When you're doing a plank, be sure that your body is creating a straight line. NO butt in the air, or hanging down. Rest if you don't have the proper form! Also, be sure that your elbows are below your shoulders and push your weight back towards your heels.
Another great thing about planks? There are so many different variations to hit different muscles and keep you from getting bored! Here are 5 plank versions for you to try out:
- Straight Arm (or forearm!) Plank: Back to the basics!

image source - Side Plank: You can either stack one foot on top of the other, or you can take the lower leg and place your knee on the ground. Another option is to go down onto your forearm if this bothers your wrists

image source - Reverse Plank: Flip it over and work some new muscles!

image source - One Legged Plank: This sets you off balance so your core works harder!

image source - Mission Impossible Plank: Start in a regular plank and then move your arms and legs out - be sure to keep your back straight!

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