The science of extra time: Why legs stop working after 90-min

For football fans, extra time is often the most thrilling part of a FIFA World Cup match. It is where heroes are made, dreams are shattered and every touch of the ball carries enormous significance. But for the players on the pitch, those additional 30 minutes represent something very different-a battle against exhaustion, pain and the limits of the human body.

The knockout stage of this year's World Cup has already produced several matches that stretched beyond the regulation 90 minutes, forcing players to find energy when their bodies are desperately trying to stop.
Sports scientists say the biggest challenge after 90 minutes is not simply tired legs-it is the gradual decline of both physical and mental performance.

By the final stages of a match, elite footballers may have covered between 10 and 13 kilometres, including dozens of high-speed sprints, sudden changes of direction and repeated accelerations. Glycogen, the muscles' primary fuel source, is significantly depleted, reducing the body's ability to produce explosive movements. Every sprint becomes harder, every recovery run slower and every tackle more physically demanding.

Fatigue also affects the brain
Research has shown that as players become physically exhausted, reaction times slow and decision-making becomes less accurate. A defender may misjudge a clearance, a midfielder may deliver a careless pass and a striker may hesitate for a split second in front of goal. At the World Cup, where the margin between victory and defeat is often measured in centimetres, those tiny lapses can decide an entire tournament.

Cramp is another familiar enemy
Contrary to popular belief, muscle cramps are not caused solely by dehydration. They are often the result of extreme muscular fatigue combined with repeated high-intensity actions. That is why players frequently stretch, receive treatment or collapse to the ground during extra time, even after following carefully planned hydration and nutrition strategies.

Modern football has responded with science
National teams now rely on GPS tracking systems that monitor every metre covered, sprint intensity and workload during matches. Performance analysts provide coaches with real-time physical data, helping them decide when substitutions are needed. Recovery drinks rich in carbohydrates and electrolytes, cooling towels, ice baths and compression garments all play a role in preparing players not only for the next match but also for surviving the final half-hour of the current one.

Coaches also plan for extra time long before it arrives.

Substitutions are often saved specifically for the closing stages, allowing fresh legs to exploit tiring opponents. Teams rehearse penalty shootouts during training, recognising that mental composure becomes just as important as physical fitness after two exhausting hours of football.

The World Cup has shown repeatedly that championships are not won by talent alone. Tactical discipline, recovery, nutrition and sports science now influence results as much as technical ability.

As the tournament enters its decisive phase, the challenge facing every remaining team is clear. Winning in 90 minutes is ideal. But if the match continues into extra time, success belongs to those who can keep running, keep thinking and keep believing when every muscle is pleading to stop.

In modern football, extra time is no longer just an extension of the match. It is a scientific examination of endurance, preparation and mental strength-where tournaments are often decided long after the clock reaches 90 minutes.