McPhail (17) ran away with the 100m and 200m sprint crowns at the 39th annual New Zealand secondary school championships in Wellington last weekend.
But things have not always come so quickly for the flying youngster.
"I remember the South Island championships in year 9 or 10 clearly, getting second to last in my 200m heat," she said.
"At that stage I hated running and it wasn't until my sister started training and dragged me along that I started to like it."
Her sister, Laura, and Dunedin-based coach Brent Ward deserved plenty of credit for her success, she said.
"Laura has always been one of my idols. Looking up to her when she was competing at nationals had always amazed me and we have been very competitive over the last few years.
"She always seems to know what's right and is great at giving advice on how to go about things.
"And my coach, Brent, has also been a huge help and I wouldn't have even got close to this if it wasn't for him. He puts so much effort into his athletes and I am very appreciative of all his help."
McPhail described claiming the dual sprinting titles as "one of the best feelings ever", adding that the 200m title was especially gratifying, as she had long been chasing it.
That pursuit had included months of training - including through winter - leading up to the national event.
Her schedule included strengthening exercises and training at varying speeds over differing distances for about six days a week.
As the championships loomed, her training schedule was scaled back to allow for more rest periods.
McPhail played touch at Waitaki Girls', but sacrificed other sports to get the most out of her sprinting.
"My school would have liked me to play every sport under the sun and have really never understood the commitment it takes to pursue athletics at this level," she said.
"It was hard saying no but good to see it was worth it."
McPhail, who recorded personal bests of 12.39sec and 25.18sec in winning the double, was one of seven Otago athletes named in the New Zealand secondary schools team after the championships.
A move to Wanaka with her family coincided with the end of the school year and Megan is now looking forward to relaxing and building strength before getting into full training for the national club championships.
Asked what it felt like to be the quickest young woman in New Zealand, she said: "I don't think it will ever truly set in," she said.
"You don't see it like that - more that you've achieved your goals and won a big race."
