A student from Warwick University approached me yesterday to take part in a study. I have to wear an Actigraph around my waist for a week. It measures how much physical exercise I do. Heaven knows how it works (it says 'by measuring movement through an internal accelerometer'). I explained that a lot of my exercise is in the gymn, and my torso may not be moving that much, but she said it didn't matter, it worked for any kind of exercise. Not sure how, if I'm sitting still lifting weights or cycling. How does it know - for example - whether I've got the exercise machine on a high or low resistance setting? It makes a heck of a difference.