Glide for gold

As coaches and athletes begin to turn their eyes to the 2012 Olympics, an Edinburgh University team is hoping to give the UK’s swimmers a head start.

Using new mathematical models of passive drag, researchers are developing software, called Glide Coach, that can analyse the shape of a swimmer during gliding, or the period when the swimmer is travelling without kicking, either after entering the water or after a tumble turn.

By minimising drag during this phase the swimmer should be able to travel faster andfurther as well as saving energy.

Movement is recorded using underwater and poolside video cameras that track water-resistant markers placed on a swimmer’s joints and head. The information is stored in Audio Video Interleave (AVI) video format and transferred to the software, running on a regular PC.

The data is then analysed using a complex mathematical model to give the drag coefficient and body shape information, such as head position and postural angles. A replay of the swim appears on a screen by the pool, which includes graphs and data on different technical aspects of the glide. The system then suggests ways a swimmer can reduce drag.

‘By actually measuring the drag coefficients based on how quickly swimmers lose speed we can fine tune their technique until they’ve got the right posture and make sure they start kicking again at the right time,’ said Prof Ross Sanders, Edinburgh’s principal investigator. ‘Most swimmers start kicking too early and instead of speeding them up it actually slows them down as well as wasting their energy.’

Once analysed, the data can be displayed on a poolside screen within moments, giving the coach and swimmer almost instant feedback during training sessions. The swimmer canthen refine his or her technique until the drag coefficient is reduced.

The software, developed with help from Sheffield Hallam University researchers, has been designed for ease of use, and coache swill not require extensive training or specialist knowledge to use it.

‘While the maths is complex the output is easy to understand. It is designed to beuser-friendly and we will explain the procedures and how to interpret the data and provide instruction manuals,’ said Sanders.

By focusing on a swimmer’s glide technique, an area often neglected by coaches, the Edinburgh team believes the system could help coaches shave valuable fractions of a second from a swimmer’s time, which could mean the difference between a podium place and finishing out of the medals.

Previous methods for glide analysis, developed in other countries, have tried tosimulate gliding by towing the swimmer through water and measuring resistance. Sanders does not believe this method gives a true representation of the swimmer’s race posture and therefore gives inaccurate results.

The system does not require complex equipment and could be used at club level with an underwater video camera held on a stick by the coach. Many coaches already use such cameras. Data could then be fed into a laptop which could use Glide Coach software toperform its analysis.

Sanders also believes it could be used to spot potential Olympic hopefuls as it could identify young swimmers with a natural talent for moving through water.

The team has so far developed prototype software and has run initial tests. It is now in the process of fine-tuning with a view to trialling it with a large group of swimmers from the City of Edinburgh and Warrender swimming clubs. Sanders hopes the system will be introduced to coaches around the country in around six months.

The work is being funded by the EPSRCand UK SPORT as part of the ‘Going for Gold’ workshops to investigate how technology can improve the performance of our athletes. The software will be made internationally available once UK SPORT has cleared it for release.