The Science of Tennis: Heat, revs and rankings
The Australian Open tennis tournament has now moved well into its second week, with the semi-finals looming on both the men's and women's sides. So far, it has been a fascinating tournament for many reasons, and I thought I'd do a short post looking at some of the more scientific and topical issues that have arisen.
The heat - Djokovic succumbs and matter wins over the mind
The first of those is the incredible heat of Melbourne and its effect on the players. The day-time temperatures have regularly approached 40 degrees (over 100F), and for those players with afternoon matches, the prospect of a 3-hour match must be the hardest thing they'll do all year.
There are a number of problems with playing a sport like tennis in such hot conditions. We've previously discussed the heat and how it affects a sport like marathon running, where the progressive increase in body temperature threatens to "short circuit" the system once the body temperature hits about 40 degrees celsius. The brain then fails to recruit muscle, and evidence exists that exercise is forced to terminate thanks to a failure of muscle recruitment.
The point we've often made in our posts on fatigue and more recently in our "Mind over matter" series is that the brain actually takes control long before this happens, and people start reducing muscle activation BEFORE they overheat. In a sport like running, this is seen as a slowing in the pace right from the outset.
In tennis, you can appreciate that it's not quite as simple as this. "Slowing in the pace" in tennis effectively means giving up on the ball, and in the first hour or two of a tennis match, no one will do that. You will not see a world class tennis player giving up on a rally that early. So the "pace" is effectively forced on the player by the opposition and the ball.
This means that the "pacing strategy" is a little more complex than in running (though of course, tactics during running may do the same thing). Having said this, there is some evidence that players "pace themselves" during tennis matches in the heat, by going for winning shots sooner and shortening the length of rallies. I am trying to find this study, which I know was done as part of a PhD thesis in Australia, and which found that players "decide" to play shorter points when it is hotter, which is quite fascinating.
However, returning to Djokovic, the problem is that when a match goes on into a third or fourth hour, and the player does a number of repeat efforts, the body temperature can climb quite quickly to reach these potentially limiting levels. We know that repeated sprints are just as effective at raising body temperature, and so the fact that they players have a short recovery during change of ends only serves to slow down the rise in temperature.
The result, as we've mentioned, is that the brain fails to activate muscle, and the player becomes lethargic, unable to sprint, dizzy, loses concentration, heavy-legged. If you watched the match between Djokovic and Roddick this morning, you'll have seen that in practice, as Djokovic got slower and slower until eventually, he was forced to retire at 1-2 in the fourth set, in a match he almost certainly was destined to lose given his physical state. He joins Victoria Azarenka who succumbed in her fourth round match against Serena Williams, while leading by a set.
What can be done about it?
Apart from rescheduling the tournament to take place later in the year, when it's cooler, there is only a limited amount that can be done. A stadium with a roof might help, provided air conditioning could be provided, but the expense and time involved (look at what has gone into turning Wimbledon's Centre Court into an enclosed arena) are likely to prevent that. One thing I have been surprised to notice is the absence of air-conditioning for the players at their chairs. Perhaps it's just not visible on television, and someone can correct me, but it seems that players do not really actively cool themselves between changes of ends. Even having half a dozen air-conditioners around the court at ground level, just to lower the temperature by 4 or 5 degrees would have an impact. That would be the only help given the current scheduling and conditions.
Speaking of scheduling, it's also amazing how many players get injured during the Australian Open. Perhaps two weeks of competitive tennis so soon after an end-of-season holiday is too big a demand on players, but the number of players nursing minor injuries, or forced to retire thanks to more serious injuries this early in the year is quite amazing. In a perfect world, the season would only start in mid-January (rather than on the 2nd), giving players 6 weeks off at the end of the year, and the Australian Open would take place in mid-February. Sport overload - threatens to run the game into the ground...
Rotations - an interesting study on Nadal
On another matter, I read in Time Magazine recently that Rafael Nadal's forehand has been measured with a high-speed camera, and he generates an average of 3,200 rpm on the ball, thanks to his extra-ordinary forehand stroke. By way of comparison, Roger Federer generated an average of 2,500 rpm on his forehand, while Agassi clocked in at 1,800 rpm. That means that Nadal's rotation is 25% greater than that of his closest rival, Federer, which is quite extra-ordinary (incidentally, Nadal's peak rotation was 5,000 rpm, even more amazing)
The implications of this are interesting, and are both positive and negative. For one thing, the enormous spin on the ball brings it down much more rapidly, which means that Nadal can clear the net by a much larger distance and still land the ball in play. In his Australian Open match against Tommy Haas, it was reprorted that his average clearance was 1.8m, while Haas cleared the net by only 1.1m. That difference represents a margin for error that reduces the errors made by Nadal substantially. The other advantage is the enormous bounce and kick Nadal gets off the court - in the Time Magazine article, Brad Gilbert is quoted as saying that a rally against Nadal is a "lesson in pain", because of the heavy shots he hits.
On the downside, the heavy spin means fewer winners will be hit, because a flatter shot takes time away from the opponent, whereas the higher top-spin shot that clears the net by 2m gives the opponent time to cover the court. This is often evident when Nadal plays, particularly towards the end of last year, when he was perhaps a litte fatigued and hit shots with a little less power and depth. The other problem, which has made the news recently, is the enormous strain on Nadal's body as a result of the effort that goes into generating that spin. The general consensues is that he is far more injury-prone than Federer, who seems to float around the court.
My opinion is that Nadal should limit his "exposure" and play only the Master's Series events, and the Four Grand Slams, and not bother with smaller tournaments. He may lose ranking points, but he has a real shot at winning more Grand Slams than any other player in history. I realise that sounds crazy, given that Federer on 13 is currently approaching that record of 14 (Pete Sampras), but Nadal is only 22 and already has 5 (Federer had only one title at the same age). Also, Nadal should win the French Open for the next 5 years if he stays healthy, and then only requires another 5 slams and he'd suddenly find himself on top of that list.
Speaking of Grand Slam titles, rankings and form players, the Australian Open has been interesting because it has featured four players all vying for the title with relatively equal claims on it. Two are now gone (Murray and Djokovic, mercifully, because their perpetual glances at their support boxes are one of my pet hates with the sport - the Oedipus complex of tennis, and they're the worst at it), and only Nadal and Federer remain.
The strangest thing about the first week was that the main protagonists were actually arguing about who the favourite was! Murray was the bookies favourite, thanks to his victories in Abu Dhabi and Doha, but seeded fourth. Djokovic felt he was the man to beat as the defending champion, while Federer was telling anyone who would listen that he and Nadal were still the two to beat. It was a peculiar approach to the mental preparation to sport, because usually the favourites are reluctant to acknowledge their status. Only Nadal has been relatively silent this week.
As it stands, it may well be 1 and 2 in the final, and a restoration of sorts to the "old order", because up until about 1 year ago, Nadal and Federer were destined to dominate the sport. Federer's star has waned somewhat, most spectacularly between June and July last year, where Nadal first destroyed him in Paris on the red clay, then ended his Wimbledon reign, and went on to win the Olympic gold. Federer recovered to win the US Open, but by then Nadal must have been close to exhaustion. So a repeat of their classic matches awaits Melbourne. It should be good entertainment.
On the science side, I'd love to see more in-depth reporting of match statistics. At present, we get only the winners, first serve percentage, and errors. I'd love to see more analysis of things like net clearance, shot depth, shot speed, angles etc. That would give me far more to write about than heat and revolutions per minute!
But let's hope it's not 40 degrees and there are no more withdrawals!
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Tuesday, January 27, 2009
The Science of Tennis: Heat, revs and rankings