On hardwood or tiled floor, place feet on two sliders and assume a high plank position (hands under shoulders, soft bend in elbows, butt and core engaged). Pull feet in toward chest, bending knees until you’re in a bear plank, knees below hips, but still lifted off floor. Slowly push feet back to high plank. Continue to repeat. To make it easier, move one leg at a time.
"This exercise is so effective because it teaches you not to rely on your bigger muscle groups (like your thighs) and focuses on using your abdominals correctly in a controlled manner without using momentum. The use of the ball gives you natural feedback of your weaker side so that you can adjust and work on symmetry of your musculature, preventing future injuries."
“For me, getting a six-pack was about paying attention to what I was eating and lifting heavy weights at CrossFit. I do have a semi-strict diet, and I loosely count macros (focusing on daily carbs, protein, and fat intake rather than blindly counting calories) to stay balanced and on track. It sounds like a lot of work, but it really isn’t. Eventually, it just became a part of my lifestyle, and it’s something I enjoy doing. I even started a custom meal-plan business based on macros because I had such great results!” —Tina Haupert, @carrotsncake