The 15-minute workout you should be doing

Straight-legged dips

Using a chair or a raised surface, grip the surface edge with your palms down, walking your legs out until your feet are as far from your body as possible, while your back remains close to the raised platform. Be sure to dig your heels into the floor, toes raised! Slowly lower yourself down for a 1-2 count until your bum is just above the floor, before springing yourself back up, arms locked. Be sure to keep your elbows narrow during the lowering phase to target the triceps.

Do: 20 reps