to obtain coordinates of key landmarks on the swimmer’s body. Processing of these coordinates enables a three- dimensional, graphical representation of the swimmer’s movements to be constructed (Figure 7) and viewed from any perspective, not just those of the cameras. Three-dimensional motion analysis is currently being used to assess how factors such as the breathing action, body roll and arm coordination, influence swimming performance.

Computational fluid dynamics (CFD) CFD is a computer-based analysis technique that allows the user to build a computer model (in this case of a swimmer) and then simulate the flow of water around the model to study the fluid forces (eg. propulsion) that are acting. The main advantage of the CFD modelling approach is that the scientist can evaluate what effect a specified change in a single variable will have on performance. This would not be possible if working with swimmers because it is highly unlikely that a swimmer could change one aspect of their technique, without affecting and altering other elements of their technique.

CFD is currently being used to

help understand the factors that influence the amount of propulsion lower arm amputees can generate with their upper arm. To achieve this, a computed model has been developed using data obtained by laser scanning an amputee swimmer (Figure 8a). Computer simulations are run using a commercially available CFD package (Fluent 6.3). These simulations, based on real data obtained from video analysis, are currently being used to quantify the effect of body roll, shoulder extension velocity and level of amputation (above or below elbow) on propulsion. Figure 8b illustrates the effect of body roll on the propulsion produced by the upper arm.

Isokinetic dynamometry

Isokinetic dynamometry is considered to be one of the best methods of assessing dynamic muscle strength. It involves measuring the joint torque

Figure 8b: Effect of body roll on propulsive force analysis production

Figure 7: Computer graphics sequence from a 3D video analysis

produced during constant joint angular velocity movements.

Land-based strength and conditioning work is an important component of the arm amputee swimmers’ training. These athletes undertake strength training exercises with their affected and unaffected arms. A Biodex II Isokinetic dynamometer is used to assess the dynamic shoulder extension strength of these swimmers (Figure 9). Tests are performed, with each arm, at slow (60° per second) and fast (180° per second) test speeds.

CONDITIONING WORK IS AN IMPORTANT COMPONENT OF THE AMPUTEE SWIMMERS’ TRAINING

LAND-BASED STRENGTH AND

Initial results show that, for the group as a whole, the shoulder extension strength of the unaffected side is significantly greater than that on the affected side, at both the slow and fast test speeds, although the level of asymmetry varies considerably between the swimmers. At the slow test speed, shoulder strength scores are significantly higher than those achieved at the fast test speed. It was thought that the better

swimmers in the group would possess greater shoulder strength and less asymmetry. This was not the case as no significant relationship was found between the shoulder strength, the level of asymmetry and the performance level of the swimmer. This indicates that shoulder strength alone is not a good predictor of performance, and other factors, such as the ability to generate propulsion and minimise resistance, must also be considered.

Figure 8a: Computer model for CFD

COACH MENTORING AND SUPPORT

The biomechanical assessments and interventions, and the applied research projects generate a considerable volume of biomechanical data. These data are of little value unless they are interpreted correctly and utilised effectively by the swimming coach. To help facilitate this, formal and informal coach mentoring and support sessions are delivered on the pool- deck and in the classroom. These take the form of workshops, seminars and one-to-one tutorials and cover theoretical and practical topics such as: principles of propulsion and resistance;

12

sportEX medicine 2008:36(Apr):9-13