"I hate even to call it running," she says, with the same, unmistakable, infectious giggle.
Fifty next birthday, the Fife woman is a general practitioner and mother of two boys. It was they who pointed out to the former Pitreavie sprinter, as they watched the World Championships in Moscow last month, that this was surely the same Luzhniki stadium where she had won Olympic bronze in 1980.
And so it was, and now there was another Pitreavie athlete, Eilidh Child, winning bronze in the same 4 x 400m relay. "I wasn't quite sure; it was the boys who told me. The coverage we got here didn't give much detail - just snippets, and the timing was way out - but it was nice to see; I was taken back. The boys both seemed to know all about it. I feel I am a different person now, though, and in a different life. It is really very strange. It does not seem like yesterday, but I can't believe it's so long ago."
Macdonald was an elfin waif in her track prime. She stood barely 5ft 3in and weighed under 7st when she went to Moscow: far removed from the stereotypical image of a sprinter. She had won the WAAA 400m title just four months and a day after her 16th birthday in 1980. Her time of 51.16 broke the five-year-old senior British record. Only two Scots have run faster since.
Macdonald also reached the individual Olympic 400m final in which she lined up against six athletes from drug-tainted eastern European regimes; she is still the youngest Brit to reach an Olympic sprint final. The winner, East German Marita Koch, is still world record-holder, while silver went to the Czech, Jarmila Kratochvilova, who still holds the world 800m best. In 1981, when Macdonald took European junior 400m bronze in Utrecht, event winners included future world record breakers Heike Drechsler (Daute) and Sabine Rieger: both later implicated in doping. Drechsler, just 16, jumped 7.02 metres, the world's best that year.
"I was naive," admits Linsey, "but I did think some competitors could be on drugs. I did not really feel a great sense of injustice, perhaps because I was so young and I would always focus on my own performance. Now, when I look back, I can see that some competitors' body shapes were very unnatural. At the time I just thought it was funny.
"Many of these athletes from Eastern Bloc countries were part of a system; they did not even know what they were given. Many thought they were given vitamins. There were so many other aspects at play. I just really loved my time competing. They  were still really innocent Games in other respects."
Speaking from her home in Hong Kong last week, she admitted she never realised how good she was. "I was just so delighted to be doing something I loved. When you're actually in something, you just feel it is natural and normal."
Yet today's statistics tell the story. Her Scottish under-17 outdoor records at 100, 200, 300 and 400 metres are now more than 33 years' old. Her prodigy is evident from the fact that these performances still rank 13th, fifth, first, and third respectively on the Scottish senior all-time lists. She still holds the Scottish indoor under-17 records at 60m and 800m, and the under-20 best at 200m. "That pleases me," she says shyly, as if embarrassed to confess it. "It's very nice still to have some records."
She won the Scottish under-13 cross-country title and the runner-up, Lynne Macdougall, ran in the 1984 Olympic 1500m final, aged 19. The pair have remained lifelong friends. In 1981 - she was still a junior - Macdonald ran for Scotland seniors at the world cross country but "not very well", she recalls. However, for a British 60m and 100m champion, it remains unprecedented. Within a few weeks she had won the UK indoor 60m and 400m titles indoors, but her father, John, 86 and still coaching Glasgow 2014 aspirants at Pitreavie, said: "She probably did far too many races."
In 1981, his daughter won European junior bronze over 400m, and, in 1982, she anchored Scotland (with Sandra Whittaker, Anne Clarkson and Angela Bridgeman) to Commonwealth relay bronze ahead of England. However, recurrent injuries meant her prodigious talent remained unfulfilled, and she never ran faster than in 1980.
Shortly after her 16th birthday, Macdonald told me she wished to become a doctor. I observed that medicine was tough to combine with international athletics. With maturity beyond her years, she said: "I think a busy person can always find time to do what they really want."
She graduated in chemical engineering, then promptly did a medical degree. "I never did do anything with my chemical engineering degree. I suppose I always thought I'd go back and do medicine. I am so glad, because I absolutely love it."
She met her husband, Christopher, at Edinburgh University. He is an orthopaedic surgeon in Hong Kong, where many of his patients have sports injuries.
"I work as a GP and an emergency medic. Sometimes I'm on-call overnight, but I work part time because I have two boys and my priority is taking care of them. Hamish is just turned 11 and Fergus is nine. They are really interested in sport and really, really good at a young age. Their main sport is football, but they can both run well.
"When we go back to Dunfermline, we go down to Pitreavie when dad is coaching, and they run round the track. They're interested in all sports and love watching athletics. They seem to know everything about it, so it's nice that they are interested."
The family will be in Glasgow next year for the Commonwealth Games.
Macdonald insists she has never wanted to compete again. "I've no desire to do that. I loved my years of competing, but when you have done something to a very high level . . . Now I am really not running, race fit. I am fit in body and mind, but not race fit. It's so far from what I did before. I've not ever really wanted to run races as such.
"I still run most days and still love doing it. Sport is a way of life for me. But I hate even to call it running. I really just jog along, most days - not far: three or four miles, something like that. I do a lot of hiking with a jog in it. I've been 15 years here, running on concrete, so I get a lot of calf strains and pulls. There are really nice trails. People think, as I did at first, that Hong Kong is an urban jungle, all buildings, but the majority is trails and trees. I can walk and run for hours and not see another person.
"I am fit in terms of overall fitness but not by running standards. And I am not in any way competitive; I can't begin to tell you how not competitive."
She confesses to having made a half-marathon debut on the Great Wall of China in May and a 10k for a landmine charity, at Angkor Wat, Cambodia's World Heritage site. "It was such a novelty, on part of the Great Wall - just fantastic - near Beijing. It's an annual event, but was just for fun. You can't really run it all. It's so steep and hilly: sheer rock face at times. It was absolutely super. We were among the last to start and had to walk a lot of it. I think we took 2 hours 20, or 2:30. We ran the first bit, but sometimes there were no steps."
It is a long way from Penicuik, where, aged 10, Linsey organised races round the block for neighbourhood kids. Injuries curtailed a senior career which promised so much, yet she reflects: "I loved my years of competing, and can honestly say I would not change a thing. I was so privileged to run in an Olympics at 16."
And if Hamish and Fergus should wish to follow her? "I just love that they love sports. If they wanted to do athletics some day, that would also be great."