I worked out with Mark Wahlberg and could barely walk for the next 48 hours

• Mark Wahlberg designed a roster of workouts for the fitness studio F45.
• Wahlberg demonstrated his strength-training routine for me and a few others, acting as trainer/hype man.

Last Friday, I ventured out into the torrential flash floods in New York City. Despite an umbrella and a hooded raincoat, every inch of me (including my head) was soaked by the time I'd walked two minutes from my apartment to the subway. The station was flooding, there was an emergency alert telling everyone to shelter in place. My grandma texted from England asking: "Are you OK?"

Yes, grandma, I'm OK. I'm going to work out with Mark Wahlberg.

Wahlberg — singer, model, actor, producer, gym bro icon, prayer app spokesperson, burger entrepreneur, tequila investor — is also the chief branding officer of fitness studio F45, for which he has designed seven Wahlberg-themed workouts (with names like "Patriot" and "Underdog"). To promote this, he stepped into the role of trainer/hype man, leading me and a few others in a resistance workout that was more intense than all of my workouts this year combined.

He arrived impossibly dry, exuding energy. Unlike me and my slightly damp comrades, he had (famously) been awake since 4 a.m. He half walked, half bounded through the studio in a pair of platformed white-and-pink sneakers (his own design), clapping his hands, saying a combination of words including "yeah!" and "we ready?!" and "let's get it going!" His energy was infectious.

Soon, I notice, we're all bouncing a little on our toes and swinging our arms. The woman next to me claps, I hear myself say "whoop!", and I feel my cringe slip away.

Not that I had time to feel cringe or any other emotion for long, because this, below, was my workout circuit.

The workout

Station 1:

• In downward dog, pedal your legs (90 seconds)

• Step-ups with hand-held weights on each shoulder (120 seconds)

Station 2:

• Spinal twist on mat (90 seconds)

• Deadlift — 70lbs (120 seconds)

Station 3:

• Toe taps (90 seconds)

• Dumbbell squat to shoulder press — 20 lbs each hand (120 seconds)

Station 4:

• Full squat with your fingers under your toes. Stand up with straight legs, your head touching your knees. Repeat. (90 seconds)

• Squat holding a kettlebell — 18 lbs (120 seconds)

Station 5:

• A rotation of yoga moves: child's pose, push yourself onto your belly, push up into cobra. Repeat. (90 seconds)

• Dumbbell chest press — 20lbs each hand (120 seconds)

Station 6:

• In a plank, lift your right arm off the floor in a circle — forward, up, and back. Do the same with the left. Repeat. (90 seconds)

• Full-body pull-ups on TRX machine (120 seconds)

Station 7:

• Shoulder stretch: Lie on your belly with arms outstretched. Lift your right foot and tap it behind your left knee. Repeat. (90 seconds)

• Sit-ups (120 seconds)

Station 8:

• Side to side lunges (90 seconds)

• Lunges with dumbbells (120 seconds)

Station 9:

• Lunge your right leg forward, lift your right arm into a stretch, then straight both your legs and touch your head to your knee. Repeat on both sides. (90 seconds)

• Barbell row — 50 lbs (120 seconds)

I am not built for Mark Wahlberg's workout

Somewhere around the fourth station I felt a sense of terror creep over me as I gazed at the studio screens showing looped video demonstrations of each move and realized I was supposed to continue.

But it's quite something, having Mark Wahlberg shouting "you got this!" as you hang limply off a TRX machine, contemplating a weekend without the use of your arms. I chose to believe him, and shakily hauled myself up once more.

Of course, Mark Wahlberg has never in his life had biceps as feeble as mine and therefore had no idea how much I did not got this, but his blind faith was touching.

Over the next 48 hours I learned what it feels like to "feel the burn." My biceps, triceps, quads, glutes, abs, and other muscles I don't know the names of were vigorously throbbing, which added a new twist to the experience of sitting in a chair or using a toilet.

I also learned, through complaining to everyone in my life about my aches and pains and inability to walk, that three (3!) of my friends are F45-goers who all thought that my 45 minutes of hell sounded like a wonderful way to spend a Friday morning. They were jealous that I got to experience this pain a couple of days early — they had to wait for "Wahlberg Week," October 2 to 8, when these tailor-made workouts would be free at participating F45 studios.

"It's intense but it's so fun!" one friend, whose chiseled abs now make so much sense, told me. "You're gonna feel incredible once you get through this burn," another said.

For Wahlberg, this was an exercise snack

Technically, Wahlberg's F45 workouts are more intense than your standard F45 circuit, with longer sets and no breaks. And yet, for him, our workout was more like an exercise snack.

After the class, he told me he's actually more about longevity and recovery these days than pushing himself to the limit.

At 52, with four kids, he's working out much less than he used to — dialing down the intensity, and doing just a couple of workouts a day (rather than seven or eight), with targeted exercises that don't overload his body.

"Getting a little bit older, I'm always now thinking about longevity, mobility, flexibility, lung capacity. Rest is equally important," he said.

"Totally," I wheezed.