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Rise of the HIIT training
Cardiovascular or 'cardio’ training has become a staple in many people's exercise routine. And, in the last few years High Intensity Interval Training, or HIIT, has become a huge craze, replacing the conventional long, steady-state training (i.e. putting in the miles on the treadmill) as the dominant form of working the heart and lungs, and, perhaps more importantly, in burning up calories to help with weight loss.
Both men and women have been turning in their running shoes for a pair of dumbbells and an interval timer, with many women preferring HIIT training to lower intensity routines. But should both men and women expect equal results from HIIT as from steady-state conventional training?
Indeed, four separate studies, all using different types of interval training and steady-state training all showed a very clear trend; that, when body weight and time was accounted for, women actually burned less calories when using HIIT type training than men, but generally outperformed men when exercising at lower intensities, a trend which, interestingly enough, seems to crossover to resistance training, as well.
On average, women who were completing HIIT workouts burned between 0.09 to 0.2 calories per minute per kilogram of bodyweight, whereas men went from 0.13 up to as high as 0.29 calories per minute per kilogram of bodyweight.
So, to put that in perspective, a normal 70 kilogram man who did 10 minutes of HIIT training could burn up to 203 calories, compared to just 140 calories for a woman who did HIIT for the same amount of time and weighed the same as her male training partner.
And if you're doing more than one HIIT workout per week, that gap in calories is going to multiply.
Slow and Steady wins the race
As stated above, the same group of studies that showed that men generally tend to burn more calories per minute at higher intensities, also showed that women tended to burn more calories per minute at lower intensities.
In fact, in low intensity jogging as well as in walking, women burned 0.6 calories per minute per kilogram of bodyweight to men’s 0.5 and, during low intensity jogging, 0.16 calories to men’s 0.12, so that would mean that, in 30 minutes of running, a 70 kilogram woman would burn 336 calories, compared to 252 for a man of the same weight; a difference of almost 100 calories. In one workout!
But why is this?
It could be due to the fact that physically active women usually have a higher number of ‘endurance’ type fibers (known as Type 1 or ‘slow twitch’ fibers) than their male counterparts. This would cause lower intensity exercise to work more of the muscle in a more optimal way, and, hence, could cause greater energy being used for the exercise than if it was performed at a higher intensity, like in interval training.