Yoga balls, also known as gym balls, exercise balls and stability balls are great for improving posture, core stability and balance. There are numerous exercises which can be done using a yoga ball, some of which may not seem obvious. For example, you can use your yoga ball to execute squats. If you rest the yoga ball against the wall and whilst standing, lean your back against the ball, slowly squat down then raise back up into the standing position and repeat six to eight times. Try some intense push ups using your yoga ball. Place your hands on the yoga ball, assuming the plank position, engage your core and glutes and bend your elbows whilst lowering your chest towards the yoga ball then straighten your arms and repeat. These exercises do wonders for strengthening your core, legs, arms, shoulders and chest.