I’m a runner. I’m a weight lifter. I climb stairs on a regular basis. I’m as fit as can be, right? Well of course, I’m Dr. Nina, exercise and fitness extraordinaire!

Nevertheless, the art of muscle confusion never ceases to amaze me.

Back in 2013, I attended Women’s Health Magazine and “Exhale Spa’s “Fusion Fest” event in Chicago where I was asked to take some of the core classes offered at the spa.

I was in for a surprise!

The “Core Fusion Cardio” class was the first on my schedule.

Now, let me start by saying this: I’m not one who regularly participates in private studio-style cardio classes that incorporate mat exercises with low-weight handheld dumbbell work.

I run.

I pump iron!

Even the group fitness classes I teach involve ‘hardcore’ weight lifting.

The type of class in which I was about to participate was totally new to me.

Since Women’s Health Magazine suggests that Core Fusion is “one of the countries hottest fitness programs”, I decided to do a little research prior to taking the class in order to find out what it was really all about.

Although Core Fusion promises a great full-body workout primarily focused on core strength, no description could have prepared me for what I was about to embark on.

Related Article: Why You Need to Change Your Exercise Routine Regularly

Upon walking in the door wearing my Nikes, the class instructor, “Mind Body Manager” Nicole, stopped me and said, “We don’t allow shoes in the studio.”

I looked at her sarcastically and said: “Wow, really?”

With a smirk on my face I continued: “A cardio class without shoes, I must be in for quite a workout.”

I didn’t know it then, but Nicole was about to make me pay for that comment.

As I removed my shoes, she announced that we would need light and heavy handheld dumbbells. I glanced at her again and said: “What’s heavy?”

Nicole replied “3 pounds for light and 5 pounds for heavy is good.”

I then started laughing.

Seriously, I pump iron!

Five pounds is not pumping iron in my book.

But, then again, Dr. Nina was enjoying the vibe at Exhale Spa so I decided to go with the flow.

The class started out with some basic yoga poses and dynamic stretching along with countless repetitions of weightless squats, lunges, planks and a whole lot of flowing upper body motions.

It was challenging indeed.

I was already sweating profusely and about 10 minutes into the class Nicole said: “Okay, you should be all warmed up now!”

So, after that I was pretty much afraid and completely at her mercy.

The workout got progressively more intense.

More planks, more lunges and squats, mountain climbers and side planks, karate kicks, shoulder presses, curls and punches with dumbbells, push-ups, and then more planks. You name it, we did it.

Related Article: 5 Cheap and Convenient Ways to Burn Fat Fast

Without shoes!

Our only breaks consisted of 5 to 10-second downward-facing dog poses.

After 50 minutes of pure Core Fusion Cardio it was time to lie on the floor and stretch?

Not at all!

Nicole had more in store for us.

We proceeded to perform some of the most intense abdominal work I’d experienced in a long while. Isometric crunches, oblique twists and, oh, more planks. I was so worn out I couldn’t even stretch right.

The funny thing is that I’d planned to take another class immediately after that one.

Well, that idea went out the window just as soon as girlfriend said: “Thanks for taking the class!”

All in all, it was truly a humbling experience and one I really learned from. I always encourage people not to have ‘routineness’ during exercise.

I took a piece of my own advice when I took this class. While I always increase the intensity of my workouts I rarely break away from the comforts of running, stair climbing, and weight lifting.

This Core Fusion Cardio workout was something invigorating and new. My muscles were thorougly confused and it felt awesome. I’d give the class a full 5 out of 5 stars!

If only I had the guts to take another one…

Exhale Spa is definitely a nice place to consider for your workout and pampering needs. Great staff, wonderful service, high-quality classes, excellent spa offerings—A full VIP experience at a reasonable cost. I’ll certainly return.