I use one type of lateral trainer for thighs for cardio. The gym I go to have two such machines. After each minute or so, one of the machines shows me: 'you've to maintain 280 spm speed' (what's spm in the context of speed, by the way?) and shows a certain amount (say x) of calories being burnt per minute. However, I almost never (unless I push myself extremely hard), can attain 280 spm speed, I stick around 140 spm speed normally, which is just half.
Here's my question: since I'm sticking to a speed which is merely half of 280 spm, the recommended speed, does it mean I'm actually burning half of the calories shown? That is, is it really x/2 calories I'm burning per minute when the machine shows I'm burning x calories per minute?
And what is spm in the context of speed?
Thanks in advance!