12-05-2025
You don't need leg raises to strengthen your deep core muscles — I'm a personal trainer, and I prefer the 'in-and-out' exercise
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Leg raises are probably known as the Holy Grail of lower abs exercises when we consider hitting these muscle groups without weights or gym machines. But what if I told you I actually swerve them more often than not for in-and-outs? (Nope, sadly, this in-and-out isn't a burger joint.)
There's no reason you can't use this exercise alongside leg raises, but the in-and-out bodyweight exercise is kinder on my lower back (when performed with correct form) using the upper-body positioning of the Russian twist. Your lower body mimics a similar motion to leg raises (moving up and down), but also from side to side.
This way, I guarantee a deep burn directly to my lower abs while also torching my waist muscles — the obliques — and strengthening my hips. Interested? Here's how.
Think of your core muscles as this giant 360-degree machine made up of small and large muscles. Some are more superficial — think the six-pack abs — while some sit deep beneath layers of muscle to help stabilize your spine and pelvis (read: abs vs core).
These muscles together are like the glue that holds us together.
We don't live in a 2D world, so our muscles should work in every plane of motion possible to keep them robust and active as we inevitably succumb to aging. Think twisting, bending and extending as the basics.
There are some motions we don't even think about, one of them being the simple act of lifting and lowering the legs. How often do you think about it?
However, your hip flexor muscles can get tight and weak very easily from underuse, strain, or sitting for long periods. Over time, this can cause issues elsewhere, commonly contributing to back pain.
Exercises that target the hip flexors — and recruit them to help lift and lower the legs — can improve hip mobility and strengthen the flexors. Plus, you're building stronger core muscles and protecting your spine, too.
For this exercise, you'll learn to lift your legs into the air, over an obstacle to the other side, then back down. I like to use one of the best kettlebells or a dumbbell standing on its end.
A yoga block or book also works well, and you can play around with the height as your hamstring flexibility and hip mobility improve.
Generally speaking, exercises that draw your knees or legs toward your body engage the lower section of the abdominal muscles — think mountain climbers, leg raises, or reverse crunches. The benefit of in-and-outs is that you also engage your obliques, quads and hamstrings.
We've put together a handy guide on how to do the in-and-out abs exercise with step-by-step instructions, or you can follow along with the video above.
To make the exercise easier, bend your knees; extend them to make it harder. While your hip flexors should be active, they shouldn't be the shining star taking center stage. If that's the case, bring in the knee bend and lean back slightly more.
I like to lean back quite a bit as it helps me engage my core muscles without hunching up. I prefer this to lying on the back as you would during leg raises, as I can actively think about my posture and sit tall.
When on your back, the lower back can arch away from the ground as the legs lift and lower, usually from a lack of core engagement, not being taught the set-up properly, or the legs gaining too much momentum and (inevitably) weighing you down, lifting and pulling on your spine.
During in-and-outs, think about pulling your shoulder blades down and back and lifting through your chest as though an invisible string is pulling you from the crown of your head. From knees to hips to head, your body should create a V-shape, which requires you to keep your spine straight.
For more engagement in the inner legs, try placing a book or yoga block between your thighs and squeezing it as you move, sweeping from side to side with control. Aim to slightly rotate your hips to engage your waist, and aim for 8-12 reps per side for 3-4 sets.
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