Messi, Ronaldo retirement buzz: Doctor explains why 40 marks end of many sports careers

Few footballers have stretched the boundaries of longevity quite like Lionel Messi and Cristiano Ronaldo.

At 39, Messi remains one of the sport's defining figures, having crowned his illustrious career with Argentina's 2022 FIFA World Cup triumph. Yet Argentina's narrow escape against Egypt in this year's tournament has once again fuelled debate over how much longer the eight-time Ballon d'Or winner will continue at the highest level.

Ronaldo, now 41, has also found himself at the centre of retirement speculation. The conversation intensified after his sister, Katia Aveiro, referred to the tournament as his "last dance" in a Portugal shirt. The Portuguese captain, however, was quick to play down the rumours, insisting he has no immediate plans to bring the curtain down on his international career.

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The ongoing discussion around the futures of Lionel Messi and Cristiano Ronaldo also raises a larger question: what makes the age of 40 such a significant milestone in elite sport?

Despite remarkable advances in sports science and rehabilitation, why do most athletes in physically demanding disciplines such as football and tennis choose - or are compelled - to bring their careers to an end around this stage of life?

For top-tier athletes, crossing the 40-year mark is not so much about the number as it is about the toll of decades spent pushing the limits of human potential.

"Elite sport is an experiment in repeated high-performance loading," says Dr Priyadarshi Amit, Sports Surgery Lead, Amrita Hospital, Faridabad. "The human body is a marvellous thing, but time is a great destroyer.

After 20 years of explosive movement, collisions, sprinting, jumping and cutting, every joint and soft tissue has a biological memory of those demands."

The invisible wear and tear

According to Dr Amit, the biggest challenge for ageing athletes is rarely a single career-threatening injury. Instead, it is the gradual accumulation of microscopic damage over time.

"The biggest problem for ageing athletes isn't a single traumatic injury but the accumulation of microscopic damage," he explains.

As athletes grow older, tendons lose elasticity, cartilage becomes less effective at absorbing shock, muscle fibres regenerate more slowly and the body's ability to recover between demanding training sessions steadily declines.

Individually, these changes may appear minor, but at the highest level of competition, fractions of a second can be the difference between victory and defeat.

Modern sports science can only do so much

Today's advances in sports medicine have extended careers well beyond what was once considered possible. Individualised strength programmes, biomechanical analysis, nutrition, sleep optimisation, recovery technologies and data-driven workload monitoring have all helped athletes remain competitive into their late thirties.

However, Dr Amit says there are limits to what science can achieve.

"Sports medicine today has pushed the career span well beyond what was once thought possible. Individualised strength programmes, biomechanical analysis, nutrition, sleep optimisation, recovery technologies and data-driven workload monitoring have helped many athletes stay competitive into their late thirties. But these advances cannot fully undo the biological effects of ageing," he says.

Experience stays, but the body changes

Contrary to popular belief, Dr Amit says it is rarely an athlete's understanding of the game that fades first.

"It's not typically skill, vision or decision-making that changes first. It is tissue resilience," he says.

"An elite footballer may still read the game as brilliantly as ever, but the repeated maximal efforts, the absorption of contact and the demand to produce the same physical output every three or four days become increasingly more demanding."

Football, in particular, places extraordinary demands on the body. It combines endurance with explosive acceleration, rapid deceleration, rotational movements and frequent physical contact.

Every match subjects the shoulders, hips, knees, ankles and spine to thousands of high-impact movements. Over hundreds of professional appearances, that cumulative stress increases the risk of tendon degeneration, cartilage wear and recurrent muscle injuries, even in players who have avoided major surgery.

Why athletes change their game

One reason elite footballers remain effective into their late thirties is that they adapt.

Rather than relying solely on physical attributes, experienced players become more economical with their movement. They conserve energy, adjust their training loads and increasingly depend on anticipation, positioning and technical excellence rather than pure athleticism.

Retirement is about biology, not ambition

Dr Amit believes one of the biggest misconceptions surrounding retirement is that it reflects a lack of motivation.

"The biggest misconception is that retiring at 40 is a sign of ambition waning," he says. "More often, it reflects a sophisticated understanding of the body's limits."

"Elite athletes understand that longevity is not just about how hard you can train, but how well your body can recover."

The one opponent no athlete can beat

Sports science continues to push the boundaries of athletic longevity, and what is considered a long career today may look very different a decade from now.

Even so, Dr Amit says there remains one opponent that no athlete can defeat indefinitely.

"Modern medicine can extend careers, optimise recovery and reduce injury risk, but it cannot permanently overcome the biological effects of ageing," he says.

For sporting icons such as Messi and Ronaldo, retirement may ultimately be determined not by a loss of talent or desire, but by the simple reality that even the greatest athletes cannot outrun time forever.