How can a Garda speed gun improve my tennis serve?

The speed at which the ball is struck in tennis, especially the serve, determines tennis success the most. The fastest service speeds are a staggering 260 km/ hour for men and 210 km/ hour for women. Understanding what determines ball speed can help players and coaches improve performance.

By far the most important factor is swing technique (so don’t rush out and buy any new equipment!). To see how important technique is, try serving or throwing a ball with your dominant and then your nondominant arm. The difference in muscle strength is only around 10pc but you can actually serve and throw more than twice as fast, and this is due to practising and getting a better technique. If you look closely when you throw with your nondominant arm it is more of a ‘ pushing’ action than a swing.

But as scientists (sports biomechanists to be precise), can we help tennis players improve their technique? Well, yes, and we do it in two ways.

Firstly, we measure technique very accurately by either using small wearable inertial sensors or using specialised cameras to track the motion of all of a player’s limbs (the same technology Hollywood uses to make films like Polar Express and Lord of the Rings).

We can then compare them to elite players and identify what part of their technique they should improve.

We even know what aspect of technique determines service speed the most... it is the speed of the internal rotation of your shoulder. This technology is expensive though. Recently we discovered an alternative way to help players, and, like some scientific discoveries, it was a bit by accident.

We started by wanting to know how much a tennis player improves their service speed using a particular type of practice. We measured their service speed with a speed gun (the same type police use for measuring car speeds) and by chance started asking them if they knew when they were serving faster. They only seemed to know about 50pc of the time.

We had assumed they would know all the time because we believed that if players repeatedly practised a skill and detected a better outcome, such as a faster speed, their brain would decide to use that technique more often.

We tested this further by training the players for eight weeks, three times a week, with half getting feedback from a speed gun, and half practising as they normally would without one.

Both groups improved, but those who used the speed gun improved significantly more. We have since found similar results for throwing and striking a ball. So sport scientists can help tennis players improve.