Anyone tried doing cardio twice a day?

[Croy]

i'd really like to get in alot more cardio, but don't really want to waste my time if it won't be very productive, so if you've tried doing an hour of cardio twice a day for a total of 2hours per day about 5 days a week, let me know, i'm really interested in finding out just how effective it is

[steveb]

Splitting your cardio workout into 2 sessions will aid in weight loss due to keeping your metabolism high, even if the total time per day stays the same. After you exercise your heart rate and metabolism drops off steadily and then plateaus for a period before returning to its base, resting rate. This plateau phase is higher than the base rate and you are burning extra calories even though you are not in the act of exercising. If you break up your routine you create a second plateau phase and thus spend more time at the elevated metabolic state. It is a proven technique for improving the efficiency of aerobic exercise and I have used it on and off over the years to good effect.