Cardio is absolutely key to burning fat. While strength training maintains your muscle mass, the cardio element is what really helps the body burn through the fat stores. When you need to lose fat, you need to start ramping up your cardio in both intensity and frequency.
The basic rule of thumb for fat loss is that you need to do 45-60 minutes of cardio five days a week. Don’t worry if you aren’t at that fitness level yet. The best thing is to work up slowly to 45 minutes a session and then begin the work of increasing your intensity.
What intensities do you need to work at? Let’s discuss each type and where they fit in your program.
Steady State or Long Cardio: This session lasts for 60 minutes (sometimes more for endurance athletes) and is done at an intensity level of 55-65% of Max HR. Working at a low level of intensity gives you the ability to go longer and do this type of activity more often.
Interval Training: This type of cardio takes you from recovery periods in the 65% range to work intervals in the 85% range. I like my cliets to do intervals of 1 min. work and 1 min. of rest. Interval Training is a great calorie burner and should be done for 30-40 minutes. (BTW…my cardio book is full of interval workouts, circuit infused workouts, and HIIT training.)
High Intensity Interval Training: This is tough cardio that makes you feel like puking when it’s over. If you aren’t completely exhausted at the end, feel like you can’t do anything else, then you didn’t do HIIT. HIIT routines are about 20 minutes in length. They are huge calorie burners and should only be done one to three times a week depending on your current level of fitness. Build up slowly to adding HIIT training into your routine.
Moderate-High Intensity Long Training: This is new to the workout world…sort of. A lot of us have been doing it informally, but it is now catching on as the way to go with the majority of your cardio. The idea is to work at the highest level you can for each 45-60 minute cardio session. You should feel very tired but not exhausted at the end of the 45 minutes. If I had to sum it up I would say, “feel like you left it all at the gym when you are done.” I advise people to work at or near their 85% range for at least 35 minutes of a 45 minute cardio session.
How do you put this all together? Easy. Take your cardio sessions and drop in the type of exercise you like and that your body is ready to do. Some people love going out for long walks or runs. Others want cardio over and done with as fast as possible, while some people love cardio but want to really challenge themselves. Your best bet is to do the style you like the most while attempting one or two of the others styles each week for variety.
Oh, in case you are wondering. Cardio in the a.m. is the best but only slightly. The real key is getting off your butt and doing it regardless of the time of day. 
Tomorrow we will talk about the value of Circuit Style Training. That’s what the PNP Girls do!