Is High Intensity Cardio Good for me?

There has been a lot of press coverage regarding HIIT (High Intensity Interval Training) as being a fitness quick-fix. HIIT is, as it says on the tin, intervals of very intense aerobic exercise. A brief timed burst of very intense cardiovascular exercise (i.e. burpees), followed by a short rest period, repeated a set number of times. This has become more popular partly thanks to the BBC’s Dr Michael Mosley, he of the 5:2 intermittent fasting diet fame.

The argument is that HIIT is quicker to do with better results than ‘steady state’ cardiovascular exercise. LISS, or ‘Low Intensity Steady State’ training involves the heart rate being slightly elevated (i.e. the feeling of being puffed, but not totally exhausted). An example of steady state aerobic training is going for a fast walk, or for fitter folk, a steady jog. It used to be called LSD (Long Slow Distance) training but the name changed to avoid confusion :)

So, is it better to go ‘hell for leather’ for a shorter time, or slower for a longer time?

There is a relatively easy answer to this. As a Personal Trainer specialising in fitness for ‘reluctant’ exercisers (or those coming back from injury), I always recommend investing in a heart rate monitor and getting out and about with the heart rate elevated to ‘slightly puffed’ for 30 minutes or more, every other day, or three times per week. Technically, this is operating at 65% - 85% of the MHR (Maximum Heart Rate), or working in the aerobic zone.

This helps build cardiovascular fitness and improves endurance. Going at a lower heart rate burns a higher proportion of body fat, which is used as a fuel in the chemical reaction producing energy. Higher intensity exercise uses more of your in extremis energy supply, which is stored muscle glycogen. This is good if you’re pre-diabetic and want to lower your blood sugar levels, but doesn’t necessarily help you change shape. HIIT takes longer for the body to recover from, and increases possibility of injury.

My approach is that an individual needs to be comfortable with having their heart rate elevated before starting on more intense cardio work. If you think about it, moving at a ‘steady plod’ regularly is what we used to do before cars, remote controls and other labour-saving devices.

Many people forget that the heart is a muscle, so it needs training like any other muscle. If you overload a de-conditioned heart, you have a recipe for disaster. I am a big believer in building up intensity with time. I certainly do HIIT with some of my established clients, but I need to be confident that firstly, they are fit enough to endure it, and secondly, they have the positive mental attitude required to work at a maximal heart rate for short bursts (in other words, it ain’t comfortable). Sprinting intervals certainly are an excellent method of building up speed once an individual is running comfortably. However I usually don’t do sprint intervals with clients who have heart conditions, lower leg injuries or a distinct lack of motivation.

Fitness should be achievable and fun, and I truly think if you’d like to do HIIT and you are already fit, go for it. However if you’re a bit out of shape, it’s wisest to get back in shape before ‘beasting’ yourself!