Researchers have long suspected there is more to measuring exercise effectiveness than just counting calories. A new study aims to identify the other crucial factors at play. Exercise scientist Dr Nigel Harris explains.

Calorie burn has long been the definitive measure of exercise success, surely it’s viable or it wouldn’t be so popular?

The science of exercise and nutrition can be confusing, but calories are something everyone gets. Calories are well known, they’re easy to understand, they’re on almost every food packet and programmed into all the latest gym equipment and fitness trackers. It’s a nice easy metric that we can all relate to. The value of measuring calorie burn is not in dispute, it’s more about what you miss when you focus only on the calorie total. Chances are some types of exercise will have a more potent effect. And it’s this potency which is being missed by just measuring how many calories you actually burn.

And this is what shaped your recent study into the effects of resistance training beyond calorie burn?

We know that often the calories burned during resistance training can seem disappointingly low, yet we are aware that many transformative effects come from resistance training. There must be more to it, and that’s why more research was required.

The theory was that, a resistance training program like BODYPUMP might have a very similar calorie equivalent to other types of exercise, like cycling, yet other harder to measure variables, such as in the blood, might give us an indication that it has a more potent effect.

So your study involved testing blood – and specific hormones within the blood – in order to gauge the effects of exercise?

The reason that we’re interested in hormones is that, with certain types of exercise, you often see quite acute hormone elevations. We can measure these elevations by testing blood – before the exercise and then immediately afterwards.

What are the hormones that matter?

Goodness knows it’s complicated, but human growth hormone is one key target because we know that it’s associated with really positive things such as fat burning. Because of the name everyone tends to think that producing human growth hormone means it’s all about growing muscle. Well, it might also have some muscle building effect, but if you get an acute, high elevation of human growth hormone, it’s a good indicator that you are then starting to burn more fat.

Blood lactate, which indicates anaerobic energy use, is also important. When lactate shoots up beyond a baseline level we know that you’ve hooked into your anaerobic energy pathways.

And there are other markers that aren’t strictly hormones, such as inflammatory cytokines. If these are present chronically in high levels it’s not a good thing. But the amazing paradox is, when we get acute elevations of them, like we do straight after exercise, the effect is really positive and chronic inflammation is reduced.

The thing is, all these different blood markers tend to come as a package, they work together, so it is interesting to measure more than just one of them.

And initial findings from the study have highlighted that resistance training can stimulate change to these important markers?

We know that when we present the body with a sufficient stimulus – such as the resistance training demands of BODYPUMP – these blood markers ramp up and downstream they cause good things to happen. When we see them go up temporarily it’s a really good indicator that longer term they might be doing good things too.

We went into it with the hypothesis that BODYPUMP would probably have a more potent physiological effect than the equivalent time and calorie expenditure of steady-state cardiovascular exercise. And that was what we observed for the most part.

Surely that doesn’t mean we should we abandon cardio and replace it with resistance training?

No, no, that is definitely not the point – the intention is not to disprove one type of exercise. It is simply to say, look, if you’re spending 50 minutes in the gym and thinking that you’re just burning X amount of calories, you need to consider what else is happening beyond the calorie burn.

The full findings of this study will be published shortly. Watch this space.

Dr Nigel Harris is a senior lecturer in Exercise Science at Auckland University of Technology. His research activities are centered on the assessment and improvement of metabolic health through exercise, with an emphasis on resistance training and high intensity intermittent exercise.

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