The San Francisco 49ers coach was back at work Friday and fired up to be there a day after undergoing a minor procedure for an irregular heartbeat that kept him away for all of half a day.

“I’m fine, I’m fine,” Harbaugh said. “No limits. Going about everything as normal. Had a little irregular heartbeat. I’ve had that before. Now that I have the procedure, a cardiovert, it’s amazing. It gets the heart rate back to normal. Atrial flutter is something I’ve had for a while, most of my life.”

The reigning NFL Coach of the Year returned to the field to lead San Francisco through a morning walk-through session, with a full practice scheduled for the afternoon. He did stop by for the final hour of Thursday’s practice for a “little bit” of coaching but “more standing.”

“It was pretty cool to see him,” safety Donte Whitner said. “We knew it was a minor heart thing, but a heart thing no matter if it’s minor, it’s serious. It felt a little different without him. Hopefully, he doesn’t have to go through it again.”

Harbaugh, who turns 49 on Dec. 23, was away from the team Thursday for his procedure at Stanford Hospital after undergoing tests Wednesday night. Several players said Friday they were initially scared for their coach, who acknowledged Friday that he underwent a similar procedure called an “ablation” 13 years ago while still playing during a 15-year NFL career at quarterback.

“He’s an intense person,” fullback Bruce Miller said. “It’s definitely a serious issue already with his heart. He’s not going to slow down. We’re glad he’s back.”

Doctors talked to Harbaugh about improving his diet and cutting down on caffeine. He said he also will take aspirin and other medication. Whether he could need a follow-up procedure down the road, Harbaugh doesn’t know.

“They’ll evaluate it as it goes,” he said.

His father, Jack, and older brother, Baltimore Ravens coach John Harbaugh, both encouraged him to “listen to the doctors and eat right.”

Does he consider himself coachable when it comes to his health?

“Sure, absolutely,” said Harbaugh, whose NFC West-leading Niners (6-2-1) host the Chicago Bears (7-2) in a key NFC showdown on Monday Night Football. “You’re not going to be stubborn like a mule.”

His players had some fun with Harbaugh once they knew he was OK.

“He gets fined $500,” linebacker NaVorro Bowman said with a grin. “He missed meetings.”

Earlier this fall, Cincinnati Reds manager Dusty Baker missed 11 games late in the regular season, hospitalized because of a mini-stroke and irregular heartbeat. He returned to manage the Reds in the playoffs, a five-game division series loss to the eventual World Series champion San Francisco Giants.

Harbaugh said he isn’t worried about burning out with the rigorous year-round schedule and pressures on an NFL coach.

“I don’t foresee that, no,” he said. “I’m just glad to be back at work, glad to be preparing for this ballgame.”

Concern for Harbaugh’s health reached his old Stanford campus, too.

“Pretty scary stuff, but it sounds like he’s doing OK now,” Cardinal coach David Shaw said. “And if I know Jim Harbaugh, it’s going to take a lot more than that to stop Captain Comeback.”

Running back Frank Gore certainly doesn’t expect the excitable Harbaugh, who regularly becomes red-faced and angry at officials, to stray from his approach.

“He’s going to be him,” Gore said. “Coach is a tough guy.”

And Harbaugh didn’t seem to mind a little bit of good-natured razzing from his guys.

“We had to,” defensive tackle Ricky Jean Francois said. “He’s the guy you never think is going to get sick. He’s good. We got him out there joking and laughing. He’s in good spirits. It’s good for him to be back on the field.”

Notes: Harbaugh said QB Alex Smith’s status for Monday is still unknown as he works back from a concussion, and he will be evaluated again by a neurologist. Backup Colin Kaepernick is getting a “little bit more work than normal,” Harbaugh said. “Alex seems like things are progressing as it does.” Smith practiced in a non-contact black jersey for the third straight day. … RB Brandon Jacobs said his series of Twitter posts Thursday in which he referenced never working “in a place where you hate your boss so much, you should always be happy at work” were not directed at Harbaugh but rather toward the unstable work environment of his big brother, Michael. “I don’t look at him as my boss. He’s our coach and leader,” Jacobs said. “I look at (GM) Trent Baalke as the boss.” Jacobs — who hasn’t played all season — also revealed he has long had an irregular heartbeat, and that the 49ers are aware of it. … The NFL fined DT Ray McDonald $21,000 for a third-quarter hit on Rams QB Sam Bradford in Sunday’s 24-24 tie.