"A doctor once told me that I had the biggest lungs he had ever seen, and that he would hate to be in a room when I took a deep breath, because I would use up all the oxygen."
Smyth said he had always been interested in running after learning in school about Pheidippides, the Greek messenger who ran 26 miles from the battlefield of Marathon to Athens to announce the defeat of the Persians.
But it wasn't until his early 20s that a plumbing colleague tempted him away from rugby and out on to the running trails.
He had been glad to make the switch - "I got smashed in rugby" - although it proved to be a steep learning curve. "I nearly died on the first run!"
It wasn't long before he was running up to 160km a week.
"It's like a disease, it must be like taking your first smoke." (Not surprisingly for such a keen runner, Smyth says he has never smoked). "When you get really fit you can just cruise along."
He started running the Rotorua marathon course in 1962, with a group of local athletes, and continued to enter after the race became a sponsored annual event three years later.
There has never been a marathon around the Lake without Smyth running in it. Even when the 1999 event was called off due to heavy rain, he simply waited a week before going out and running the course.
Over the years he has run marathons from Edinburgh to Honolulu, but remains convinced that Rotorua is the best of them all. "It's one lap, so every step you take you are getting closer to the finish."
Smyth might not be taking part in future marathons, but he plans to stay involved with the Lake City Athletics Club walking and running groups.
He had one piece of advice for any runner doubting their ability to take on the marathon.
"There is no such thing as impossible. You can do anything you want, you have just got to try."
