But a Leeds schoolgirl has taken on the distance tackled by elite triathletes and marked herself out as one of the sport's future stars.
Aideen McQuillen-Strong, of Alwoodley, has completed a 750m swim, a 20km cycle and a 5km run - the sprint triathlon distance raced by competitors at last year's ITU World Series age-group event in Leeds.
The youngster, a member of Leeds Bradford Triathlon Club's junior section, only took up the sport a year ago, racing short distances in the Tri Start category. She and her two older sisters were inspired to join the club after taking part in Active Schools sessions run by the Brownlee Foundation.
She decided to undertake the triathlon challenge to raise money for Macmillan Cancer Support after two of her grandparents were both diagnosed with the disease.
"Aideen decided in the build-up to Christmas that she wanted to do something challenging to raise money for a cancer charity. She had looked up the distances the Brownlees and (Leeds-based Olympian) Non Stanford do, and had found that there was a thing called a sprint triathlon that was part of the World Series - 'that thing they did in Leeds, Dad!," said her father Pete, a teacher.
"Aideen was confident she could swim 750m as she did it in her Swimbrite club session. We then looked at the cycle distance, 20km, and run, 5km. She thought they would be a challenge, but it would be possible. Aideen wanted it to be a real challenge and insisted she had to do it all consecutively like the Olympians do. We had suggested doing it in three parts over two or three days."
The determined triathlete, who attends St Paul's Catholic Primary School in Alwoodley, did her swim in the pool at the David Lloyd health club in Moortown, before cycling through Shadwell, Thorner and Bardsey. She transitioned at Shadwell and ran the 5km home to Alwoodley.
"Along the route Aideen had amazing support from family, friends and fellow pupils from her school, who followed her progress on Twitter during the day, and a large contingent came out to cheer her on in the last few hundred metres of her run," added Pete.
So far, Aideen has raised over £2,000 for the charity, after originally setting herself a target of £500.
"I love doing sport and last year I took up triathlon with the Leeds Bradford Tri Club juniors. I have taken part in the Yorkshire Series and have really enjoyed competing with my friends. The races for my age normally consist of a 50m swim, 1.5km bike ride and 600m run. I was successful at these events and achieved a first, second and third place during the season," said Aideen.
"I wanted to raise funds for a cancer charity as my grandma Rose and grandad Jim are both living with terminal cancer. They have been very poorly, but are both fighting the illness and trying to continue life in the best way they can. They have both supported me to buy clothes and equipment to help me in my triathlon training and racing. I hope any money I raise will help other people and families who have to cope with loved ones who are very ill."
She spent two hours on the bike and achieved sub-30 minute times for both the swim and run legs.
"The amazing number of people out cheering her on really helped to inspire her and keep spirits high. As parents we were really proud that she had wanted to do such a challenge to raise money for charity. My wife Annemarie and I both have a parent who is living with terminal cancer," added Pete.
"We were very worried that it would be too hard for Aideen. She was determined it had to be a real challenge to be worthwhile people sponsoring her.
"It was a very emotional day as both grandparents came to support her. When she arrived back at home there was an outpouring of emotion as we were all so proud, relieved and overwhelmed by what she had achieved."