Ask anyone to guess which age group is least likely to be meeting recommended physical activity guidelines, and they'll opt for children. So here's a statistic that may surprise you: in 2007, 72% of boys and 63% of girls aged 2-15 met the '60 minutes a day, every day' target. Grown-ups (aged 16-64) didn't fare so well - with 40% of men and just 28% of women achieving the recommended level of physical activity for adults (five or more sessions of 30 minutes' moderate activity a week).

But it's older people who sit firmly at the bottom of the class. Department of Health figures show that only 17% of men and 13% of women over the age of 65 are sufficiently active. Other research shows that 44% of adults over the age of 70 years take a 20-minute walk less than once a year - or never.

It seems that the older we get, the less active we are. But why? According to the findings of a study from the University of Dundee, published in the journal Age and Ageing, the most powerful 'deterrent' among the over-65s is a lack of interest, and disbelief that exercise can enhance and/or lengthen life. It's what Bob Laventure, a consultant on older people and physical activity at the British Heart Foundation National Centre for Physical Activity and Health, classifies under the "it's too bloody late for me" excuse.

The benefits

But is it too late to improve your fitness and health once you are past the first flushes of youth? "Absolutely not", says Laventure. "You can train the older body, and markedly so." And, he says, with so much "untrained reserve" it's possible for sedentary people to make huge gains, and fast.

Studies show improvements in balance, strength, gait, muscular power, blood pressure, endurance and bone density as a result of regular physical activity in older age. For example, one study on 90-year-old women in a nursing home found that 12 weeks of strength training took the equivalent of 20 years off their thigh muscle age, resulting in improved walking and mobility.

Another study found that six months of regular exercise increased VO2 max (a measure of aerobic fitness) by 30% in 60-70-year-olds. Exercise even helps you live longer - research from Harvard University found that men who burned 2,000 calories a week through exercise lived two-and-a-half years longer, on average, than sedentary men.

"There's also good evidence that physical activity has important effects on the mental health of older adults," says Laventure. A joint study by the National Institute of Mental Health and Age Concern in 2006 found that regular exercise was associated with reduced stress, depression and anxiety; enhanced cognitive function and overall psychological wellbeing; and increased self-esteem and contact with the community.

The barriers

It would seem, then, that physical activity can add not only years to your life, but life to your years. But back to those "perceived barriers". Aside from not having much interest in working up a sweat, respondents in the Scottish study also cited physical symptoms - such as painful joints, a lack of energy or shortness of breath - an unwillingness to go out alone or in the evening, and reluctance to join a group or make new friends, as reasons not to exercise. They are all factors which Laventure puts down to fear and lack of confidence.

"There's often a perception of risk among older people regarding physical activity", he believes. "People worry 'is this safe for me? Will I have a heart attack? Will I make an existing condition worse?'"

And it's not just the physical exertion itself that is perceived as risky. "It's all very well talking about brisk walking for 30 minutes per day - but for some older people the very environment is a potential barrier. They wonder 'is my neighbourhood or local park safe to walk in?' These sort of concerns put many sedentary older people off becoming more active."

Research backs Laventure up. In a study by the Women's Sport Foundation, 60% of women over 60 said they would exercise more if they had someone to go with. Other research, published in the Journal of the American Geriatrics Society, found fear of falling to be a significant factor in low physical activity levels in older women.

But are such fears valid? In most cases, no. As the Age and Ageing paper states: "shortness of breath may be interpreted by older people as a symptom of disease, rather than a normal response to physical activity. Similarly, patients with osteoarthritis may need reassurance that physical activity can be beneficial and may alleviate painful joints."

In fact, the benefits of physical activity - at any age - are so compelling that it could be argued that a bigger threat to health and longevity is not exercising. "Inactivity is life-limiting", says Laventure.

He draws an image of concentric circles around an armchair, a kind of comfort zone. "The less we do, the more function we lose", he explains. "So at 65, you might be comfortable going down the road to the shops, getting in the car, visiting friends. At 75, you might be comfortable going to the kitchen but not up the stairs or down the street. At 85, it's difficult to get out of the armchair at all … The circles get smaller and smaller as you become less mobile, have less social contact, an increased loss of independence and an increased risk of disease ... It's a downward spiral."

OK. So physical activity works, even if you've been sedentary for some time. And it's well worth doing. But how much do you need to do?

The target

"The government goal is 30 minutes of moderate intensity activity on at least five days of the week, but at the beginning, your goal should simply be to start moving more," says Laventure. That might mean around the home, or in the garden - and it certainly doesn't have to be in a brightly lit, noisy gym.

But whatever you choose - Tai Chi or Thai boxing, chairobics or cheerleading - the activity you do needs to be consistent, in order to reap the benefits. "The challenge is sustaining physical activity in the long-term - so it has to be something that will keep you motivated," says Laventure. And if the findings of the Scottish study are anything to go by, you'd be advised to recruit a friend or partner to go with, both for motivation and support and safety.

And what about exercise type? Aerobic activity - brisk walking, cycling or swimming - is the gold standard, as far as government guidelines are concerned, but something that Laventure believes has been neglected in the UK is the importance of strength, flexibility and balance training. "We're a bit behind the times here - the American College of Sports Medicine and World Health Organisation both recommend twice-weekly training in these important attributes for older people, to assist with fall prevention and for the maintenance of independence."

Through his company, Later Life Training, Laventure trains health and fitness professionals to work specifically with older and frail people, addressing fall prevention, and those who have already had falls (find a directory of qualified instructors at laterlifetraining.co.uk).

Unfortunately, this type of class isn't available in any of the major gym chains, as yet. Indeed, the average gym does little to cater for the needs of older, less mobile exercisers, perhaps rooted in a belief that it's 'too late' for them to get active. "Part of the problem is that gym staff aren't trained to work with older people", says Laventure. "They don't know how to adapt standard fitness programmes to suit older clients."

Not that programmes always need to be adapted … "We have the potential, even in advanced years, to enjoy very vigorous activity," says Laventure. Yoshihisa Hosaka, the 60-year-old runner who, earlier this year, broke the 60+ world marathon running record with a time of 2 hours 36 minutes, would agree. So would David Shepherd, who attained a British record at the 2000m indoor rowing championships last year (8.55.9) - in the 85-89-year-old category.

It's unlikely, I imagine, that you'll be bumping into either of them at a chairobics class any time soon.

Resources

Later Life Training
laterlifetraining.co.uk
Has a directory of exercise instructors with postural stability instructor training for fall prevention and for those who have suffered falls.

British Heart Foundation National Centre for Physical Activity and Health
bhfactive.org.uk
Has a section devoted to older adults and useful links to many other relevant websites.

The Lifelong Fitness Alliance
50plus.org
Offers advice and encouragement on getting and staying fit beyond 50.