JOINT EFFORT IN MOTION -

collaborative work by the Biomechanics Laboratory team at the Sports Science Institute of South Africa MRC/UCT Medical Imaging Research Unit,Department of Human Biology, University of Cape Town

Figure 1: The Cape Town team (from L to R): Quinette Louw, Regan Arendse, Janine Gray, Kit Vaughan and Rebecca Campbell

The Biomechanics Laboratory, located within the Sports Science Institute of South Africa, was established by Professor Kit Vaughan in 1998 with the award of a competitive equipment grant from The Wellcome Trust. The lab is also affiliated with the Department of Human Biology at the University of Cape Town (UCT) and with the Medical Imaging Research Unit, which is funded by the Medical Research Council (MRC). Current equipment in the lab includes:
- A 6-camera Vicon 370 system (120 Hz data capture rate)
- One AMTI force plate
- Two 8-channel EMG systems (from Thought Technology and Noraxon)
- One digital video camera
Since its inception four years ago, the lab has benefited from a diverse research team (cf. Figure 1) and has undertaken a variety of projects in the medical and sports biomechanics fields, including those detailed below.
Kit has used the laboratory to focus on the gait patterns of children. The University of Cape Town made a pioneering contribution to the treatment of children with cerebral palsy and, in particular, the role of rhizotomy surgery to reduce the degree of spasticity. The early studies took place in the mid-1980s and a long term follow-up was performed in the late 1990s. The results suggested that the beneficial effects of rhizotomy were still evident more than a decade after the surgery (Subramanian et al., 1998). In addition, Kit has also been studying the acquisition of gait in normal young infants. In a large cohort of over 200 children he and his students have demonstrated that a mature gait pattern does not emerge until at least five years of age. Prior to this stage of development, young toddlers tend to walk with a shorter step length, lower cadence, wider base of support, and shorter single-limb stance times (Vaughan, 2002). Note that these findings are based on scaling the data to account for different body sizes (Figure 2). Despite their delay in acquiring a mature gait, the youngest walking infants have walking patterns that are more robust than the most sophisticated bipedal robots!

Figure 2: Scaled dimensionless gait parameters demonstrating that children do not attain a stable and mature gait pattern until at least 60 months (i.e. 5 years) of age.

Dudley Tabakin (biomedical engineer) played an invaluable role in establishing the laboratory and developing the BodyBuilder models necessary to process the data for most of the sports biomechanics research at UCT. During an intensive three-year period as student and lab engineer, he completed a master's degree in biomedical engineering. The focus of his research was a comparison of the different 3D gait models based on the Helen Hayes marker set. At the end of 2001 Dudley accepted an offer of employment from Vicon Motion Systems in Oxford. He continues to be a vital source of technical support and advice to all the students in the laboratory.
Rebecca Campbell is the post-doctoral fellow in the lab and is involved in the clinical gait analysis of pre- and post-operative children. Most recently she has begun a collaboration with Dr Graham Fieggen, a paediatric neurosurgeon, to study the gait of children with tethered cord syndrome. There is some controversy in the literature about the efficacy of surgical release of the cord, and Rebecca will be looking at the gait of these children who present at the Red Cross Children's Hospital, the only paediatric hospital on the African continent. Rebecca, who hails from Brisbane in Australia, is also involved in the teaching of biomechanics to the post-graduate students in exercise science, sports physiotherapy and sports medicine.
Dr Regan Arendse is a sports physician with a special interest in the common musculoskeletal running injuries of recreational runners. He is currently enrolled for a PhD in exercise science and sports medicine and is determining the link between running biomechanics and injuries. The objectives of his study are: (1) to determine the relationship between lower limb kinetic and kinematic variables and specific foot types (pronated, supinated and neutral feet); (2) to identify biomechanical variables that are predictive of common injuries in runners; and (3) to determine the effect of footwear and prescription on selected lower limb kinetic and kinematic variables. In collaboration with students Lungelo Ndaba and Heidrun Mueller-Bothen, subjective perceptual data and objective biomechanical variables have been collected for 85 normal athletes, each running with different shoe types. Preliminary results suggest that footwear provides sensory input that is integrated centrally to cause motor responses specific to the footwear condition. The role of footwear as sensory information modulators rather than mechanical posts is recognized. It is envisaged that Regan's research will assist our understanding of the conservative management of common musculoskeletal running injuries.
The increasing participation by juniors in basketball in South Africa was the basis for a study by Quinette Louw, physiotherapist and PhD student, using Vicon to investigate the relationship between injured and non-injured players during the landing phase of a jump shot. Her focus is on injuries to the knee joint. Information obtained from analysis of the landing kinematics and kinetics will be used in the design of a preventative exercise programme. It is anticipated that this programme will help to decrease the prevalence and severity of knee injuries among young basketballers in Cape Town.
Associate Professor Martin Schwellnus is a sports physician who has established a working group with students Nicky Sulzer and Scott Richardson to study scapular kinematics. This is in response to the concern for the high incidence of shoulder injuries in throwing sports. It is hypothesized that abnormal scapular tracking may contribute to the risk of shoulder injuries. A surface marker set for the tracking of scapular movements during a variety of shoulder tasks has been established and validated. A clinical trial involving the use of scapular stabilization exercises in the management of shoulder injuries is currently under way. The Vicon motion analysis system is used to determine objectively the response to treatment.
An interesting study investigating the fast bowling action of cricketers has been undertaken by Janine Gray, physiotherapist and PhD student. The literature has suggested that a "mixed action" bowling technique is associated with an increased risk of lower back stress fracture development. The Vicon system allowed for very accurate assessment of the various components of the delivery stride. As a result of Janine's study the previous classification models were revisited and refined. Using this classification model the bowling actions of a group of 45 adolescent fast bowlers were assessed. A set of 32 reflective markers was used to define body segments and preliminary findings indicate a high incidence of the mixed bowling action in this group of young cricketers. The key is to develop an intervention strategy early enough in the cricketer's career that allows him to change his bowling action, thus minimizing injury risk, while not compromising his ability to bowl fast and accurately. We have also had an opportunity to undertake the biomechanical analysis of one of the more unusual styles of spin bowling - that of South African international test cricketer Paul Adams (cf. Figure 3). Our analysis indicated that extraordinary demands were being placed on his spine and subtle changes to his bowling action were suggested in order to prolong his bowling career.
As can be seen from the variety of projects undertaken in the first four years of its existence, this biomechanics lab in South Africa is gaining much from the interdisciplinary collaboration of doctors, engineers, physiotherapists and scientists.

Figure 3: Spin bowler Paul Adams undergoing biomechanical assessment of his bowling action.

Recent Publications from the Lab

Subramanian N, Vaughan, CL, Peter JC, Arens LJ "Gait before and ten years after rhizotomy in children with cerebral palsy spasticity", Journal of Neurosurgery, 88: 1014-1019, 1998.

Vaughan CL, GaitCD, a CD-ROM containing four separate packages, including Animate, GaitBib, GaitBook, and GaitLab, Kiboho Publishers, Cape Town, 1999.

Vaughan CL "Theories of bipedal gait: an odyssey", Journal of Biomechanics, 53: 2002 (in press).