This equipment-free, five-move abdominal workout will set your core on fire, says creator Senada Greca. If you haven't heard of her, she is Kim Kardashian's trainer and a well-known fitness entrepreneur. As such, she knows a thing or two about building muscle and strengthening the core.

Greka's abdominal training can be done anywhere. Just add the best resistance band or a towel to make the exercises harder." I dare you to try this workout." Greca challenges. With over 800,000 views on Instagram now, it's likely that many of her followers have worked their core muscles by now.

You don't have to be poolside or in a bikini like Greca to do these abs exercises. Check out the exercise below and add weights if you need more intensity. Here it is.

Like most of the best abdominal workouts, this one will challenge the various core muscles around your torso, not just the rectus abdominis, or six-pack muscles, as they are also known.

Greka recommends performing each exercise as a core circuit, with 8-12 reps and 4 sets. Watch the video below to review each movement and practice your form. This may seem obvious, but keep your core engaged throughout the exercise. If you don't know how to do it, imagine someone is about to punch you in the stomach and tense up for the impact.

Thankfully, this workout is short. Once you've completed your allotted set, that's it. Unlike Kim Kardashian, she and Greca go to the gym for two hours a day. Ouch.

Here's the exercise:

Tilt your pelvis toward your spine, keeping your upper back off the floor. Hold a resistance band or towel over your head and raise one leg at a time to touch the band. Performing leg raises when the trunk is isometrically contracted (muscles contract without moving) will ignite the abdominal muscles.

The oblique muscles run through the waist, so twist and side crunch exercises target the oblique muscles. Lie on one side, pull hard on a resistance band or towel, and extend your arms over your head. Always look forward, use your center, and lift your upper body toward your hips. Click here for tips on side crunches.

Lie on your back with your legs extended. Hold a band or towel above your head. Tilt your pelvis down to engage your core and slowly lift your upper back off the floor, always looking at the ceiling as you do your crunches.

This movement is similar to a reverse crunch. Starting in a hollow hold position, hold the band or towel firmly and extend your arms above your head. Bring your knees down toward your chest and extend both legs over your head while thrusting your feet toward the ceiling. Form a gentle c-shape of the spine.

Sit on an exercise mat and lean back slightly, keeping your core engaged and your back straight and neutral (click here to learn how to do V-shaped sit-ups). Extend your arms out to the sides at shoulder height and lift both feet a few inches off the floor. Quickly raise and lower one leg at a time and begin a flutter kick. This movement also targets and strengthens the hip flexors.

Greka's five-move abdominal workout proves that you don't need gym equipment to work your core muscles hard. None of the movements reinvent the exercise wheel, but they are tried-and-true ways to work a variety of muscles to build a strong core.

If you are a beginner, I suggest sticking to the sets and reps you are given. However, if you need more of a challenge, add more reps. If that is not enough, set a time limit for each exercise. For example, I chose five rounds of 45 seconds per exercise. If you want to test your core strength further, try 60 seconds per exercise, with a rest between rounds.

I like to use weights like dumbbells or kettlebells when training abs, but this was amazingly hardcore. I woke up the next day with pretty sore abs, even though I didn't expect to feel anything.

But remember that developing a more sculpted midsection requires a lower body fat percentage. Fat loss is different for everyone, but body fat determines how the abdominal muscles look. It is not all doom and gloom, as there are ways to improve fat loss. First, we suggest checking out your diet, which can affect how toned your muscles are.

We also recommend adding compound exercises like squats and deadlifts to your strength training program. These movements are not considered "core" exercises, but they do use a lot of the muscles that power the movement. Also, compound movements require more energy and muscle involvement and will burn more calories than sit-ups and crunches.

Consider how much you move throughout the day. This is called non-exercise activity thermogenesis (NEAT: Non-Exercise Activity Thermogenesis) and helps boost your metabolism throughout the day.

Looking for more abdominal training? Check out some of our favorites below.