Just don't get that number wrong. A week has passed since the Fife pensioner was recognised for his voluntary work at the sportscotland Scottish Sports Awards, yet he is still bridling at one minor factual inaccuracy.
"Whoever nominated me for the award put me down as 86," he says. "Can you believe that? I'm only 85!"
The outrage is only for effect, of course, but within his mock indignation is an insight into a remarkable character. After all, how many 85-year-olds can be found at an athletics track five times a week? Or lifting weights in the gym? Or clambering up hills for seven or eight miles at a time?
"Ach, I'd be frightened to give it up," Macdonald says, when asked about his motivation. "What would I do with myself? I don't feel anywhere near 85; I feel more like 60 and my health is fine, so I've no intention of stopping, even if it means they end up carrying me off the track one night."
Macdonald's attitude is that there is little point in him sitting around the house festering when he could keep himself fit, both physically and mentally, by occupying himself in a variety of pursuits. Indeed, even on his days off from coaching youngsters at Pitreavie AAC he cannot be still, instead spending hours trout fishing.