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‘High intensity intermittent exercise’ looks like a time-efficient way to improve fitness and health

Posted Apr 08 2011 2:25am

‘Aerobic’ exercises such as walking, running and cycling can undoubtedly have benefits for health and wellbeing, but as I’ve written about more than once, there is scant evidence these forms of activity do much in terms of weight loss. One reason for this is the fact that these activities, unless quite-intense and extended in duration, do not burn a whole lot of calories. Exercise can make us hungrier too. And some evidence suggests that increasing formal exercise can lead to us being more sedentary in the rest of our lives.

In recent weeks I have started to become interested in a form of exercise that appears to offer more potential for fat loss – ‘high intensity intermittent exercise’ (HIIE). This entails periods of relatively brief, intense exercise, interspersed with periods of rest or relatively rest. In the days when I was an avid runner, we used to call this sort of exercise ‘interval training’ (a version of this is known as ‘fartlek’). In those days my goal was not to lose weight, it was to improve my running speed. And boy did it seem to do the trick here. I remember one summer within a few short weeks taking my 7-minute mile pace down to just over 6-minute mile pace with some interval training.

HIIE is often performed on a stationary bicycle, though it is possible to use other forms of exercise such as running or rowing. One quite-often used regime (known as Wingate test) uses 30-second ‘sprints’ interspersed with ‘rest’ periods of 3-4 minutes. Usually 4-6 of these individual cycles will be completed per session. Total session time will be about 20 minutes.

It is certainly true that 30 seconds of high intensity sprinting is hard work for even highly trained individuals. Also, such intensity of exercise is not to be recommended for individuals who are relatively unfit or who have medical concerns that preclude hard exercise. An alternative is to reduce both the sprint and recovery times. One common protocol employs 8-second sprints, interspersed with 12-second rests for a total of 20 minutes (60 cycles).

I’m planning a post about HIIE as it relates to fat loss specifically. However, a recently-published study caught my eye which I felt was worth sharing.

The study took 47 boys and girls (average age 16) and randomized them to one of three exercise groups:

1. 20 minutes of continuous running at 70 per cent maximum capacity, three times a week.

2. Sprinting for 30 seconds followed by 20-30 seconds of rest repeated 4-6 times, three times a week.

3. No exercise (control)

The whole study lasted 7 weeks.

Both exercise groups saw, compared to the control group, significant improvements in a range of areas.

For the steady-state exercisers, improvements were seen in fitness, body fat percentage, BMI, insulin levels, and markers of blood clotting.

In the HIIE group, improvements were seen in fitness, systolic blood pressure (the higher of the two blood pressure readings), and BMI.

Both forms of exercise had benefits, in other words. But now let’s compared the total amount of time spent exercising in the two exercise groups.

For the steady-state exercisers this amounted to 420 minutes (7 hours).

For the HIIE group, total exercise time was 63 minutes (3 minutes of sprinting per session).

This study showed was that actually very brief periods of strenuous activity can reap significant health dividends. In short, HIIE looks a like a potentially very time-efficient way of getting health benefits from exercise.

HIIE is not for everyone. Someone who is quite-unfit, very overweight, and has a history of heart disease is probably not a candidate for HIIE. However, it may be that someone like this might progress to HIIE after improving base levels of fitness and health. Individuals should consult with a doctor or suitable health professional before undertaking a programme that includes intensive exercise.

References:

1. Buchan DS, et al. The effects of time and intensity of exercise on novel and established markers of CD in adolescent youth. Am J Hum Biol 4 April 2011 [epub ahead of print]

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