[Mike] Let’s back track for a moment.  The reason why I recommended Lisa do high-intensity aerobic exercise is because it is less aerobic. I won’t get deep into the science of exercise, I know you just want answers but allow me to quickly explain that the more intense an exercise becomes the more anaerobic it becomes.  The primary difference is, aerobic exercise relies on oxygen to produce energy whereas the anaerobic exercise does not.  Anaerobic exercise burns more calories per unit of time and has a greater effect on the metabolism.

While it is also true that aerobic activity uses fat for energy compared to anaerobic exercise which uses glycogen (carbohydrates stored in the muscles) the belief that aerobic activity will help you burn more body fat is inaccurate.  To put it perspective, the most aerobic activity you can do is sleep.  As you go from sleeping to waking to walking to jogging to sprinting, the energy systems involved in fueling each of these activities moves from varying degrees of aerobic to anaerobic.  As you might guess, jogging burns more calories than walking because of the level of effort required.  At the end of the day it is the total number of calories burned compared to what is taken in that determines fat loss.  So although aerobic exercise uses fat for energy it does not burn more fat compared to higher intensity activity.

One of the most effective and time efficient forms of high-intensity aerobic exercise is what’s known as interval training.  High Intensity Interval Training (H.I.I.T.) is characterized by periods of maximum effort followed by periods of low to moderate effort.  For example, if we were to relate it to running, a person could sprint for 20-60 seconds and then jog or walk for, 20-60 seconds—repeating this process for say fifteen minutes.

You could do the same by jumping rope or doing other calisthenics such as jumping jacks, squat thrusts, hop-overs, mountain climbers, or lunges.  Another option is to walk (or run) hills like the steep one down the street from Lisa.J  If you do like biking or the elliptical you could do intervals by either increasing the resistance for the high-intensity interval and then dial it back for the low to moderate interval or keep the resistance consistent and alternate between sprints and slow paced intervals.

The combinations and forms of exercise are countless as is the amount of time you perform your hard and easy intervals.  The only “rule” is that you push the upper limits of your conditioning during the hard periods.

Sample of a 10 minute H.I.I.T. workout:

Warm-up – 2 minutes of light Jogging in place

30 seconds Squat Thrusts (hard) followed by 30 seconds Jumping Jacks (easy-moderate) repeat 2x

30 seconds Mountain Climbers (hard) followed by 30 seconds Hop-overs (easy-moderate) repeat 2x

30 seconds Jumping Jacks (hard) followed by 30 seconds Squats (easy-moderate)  repeat 2x

Cool down – 2 minutes light Jogging in place