The Surprising Science of Exercise (and why it’s good news)
This week’s Better You, Backed by Science is about some surprising science of exercise — and what it means for you.
Here’s the first surprise:
Running burns more calories than walking — but not as much most as most people think. And at some brisk walking speeds it’s more or less the same.
And here’s the second:
When it comes to running, speed matters far less than people assume.
Here’s how it works.
Why speed matters less than you think
If you run a set distance — say 5 kilometres — you’ll burn roughly the same amount of energy whether you jog slowly or run faster.
When you run faster, you burn calories at a higher rate, but you also reach the finish sooner.
When you run more slowly, you burn calories at a lower rate, but for longer.
You can think of total energy expenditure a bit like this:
rate of energy use × time spent moving
Do the maths and you’ll find that total energy burned over a distance is surprisingly similar, regardless of running speed.
What mainly changes is how fast you get there, not how much energy you expend overall.
And what about walking?
Walking does burn fewer calories than running — especially at slower speeds, but not so must at brisk paces. And it’s to do with the actual movement mechanics.
But here’s the encouraging part:
Walking still burns meaningful energy, especially if it’s brisk, and it delivers many of the same health benefits.
And those benefits don’t just come from intensity — they come from total movement over the day.
That’s why researchers increasingly focus on something simple:
Energy expenditure across daily life.
Anything above the baseline of sitting on the sofa counts.
Moving around the house, cooking, cleaning, doing chores, walking your dog, walking for the bus — as well as more traditional exercise like the gym, classes, or sport — it all adds up.
The key message is still this:
Move.
Realising that movement counts
There’s another fascinating piece of science here.
A Harvard study split hotel cleaners into two groups.
One group was told that the work they already did — cleaning rooms, changing beds, moving carts — counted as exercise and even met recommended physical activity guidelines.
The other group wasn’t told this.
Four weeks later, the group who realised their work counted as exercise had:
- lost weight
- lowered their blood pressure
- reduced their waist-to-hip ratio
- reduced body fat
- reduced BMI
Their behaviour hadn’t changed — only their mindset had.
Upping the intensity (without a gym)
Now suppose you’re able to add in a few short bursts of more intense movement.
You don’t need a gym membership or fitness classes to do this.
(For the record, I love gyms and classes — not just for fitness, but for the social side too. But many people can’t access them easily, and this science is especially encouraging for those people.)
Researchers at the University of Sydney found that just three bursts of intense activity a day, each lasting about one minute, reduced the risk of death from cardiovascular disease by almost 50%.
These bursts didn’t have to be “exercise” as such. They included things like walking fast to catch a bus or walking up a hill quickly — essentially any activity that leaves you out of breath.
Another study found that climbing stairs vigorously for just 20 seconds, three times a day, on three days a week, for six weeks, increased people’s VO₂ max by about 12%.
It suggests you can increase your VO2 max using:
- a flight of stairs in a shopping centre
- choosing the stairs over the escalator
- use the stairs instead of an escalator when there’s a choice
- or simply going up and down the stairs at home a couple of extra times
And VO₂ max matters.
Why VO₂ max is so important
VO₂ max is the maximum volume of oxygen your body can use during exercise.
(V stands for volume, and O₂ is the chemical symbol for oxygen.)
It’s one of the strongest indicators of cardiovascular fitness, and it’s closely linked with long-term health and longevity.
In simple terms: the higher your VO₂ max, the fitter and healthier you tend to be.
Getting fit fast
Now suppose time really is tight, but you want to build fitness quickly — and you have the mobility to do so.
This is where High-Intensity Interval Training (HIIT) can help.
A Japanese study compared two groups:
- One group did one hour of moderate intensity endurance training, five days a week
- The other group did just four minutes a day
But those four minutes were structured.
They alternated:
- 20 seconds of very intense effort
- followed by 10 seconds of rest
Repeated for four minutes.
After six weeks, the four-minute group improved their aerobic fitness (VO2 max) more than the group exercising for an hour a day.
Fast fitness for busy people — especially when you factor in changing, showering, and grabbing food during a lunch break.
Do what works for you
The takeaway is simple.
There are many ways to exercise, and many ways to benefit — depending on your mobility, health, time, energy, and circumstances.
You don’t need fancy gear or a gym membership.
And if you do enjoy gyms, classes, or sports, there are wonderful social and mental-health benefits too.
But whatever you do:
Do what works for you.
Try this
Build movement into your day.
If it’s healthy for you to do so:
- Walk briskly up the stairs at home once or twice a day
- Walk fast up a short hill rather than plodding
- Add intervals to everyday walks: one minute faster, one minute slower
Whatever you do:
Just move.
No matter how slow.
The science behind this week’s article
- Margaria R. et al. (1963). Energy cost of walking and running. Journal of Applied Physiology. Link.
- Stamatakis E. et al. (2022). Vigorous intermittent lifestyle physical activity and mortality risk. Nature Medicine. Link.
- Allison M.K. et al. (2017). Brief stair climbing improves cardiorespiratory fitness. Applied Physiology, Nutrition, and Metabolism. Link.
- Tabata I. et al. (1996). Effects of high-intensity intermittent training. Medicine & Science in Sports & Exercise. Link.
- Crum A.J. & Langer E.J. (2007). Mind-set matters: Exercise and the placebo effect. Psychological Science. Link.
(All studies summarised in plain English in this article.)
More
Want to read more like this? Subscribe to my free Better You, Backed by Science weekly email (sends every Wednesday).