Try a marathon a day to keep you feeling young

At an age when many of his contemporaries are taking up golf, Terry Diamond decided to launch himself into running marathons.

The 56-year-old associate professor of endocrinology and metabolic bone disease at St George Hospital enjoyed athletics while growing up but has had an on-off relationship with running over the past few years.

When family friend, Pnina Kraus, was diagnosed with the hereditary eye disease retinitis pigmentosa, he decided to take matters into his own hands. Or feet.

Over the past week, Associate Professor Diamond has run six marathons at six iconic locations around Australia.

Dubbed the Eye-Con Run, he will complete his seventh and final marathon at Bondi Beach this morning.

He does not follow a special diet but believes in regular training and overcoming the psychological barriers to endurance running.

''Now that I am older I can tolerate the distance far better,'' he said. ''Your speed drops off but your endurance and mental strength improve. You learn how to conquer the mind games. You have pain and you have exhaustion but you're very disciplined in the way you rationalise it to yourself.''

Another Sydney man, Luca Turrini, is also going the distance in the name of a good cause. He will run 20 marathons in Italy to support cancer research, covering a total of 844 kilometres.