3D motion analysis facility could help prevent injuries

Run3D is a private biomechanics service at the Oxford Gait Laboratory — a joint initiative by Oxford University’s Department of Engineering Science and the Nuffield Orthopaedic Centre.

The initial aim of Run3D will be to identify subtle idiosyncrasies in technique that are the root cause of injuries, but it could also act as a preventative tool to minimise the chance of a person developing an injury in the first place.

‘In distance running, the ability to train consistently is key to an athlete’s success,’ Dr Jessica Leitch of Oxford University, who leads the Run3D team, told The Engineer.

Around half of all elite-level runners are believed to be sidelined with injuries at some point each year.

‘Most running overuse injuries are caused by biomechanical weaknesses, which cause excessive stresses and strains to be placed on the joints, bones and soft-tissue structures of the lower limbs,’ Leitch said.

‘By identifying these biomechanical problems, we can identify the underlying cause of a running injury and this information can be used to optimise treatment procedures and prevent the injury from recurring.’

The current video analysis facilities available to runners only record in two dimensions and are not sensitive to the subtle biomechanical problems that might lead to injuries.

With the Run3D facility, a physiotherapist attaches small reflective markers to the lower body. As the individual runs on a treadmill, 12 infrared cameras record the 3D positions of each marker 200 times a second to create a biomechanical model.

‘The model represents each portion of the lower extremities as a rigid body segment and can therefore be analysed using the principles of classical mechanics,’ Leitch said.

The positions of the markers are used to create local co-ordinate systems in each of the segments of the lower limbs — the pelvis, the thighs, the shanks and the feet. These co-ordinate systems are defined so as to correspond with the anatomical planes of the body – the sagittal plane, the frontal plane and the transverse plane.

‘Joint kinematics is simply the description of the relative motion between two adjacent body segments,’ Leitch said. ‘For example, the relative motion between the thigh co-ordinate system and the shank co-ordinate system represents the kinematics at the knee joint.’

After the Run3D team has calculated the joint angles as a function of the gait cycle, they select a number of parameters from the angle-time graphs, including peak pronation, peak hip extension and heel-whip among others.

These parameters are selected because they have been shown in the scientific literature to be associated with injuries in runners.

Next, the team compares each of these parameters with a database of uninjured ‘controls’ to identify whether a person’s running biomechanics lie outside the normal range — essentially, whether there are any strange patterns in the way athletes run.

The custom-built software allows this stage of the analysis to be completed in around 10 minutes.

‘Last week, a three-time Olympic athlete had an assessment at Run3D. She had suffered from two stress fractures in her left foot during recent years.

‘We found that her left foot had reduced pronation and, since this reduces the shock-absorption capacity of the foot, this explains her predisposition to stress fracture,’ Leitch said.

At the moment, the current system is not set up to identify individual quirks in a runner’s biomechanics that might actually give a crucial advantage in competition.

However, in partnership with the Running Injury Clinic at the University of Calgary, the Run3D team is currently working towards creating a performance database that would combine the key variables in injury prevention with those necessary for optimised performance and efficiency.