Originally Posted by abergdc
But much more intense exercise, such as intervals, can lead to after-exercise higher metabolism for at least several hours. I don't think that's true of lower-intensity. Also, it doesn't really matter what you burn (fat or carbs). The main point is to burn calories, so again the higher intensity shorter workout does fine. Also also, I believe there is some evidence that longer low-intensity workouts are catabolic, that is that they can lead your body to eat into muscle more than shorter more intense workouts (this hardly proves it, but look at sprinters vs long-distance runners for body composition).
But I thought you were worried about overtraining? Intervals are great, but they will wear you out. I do intervals in the winter when I'm riding less. They make me tired! A 60 minute ride with a few intervals wears me out more than a 180 minute ride at a steady pace. Do you have good backing for the catabolic theory? It might be true, but it kinda sounds like BS from a weight trainer.
Finally, the nutrients you use depend on the macronutrient balance in your diet, as I understand it. If you are on a low-carb diet, for example, your body can get the energy from fat. So, I wonder whether those results in those graphs are invariant to the sort of food they're eating, particularly the macronutrient balance.
I'm not sure about this. I think your body gets energy (glucose) for endurance exercise from blood glucose and from glycogenstores, and also from the metabolism of fat and protein. All 3 sources are present in the normal body. I think which form the body uses depends on the duration and intensity of activity, not which one is most abundant in your diet. This is what mothra's graphs are showing, and what I tried to explain in a previous post. And I don't know of any writers on exercise physiology who advise imbalances of macronutrients such as a low carb diet.
I just reread your original post, and I see we've gotten pretty much off topic. You realize that you have to come up with your own exercise program. I think you're smart to put a little more emphasis on cardio than you used to. I alos think you would be wise to invest more time in exercise. Personally, I do only a few upper body exercises with weights. I do basic multi-joint exercises with free weights about twice a week, mainly with strength as my goal. I do squats, deadlifts and calf raises in the winter, and core twice a week. I don't enjoy lifting, but it does make me feel good. I ride for 60 minutes in the winter and up to 180 minutes in the summer, 6 days a week. I walk or row on the seventh day. I also take a 4 day stretch off the bike every month. My main fitness goals are endurance, weight loss/maintenance and health (history of diabetes and heart attack). I hope this gives you some ideas about how to fit more exercise into a busy schedule.