High-intensity interval training for just four minutes at a time can stop the aging process.
Short bursts of super-intense exercise, used in spinning classes, have been found to reverse damage to cells which decline with age.
Many people may think long bike rides are the best exercise, or at least a half-hour session pedaling at the gym. But a US study found just four minutes of all-out cycling, followed by three easier minutes, are needed 12 times a week, along with another 90 minutes walking on a treadmill.
High intensity interval training, as it is known, works better than longer cycling sessions and weightlifting to halt the damage to the cells' 'batteries' which may kickstart the aging process.
Fixing defects in the DNA of these batteries, the mitochondria, is believed to help people live longer before falling ill with diseases of old age like heart failure and cancer.
Researchers at the Mayo Clinic in Minnesota found short bursts of exercise improve fitness, cut body fat and can ward off diabetes, as well as tackling cell aging.
They signed up 72 men and women aged 18 to 30 and 65 to 80 for high-intensity training, resistance training using weights, and combined training with longer bouts of cycling and fewer weights sessions.
In good news for time-poor office workers, senior author Dr Sreekumaran Nair, concluded the short bursts were the best.
He said: 'Based on everything we know, there's no substitute for these exercise programs when it comes to delaying the aging process. These things we are seeing cannot be done by any medicine.'
High intensity interval training works to burn more fat by producing 'excess post-oxygen consumption'. Four minutes cycling at close to maximum effort, before collapsing red-faced on the handlebars, leaves someone's resting metabolic rate elevated for longer after exercise.
The latest study shows it also works particularly well in causing cells to make more proteins for their energy-producing mitochondria. This ability is lost as people grow older.
The study, published in the journal Cell Metabolism, took biopsies from the participants' thigh muscles and compared the molecular makeup of their muscle cells to samples from sedentary volunteers.
The younger volunteers in the interval training group saw a 49 percent increase in their mitochondrial capacity, and the older volunteers saw an even more dramatic 69 percent increase.
Some of these reversed the decline in mitochondria caused by age, and the decline in proteins needed for muscle-building, which makes people increasingly frail as they get older.
These people did four minutes of high-intensity cycling, followed by three minutes of easier pedaling with no load, repeated only four times. The cycling sessions, on three days of the week, were coupled with two 45-minutes walks at a lower intensity on a treadmill.
It was better for aging than resistance training, involving lower and upper body weightlifting repeated eight to 12 times on four occasions twice a week. It also beat five days a week of cycling for half an hour at a lower intensity, plus four days of weightlifting with fewer repetitions.
However, interval training was less effective at improving muscle strength, which typically declines with aging.
Dr Nair, whose participants did not regularly exercise before joining the study, said: 'If people have to pick one exercise, I would recommend high-intensity interval training, but I think it would be more beneficial if they could do three to four days of interval training and then a couple days of strength training.'
The team hope a drug could be developed to mimic the effects of exercise in warding off old age.