At last: a ‘snack’ that’s good for your body
It’s not chips, sorry. But the good news is that exercise snacks – that is, short bursts of vigorous movement – can improve cardiovascular fitness as much as a full workout. Paula Goodyear finds out more.
Back in the early 1980s, when fitness became a thing, the only way to exercise for a healthy heart was to do 20 to 30 minutes of non-stop aerobic activity, like running – or so exercise science thought.
‘‘Now we know that fitting frequent short bursts of movement, even as brief as one or two minutes, into the day can benefit heart health and have positive effects on blood glucose levels and insulin sensitivity,’’ says Professor David Dunstan, head of the Physical Activity Laboratory at Melbourne’s Baker Heart and Diabetes Institute.
A 30-minute jog is still good – but clocking up multiple exercise ‘‘snacks’’ during the day helps too, and breaks up the prolonged sitting that ups the risk of rising levels of blood sugar and sluggish blood flow.
Frequent breaks to interrupt sitting with leg raises, squats and calf raises significantly improved blood vessel function. Taking sixminute breaks every hour was good, but three-minute breaks every 30 minutes was better.
‘‘When blood flow is reduced, blood pressure increases in an effort to pump blood around the body, and when muscles don’t move there’s less need for them to take up glucose from our blood to use for fuel,’’ Dunstan explains.
There’s also another way that prolonged sitting messes with blood vessels. When the forward flow of blood slows down, it reduces the force of blood pushing against the wall of the blood vessels.
‘‘That continuous force is a benefit – it helps prevent plaque building up inside blood vessel walls,’’ says Frances Taylor, a PhD student at the Institute’s Physical Activity Laboratory.
‘‘You want blood to keep flowing forward rather than slow down or stagnate – which can happen if you sit for long periods,’’ says Taylor whose recent study of sedentary workers with type 2 diabetes shines new light on improving blood vessel health in people with the condition.
‘‘We found that frequent breaks to interrupt sitting with leg raises, squats and calf raises significantly improved blood vessel function. Taking six-minute breaks every hour was good, but three-minute breaks every 30 minutes was better. This suggests that shorter, more frequent breaks from prolonged sitting may be better for people with type 2 diabetes – a problem that already compromises blood vessel health.’’
Not everyone needs to leap out of their chair every 30 minutes – but we should get serious about interrupting long bouts of sitting, stresses Dunstan. He suggests identifying ‘‘danger zones’’ of continuous sitting like the first three hours of the working day, the post-dinner slump – or the summer holiday Netflix binge – and set a timer as a prompt to get up and move for a few minutes every hour.
But although ‘‘every move counts’’, as the catchcry of the World Health Organisation’s new physical activity guidelines goes, it’s the more vigorous bites of movements, like climbing stairs, walking uphill or playing with kids that deliver the most benefit, says Emmanuel Stamatakis, Professor of Physical Activity, Lifestyle and Population Health at the University of Sydney’s Charles Perkins Centre.
‘‘Vigorous physical activity embedded in daily life is time efficient – as a rough guide, one minute of vigorous movement like walking fast uphill equals two minutes of moderate movement like a brisk walk on the flat. It also has a more profound effect on our cardiovascular fitness compared to light or moderate exercise: by increasing the body’s capacity to transport oxygen to muscles, it makes any physical activity easier so that we can do more for longer,’’ he explains. ‘‘This is important for less sporty people, especially as we age, because it improves our ability to stay independent.’’
He believes that splicing enough vigorous ‘‘exercise snacks’’ into our daily lives could also be a valid, more achievable alternative to structured exercise.
‘‘The gym or sport are great but many people are time poor and not keen on structured exercise,’’ says Stamatakis whose recent paper in the journal Sports Medicine calls for more research into what exercise scientists call ‘‘vigorous intermittent lifestyle physical activity’’ – or VILPA.
Some small studies show a benefit. Just three minutes of brisk stair climbing a week improved fitness in young adults, according to one 2019 study.
But we still need to know more – like how many minutes of VILPA each week are ideal, and how can we be persuaded to fit these activities into our daily lives?
‘‘Making physical activity convenient helps,’’ he says, pointing to Copenhagen, where changes to the city centre mean it’s now faster to get around by bike than by car.
At his own workplace, the stairs are a broad, attractive feature. ‘‘They invite you to climb them – but in many office buildings, stairs are hidden. If we make stairs appealing and visible more people will use them.’’
But while we wait for urban planners and architects to fix the environment, let’s grab as many exercise snacks each day as we can – a walk around the block, some brisk vacuuming or a play date with the dog – and embrace climbing stairs and escalators. –