Science explains why 400m is the hardest race in the Olympics that 'no-one can run all-out'

A scientist has explained why the 400 metres is the toughest individual race at the 2024 Olympics - and the toughest race in all of athletics.

The men's 400m final has just been concluded in Paris, with Team GB's Matt Hudson-Smith winning the silver medal.

The 29-year-old, who now holds the European record in the event, ran a time of 43.44 and led as the athletes entered the final bend, but he was overtaken just metres from the line after a late surge from USA's Quincy Hall.

Fans watching the event at the Olympics will have noticed how athletes tend to tire hugely as they run towards the line after generally starting strongly.

Hall did the reverse in Paris, having been trailing towards the back of the eight-man field before saving his best until the very last.

The 400 metres is considered as a sprint event, and it is longest of such type that is competed in individual IAAF-sanctioned competitions.

Most of the elite male athletes will average just over 11 seconds per lap, compared to the upper end of nine seconds that top 100m runners will produce.

When you see those numbers, it perhaps hits home as to just how challenging the event is. But just how tough actually is it?

According to science-based YouTube channel Outperform, it is actually the hardest of any Olympic race.

The principal reason for this is down to the energy that the body produces throughout the race, and the three energy systems that the body uses.

An athlete's body first uses an energy store that allows them to have a short, sharp burst to get them up to top speed across the first five to 10 seconds across 50 metres.

The next 150 metres sees runners run at below their maximum speed, with lactic acid causing the muscles to fatigue.

The body will then produce anaerobic energy over the next 100 metres. But will produce it much more slowly than the other two energy sources - meaning the demand outweighs the supply.

The body will attempt to produce more aerobic energy, but struggles to produce enough to aid the final sprint towards the line, causing muscles to then be negatively affected.

You can watch the full explainer below.

US sprinting legend Michael Johnson replied to the video on Twitter, writing: "Understanding this process was key to me breaking the world record and consistently running 43 seconds.

"If a 400 sprinter doesn't understand this process it will always feel like death!"