Question and Answers

I received an email from a reader asking me about high intensity interval training (HIIT) and its effectiveness in fat loss.

"The question I would like to ask is why you feel HIIT or interval training is more effective than steady training as you are probably burning more calories in say 50 mins of steady running opposed to 30 mins of the previous running?"

Here is my reply:
"To answer your question, it depends on what your goals are. If it is loss of body fat, you are best approaching it like this:

1) build an aerobic base to prepare your muscles for the demands of heavier training
2) As well as some base training, incorporate some high intensity interval training into your workouts. As well as using nearly the same amount of calories, it is what happens AFTER these workouts that is more important. There is a phenomenon called EPOC (Exercise Post Oxygen Consumption) that occurs which keeps our metabolisms running higher for a few hours afterwards depending on the intensity. Also interval training raises anaerobic threshold, the point where the body stops relying on the aerobic energy system (which uses oxygen) and starts relying on the anaerobic energy system. Put simply, go too much past this point and you simply run out of gas.
Raising anaerobic threshold does two things - gives you a greater heart rate range in which you can work out hard (and thus use more calories) and b) causes changes in our muscles at a metabolic level which encourages our bodies to utilize fat (converted into carbohydrate) during rest and whilst exercising. An unfit individual simply doesn't do this.

I hope this doesn't sound too simplistic, but it is really what happens when we are recovering with both strength training and aerobic exercise that makes a difference.

Hope that sheds some light on the subject."

To sum up, especially in endurance sports (my correspondent is a keen runner), both forms of training have their place in the "big" picture.