Top tennis players are among the fittest athletes in sport. An average best of 3 set match can last anywhere from an hour to 4 hours. They get 90 seconds' rest every 2 games and two and a half minutes between sets. 

Being a good tennis player just isn't enough in the modern game. They need to be able to sustain an exceptionally high level of physical output as well as intense concentration. The top players like Djokovic and Murray have a punishing fitness regime. Murray trains in Miami and he was being watched in one of his fitness sessions by some American footballers. They were amazed by the brutal training session that Murray was enduring.

But what if a player has the raw tennis talent and is able to make it into the top 50? As hard as they try they cannot consistently get any higher and the top guys are physically stronger, faster and have more endurance. There is a lot of money involved in tennis and being inside the top 20 or 30 players makes a huge difference to their income. They will go straight into the main draw without the need to play the 3 qualifying rounds. At Grand Slams they will be seeded and therefore guaranteed a lower ranked player in the first round. Their prize money will increase dramatically.

Steroids have been used for years to help players get stronger and have more stamina. Tennis' anti-doping regime has been criticised for being too easy to get around. The problem has been that not enough tests were carried out outside competition. In 2011 just 21 out of competition blood tests were carried out on tennis players. In 2014 1139 tests were carried out. The top players are required to provide their exact location for one hour per day 365 days a year so that they are available to be tested.

With high profile cases in other sports such as Lance Armstrong in cycling and the huge Russian doping scandal from the London Olympics it is tempting to think that all sport is tainted. I think it is reasonable to assume that in any sport where prize money and sponsorship deals are huge then so is the temptation to cheat. The vast majority of tennis players are clean and the top 50 players are subject to very strict rules on blood testing but there will always be a minority who want to reach a higher level of performance than they can achieve naturally.

Following the news of the doping by the Russian athletes Andy Murray, Roger Federer and Rafael Nadal all called for improvements in the anti doping measures used in tennis. Federer has said that anti doping testing is essential in the latter stages of tournaments. He said he was always surprised that when he walked off the court after a final that the anti doping testers were not there. He added that when you reach the quarter finals of a tournament where the points and prize money are higher, you should know you will be tested. 

Federer, who has won 17 Grand Slam titles, said, "Players need to feel that they're going to be tested so they will shy away from any stupid thoughts they might have."

Federer also said he would be in favour of the tests being kept longer. He said keeping the tests for years was the way to scare people.

Britain's Andy Murray, who is competing in the Davis Cup final this weekend, says that simply increasing the number of tests is not enough. He claims to have been tested more than any other player this season but says it makes no difference. He said that Lance Armstrong was the most tested athlete on the planet but never failed a drugs test. The number of tests doesn't guarantee anything.

The Russian athletics scandal was all about falsified records of tests. The corruption went beyond individual athletes. Murray stressed that the sport must ensure that proper procedures were adhered to. 

"Prize money now is so high, there's no reason not to have as perfect a process as possible." He added, "I think the more transparency the better, there's absolutely no question about that." 

Nadal said he felt all the test results should be made public. He also said he would agree to any improvements to the testing process being paid for from prize money.  

World number 1 Novak Djokovic has said that the anti doping procedures are adequate. He has expressed his feelings regarding the unprofessionalism of some of the staff who carry out the testing and in particular regarding the case of his fellow Serbian, Viktor Troicki. 

Personally I feel that for the tennis authorities to have a procedure in place which requires the top 50 players to inform them of their exact whereabouts 365 days a year that they are doing a great deal to combat the problem. I do feel that this should be extended to the top 100 players on both the WTA and ATP tours. This will of course be expensive to implement but tennis is not a poor sport by any means.

The anti doping process needs to be much more open and the results made public. It would be naive to think that there were no players taking performance enhancing drugs. The temptation of higher prize money will always tempt some players but it needs to be kept to an absolute minimum.