion. The mean distance between the unconstrained FE and RUD axes, in the direction of the long axis of the forearm, was 2.5 ± 3.9mm and this was statistically different (p < 0.03) from that of the constrained axes (1.6 ± 4.0mm). The mean angular distance in the plane perpendicular to the long axis of the forearm was 53.2 ± 10.8◦. Again, this was statistically different (p < 0.001) from the constrained axes where the angular difference was 107.8 ± 17.7◦. The distance and angular difference between the constrained FE axis with the unconstrained RUD axis were similar to those documented in the literature. This suggests that the reason for the inconsistencies is that the motions were performed in different ways, rather than that they resulted from anatomical differences. Proposed alternate joint coordinate systems were compared to the ISB recommended system. Landmark palpation repeatability, axes direction repeatability, and amount of secondary rotation (e.g. rotation in RUD and PS axes during FE) were the metrics used to compare the systems. No difference was found between the ISB recommended JCS and those created as part of the study in any of the three metrics. This means that, for the given metrics, the proposed JCSs performed as well as the ISB recommended system and thus could be used instead, making the quantification of kinematics more feasible in a clinical setting. As a result, I recommend that an alternate JCS that uses the medial and lateral epicondyles, radial and ulnar styloids, the base of the third metacarpal, and the heads of the second and fifth metacarpal is used for in vivo clinical and research use. EMG signals were normalised by activity during maximal voluntary contraction (MVC) of the observed muscles. Nine tasks, selected from the literature, were performed and the task most likely to elicit MVC in each muscle was noted. The non-dominant limb was also investigated to determine whether dominance had an effect on the task most likely to elicit MVC. Dominance had limited effect with statistical differences being found only in the finger flexors and extensors (p < 0.031). Tasks most likely to elicit MVC were identified for each muscle. These results can be used to produce MVC protocols tailored to the muscles being investigated, can help check for crosstalk during electrode placement, and show that limb dominance needs to be considered when recording EMG for the finger muscles. The collected MVCs were used to normalise the EMG data that are presented in the thesis. It was found that the EMG pattern for each participant was statistically different from the others (p< 0.001) meaning that each individual employs a unique neuromuscular control algorithm for motions of the wrist. The primary differences were levels of co-contraction. This was consistent within the participants’ trials which suggests that there may be an anatomical reason for the level of co-contraction as this would be unique to each participant. The EMG data were also used to validate a musculoskeletal model of the wrist, previously developed at Imperial College, for in vivo applications. The kinematics for each participant were input into the model and the muscle forces were calculated. Simulated muscle activity was then calculated by normalising the muscle force by the maximum muscle force for each muscle. Five simulated muscle activities could be compared with the EMG data. The simulated muscle activity patterns matched the recorded EMG patterns both qualitatively and quantitatively, using statistical parameter mapping. No statistical difference was found between the recorded and simulated muscle activity. Thus the model is considered to be valid for predicting muscle activity during in vivo motion of the wrist. Though there was poor correlation between the model results and the EMG (r |0.65|), with the model producing the pattern with the smaller magnitude. It is hypothesised that this is again due to the lack of co-contraction, as agonist muscles would need to be more active to counter the forces generated by antagonists. Thus a JCS for the wrist that is employable in a clinical setting and performs as well as the ISB JCS has been identified; muscle activation patterns for the wrist have been identified; and the Imperial College London wrist model has been validated for in vivo use.Open Acces