Short six-second bursts of vigorous exercise have the potential to transform the health of elderly people, say researchers in Scotland.
A pilot study involving 12 pensioners showed going all-out in very short bursts, reduced blood pressure and improved general fitness over time.
The team at Abertay University believe it could help avert the "astronomical" costs of ill health in elderly people.
Experts said the study emphasised the benefits of exercise at any age.
High Intensity Training (HIT) has attracted a lot of attention for promising some of the same benefits as conventional exercise but in a much shorter time.
Instead of a comfortable half-hour jog or a few miles on the bike, HIT involves pushing yourself to your limits for a short period of time.
The team in Scotland say they were conducting the first trials in older people.
Get a sweat on
A group of pensioners came into the lab twice a week for six weeks and went hell for leather on an exercise bike for six seconds.
They would allow their heart rate to recover and then go for it again, eventually building up to one minute of exercise by the end of the trial.
"They were not exceptionally fast, but for someone of that age they were," researcher Dr John Babraj said.
The results, published in the Journal of the American Geriatrics Society, showed participants had reduced their blood pressure by 9%, increased their ability to get oxygen to their muscles and found day-to-day activities like getting out of a chair or walking the dog easier.
Dr Babraj told the BBC the benefits could be huge: "We've got an ageing population and if we don't encourage them to be active, the economic burden of that is going to be astronomical.
"A lot of diseases are associated with sedentary behaviour - like cardiovascular disease and diabetes - but if we can keep people active and functioning then we can reduce the risk.
"Also on the social side, they are less likely to be socially active and will interact with people more."
More than 10 million people in the UK are over 65 and that figure is set to rise.
Dr Babraj says older people struggle to exercise as many are full-time carers, but argues High Intensity Training would be easier to fit in.
He said people could try it at home, but should see their doctor first to ensure there were no underlying health issues.
"Then the easiest way to do it yourself is to run up a hill, the steeper the hill, the harder it's going to be, give it everything you've got for six seconds."
There is an argument that short and strenuous exercise may be safer than conventional exercise.
A higher heart rate and blood pressure caused by exercise can be a trigger for heart attacks and stroke.
Dr Babraj said running for a long time "puts a greater strain on the heart overall" even if it is worked harder in the short-term in High Intensity Training.
Larger trials are now planned.
Dr Adam Gordon, a consultant and honorary secretary of the British Geriatrics Society, told the BBC: "This is a brilliant, fantastic piece of work challenging assumptions about what the right type of exercise is in old age, but I'd encourage them to investigate the benefits in even older and even more frail people.
"The broad message is that you're never too old, too frail, too ill to benefit from exercise, as long as it's carefully chosen.
"We know even into your 80s and 90s there's a benefit from developing a very slight sweat by exercising on multiple occasions per week."