John Moores University
The Research Institute for Sport and Exercise Sciences (RISES) was established in 1997. Researchers working within this 5**-rated Institute have, since 2001, published over 200 papers that are listed in the Science Citation Index and attracted over £2 million of external grants. The Institute provides a focus for research activities in the subject area, ranging from studies at cellular level to whole-body responses to exercise and from elite athletes to novices at physical activity. Members of RISES include all staff and research students from within the School, honorary members from external institutions who are collaborators, visiting Honorary Professors and visiting Research Associates. The world-leading programmes are organised into three main areas; chronobiology and exercise, exercise and health, exercise and performance. The research projects are funded by grants from charities, industrial sponsors, international agencies, governments and sports bodies. A thriving post-graduate research community provides a cosmopolitan culture and an environment in which international students may flourish.
BALANCE STUDIES in Movement Function Research (Exerpt from VICON Journal)
by Dr. Gabor Barton Senior Lecturer in Biomechanics,
Research Institute for Sport & Exercise Sciences,
Liverpool John Moores University, Liverpool, England
Figure 3: The “Bumpy Road” scene represents a simple feed-forward environment. A pre-determined function drives the platform and the video in synchronism and the subject’s balance reactions are measured by the Vicon system.
Figure 4: In the “Boat” environment the underlying logic can be described by real time feedback loops. The subject’s movement drives the boat on the 3D video screen and the platform responds at the same time. The feedback is that the movement of the platform has an effect on the subject’s balance.
A lot of delicate details of human balance and posture have been uncovered following the conventional scientific approach of breaking down the phenomenon of standing balance into its conceptual building blocks (inputs, processing and outputs) and examining the components in great detail. The complexity of the experiments however is still inferior when compared to the challenges of real life situations where balance seamlessly or consciously plays an integral part of coping with our environment. How a figure skater can land after a jump on a narrow blade, how a child learns to ride a bicycle, how a mother can manoeuvre a buggy on a bus braking in a bend, or even how a frail old lady can stand by the kitchen sink with poor vision and painful hips, are all challenges to the experimenter which so far had to be avoided or largely simplified before they could be approached.
Vision, proprioception and the vestibular system are the three main components which determine human balance. The continuously flowing signals are interpreted by the neuro-musculo-skeletal system which is able to maintain an upright position even under highly dynamic conditions. The balancing subject’s performance can be measured by standard methods used in biomechanics, including the movement of the center of gravity, center of pressure, video, three-dimensional movement analysis and electromyography. A slightly more complex task is to influence the senses determining balance by controlling what the human sees and feels. Vision can be influenced by projecting an image on a screen or into a head mounted display. Proprioception and the vestibular system can be influenced by placing the human onto a movable platform.
The tool needed to approach balance in its entirety has to have an all encompassing scope. A comprehensive model of a balancing human includes the inputs that influence the neuro-musculo-skeletal system, the processes of the central and peripheral nerve system, and the outputs which are the three-dimensional movements of the body (Figure 1). The CAREN system (MOTEK, Amsterdam, The Netherlands) is the only super-system available commercially at present which combines various tools in an integrated environment in a way that gives control over the standing subject’s proprioception, vision and vestibular system, and registers the person’s responses by recording quantitative measures of movement. The equipment includes a software driven six degrees of freedom movable platform together with a virtual reality video screen and a complete clinical motion analysis system including a Vicon 612 system with eight M2 cameras, video, force platforms, analogue inputs, and electromyography (Figure 2).
Figure 1: A systems approach to human balance including the inputs determining balance, processing of inputs, and movement of the person as outcome.
The D-Flow software manages all components of the system in a seamless way, thanks to an intuitive user interface which simplifies the building of a virtual environment dragging modules onto a canvas and connecting them with data flow channels. The simplest experiment puts the subject standing on the platform into a “Bumpy Road” environment (Figure 3). The subject’s vision is controlled by projecting a 3D moving road scene on the video screen. Proprioception and the vestibular system are controlled by the 3D rotation and translation of the moving platform faithfully matching the road surface. The movement of the subject balancing on the moving platform is measured using the Vicon system, a force platform and surface EMG.
The “Bumpy Road” scene has a feed-forward arrangement as the road’s bumps are pre-programmed and are simply driving the OpenGL graphics providing the video, and also driving the platform’s movement, while the person’s balance responses are recorded. The next level of complexity is based on the additional extra that comes with the CAREN system. All inputs and outputs are handled in real time and so it is possible to create feedback loops by connecting the outputs to the inputs. The Vicon Workstation pumps the marker co-ordinates in real time into a data stream which is processed by the RealTime Engine software running on a dedicated Vicon PC. The D-Flow program (running on yet another PC) receives the data and integrates it into the virtual environment. In case of the “Boat” scene (Figure 4) the subject with Vicon markers attached to his body is standing on a virtual boat (the platform). The boat can be accelerated and decelerated by leaning forward or backward. The subject’s tilt sideways turns the boat to right or left and of course the supporting platform rolls at the same time. Visual feedback is provided by a scene which puts the subject in the boat, on the waves, approaching an island with harbours. Even the shark fins are thrown in for reality. The “Boat” scene manipulates the subject in two real-time feedback loops running in parallel, involving vision and proprioception. The movement of the subject drives the 3D video scene and the perceived visual sensation feeds back onto the movement of the subject. Also, the sideways lean tilts the supporting platform which inevitably moves the subject. The platform really behaves like a boat and the visual scene is also breathtakingly responsive.
Figure 2: The layout of the laboratory. A local network of computers controls the Vicon 612 and the virtual reality components including the movable platform and 3D video.
The Research Institute for Sport and Exercise Sciences (Liverpool John Moores University, United Kingdom) has received funding through the Science Research Investment Fund (SRIF2) scheme from the Higher Education Funding Council for England (HEFCE) to establish a dedicated Movement Function Research Laboratory (MFRL) which houses the only CAREN system in the UK. The mission of this state-of-the-art laboratory is to assess movement function, dysfunction and rehabilitation with a focus on movement re-training (Figure 5). The multidisciplinary team has an exceptional mix of expertise covering biomechanics, gait analysis, musculoskeletal injuries and motor control.
The key individuals involved in the laboratory are Dr Gabor Barton (Lecturer in Biomechanics), Prof Adrian Lees (Professor of Biomechanics), Dr Mark Lake (Reader in Biomechanics), Dr Jos Vanrenterghem (Research Fellow in Biomechanics), Prof Mark Williams (Professor in Motor Behaviour), Dr Mark Scott (Lecturer in Motor Skills) and Dr Raoul Huys (Research Fellow in Motor Control).
One of the workshops of the British Association of Sport and Exercise Sciences (BASES) Annual Conference in 2004 was held in the MFRL. The participants were introduced to the concepts, and the capabilities of the system were demonstrated. The research topics addressed in the MFRL are ranging from fundamental areas to highly specialised topics reflecting the multiple interests and experiences of staff. Since the official opening of the laboratory in October last year, the initial studies aimed at describing the technical characteristics of the CAREN system with an intention to explore its potential in balance research. Several papers and conference presentations related to the first projects are already in the pipeline which will pave the way towards application focused research. The most recent development is the collaboration between the Movement Function Research Laboratory and the Research Unit into Human Ageing and Development, directed by Prof Dave Goldspink within the same Research Institute. The first CAREN User Group Meeting and Workshop is scheduled for June of this year in the MFRL, following the decision by Michiel Westerman (CEO of MOTEK) to declare the MFRL as MOTEK’s reference laboratory.
Figure 5: Potential applications which can be targeted with the equipment available at the MFRL.