Written by: Bradley Land
Bradley is an M.Sc. student in the School of Engineering at USW. His research project concerns the design and development of wearable technologies to support biomechanical analysis and rehabilitation.
While studying the principles of engineering, my desire was to apply these principles in a wider context than just the traditional routes, so I turned to sport and sought any possibility to intertwine the two areas to make my work something I would enjoy.After much deliberation the project became the conceptual design of a pair of compression shorts, which, using an integrated inertial sensor arrangement, could measure the range of motion and other performance metrics at the hip joint, to support an athlete’s rehabilitation after an injury.
The last 20 years have seen injuries to the hip joint occurring at a consistent frequency, comprising of six per cent of all injuries (see Common Hip Injuries in Sport). Kinematics, joint forces and moments applied to a joint can all vary depending on the motions being performed at the hip. Non-contact repetitive mechanisms of twisting, kicking and running are common in many sports and have been shown to exert excessive loads through the synovial joint increasing the risk of injury. Since these movements lie at the foundation of most, if not all sports, the likelihood of reducing the risk of hip injury mechanisms is very low. The anatomical complexity of the hip joint is a key issue during the diagnosis procedure of any injury. A vast array of plausible pathologies for defining symptoms can all help to muddy the true cause of an injury amongst the densely compact musculature of the hip. The extensive reach of nerves about the joint can see the masking of underlying biomechanical faults as pain in differing regions (i.e. intra-articular pathologies may radiate to anterior or medial hip regions – see Hip Pain in Athletes). Injuries about the hip, are notoriously difficult to narrow down because of the complexity of the encapsulating region, hence my work looked to increase the efficiency of diagnosing injuries about the hip.
The regular capture of “range of movement” (RoM) data can help a coach to observe for signs of fatigue and similar signs of performance inhibition that may result in an injury, allowing an opportunity to intervene prior to serious damage. However, in the event of an injury, it has been well documented that the evaluation of a patients RoM at a joint, can be used as an indicator as to the extent of an injury. Within the confines governed by ligaments and skeletal geometry limiting the maximal range of motion, the actions of the encapsulating musculature are responsible for the movements of the hip joint. Differentiating the onset of pain between active and passive movements at the hip, can help a clinician begin to consider the intra/extra-articular nature of an injury (e.g., within or outside of a joint). Pain during the passive manipulation of the hip can lend itself to the root-cause being unnatural motion of the joint as a result of a bone deformity. Opposingly, pain whilst the individual is actively actuating the joint suggests a particular muscle group contains the damaged muscle.
Identifying the onset of pain can constrict a broad range of possible cause of injury. Yet reductions or pain during the basic RoM measures of the hip alone is not the only symptom identifiable through the motions at the hip. Compensatory methods can temporarily prevent the onset of pain and can present themselves both statically and dynamically. Functional performance tests will often see athletes exhibit these compensations as they seek to complete a set task, focusing on performance rather than execution. Single leg squats, for example, can elicit weaknesses in hip adductors, as observed by excessive pelvic tilt during the execution of the movement (see Utility of Frontal Plane Projection).
These precursors or symptoms of injury have been known for some time now, yet having the capabilities to identify the signs takes a well-trained eye. Better yet a device capable supporting the evaluation of an athlete’s execution. Optical motion capture systems are responsible for some of the greatest feats in motion capture and motion analysis to this day. Its accuracy in recording motion has been unparallel for some time. Yet the miniaturisation of inertial sensors has seen the introduction of “smart clothing” solutions to motion capture. The Inertial Measurement Unit (IMU) based motion capture suits removes the need for high-quality optical camera set-ups, time-consuming calibration and initialisation procedures. For some, the optical solutions can provide the pinpoint accuracy needed for in the analysis for finer motions like a golf swing. Whereas the IMU-based solutions offer the freedom for the same analysis to be performed outside of a specialist environment. This freedom was something I wanted to capture in my design, although for many the freedom to use any motion capture solution is significantly hindered by the large capital needed to acquire any motion capture equipment. The use of motion capture has been restricted to those in the higher reaches of their respective sports who could afford it. The renowned optical tracking of Vicon and IMU tracking of Xsens MVN will set you back a minimum of $16,000 and $12,000 respectively. Yet further developments in the sensors technology have seen the components within the IMU motion capture systems become cheaper, meaning it could moreover be possible to replicate the results of inertial motion capture for a fraction of the price.
My compression shorts design was simple yet promised to meet the demands for a cheap and accurate motion capture system for the hip joint. In the same way, the femur rotates away from the midline, an IMU can measure the independent inclination of each axis from its initial position. Attaching the sensor to a skeletal landmark much like the optical tracking systems, it was possible to observe all the motions of the pelvis, femur and consequently the hip joint. The lower cost of the components within the compression wear does not hinder the system’s accuracy. Through an effective post-processing routine, data from the sensors can be passed through data filters to increase the accuracy and allow a clinician to observe the motions of the patient’s hip joint.
The promise the design showed in my time as an undergraduate student lead to me continuing the project as a postgraduate student (see USW Engineering for course information). It wasn’t long into the master’s programme that we all saw unprecedented and unpredictable times brought about by the COVID-19 pandemic. With everyone working from home the typical day-to-day run of things came to a sudden hold. But the world hadn’t stopped turning. With hospitals, GP’s, rehabilitation clinics and physiotherapists alike all seeking alternate methods to provide support, those who had sustained an injury or a minor medical condition had to adapt to a new way of seeking consultation or guidance during rehabilitation.
In using means rather unprecedented, society has found a way to function. However, one of the hardest things to replicate under the COVID-19 enforced rules has been the interaction between a professional clinician and their client. The society of chartered physiotherapists recommended remote consultations where possible via commercial video chat software. However, evaluations performed throughout the entirety of a rehabilitation programme can be immensely difficult over webcam. Poor video quality, observation angle and distance from the subject can all hinder a clinician’s evaluation during remote consultations. Yet these constraints can be mitigated through the use of the compression shorts designed through our research, enabling the clinician to see the entire picture of the joint without having to rely heavily on patient competency. The reduction in both size and price of the once expensive technology enables the implementation of the technology into our daily lives and supports the self-monitoring of our health. This project, now more than, ever could be another step in that direction. Indeed, the collection of quantitative data away from the examination office has the potential to greatly subsidize a patients’ rehabilitation more than the remote consultations alone.
Note: Bradley’s research is being supervised by Dr Rae Gordon (USW), Dr Colin Morgan (USW) of the School of Engineering, and Dr Morgan Williams (USW) of the School of Health, Sport & Professional Practice.