the coach and swimmer with rapid feedback on the swimmer’s starting, turning and swimming technique. Analysis software (Quintic 9.03) is used to enhance the feedback process. Theoretical technique models of swimming, starting and turning are used to help identify the biomechanical factors limiting performance and to guide the analysis and feedback. All swimmers joining the World

Class Pathway undergo an initial assessment, which involves filming of their starts, turns and strokes, followed by a 30-60 minute feedback session to identify general strengths and weaknesses. Where appropriate, basic performance parameters, eg. stroke rate, stroke length, start time, dive length, are derived from the video recordings.

Pool-based intervention sessions

are used subsequently to monitor progress and provide immediate qualitative and quantitative feedback for fault correction. Intervention sessions usually focus on one or two specific aspects of the swimmer’s technique, identified by the coach and biomechanist as being priority areas.

Race analysis Race analysis has been undertaken at the major disability swimming competitions since 2000, including the Sydney Paralympics.

A five-camera

system, developed at Manchester Metropolitan University (MMU), enables race data to be obtained from all eight lanes of a pool. Race analysis provides information on key performance parameters such as start time, turn time, clean swim speed, stroke length and stroke rate, under ecologically valid conditions. Race data are provided to the

coach in numerical and graphical formats (see Figure 2). Race data enable the swimming

coach to: n Identify their swimmer’s strengths and weaknesses, relative to other performers in the swimmer’s class, and organise their training accordingly. n Develop a competition model. Once the coach has compiled data from a series of races, they can use these to

plan the most effective strategy for the swimmer to use in future races. n Monitor whether progress is being made in race skills eg. starts, turns and finishes, throughout the season. Identify changes in stroke efficiency or ‘stroke index’ (swim speed × stroke length). As a swimmer becomes more efficient, they waste (lose) less energy to the water. This is reflected in an increase in stroke index, whereby the swimmer uses longer strokes (and consequently fewer strokes) to achieve a given speed.

Velocity meter analysis A velocity meter is a device that measures the instantaneous speed of a swimmer, continuously and in real time. In 2004, technicians at MMU developed a velocity meter in order to enhance the biomechanics support provision to disability swimming. The device is portable, accurate and causes minimal disturbance to the swimmer. The speed-time curve produced

by the velocity meter can be superimposed on a video recording of the swimmer, in real time, and is available for immediate viewing on the pool deck. The software then enables immediate feedback of stroke data to the coach and swimmer. The velocity meter provides the coach with useful, objective evidence on which to base their practice. Figure 3 shows a typical speed curve for a breaststroke swimmer over two full stroke cycles. The velocity meter software allows the curve to be analysed immediately post swim to provide the coach with the swimmer’s clean swim speed, stroke rate and stroke length. The software can also be used to quantify how much speed the swimmer gains from their kick (A to B), how much they lose during the glide (B to C), the speed increase due to the arm pull (C to D), and the speed lost during leg recovery (D to E).

Application 1: Monitoring asymmetry in an amputee swimmer’s stroke Until recently the extent to which swimmers with an arm amputation at elbow level were able to propel themselves with the affected limb

Figure 1a:

Underwater filming rig

Figure 1b:

Split screen video image

Figure 2: Examples of race data presented in graphical format LC = Long Course Championships

was unknown. The velocity meter has provided some insight into this question.

Figure 4 is a typical speed curve for a single arm amputee swimming front crawl with a pull buoy (a flotation aid held between the thighs). The large and small peaks on the curve correspond to the push phases of the sound and affected limbs, respectively. The curve presents clear evidence that arm amputee swimmers are able to generate propulsion and increase

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