Air Zouma: How does Chelsea defender jump so high?

After a summer in which Chelsea spent more than £150 million on three of Europe’s most exciting attackers, it is a strange quirk of their season that none of these players have scored more league goals than Kurt Zouma.

After 11 matches, the Chelsea centre-back has already notched four goals for Frank Lampard’s side — the same tally as £47m striker Timo Werner. Zouma is the league’s top scoring defender and, so far, he has found the net more times than the likes of Raheem Sterling, Pierre-Emerick Aubameyang and Marcus Rashford this season.

On Saturday, Zouma goes back to Everton, where he spent the 2018/19 campaign on loan. He returns in arguably the form of his life, with this already the most prolific season of his career, and his former side must be wary of a centre-back who is fast becoming one of the most dangerous attacking weapons in the Premier League.

“The eye-catching thing is the number of goals he is scoring from set-pieces and for me, that is a result of more confidence and more belief in himself,” said Frank Lampard earlier this week. “He has always had the size and strength, and now you see him in all parts of the pitch. Aerially he is a real threat and he is doing his job.”

In the Premier League this season, only Manchester United’s Harry Maguire has a better success rate in aerial duels than Zouma, who has been dominant in the air at both ends of the pitch.

A 6ft 3in tall, Zouma has the height and the frame to impose himself on opposition attackers. More important than that, though, is the 26-year-old’s remarkable leap. There are plenty of tall forwards and defenders in the league, but few if any can match Zouma when it comes to reading the flight of the ball and launching themselves into the air.

Zouma’s jumping ability is one of the most impressive physical attributes among players in the top flight, not least because he is also one of the league’s most visibly bulky athletes. His ability to explode upwards marks him out from other defenders and his harnessing of that power, coupled with excellent set-piece delivery from his team-mates, has been crucial to his goalscoring exploits this season.

So how does he do it? Here, Professor Paul Worsfold, the head of biomechanics at the English Institute of Sport, explains the science behind the leap, and why Zouma is one of the most impressive athletes in the league.

Power in his hips

“For a jump, the action will start around the hips, and then it will transfer through to the knees and the ankles,” says Worsfold.

When Zouma is able to drop low and leap into the air, his hips are acting like a coiled spring. The acceleration into the air comes from a chain of events, starting with Zouma’s hips and then moving down through his knees and ankles.

“It is about getting those joints in the right angle and the right position for the muscles to work effectively,” says Worsfold. “It’s the timing, the angles, the mechanisms.”

Core strength

“The glutes, the quads, the hamstrings — the larger muscle groups — are dictating the core stability and the power of the jumping movement,” says Worsfold. “Undoubtedly Zouma is extremely strong around the core, so he is able to transfer that power through a really stable base.

“He has fast-twitch muscle fibres, as a powerful and explosive athlete. His body has an elastic response and that is definitely an advantage for him, giving him this spring-like mechanism.”

Springing off his toes

Zouma is not always able to fall into a squat before using those hips to explode upwards. In these moments, he relies on other parts of his body. “Often as a defender you don’t have that time to drop low and accelerate out,” says Worsfold.

“Zouma can clearly jump high without dropping too low to the ground. For some of the goals he has scored this season he is almost jumping off his toes. He is using that end-point of his body to transfer force into the ground. The faster and stronger you can push down, the faster you are going to accelerate upwards.”

Arms add momentum

“People often forget about the arms,” says Worsfold. “But they are fundamental. By using his arms on that upward movement, Zouma is shifting the momentum upwards as well. Anyone can see this by trying to jump with their hands behind their back. It’s staggering to see how much you use your arms without thinking about it.”

The risk that comes with fatigue

In 2016, Zouma suffered a serious anterior cruciate knee ligament injury after landing horribly on one of his trademark leaps. Such injuries are common in sports such as netball and basketball, where jumping is a key part of the game.

“You have to make sure the technique and the strength is there to cope with the explosive power upwards, and also that ability to repeatedly land,” says Worsfold.

“Often it is after the 70th minute when these injuries occur. That is due to players being tired. The body does not react as quickly as it would in the first half of the game, due to neurological or muscular fatigue.”