I did 50 frog crunches every day for a week — here's what happened to my abs

Woman in white activewear performing a crunch exercise against blue background
(Image credit: Shutterstock)

It’s a common misconception that crunches are ineffective or only work the rectus abdominal muscles — the “six-pack” muscles. Unlike traditional crunches, the best crunches and variations hit various core muscles, which brings us to frog crunches. 

I don’t often add crunches into my exercise routine, and probably prefer lifting heavy weights to strengthening my core with isolation ab exercises. Keen to mix things up, I did 50 frog crunches every day for a week to see what could happen to my ab muscles.  

I hit my yoga mat to crunch it out for 50 reps a day for seven days to see if this crunch variation could do anything for my core. Here’s how I got on and why the frog crunch surprised me.  

How to do frog crunches 

Here’s how to do one of the best ab exercises step-by-step.

  • Lay on your back with your lower back supported on the mat
  • Create a diamond shape with your legs by pressing the soles of your feet together and letting the knees drop open to the side
  • Place your hands behind your head and pull your elbows back, squeezing your shoulder blades together
  • Squeeze your stomach muscles, then lift your upper back off the floor and drive your elbows toward your knees. At the same time, lift your legs and draw your knees toward your elbows
  • Slowly lower back to the starting position.

I’ve seen a few variations of frog crunches, similar to butterfly crunches but with a greater range of motion. Insects and amphibians aside, the move has a few core strengthening benefits for your body. 

Sure, the move targets your abs and obliques, but it also builds flexibility in your hips and adductors (the muscles that run down the inner thighs) and activates the upper back muscles. The open leg position removes the emphasis from the hip flexors and gently stretches the groin, which can get tight if you sit down all day.  

I did 50 frog crunches every day for a week — here are the results for my abs

Setting off into this challenge, I didn’t expect much. According to the American Council on Exercise (ACE), bicycle crunches are one of the most effective exercises for your torching midsection, but could the frog crunch do just as much? 

My lower back kept arching

I noticed immediately that my lower back kept lifting away from the floor. It could indicate several “problems” — a lack of flexibility, mobility or engagement, or poor form. I focused on gently re-engaging my core, pressing my lower back into the mat and experimenting with my foot placement. 

A slight arch in the spine is safe, but be sure to tilt your pelvis toward the spine to keep a neutral back position and generate movement from your core, not your lower back. If it feels better to move your feet further away from your bum, or closer if you prefer — it comes down to preference. 

My hips felt tight

Surprisingly, I felt the core exercise in my hips. I decided to tack on a quick warm-up exercise beforehand to improve my range of motion. And what better way to do it than by adding an exercise of the same name — frog pose

Hands down, this is one of the best hip stretches on the planet. If you have tight hip flexors or tension in your lower back, give it a go before repping out the frog crunches or even before squats.

I struggled to breathe properly

Some crunch variations limit my ability to breathe, and frog crunches were no exception. I always bang on about the importance of diaphragmatic breathing, meaning an expansive breathing technique, but this time, I just couldn’t regulate myself.

Ideally, you should exhale as your muscles meet the most resistance — the concentric phase of the exercise. In this case, you exhale as your elbows and knees draw together. During sit-ups, this would be as you sit up, and during squats, it would be as you stand up, for example. 

For some reason, my breath felt super restricted by the crunch, which is something to work on in future attempts.

I didn't notice any difference in my abs

I didn’t find the move very difficult, so I tackled the 50 reps in one go and slowly, using the method of time under tension to work the muscles longer.

I didn’t feel the exercise the next day or notice any difference after a week. Sculpting a svelte midsection takes more than just strengthening your muscle groups. Building core muscle gets you part the way towards rippling torso muscles — it helps develop definition. 

But revealing those toned ab muscles depends on factors like lifestyle and genetics. I know, boring, right? We cover 5 reasons you can’t see your abs yet, despite working out for the low down. Still, I at least expected a burn in my core muscles. 

I got bored

Usually, I leave these challenges full of gusto, but the frog crunch didn’t give me much food for thought. Although, I focused on what my body was doing to maintain good form, which I enjoyed.

I also loved that while I crunched my abs, my hips and adductors were firing up. It serves as a reminder that bodyweight ab exercises can still be practical tools for building ab strength. 

I did 50 frog crunches every day for a week — here’s my verdict

Time to reflect. 

On day seven of this frog-themed fitness challenge, I decided to mix it up. Instead, I performed every rep holding a dumbbell in both hands and reaching my arms toward my feet between my legs. Hello, abs. 

If you struggle to activate your core during frog crunches, try it. I learned too late that this could have transformed the whole week, but at least I know for next time — and now, so do you. 

That said, if you experience lower back pain and struggle to keep your back supported on an exercise mat, frog crunches might not be the core exercise for you. Remember, always check in with a qualified medical professional if you’re being treated for injury. 

Although the frog crunch is a beginner-friendly bodyweight exercise, you’ll need a degree of coordination and flexibility in your hips and groin to do it safely. And if it’s off the table already, we’ve got you covered with more ideas below.

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Sam Hopes
Senior Staff Writer - Fitness

Sam Hopes is a level III qualified fitness trainer, level II reiki practitioner, and senior fitness writer at Future PLC, the publisher of Tom's Guide. She is also about to undertake her Yoga For Athletes training course. Having trained to work with mind and body, Sam is a big advocate of using mindfulness techniques in sport and fitness, and their impact on performance. She’s also passionate about the fundamentals of training and building sustainable training methods.  When she's not writing up her experiences with the latest fitness tech and workouts, you’ll find her writing about nutrition, sleep, recovery, and wellness.