BEFORE he was into his teens, Jax Thoirs represented Scotland in gymnastics, but grew so tall that he had to quit the sport.

When he shot up six inches in a year, even walking was agony. Now he stands 6ft 6in., weighs 14st, and has grown into Scotland's most successful pole vaulter in 150 years.

He has broken the national record three times since his 20th birthday in April, and a 5.50 metres clearance last weekend booked a place at the European Under-23 Championships which start in Finland on Thursday. He beat the deadline by just two days. Last year, he jumped the world junior qualifying mark a week after the team was selected. "That was pretty frustrating," he admitted.

A student at Washington University, Thoirs seemed destined for greatness from the moment he first picked up a pole. In awed tones, Glasgow coach Brian Donaldson described half a dozen kids turning up for a come-and-try session at Scotstoun, one Sunday in 2007: "One of them made the hairs on the back of my neck stand on end. Within a couple of hours Jax was clearing three metres. You knew he was something special."

Donaldson was with him in Somero last Saturday when Thoirs cleared 5.50m. "He also had two very good attempts at 5.60 in Finland. He is capable of that now."

Thoirs, who admits to huge impatience, agrees. "I can do it if I have a really good day," he said. "That's usually good enough for a medal at the European U-23s, but it's also the qualifying height for this year's world championships in Moscow. I won't get another chance. The trials are in Birmigham at the same time as the final in Finland."

Thoirs is equal eighth on an entry list topped by Valentin Lavillenie (5.65), brother of the French Olympic champion. "It will take 5.55, 5.60 to get a medal, but it's the first time I have had a chance of doing well at a big championships. I'm confident I will make the final."

The former Jordanhill school pupil began gymnastics aged eight, and finished 10th in the British championships. "I was about 11, and had the best score on high bar, in the all around. They did not have individual apparatus then," he said. A contemporary, Ryan McKee, competed in the Commonwealth Games in 2010.

"For me, some moves had become near-impossible, with my height. I was pretty sad to give it up. It had been my life for two or three years, but still helps now. I have a better feeling for where the bar is than most people. The run and take-off are more long jump, but once you are off the ground, it's all gymnastics."

Athletics quickly filled his life. He took silver in the Scottish U-13 long jump, and bronze over the hurdles, but grew six inches in a year, enduring severe growing pains while setting U-15 and U-17 national vault records.

"It was pretty horrific. I was so uncomfortable in my own body. My shins would be throbbing and I could hardly walk, but I knew I'd come out of it. There was no risk of me stopping. My back has always been a problem. Pole vault is not good for your body. I do core body strength, stretching, and flexibility exercises daily. If I didn't, I'd seize up. He "hasn't a clue" where he gets the height from: his mum, Alison, is 5ft 5in. and dad, Brian, is 5ft 11in.

That Scotland has a stock of some 100 poles, worth some £60,000, owes much to Thoirs, though he has bought only one himself. He pays tribute to scottishathletics, Glasgow City Council and Glasgow Pole Vault School, as well as his university. "I've been very lucky. Most people have to buy their own. All but one of my poles has been bought by others. I improved so much in 2011 [35cm] that I went through 16 poles. I started with a pole 15 poles smaller than I ended up with.

"I have improved 30cm this year, but that's more to do with refining my technique. I am basically stronger, and being faster on the runway puts more energy into the jump. So, when I leave the ground, my body is in a stronger position, and I invert better."

He met Sergey Bubka [world best, 6.15m] at a coaching session in Glasgow, but was so in awe he can remember little. As a kid, Bubka had a reputation as a dare-devil: walking along the ridge of his roof and almost drowning in a barrel.