A team of US researchers from the University of Texas says that walking, weightlifting, flexibility training and other forms of exercise can help older people avoid the disabilities normally associated with ageing - and even reverse the ageing process itself.

The researchers, writing in the journal Behavioural Medicine, argue that some decline in physical activity is an inevitable result of normal ageing.

But they warn that physical inactivity can hasten this decline and lead to the rapid onset of muscle wastage, decreased endurance and loss of flexibility and balance.

Older people, they argue, can slow down ageing and prevent chronic conditions by taking regular exercise.

The researchers cite several studies that demonstrate the benefits of exercise on the ageing process. These include:

• A walking programme for people in their seventies that reversed 22 years of declining lung capacity in 22 weeks;
• A 12-week weights programme that more than doubled the leg muscle strength of some women aged 64 years and over;
• A study in which people who exercised by walking several days a week decreased their risk of disability and improved their ability to climb stairs, stoop, crouch and kneel.

Exercise can keep you young

They cite a study in which patients who already had coronary artery disease reduced their risk of fatal heart complications by 20-25% through exercise.

A sedentary lifestyle, they warn, also increases the risk of hip fractures. In one study women who spent less than four hours a day on their feet had nearly twice the risk of hip fractures than their more active counterparts.

Alison Rose, a spokesperson for Help the Aged, said: "We do know a small amount of exercise is good for you at all ages, particularly as you get older.

"However, you ought to be starting in middle age and need to be careful about doing anything too strenuous.".