The fastest men on Earth don't hold that title for very long.
Age and injury inevitably catches up with them, and whatever greatness they achieved on the track is gone almost as quickly as it came.
Usain Bolt is the exception.
Before Bolt, only one sprinter in 120 years managed to extend his reign over the 100 metre beyond a single gold medal.
Competing in Rio de Janeiro a week before his 30th birthday, Bolt has now won the glamour event at the Olympics for a third consecutive time.
Sprinting records are made to be shattered, but this may be the one that sticks. Speed will always be achieved through the onward march of science, which brings advancements in training, improvements in form and – cynically – the ability to sidestep doping rules.
But longevity, consistency and repetition are achievements the sport has never seen.
Bolt won the 100 metres in a time of 9.81 seconds on Sunday night, breezing across the finish line ahead of Justin Gatlin in 9.89 seconds and Canadian Andre De Grasse, who won the bronze medal in 9.91.
Bolt, who is typically a slow starter, came out of the blocks behind Gatlin, who started quickly. After 60 metres, Bolt reeled in the American and never relinquished the lead. As he approached the finish line, Bolt celebrated, pointing at his chest with his thumb.
The race was nowhere near the lightning-fast 9.58-second world record Bolt set in 2009.
But at 29, the Jamaican legend is practically a pensioner by the sport's youthful standards. Only Gatlin, 34, and Kim Collins, racing in his sixth Olympics for Saint Kitts and Nevis at the age of 40, are older than Bolt. However, the ageless Collins was never really in contention, bowing out in the semi-final with a time of 10.12 seconds.
Bolt, on the other hand, never looked as though he wasn't destined for gold. His race in Saturday's heats saw him cruise across the finish line in 10.07 seconds – slow for him, but likely impeded by the fact that, as he approached the end, Bolt turned his head theatrically to the side as if to check that the other sprinters had even left the blocks. "I felt kind of slow," Bolt said after that race. "It wasn't the best start."
If there were records for flourish, Bolt would probably hold those too. His semi-final time of 9.86 seconds on Sunday night also looked like he was holding back. But when it came to the main event, Bolt was his usual self, holding off sprinting's version of mortality for yet another year – and expanding his own brand of immortality – in one electrifying performance.
If ever there was an opportunity to defeat Bolt at an Olympics, this was probably it. Hampered by a tender hamstring in the lead up to the Games, there were concerns heading into Rio that he may not even compete. When Bolt arrived in Brazil for the third instalment of his Summer Olympic blockbuster trilogy, the city reacted just as its predecessors did in London and Beijing. Cameras pursued him, fellow athletes swooned over him and by the time Sunday arrived, there was no mistaking that the 100 metre was once again his show.
Rio's Estadio Olimpico, ensconced in one of the city's grittier neighbourhoods, was suddenly a shimmering, glitzy place to be. The gun-toting soldiers who have been so visible throughout the Olympics seemed to have doubled in number outside the stadium.
Bolt, who won his first Olympic gold medal at 21, looked slightly different for his third title, having shaved his head for Rio. But the towering 6-foot-5, 207-pound frame that made him a sight to behold in the sprinting world for his remarkably long stride and unrivalled cadence was unmistakeable.
After Bolt won gold in London, he declared, "I am now a legend." His performance in Rio was merely confirmation of that.
Bolt won't be the world's fastest man forever. But he has held that title longer than anyone else. And if his world record is ever broken – and it probably will be – his longevity will be Bolt's legacy.
Any sprinter wanting to defeat Bolt on the track will have to wait until time finally catches up with him. But Bolt will probably be retired before that happens.
"I'm going to beat him," Rodman Teltull, a sprinter from Palau, joked this weekend. "Ten years from now."