The "Y" Exercise on Mat is designed to strengthen your lower trapezius muscles, which are essential for pulling your shoulder blades down and and helping to maintain proper posture. Proper posture of your mid back region helps to prevent thoracic spine compression fractures.
Get into position by lying on your stomach with a pillow lengthwise under your chest and a small towel roll under your forehead. Your arms should be positioned in a "Y" above your head to start with your thumbs pointed up toward the ceiling.
If you find that this exercise is too easy and does not cause muscle fatigue, you can progress the exercise by adding free weights. You should begin with very light weights, such as 1 pound weights. If you don't have 1 pound weights, you can try using a 16 ounce water bottle in each hand.
Lift both arms up a few inches from your initial starting position by pulling your shoulder blades down and in. The movement should be initiated by your shoulder blade muscles. Return your arms to the starting position.