The running world is on fire after a stunning five-word explosion from rising American marathon star A.B.

Hernandez: “ENOUGH! YOU’RE TOO OLD!” The brutal shot was fired directly at two-time Olympic champion and marathon legend Eliud Kipchoge just minutes after the Kenyan icon publicly backed World Athletics’ controversial new age-limit proposal for elite marathon competition.

What started as a policy debate has now detonated into the most personal and bitter war of words the sport has seen in years.

The spark was lit on Wednesday evening when Kipchoge, 41, posted a measured but firm statement on his social media channels supporting World Athletics’ plan to introduce a gradual age cap starting at 40 for World Marathon Majors and championship events from 2028 onward.

The Kenyan great argued that the rule would “protect the long-term health of athletes, refresh the professional field, and give younger talents a clearer pathway to the very top.” Kipchoge stressed he would respect any decision and was already planning to transition into a mentor and ambassador role after the 2027 season.

Most expected the running community to react with the usual mix of praise and polite disagreement.

Instead, within eleven minutes of Kipchoge’s post going live, Hernandez – the 27-year-old American who smashed the national record with 2:04:58 in Chicago last month – unleashed a reply that left jaws on the floor.

“ENOUGH! YOU’RE TOO OLD!” Hernandez wrote in all capitals, adding a single fire emoji before pinning the tweet. The post has already surpassed 4.8 million impressions and triggered an avalanche of reactions from athletes, coaches, and fans across the globe.

Hernandez did not stop there. In a rapid-fire thread that many are calling the most savage takedown in distance-running history, the Texan-born runner accused Kipchoge of “trying to pull the ladder up behind him” after enjoying an unprecedented 20-year reign at the top.

“You broke every rule of aging for two decades and now you want to ban the next generation from even trying?” Hernandez wrote. “This isn’t protection – this is fear. Fear that someone hungrier, faster, and yes, younger will take what you spent a lifetime building.”

The American, who has never hidden his ambition to become the first man under two hours in legal conditions, went on to claim that Kipchoge’s support for the age cap was “the ultimate act of selfishness dressed up as wisdom.” He pointed out that Kipchoge himself was still winning major marathons at 38 and 39, beating entire fields of runners fifteen to twenty years younger.

“If anyone proved age is just a number, it was you,” Hernandez wrote. “So why punish the rest of us for it now?”

By Thursday morning, #YoureTooOld was trending worldwide, with memes flooding timelines showing Kipchoge’s famous “No human is limited” slogan crudely edited to read “No human over 40 is limited.” Former pros, physiologists, and even casual joggers picked sides in a debate that has exposed a deep generational fracture in the sport.

Kipchoge has so far remained silent on the personal attack, though sources close to his NN Running Team camp say the normally serene Kenyan was “visibly hurt” by the tone of Hernandez’s words.

One training partner, speaking on condition of anonymity, told reporters: “Eliud has nothing but respect for the new generation. He genuinely believes the sport needs renewal. To be called scared and selfish… that’s not something he ever expected.”

Meanwhile, Hernandez doubled down in a thirty-minute Instagram Live on Thursday evening watched by over 420,000 people. Dressed in a black hoodie with the words “Future is Now” printed across the chest, he refused to apologize. “I said what I said,” he declared.

“Legends deserve respect, but they don’t get to write the rules forever. If Eliud thinks 40 is the finish line, that’s his choice. Don’t make it mine.”

The timing could not be more dramatic. Hernandez and Kipchoge are both confirmed for the 2026 London Marathon – potentially the last time the two will share the same elite field before any age-cap rule could theoretically take effect.

Bookmakers have already slashed odds on a head-to-head duel, with many predicting the race could produce the most watched marathon in history.

World Athletics president Sebastian Coe has tried to calm the storm, releasing a statement emphasizing that no final decision has been made and that “all voices, especially those of active athletes, will be heard.” Behind the scenes, however, insiders say the governing body is rattled by the intensity of the backlash and may delay the vote scheduled for next year’s congress.

Sponsors are watching nervously.

Kipchoge’s long-term partner Nike released a cryptic statement saying only that they “support athletes of all ages who inspire the next generation.” Hernandez, who signed a landmark ten-year deal with On Running earlier this year reportedly worth north of $20 million, saw his follower count jump by 180,000 in 48 hours – a reminder that controversy often pays in the modern sports economy.

For older runners still competing at a high level – athletes like 39-year-old British record holder Charlotte Purdue and 40-year-old Japanese veteran Yuki Kawauchi – Hernandez’s outburst has felt like a slap in the face.

Purdue posted a simple broken-heart emoji in response, while Kawauchi told Japanese media the comments were “disrespectful to everyone who has ever laced up after turning 35.”

Yet a surprising number of younger pros have quietly signaled support for Hernandez’s position. One top-15 marathoner, speaking off the record, said: “We train in the shadow of Eliud’s records every single day.

The idea that we might never get a fair shot at them because of an arbitrary cut-off feels wrong.”

As the dust refuses to settle, one thing is clear: A.B. Hernandez has transformed himself overnight from America’s great hope into the sport’s most polarizing figure.

With five simple words – “ENOUGH! YOU’RE TOO OLD!” – he has drawn a line in the sand between past and future, between reverence and rebellion.

Whether this fiery exchange ends in reconciliation or an all-out generational war will play out on roads and tracks over the next two years.

But for now, distance running has its hottest rivalry since the peak of Mo Farah versus the East Africans – only this time, the battle is as much about years lived as minutes run.

The marathon world has never felt so young, and so old, at the same time.