Yvette Nevrkla: "Decline in health"

"From then it can be quite a downward spiral in their physical health and mental health."

Adults lose 10% of their muscular strength for every decade of life, but exercise can reverse that trend.

A study by the Royal Free Hospital in London found that after a 12-week exercise programme, older adults had increased their strength by 30% - equivalent to regaining three decades of lost strength.

The types of exercise recommended, such as aqua-aerobics or seated aerobics, also help improve balance - essential if falls are to be avoided.

Individual programme

Dr Dawn Skelton is an exercise physiologist at Imperial College London. She specialises in exercise for the elderly.

She said that classes run by a qualified instructor could be very valuable.

The important point was that an exercise regime should be tailored to the individual, she said.

Dawn Skelton: "Social benefits"

"A lot of work has shown that you can do a general regular exercise class weekly for years and although it may improve your independence but it may not reduce falls.

"You have to tailor the exercise to suit want you want to improve in the same way an athlete would want to work on their particular sport. It's the same thing for older people."

She added that there were significant benefits in terms of social contact to be gained from group exercise.