This exercise series is an excellent way to challenge the core musculature which is essential to the maintenance of a healthy posture and effective human movement.

As the name implies this series involves four separate exercises. Each exercise is performed with the individual’s feet on a Swiss Ball (stability ball) from a plank or modified plank position.

Four-Way Torso Exercise step 1 Four-Way Torso Exercise step 2
1.  From a push-up (face down) position with feet on the Swiss Ball and hands on floor bring knees to chest and back while refraining from allowing the hips to sag throughout movement.
2.  From a push-up (face down) position with right hip down and right ankle on the Swiss Ball and hands on the floor bring knees to chest and back while refraining from allowing the hips to sag throughout movement. 
Four-Way Torso Exercise step 3 Four-Way Torso Exercise step 4 
3.  As in exercise #2 but with left hip down and left ankle on Swiss Ball. 4. From a prone face up position with heels on Swiss Ball and shoulders on floor bring heels up to buttocks and back while refraining from allowing the hips to sag throughout movement.
 Four-Way Torso Exercise step 5  Four-Way Torso Exercise step 6
The degree of difficulty can be adjusted by placing the Ball closer to the hips (easier) or closer to the feet (difficult). In  exercise #4 by spreading arms away from body stability is improved (easier) and by keeping arms crossed on chest stability is decreased (difficult).