In an attempt to add more movement to my day, I recently started walking up the 88 very steep stairs to my fifth-floor office. While wheezing on one of the landings, I realized there was enough space there to sneak in some strength-training moves. Lunges seemed like a smart choice.  Here’s how to do the perfect lunge: (Got 10 minutes? Then you’ve got time to lose the weight for good with Prevention’s new 10-minute workouts and 10-minute meals. Get Fit in 10: Slim and Strong for Life now!) Lunges don’t require any equipment, and they’re a great way to work your calves, glutes, hamstrings, and quads. They also help with balance and core strength. That’s pretty efficient for one basic move!  My plan was simple: I’d do as many lunges as I could every day. Here’s how it played out.

I’m stronger than I thought.

The first day I was able to do 70 basic lunges before my quads started shaking. I was pretty impressed with myself and figured I could do more, so I revised my goal to do 100 lunges a session. The new plan was to do four sets of 25, taking breaks between each set. I’d add lunge variations (forward, back, side, and pass-through) when I got bored.  MORE: 5 Easy Moves To Tone Your Legs Fast​

My knees didn’t hate me.

I have a partial tear in my left knee due to a home renovation mishap, so I’m tentative about bending exercises. But after doing some research, I found that lunges are easily modifiable—you just need to stop bending before it hurts and engage your core to help support your leg muscles. (Here’s how you can do lunges and squats without killing your knees.) I found that I was able to bend 90 degrees without pain as long as I moved slowly and paid attention to form: I was careful to keep my front knee tracking over my ankle, my back knee bent but not touching the ground, my chest and chin up, and my core engaged.

I learned to focus on the details.

I worried that a single-move workout was going to be boring, but there are so many important, yet subtle, elements of the lunge that make it effective. I took my time so I could maintain proper form for every last lunge. I made sure there was no tension in my jaw, my eyes were level, my chest upright and centered. At the end of each session my legs were shaking, and I felt like I’d gotten a good workout. PREVENTION PREMIUM: This Move That Targets Your Outer Thighs AND Lower Belly, Plus 5 More Fitness Updates You Need To Know​

You really can workout at work.

When I started this challenge, I worried that I wouldn’t have enough time to sneak away from my desk, that my work clothes wouldn’t be conducive to lunging, or that I’d be too tired or sweaty to get back to work. (One of our editors tried taking a plank break at work every day—here’s what happened.) None of those turned out to be true. It only took me 15 minutes to do all 100 lunges, and I never got sweaty—maybe a little out of breath. I was able to lunge in most of my typical work outfits, though I was most comfortable when I was wearing a loose dress or stretchy jeans. All I had to do was change into a pair of sneakers that I kept under my desk and I was good to go. (Thinking about working out at work? Try one of these stylish summer tops that hide sweat stains.)  

Lunging is a good energy-booster.

Whenever possible, I stopped for my lunge break before noon; lunging with a full stomach didn’t seem ideal. That being said, lunges also saved me a few times when I found myself dragging around 3 PM. Instead of forming a search party to find snacks or loading up on caffeine, I’d do some lunges and feel much more alert. (You can also try this new way to get your caffeine fix, from Prevention Premium.) MORE: 35 Teeny Tiny Tips To Boost Your Energy And Reduce Fatigue​

People don’t take the stairs.

I spent 15 minutes every day in that stairwell for an entire month, yet I only ran into coworkers twice. I guess people don’t take the stairs much. Just saying. (Take advantage of an open staircase with these awesome toning moves using stairs.) 

Lunges work!

As the month went on, I was able to hold poses longer and I could handle more resistance on climbs in spin class. I saw definition in my quads. And, as a nice perk, my cellulite smoothed out. I also felt stronger, and climbing those 88 stairs became more tolerable. The benefits were so dramatic that I now feel less guilty about binging on Bravo shows. (If you’ve been working hard, relieve your tight leg muscles with these foam rolling moves.)