Tennis: The science of fast serves

When it comes to fast humans, you might be thinking of sprinters like Jamaica’s Usain Bolt or America’s Flo-Jo... Florence Griffith Joyner, but given that we made a show about running earlier in the year, we thought we’d bring you something different. Anyone for a spot of tennis?! This speedy sport involves players sending a ball flying at dizzying speeds, often quicker than your brain can process. With Wimbledon just around the corner and the French Open in full swing, Izzie Clarke picked up her racket and went to explore the quick pace of tennis.

Izzie - Tennis serves up some serious speed. In 2012, American player Sam Groth sent a ball flying with a serve at 163.7 mph, that's 263.4 km an hour and remains in the history books as the fastest tennis serve on record. But how on earth can and opponent try and return the balls at such fast speeds? I met up with sports scientist Mat Timmis from Anglia Ruskin University at a local tennis club to try and find out...

Mat - The first service, typically associated with a very fast powerful shot, hit the ball so hard that the returner doesn't have chance to get to it. Obviously, you're looking to generate a huge amount of power. Now if we think about the fundamentals of the action of the actual server you'll notice that the tennis server doesn't stand square on, they do stand side on. So as they toss the ball in the air they then go to hit the ball and then this rotational perspective that they generate allows them to generate more linear velocity, hit the ball faster, to hopefully get past their opponent.

Izzie - Right, so I'm taking that on board. Hopefully, all things go well, that then travels to an opponent, what should an opponent be looking out for in order to return a fast serve?

Mat - If you think about the speed of the fastest tennis serve that's been recorded in the length of the tennis court an individual will have about 0.3 of a second before the ball's passing them. So thinking about the time it takes typically to process and react to visual stimuli of about 0.15 to 0.2 of the second, then you've got very little time to actually do anything if you were waiting until the tennis ball had been hit before you make your response. So that clearly shows that we need to do something before the tennis ball has actually been hit and this is when it gets really exciting and really interesting that a lot of my research considers where do expert, novice performers look when making decisions prior to a tennis serve being made.

And what researchers found is the novice tennis players are a lot more distracted by irrelevant features within the environment so they attend or look to, for example, the head and the arms, legs, which don't give a huge amount of information with regards to what's going on. Now the experts or elite tennis players focus much more on the shoulders, the trunk, the hips, and this gives a lot of information with regards to the direction of, for example, a tennis serve. So these are the key differences that help the experts perform better because they're more likely to work out where the tennis ball's going to go.

Izzie - Now how do you actually explore all of this, this visual system?

Mat - We have really a nice bit of kit called and eye tracker, so that allows us to record where somebody is looking within the environment and then allows us to breakdown the analysis into step-by-step phases and look at okay, at ball contact where's our participant looking?

Izzie - Now I gather that you have brought this bit of kit with you?

Mat - Yes, I have.

Izzie - Shall we give it a go?

Mat - Absolutely Izzie.

Izzie - Mat led me into a busy sports hall. Three courts were taken up by children but on the fourth distant tennis court stood my opponent, Sally Pearson from Anglia Ruskin University who's also a county tennis player. And there was also a laptop and a very odd pair of goggles resting on a bench.

Right, so the goggles have just gone over my head. The goggles themselves look like a ski mask but without the lens. There was a tiny high definition camera at the front of the goggles and inside of them, just at the bottom of the frames, were an infrared beam on each side. This was responsible for tracking the actual movements of my eye. A wire out of the back of the goggles then fed all this information into a small laptop.

Mat - We're now able to map where you are looking onto the scene camera and seeing where you are seeing.

Izzie - I popped the laptop in a rucksack and picked up my racket, and all that was left to do was for speedy Sally to serve my way...

Pff, I'm tired. Some excellent serves Sally.

Sally - Oh, thank you. I tried my best.

Izzie - Very consistent. And I was quite consistently rubbish!

Right, let's go and see what the results show.

Mat - We've loaded up the data, and what we've got on the screen in front of us on the laptop is there's a red crosshair, and this red crosshair denotes where you're looking within the environment. So we've got the video where we can see Sally just about to serve, and we can see straight away that you are looking quite high within the environment, so you are clearly getting a little bit maybe distracted. You'll notice that as Sally strikes the ball, you've actually shut your eyes.

Izzie - That's probably not ideal I would imagine. I'm no expert.

Mat - Yeah, it's probably far from ideal if I'm being polite shall we say. Then you also, one of the things I noticed is, you don't actually look at where the ball bounces. Now the ball bouncing provides a really key bit of information with regards to the spin, the direction that that ball is going to bounce when it comes off the tennis court. We need to look at where that ball bounces because it gives a lot of information with regard to where the ball's going to go after that bounce.

Izzie - Safe to say, I didn't do very well. But there was one very mild improvement...

Mat - When you faced your first few serves from Sally you were very close to that baseline and you were really struggling to get your racket onto that tennis ball. So you took three or four big steps back, you clearly thought flipping heck, this is travelling really quite fast.

Izzie - I could not keep up, it was quite intense.

Mat - Absolutely! And this is something that we observed, you're giving yourself just that little bit more time to react to the speed that Sally had when serving the tennis ball towards you.

Izzie - Okay. Fair enough, blinking while Sally serves is not an ideal practice. What should I be doing going forward to try and return such fast serves and keep up with Sally?

Mat - There's a lot of research to show the importance of mental training on mental quickness to help people attend to key features. For example, if you were to track a red ball moving around a screen and there were lots of blue and green balls, your ability to almost filter out the unnecessary stimuli, to really attend to that key bit of information in a chaotic environment helps just to tune that information to then hopefully transfer towards something like this where you're going to be a little better at picking at the key features. And obviously, practice is a key element of improvement in any sport.

Izzie - Right. Well I better get back in there get practising.