There are a lot of different sports out there, and they all have their own unique physical challenges. But if we're talking about the hardest sport physically, it's hard to go past boxing.
Boxing is a sport that demands incredible levels of fitness and stamina from its participants. A typical boxing match can last for up to 12 rounds, each round lasting three minutes. That's 36 minutes of constant physical activity, with very little rest in between rounds.
And it's not just the duration of the bout that makes boxing so physically demanding - it's also the intensity. Boxing is a full-contact sport, meaning that punches can (and do) land with significant force. A single punch can be enough to knock an opponent unconscious or cause serious damage to their internal organs.
So what does it take to be a successful boxer? In addition to immense physical conditioning, boxers need lightning-fast reflexes, hand-eye coordination and split-second timing. They also need mental toughness and resilience - the ability to keep going even when they're taking punishment in the ring.
There are few sports that test athletes as comprehensively as boxing does - which is why it remains one of the most popular spectator sports in the world today.