The Tennis App 4+

The Tennis App is an app that helps people involved in tennis (players, coaches, spectators, parents etc.) understand peaks and troughs in performance that occur during a match or practice session.
Peaks and troughs in performance tend to be interpreted as times at which the player is playing well or badly, however The Tennis App shows how many of these conclusions may be incorrect and that the observed good and bad patches of play are merely what would be expected to happen when a player is playing at a consistent level.
At first sight this may not seem to make sense, but the idea is fairly simple when we see each shot as an individual event that can either go in or out in the same way that a tossed coin either lands on heads or tails. When we toss a coin repeatedly we do not expect to get a regular alternating pattern of heads and tails (e.g. head, tail, head, tail etc.). Instead we expect a random assortment of heads and tails (e.g. head, head, tail, head, tail, tail, tail) that over time averages out to be a roughly equal number of heads and tails.
Exactly the same thing happens in tennis. A player who gets half of their serves in does not hit a serve in followed by a serve out followed by a serve in followed by a serve out in a strictly regular pattern. Instead they play a random assortment of serves that go in and out (e.g. out, out, in, in, in, out) that over time average out to be half going in and half going out.
If the player does a block of 10 serves in a practice session they may expect to hit 5 of these in. If they were to get all 10 serves in they would probably think that they are serving really well. If they were to miss all 10 serves they would probably think that they are serving really badly. The reality is that a player who is getting half of their serves in would expect each of these extreme scores to happen about 1 in every 1,000 times in the same way that someone tossing a coin in blocks of 10 tosses would expect to get all heads about 1 in every 1,000 times and all tails about 1 in every 1,000 times.
If we think about slightly less extreme scenarios we see something that players will face more frequently. If the player gets 3 or less serves in they may think that they are serving badly. Similarly, if they get 7 or more serves in they may think that they are serving well. However, this player would be expected to get 3 or less serves in about 1 in every 6 times (they would also be expected to get 7 or more serves in about 1 in every 6 times). This has nothing to do with whether they are serving well or badly, it is simply what happens through natural variation (in the same way that we don’t think a coin has been tossed badly if it only comes up heads 3 or less times from 10 tosses or well if it comes up heads 7 or more times).
The Tennis App lets you explore how skill and natural variation (luck) combine to produce different outcomes for different skill levels. It also highlights the variety of outcomes you would expect if you repeat the same thing over and over again (i.e. how you do not have total control over the outcome even if you can control other aspects of the situation such as the level of skill).
Tennis players need to work on a number of skills to develop their game. They need physical skills that allow them to move and play the shots that they want to; tactical skills that allow them to outwit their opponents; and mental skills that allow them to keep calm and think clearly under pressure. The last of these (the mental skills) are the ones that tend to receive the least attention from players and their teams. In sport there is a lot of talk about controlling the controllables. This app can be used as part of a toolkit for identifying some of the uncontrollables in tennis. Gaining an understanding of what’s controllable can help a player and their support team stay calm when things aren't going well and trust that shots will start going in again if they just carry on doing what they are doing.