Bored with planking and crunches to strengthen your core? Try challenge yourself by doing Ys on the floor.
This exercise will work on your upper back and shoulders:
Step One: Lie on the floor on your stomach with your face down and make a Y-shape with your hands by raising them above your head. Make sure your hands are wider than your shoulders.
Step Two: Pull yourself up (or your abs toward your spine) while ensuring that your hands are still making the Y-Shape and then lift them up from the ground.
Step Three: Hold this position for at least three seconds then lower yourself to the starting position. This will count as a single rep.
Step Four: Do three sets of eight reps.