Moreover, this kind of intensity (which would be a sprint training), would increase your metabolism and burn a lot of calories after the actual workout.
It's a myth that fat is only burnt with low intensity.
I'm glad you brought that up.... I'm a huge fan and proponent of HIIT (High Intensity Interval Training). It:
1) increases cardiovascular and respiratory capacity. Measurements of V02 capacity have shown that one HIIT session (20 mins) a week gives greater gains in this area than multiple slow, steady-state cardio over the same amount of time.
2) is primarily anaerobic... and large muscle groups are put into play. This greatly increases metabolism throughout the whole day, not just while you are on the machine.
3) can be worked into training days quite easily. If one prefers separate sessions that's fine, but it can be done following an upper-body workout. Following a lower-body workout is not advisable as the muscles are already fatigued and you'll pretty much die trying an HIIT after that.
I used to do an hour SS cardio a day last year and 1 hr training (am/pm). Piddly results. This year I dropped cardio down from 7 hrs to 2 SS sessions (30 mins ea/week), and 1 HIIT session (20 mins). Dropped training from 6 hrs /week to 40 mins 4x/week. Very fast results within a matter of months.
It's quality... not quantity that counts.
My add to the list? Learn how to train most effectively, getting the most 'bang' for your buck. Spending hours in the gym won't help you cutting or bulking if you aren't getting results. Time doesn't mean you are doing it RIGHT.