The torso and shoulder are comprised of a complex series of muscles that provide a vast amount of physical mobility. Your torso muscles help support your mid and lower back, and your shoulder muscles are designed to stabilize your arms while enabling fluid rotation and flexible movement in your upper limbs.
Torso Muscles
Your torso contains flexors, entensor and side bender muscles. The rectus abdomnis extends to your mid and lower back, while the psoas and iliacus muscles stretch between your anterior thigh and lower back. The spinalis, longissimus, iliocostalis and multifidus muscles support your spine, the quadratus lumborum muscle keeps your hips in alignment and the gluteus medius muscle helps rotate your hips.
Torso Muscles Function
The multifus and quadratus lumborum muscles are most commonly associated with lower back pain. In addition, the gluteus medius can also be a common offender. A tight rectus abdomnis is common in people who slouch. However, strengthening this muscle by maintaining good posture can bring your hips into alignment and prevent back pain.
Shoulder Muscles
Your shoulders contain a complex array of important muscles. The trapezius, levator scapulae and rhomboids muscles extend from your spine or skull to the truck of your body. In addition, the pectoralis major, pectoralis minor, latissimus dorsi, teres major and deltoid stretch from your humerus bone to your body's core. Your shoulder also contains four rotator cuff muscles, the subscapularis, supraspinatus, infraspinatus and teres minor. Plus, the biceps brachii and triceps brachi are arm muscles that extend into your shoulder region.
Shoulder Muscle Functions
The pectoralis major is responsible for most of your shoulder's anterior support and movement, and the trapezius muscle supports your spine and the back of your skull. This is also the muscle you use when you reach upwards. Similarly, the latissimus dorsi helps you rotate your arm downwards and backwards. However, most of your range of motion stems from your rotator cuff muscles, the subscapularis, supraspinatus, infraspinatus and teres minor. Your shoulder's strongest muscle is the deltoid, which also creates its shape.
