There isn't really a right answer to this question, I suppose it depends what you want to get out of your workout really. Some people do it in the middle of the day or do it just before bed....or 'whenever I have time' is the most frequent reply. What ever the time you decide to cardio, you are going to be burning calories!
However the best time to burn calories and thus burn fat is.... first thing in the morning on an empty stomach! This can be quite tough but, it works a treat! Whether you run, jog, swim, skip with a rope, ride a bike, doing it first thing in the morning is the best time for maximum fat loss..why?? When you do cardio first thing in the morning, you haven't eaten for the last 8 hours or so because you were sleeping, so when your body see's that there are no carbs to burn, therefore it goes directly to stored body fat and this is the fat that you want to lose!
This can be quite a tiring and grueling task for some which is why people often use sports supplements to give them an extra boost and therefore burn even more calories!
To help with cardio workouts in particular, pre-workout supplements are designed to give you nutrients to enhance your workout! Increase blood-flow, better mental focus, enhanced muscle pumps and increased energy are just some of the reasons people are using pre-workout supplements.
The best cardio exercise is simply the one that you will do day in and day out consistently. Choose one which you will enjoy doing and don't be afraid to mix the exercises up. For example, run on the treadmill for 15 minutes, then switch to the rower for 10 minutes and finish off with a bike ride for 10. Interval training is a great way to mix everything up and a great way to keep everything fresh!
There are two categories when it comes to cardio training the "slow and steady" group and the "high intensity" group.
The two groups break down like this:
Slow and Steady Cardio
Long duration (45min-1 hour)
Low intensity
Burn fat and not carbs
preserve joints
High Intensity Cardio
Short duration (20min- 30min)
High intensity (interval training)
Burns a large amount of calories and revs up your metabolism throughout the day
Treat cardio like weights- explosive movements (sprinting etc)