With the Olympics nearly upon us, and the Tour de France just having wrapped up, sport performance is the hot topic right now. Even our office- normally a hotbed of discussion about relative risks and numbers needed to treat- is abuzz with talk of who has tickets to what, and if Usain Bolt is really going to repeat his titles in the 100m and 200m.

And with the Olympics comes a predictable pattern of people who have been just a little bit too sedentary- which we know is bad for us - perking up and deciding to get back in shape.

To get going on these new exercise programmes, everyone knows that a flash new pair of training shoes will help ensure you can exercise safely and prevent injury, right? And that when you finish that run, there’s nothing that will quench your thirst and replace what you’ve lost quite like a specially-formulated sports drink.

Whether it’s ‘faster, stronger, for longer’, ‘enhances recovery’, or ‘gives you that extra boost’, sports product marketing is everywhere. Even the official drink of the Olympics this year is Powerade, whose ads claim that ‘Water is Not Enough’.

But our team here in the Centre for Evidence Based Medicine at the University of Oxford, working in conjunction with the BMJ just published a series of studies assessing those claims, and found the evidence worryingly lacking.

Of 431 performance enhancing claims identified from magazine adverts and product websites, we found 146 references underpinning claims like ‘get in the zone with energy to burn’. When we critically appraised these results- about half of which were expert opinion, position papers, narrative reviews, and animal studies so they were not suitable- we found that only 2.7% of the available, appraisable evidence was of high quality and low risk of bias.

So the next time you reach for that sports drink, or are tempted by the latest and greatest training shoe, just think- is there actually any evidence that this is going to help my performance, or help me get fit faster?

Graeme Obree- 'the flying Scotsman' , former cycling world-record holder and Olympic champion- insists that his secret to success was bread and jam sandwiches and eating a balanced diet.

His point? That what you need to do is train hard and eat well, not follow the latest and greatest sport supplement. Our point? That the only available studies that underpin these claims are of strikingly poor quality.

Decide for yourself. It’s all in the evidence.