In fact, a top runner could have completed three marathons during the six hours 43 minutes the Cuban President took to deliver his speech. And that on his feet, without notes or a teleprompter.
It was vintage Castro. Foreign correspondents were barred, but TV news clips showed the Comandante in full command of his memory, switching from his traditional patronising whisper to heated condemnation of his old enemy and neighbour, the United States.
His words were predictable: No surrender. No other political parties. The collapse of the Soviet Union had battered the economy. The US was to blame for the rest of the island's woes, including a series of package bomb attacks against foreign tourist hotels during the summer.
But his concentration and stamina quashed suggestions that ill health might force him to hand over to a successor or, as had been rumoured, a collective leadership. Diplomats had looked on the congress - the first since 1991 - as akin to Cold War-epoch Kremlin-watching, to see who would make the key speeches, who might be elevated to the Politburo.
As the three-day congress closed late on Friday, it confirmed Fidel Castro, 71, as Communist Party leader and his brother Raul as his deputy. The Politburo was slightly reshuffled to include a few younger members and the party Central Committee was slashed from 225 to 150 members to make it "more agile" and prevent the "ideological viruses" blamed for the break- up of the Soviet Union.
In the end, diplomats came away with the impression that, barring death, a coup d'etat or a popular uprising, it will be Fidel Castro himself who leads Cuba into the 21st century. His critics, of course, say he has not yet led the island into the second half of the 20th.
There are no signs of popular uprising on the horizon, despite increased economic hardship since he imposed the euphemistically named Special Period following the Soviet collapse, and despite continuing repression of dissidence and free speech. The overall impression for visitors is that Cubans who lived through the revolution are still prepared to tolerate, if not support, their president.
Whether they would tolerate anyone else, even 66-year-old Raul, is extremely doubtful. As for the younger generation, who see the affluence of Canadian and European tourists, loyalty to the Comandante is hard to find. The glorification of Castro's fellow guerrilla, the Argentine-born Ernesto "Che" Guevara, on the island this week appeared at least partly aimed at diverting the minds of the young.
Since he legalised the holding of dollars two years ago, there has been increasing resentment over the two-class society that has built up between dollar haves and have-nots. Medical students and others are giving up their studies to try to muscle in on the tourist trade as waiters, one of the most coveted professions in the country. They can earn more from tourist tips than surgeons in state hospitals.
As for the possibilities of a coup, diplomats consider it unlikely unless Castro were to die or fall seriously ill. The anti-Castro lobby in Miami claims disgruntled military officers were behind this summer's bombings of hotels and Hemingway's favourite bar, the Bodeguita. Castro blames Miami-based paramilitary groups.
What appears certain is that there will be no Castro dynasty. The Comandante's only legitimate son, widely known as Fidelito (Little Fidel), 49, was largely disgraced for apparent mismanagement of the Atomic Energy Agency. Fidelito's mother Mirta Daz, Castro's first wife, whom he divorced, lives in exile. His 40-year-old daughter Alina, born of his 1950s lover Natalia Revuelta, fled to Miami a few years ago, slamming her father as "a heartless dictator".
Castro was said to have been madly in love with "Nati" and wanted to make her Cuba's First Lady after the revolution but she refused to leave her husband, a prominent Cuban heart specialist Orlando Fernande. She remains in Cuba, but the President's full sister, Juanita Castro Ruz, also fled the island and runs a pharmacy in Miami.
The Cuban leader, who himself was born out of wedlock to his father's maid, Lina Ruz, is widely believed to have several other illegitimate children, including five sons from his former live-in partner, Dalia Soto del Valle.Reuse content