Slow and steady wins the race, and like a wall sit [1], an isometric dumbbell hold [2], or a one-minute plank [3], maintaining a stable position starts off easy, but the burn slowly builds until you can hardly stand it — that's when you know it's working. If you love that burn, you'll love this core-strengthening move called the flat-back forward bend.

• Stand with your legs in a wide straddle position, feet parallel, with about two to three feet between your heels.
• Extend your arms straight into the air.
• Take a breath in and as you exhale, slowly hinge at the hips, lowering your torso so it's parallel to the ground.
• Be sure to shift weight forward into the toes and really reach your fingertips away from you. Keep the abs pulled in as you breathe deeply.
• Hold here for 30 seconds. Then slowly rise back up.
• Then lower halfway and rise back up, repeating 10 times.
• Lower and hold for another 30 seconds.
• Rise up to stand.

If your hamstrings are tight, feel free to bend at the knees a little — you'll still be firing up your core. And if your lower back hurts, bring your hands to your hips, and shift weight back into your heels a little.