I have been using the gym since September at university and my workout includes burning 300 calories walking at 15% incline at 5.5mph and I reduce this little by little as I feel necessary (takes me 26 mins) and I spend ten minutes on a bike which burns about 50 cals. The last two times I've been on them though my heart rate has been all over the place. Its usually between 134 and 160 when I get going but then dropped to 78, then 48 which panicked me a bit as I hadn't slowed down, the numbers then rose gradually back to 78 then I felt a little jump in my chest and it went back to 134. Needless to say I slowed down after that and on the bike my heart rate started at 114 and then stayed at about 134 till I finished. Are they just dodgy machines or should I be worried? Theyre only a year old. I'm asthmatic but never suffered an attack - touch wood - but I did panick for a short while at the gym. I just googled what your heart rate should be though and it said 40-100 at rest so Im not dying but any advise I would be very gatefull for.