I'm a month into Kayla Itsines's viral 12-week workout - here's what it's like

I am no stranger to working out.

I have run four half-marathons, completed the Physique 57 workout program and Ruth Bader Ginsburg's workout, and exercise regularly. I even finished one round of the Bikini Body Guide last year.

Regardless, I was prepared to be sore because the workout program is designed to target all of your muscles — including ones you didn't know you had.

I was up for the challenge, especially after scrolling through Bikini Body Guide Transformation pictures people proudly post on Instagram.

Speaking of Instagram, The Bikini Body Guide hashtag has almost seven million posts from a supportive community of women who leave encouraging comments and advice on each other's posts. They even plan local meetups to do the BBG workouts.

Each high-intensity plyometric training workout includes two series of four exercises that you complete in seven-minute circuits, twice. For each circuit, you do each of the four exercises as many times as you can in the seven minutes.

I often end up doing each exercise (for example 15 squats, 15 burpees, 15 sumo squats, 30 weighted step-ups) twice per circuit. There is a one minute break between circuits and a much-needed cool down to stretch when you're done.

It's tough … really tough. You'll be sweaty, and you'll savor the minute-long break between sets, but at least your hard work pays off. I find the abs day to be the most difficult, in part because I have scoliosis and can't do all of the crunches correctly. I make modifications, like doing regular crunches instead of full-body crunches. Listen to your body and don't be afraid to modify.

If you have the app, you can also check the alternative exercise to see if it works better for your body.

Each week, you do three low-intensity steady state cardio workouts (LISS) for 30 to 45 minutes. Itsines recommends power walking, but she says that you can also do yoga, swim, go for a slow jog, or take a leisurely bike ride.

The key is to keep your heart rate low and to go at a steady state, unlike in Itsines's high-intensity interval training (HIIT) workouts, where you sprint for 30 seconds then rest for 30 seconds, repeating for 10-15 minutes. I usually speed walk in Central Park as LISS and run in the park for HIIT.

You can do the traditional BBG program from home. Most workouts have little to no equipment other than a mat.

Although you don't need a gym membership to do BBG, I find that going to the gym makes me work harder. I take fewer breaks and feel energized by the people around me.

When I see people working with their personal trainers, I get some satisfaction knowing I'm also "working out with a personal trainer," just through my phone. I've even had people come up to me to ask what app I use while I'm working out with SWEAT.

The updated SWEAT app released last year has three additional 12-week workout programs to add variety to your workout routine.

The new workouts feature multiple trainers and programs like yoga instructor Sjana Elise Earp's "Body and Mind" (a Vinyasa-style yoga and recovery workout), Itsines's BBG Stronger (a BBG-style workout that incorporates gym equipment), and certified trainer Kelsey Wells's Sweat PWR (a weight training and resistance workout), and Post-Pregnancy (a post-natal program that focuses on core strength).

I haven't done the full 12-week BBG Stronger program yet, but I've tried a few sessions and like that it teaches you how to use various fitness equipment correctly.

I am done with week four and I feel stronger and more toned already. Even though the workouts are difficult and I often want to stop after one circuit, I always feel proud of myself at the end of the workout. I often feel sore the next day, so I alternate between HIIT workout days and LISS days.

So far, I feel healthier and empowered, in part because of the supportive BBG community. The women on Instagram and it's been fun having people leave encouraging comments on my posts and vice versa. I am excited to see the results at the end of the 12-week program. (Wish me luck!)

If you are thinking of trying Bikini Body Guide, I highly recommend it. The 28-minute workouts and short HIIT sessions are quick and convenient. Check off LISS by speed walking with your dog or walking or biking to work.

It can fit into your busy lifestyle better than an hour-long class or long run. Everyone's fitness level and experience is different, but it has been beneficial for me.