Popsugar Fitness Workouts Stretches to Improve Posture and Core Strength Crunches Are Bad For Your Posture — These 2 Stretches Will Lengthen Your Tight Muscles March 8, 2020 by Tamara Pridgett View On One Page Photo 2 of 3 ADVERTISEMENT () Start Slideshow Share This Link Copy ← Use Arrow Keys → 2 Thumbs-to-Pits Stretch This stretch will open the chest and extend your midback. Place your thumbs under your armpits with your fingertips pointed up to the ceiling. Tilt your head back, and lift your thumbs up as high as possible. Hold for 10 to 15 seconds. Repeat three to four times a week. Previous Next Start Slideshow Fitness TipsWorkoutsStretchesInjury Prevention