Hold a plank
Find a soft spot on the floor, or grab a towel or yoga mat. Lay on your stomach. Bend your elbows. Peel your stomach off the ground as you put your weight on your elbows. Keep your knees bent as you hold your weight on your elbows (below your shoulders). Count down from 30. Rest. If this was too easy, come onto your toes so your stomach is off the ground completely. Count for 30 seconds. Drop to your knees anytime. Congratulations! You just did a plank.
Your strength goal: 1 pushup, 1 tricep dip, 1x 30-second plank (knees or toes)