Energy System Training: Get More in The Same Time

Neil Wolkodoff, PhD

Everyone has limited time, so the question is how to get more out of your aerobic workouts. Yes, it’s all about how many calories you can burn in the session, and how many sessions you can get in a week. Most people average three to four workouts of this type per week, so determining how to spend those workouts from a scientific perspective will improve your results on whatever piece of equipment you use. Like all exercise advice, make sure you check with your physician to make sure the program and progressions you use are suitable for your level of fitness, health and any medical conditions.

A good starting point is to term this kind of training Energy System training rather than “cardio” training. The reason is that we can produce energy at low-levels, which relies on fat for very easy exercise, and as the exercise increases in difficulty, more carbohydrates or sugars are needed. Unfortunately the term “cardio” really doesn’t get to the fact that the intensity of the exercise determines the fuel being used, and the ultimate results.

Exercise that occurs below your anaerobic threshold, or level where you start to sprint, uses a combination of fats and carbohydrates. This is a primary zone for weight loss because after 30 minutes of exercise at this level, you start to use more and more fat in exercise. The optimal duration at this level of intensity if 45 minutes or more. The best level is 6/10, like cruise control in your car, just below the burn level. Remember, this is where the body will make weight loss happen with long-term exercise. 

Just above that AT or sprint level is your race pace zone.  This is where you could run the Bolder Boulder or another 10K race, it’s a mild sprint extended for 20-35 minutes. It has a slight level of burn because you have switched to all carbohydrates as fuel even though the pace or intensity is just one or two notches above your aerobic level.  On the 10-point scale, this is a 7/10. If time is short, a 30-minute workout in this zone provides good benefit. 

Interval training requires training above your AT for a short period, then recovering way below your aerobic level, and alternating this system for 20-45 minutes. The intensity of the 45-90 second sprints or efforts should be 9/10, where you feel a moderate burn and increased breathing rate. Recovery periods between sprints should be one to two times the sprint time, and performed at a 5/10 level, a moderate walking speed. That enables your body to recover for the next interval. The real benefit of interval training is not the calories burned in the exercise, rather the increased ability to go faster in your aerobic training and burn more energy. 

For example, if you can cruise along on the treadmill at five calories per minute at a comfortable pace, that equals 300 kcal in an hour. With even a few weeks of interval training once or twice a week, your cruise control speed will increase to six or seven calories per minute, radically improving weight loss results for that hour.

Interval training is easily performed with a 3-5 minute warm up, and then alternating 45 seconds of higher intensity to that burn level of 9/10 with 90 seconds of recovery at a 5/10 level, or a moderate walk. After 20-30 minutes of intervals, include a 3-minute cool-down.

Just about any machine from a rower to a bike will allow you to perform these varying intensities, but what is the best progression? If you had four sessions per week, then two days per week of 45-55 minutes in your aerobic zone (6/10) is the starting point. One day of pace training in that zone of 7/10 for 30 minutes would have a good fitness benefit when time is short. To bump up your ability to burn more kcal in your aerobic training, one day of interval training added to the mix is optimal. This will give your body training variety, increased energy and enhanced results compared to performing the same program day after day.