Whether or not you’ve spent time listening to Imagine Dragons (though, if you’ve switched on a TV or gaming system in the last couple years, you’ve probably heard “It’s Time” and “Radioactive” more than once), you need to give it up for singer Dan Reynolds. For the band’s latest video, “Believer,” the dude went all in getting into fighting shape for his role as a boxer facing off against ’80s villain poster boy Dolph Lundgren (who plays Reynolds as an older man).

“I had to get in shape because he’s the biggest badass of all time,” Reynolds says. “I told my trainer we had to step it up.”

Reynolds had already been working with trainer Brad Feinberg after being diagnosed with Ankylosing spondylitis, an inflammatory arthritis that caused Reynolds constant pain. But he’d never done any Olympic weightlifting — or any boxing, for that matter. Stepping up his program meant not only uncharted territory exercise-wise, but also a diet that looks not unlike a bodybuilder’s grueling prep routine. Reynolds broke down his last two — miserable, bland-tasting, cranky — months leading up to the shoot.

DIET

Two months from the shoot: 2,900 calories a day, 175 grams carbs, 220 grams protein, 120 grams fat.

Meal 1: oatmeal, 2 scoops peanut butter, 4 eggs, 2 tablespoons olive oil, 1 cup veggies.

oatmeal, 2 scoops peanut butter, 4 eggs, 2 tablespoons olive oil, 1 cup veggies. Meal 2: 2 scoops protein powder, 1 cup berries, 1 cup almond milk, 1 cup water.

2 scoops protein powder, 1 cup berries, 1 cup almond milk, 1 cup water. Meal 3: 6 oz sweet potato/half cup rice, 1 cup veggies, 8 oz chicken breast.

6 oz sweet potato/half cup rice, 1 cup veggies, 8 oz chicken breast. Meal 4: 6 oz sweet potato/half cup rice, 7 oz chicken or steak.

6 oz sweet potato/half cup rice, 7 oz chicken or steak. Meal 5: 2 rice cakes, 2 tablespoons peanut butter.

*Every third day, Reynolds’ trainer would take carbs off the menu to help the singer get shredded. “It was the worst,” he says. “But it was great compared to the next month.”

One month from the shoot: “We cut,” Reynolds says. “For three weeks we did the all-keto diet, which puts your body into ketosis, but it takes a week and half to get there. It was just that third no-carb day, but every day. Total carbs were under 40 grams, which was super shitty. I was really cranky, eating big plates of gray eggs with no salt.” In other words, think of the already-strict diet from the first month. Now drop almost all of the carbs until you’re left with fats and proteins.

WORKOUT

Two months before shooting, Reynolds did three sets of eight to 15 reps for each of the movements below, except for Olympic movements, which were in the three- to five-rep range. For the second month, rep ranges were 15 or more for each movement (10 for Olympic moves), with more focus on upper body. Then came what you could call the method-actor part: Reynolds picked up boxing. His weekly exercise broke down to three days of lifting weights, two days of boxing, and a day of yoga. Here’s how he spent his time with the heavy metal:

Day 1: Olympic training: Snatches, cleans, different pulls.

Olympic training: Snatches, cleans, different pulls. Day 2: Chest and legs: Bench press, incline bench press, dumbbell press, front squats, back squats, shoulder press.

Chest and legs: Bench press, incline bench press, dumbbell press, front squats, back squats, shoulder press. Day 3: Pull exercises: Romanian deadlifts, deadlifts, rows.

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