Ed Whitlock, an 85-year-old marathon runner, is dumbfounding medical experts after breaking another record this year. The London-born athlete ran a marathon three hours 56 minutes and 34 seconds in October, breaking the existing record for his age group by a staggering 40 minutes.

Now living in Ontario, Canada, Whitlock took up competitive running in his 40s and has since set dozens of age-group records, according to the New York Times.

When Whitlock was 75, he broke the age group record with a finish time of under three hours – a record which has yet to be surpassed by anyone else.

His achieving these incredible feats, despite having a fairly unremarkable fitness regime, following no particular diet and no other training other than laps around a local graveyard, have caught the attention of scientists.

Dr Michael Joyner, who researches performance and aging at the Mayo Clinic, puts the incredible performance down to "minimal aging" by Whitlock.

Though Whitlock had an incredible VO2 max reading (the amount of oxygen his blood can hold), when undergoing tests four years ago at the University of McGill in Montreal, Whitlock himself puts his tremendous feats down to a willingness to try.

He told The New York Times: "I believe people can do far more than they think they can – you have to be idiot enough to try."

VO2 max measures the maximum amount of oxygen an athlete can use. Oxygen consumption increases during physical exertion, but for each individual there is a maximum level for this consumption. Though it can be increased with training, it is largely determined by genetics.

Scientists found that Whitlock had a VO2 max reading of 54, which would be considered in the excellent range for a male aged between 13-19 and better still for a male athlete aged between 20-29. Additionally, Whitlock had well-preserved muscle mass as well as muscle motor-units.

Of Whitlock's achievements, Joyner said: "There are biological factors; I'm not naïve about that, but the message with these people is not that they're freaks. It is that a whole lot of ageing, with a bit of luck, is under some volitional control."