Q: if one person burns 600 calories bicycling in 45 minutes and another burns the same amount of calories in 90 minutes isnt the first person's workout more beneficial because it is more intense and his/her's metabolism will be at a higher level for a longer period of time after the workout is over ? although the seond person will burn more fat calories during the exercise ,I suspect the first person will burn more calories for several hours after the workout is over

A: That's a very interesting question. I haven't seen any hard data on something like this, but my response would probably be that no, they would not have significantly different metabolic response while recovering. That is assuming both of them stayed within their aerobic threshold, meaning that they kept the same pace for the entire 45 or 90 minutes (one faster pace, one slower, obviously, but both keeping consistent pace). On the other hand, if one of them was doing to-exhaustion sprints, followed by rest periods followed by more to-exhaustion sprints, and so on then he probably would really have higher metabolic response when recovering. That sort of exercise would be along the lines of HIIT -- I mentioned it answering question # 33.