Single-Leg Chair Squats
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Holland's Single-Leg Chair Squat can cause some serious burn: Using one leg at a time, lift your butt off the chair one inch and sit back down, alternating legs with each rep. Perform 3 sets of 20 reps.

Pro Tip: If your office chair is on wheels, swap it out for a stationary seat lest you smack your butt on the floor.