'Fitness apps could be doing more harm than good'
Health apps such as those that count your steps could be doing harm - by driving people to chase over-ambitious goals.
Dr Greg Hager, from Johns Hopkins University in the US, maintains "very few" of the estimated 165,000 available healthcare apps are based on scientific evidence.
Yet after being downloaded more than a billion times, they were likely to have an enormous impact on public health.
Dr Hager was especially critical of apps and devices that set the user a target of 10,000 steps.
Speaking at the American Association for the Advancement of Science's annual meeting in Boston, he said: "Some of you might wear Fitbits or something equivalent, and I bet every now and then it gives you that cool little message 'you did 10,000 steps today'. But why is 10,000 steps important? What's big about 10,000?
"Turns out in 1960 in Japan they figured out that the average Japanese man, when he walked 10,000 steps a day, burned something like 3,000 calories and that is what they thought the average person should consume so they picked 10,000 steps as a number.
"But is that the right number for any of you in this room? Who knows? It's just a number that's now built into the apps.
"The 10,000 steps example typifies the problem in many ways.
"We all know that probably the more you exercise, the better it is for you. But if you are elderly or infirm then this is not going to be good for you."