The horse stance vertical exercise can be used to increase stability of the low back. This exercise increases the endurance of the supporting musculature.
This stretch is aimed at stretching out the hip flexor muscles (predominately psoas and iliacus). These muscles can become tight with prolonged sitting and can be a factor in low back stiffness.
Pec minor originates from the top of the scapular at the coracoid process and inserts into ribs 3, 4, and 5. When this muscle is short it can contribute to rounded shoulders and shoulder issues such as impingement.