The 86-year-old revolutionary icon also praised Cuban election officials for building a new entrance to his polling site, eliminating the need for him to climb stairs, which he indicated had been difficult since a fall in 2004.
"I asked various people who work with me the number of steps and the height of the stairway at the entrance," Castro said in an informal back-and-forth with several Cuban journalists conducted on Feb. 3, the day he cast a ballot in a legislative election. "My shattered knee ... has taken its toll."
Castro is rarely seen in public, and more rarely still speaks about Cuban affairs. While his appearance at the voting station had been reported earlier, the majority of his comments had not.
Tuesday's edition of the Communist Party daily Granma transcribes the entire encounter over five full pages, and reports that the transcript has been "revised and updated by the interviewee."
Castro acknowledges having difficulty reading the small print in Granma and on his television screen, adding that "changes in light bother my eyes."
The former Cuban leader's comments were published a day after 85-year-old Pope Benedict XVI shocked the world by announcing he was stepping down due to physical and mental weariness, becoming the first pontiff to do so in nearly 600 years.
The Vatican newspaper, L'Osservatore Romano, said Benedict made the decision to resign after his March 2012 trip to Mexico and Cuba, an exhausting visit under the broiling Caribbean sun where he met the two Castros and was treated to a raucous and warm welcome.
The meeting with Fidel began with the two men joking about their ages.
"Yes, I'm old, but I can still do my job," Benedict said, according to a Vatican spokesman. He left Cuba the next day with the farewell: "Goodbye forever."
In the newly published comments, Castro speaks passionately about his ailing ally and friend, Venezuelan President Hugo Chavez, who is battling cancer at a Cuban hospital and has not been seen in public for more than two months.
"When he was in full (political) combat, he neglected his health and he dedicated himself to the fight," he said.
Castro also lauds the economic changes being carried out under the leadership of his 81-year-old brother, Raul, who has been president since 2006, saying the state has "a duty to bring itself up to date."
He also applauds the Cuban people for electing more women than men to the 612-seat National Assembly.
In Cuban elections, there is only one candidate for each seat, and no suspense over who will win. Voters' only choice is whether to approve of them or not, and most candidates receive well over 90 percent.
In an echo of the broad-ranging style of his past, Castro's comments stretch from the bombing of Hiroshima and Nagasaki, to the colonization of Mars, to the 1794 execution of Robespierre during the French Revolution, and to environmental threats facing the world today.
Perhaps betraying his age, he questions journalists about their recording equipment and marvels at a smart phone one used to tape the interview.
"What's that apparatus?" Castro asks.
"It's a telephone that also functions as a recorder, Comandante," journalist Amaury del Valle replies.
"Oh really?" asks Castro. "I have to use a lot of gadgets of that kind but people help me."
The journalists praise Castro effusively, complimenting him on his memory, inviting him to a journalists' conference and telling him that they and the Cuban people carry him in their hearts.
"Thank you for seeing us. We are so happy because of it," Cuban television reporter Gladys Rubio says.
As Castro leaves, there are chants of: "Fidel! Fidel! Fidel!"
Castro has been increasingly private in recent years after re-emerging in 2010 following a long illness. Last year, he announced that he would no longer write his trademark opinion pieces, known as "Reflections."
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