They say regular exercise can help you live a longer life - and for Mr Moninda Marube, this proved especially true when two black bears charged at him during a training session early in the morning.

In an interview with the Sun Journal, Mr Marube, a student at the University of Maine, said he had been running in the woods on Wednesday (July 5) when he encountered the two bears crossing a road.

He said: "When they spotted me, they stopped, and I stopped (too)."

He said that at that moment, he knew he had to quickly decide between three options: climb a nearby tree, run back the way he came, or dive into a lake nearby.

However, he realised he could not climb the tree as he believed bears could climb trees as well.

Escaping to the water was also out of the question. He told the Sun Journal: "In my head, I know I can't swim. I fear swimming. I fear water."

He therefore decided to run back the way he came, despite having already run part of his 18-mile (30km) training route.

The moment he turned and ran, the bears began to charge at him.

Fortunately, running is Mr Marube's speciality, having finished third in the 2012 Maine Marathon and first in the 2013 Maine half-marathon.

According to local media, Mr Marube, 38, who is a professional runner from Kenya, managed to outpace the bears, sprinting into the porch of a vacant house and closing the door, with the bears just 9m behind him.

However, his troubles were far from over - the door was a flimsy screen door, made mostly out of wire netting.

"If (the bears) wanted to get in, this (door) would not have prevented them... they could see me, I could see them," he said, adding that it would have been very easy for the bears to claw the door open and get to him.

Fortunately, however, the bears only sniffed around the door for a while and then went back across the road into the woods.

When the bears wandered off, he took the chance to slip out of the door and run as fast as he could in the opposite direction.

Mr Marube felt that his survival had been nothing short of a miracle. "I'd say my legs saved me a third, but two-thirds it's God who saved me," he told Sun Journal.

He added that he is not stranger to wildlife, having encountered a leopard once while living in Africa, but Wednesday's incident had scared him.

"I don't fear lions," said Mr Marube, who has lived in the United States since 2010.

"But a bear is scary... I've been running this road for four years, I never thought of meeting a bear here."

He later quipped: "The only good advice I can give (to others) is, please, don't be here at 5 o'clock in the morning."