The overhead press is a popular exercise used to target the shoulder, specifically the deltoid muscle. As its name implies, the overhead press involves pressing the arms over your head, usually with weight and usually at end ranges of normal shoulder flexion. If done incorrectly or by someone with inadequate shoulder motion, repeated overhead presses can contribute to both shoulder and low-back injuries.
Shoulder
Your shoulder is made up of a ball-and-socket joint. The humeral head, or ball, articulates with a part of the shoulder blade known as the glenoid. The shoulder joint resembles a golf ball sitting on a tee and is collectively referred to as the glenohumeral joint. As you reach overhead, the humeral head must translate downward as the shoulder blade, or scapula, rotates upward to preserve the integrity of the joint.
Thoracic Spine
The thoracic spine is composed of the 12 vertebrae that make up the middle back. It is characterized by a natural curvature referred to as a kyphosis. Thoracic extension, or midback, backward bending generally accounts for the last 10 to 15 degrees of overhead reach. Excessive kyphosis or increased stiffness of the thoracic spine can compromise normal shoulder biomechanics and contribute to shoulder injury.
Lumbar Spine
The lumbar spine are five vertebrae that make up your lower back. The normal curvature of the low back is referred to as a lordosis. The lumbar spine should not move during an overhead pressing motion. However, if the thoracic spine is tight, individuals preforming the overhead press can compensate with lumbar extension. This movement is often observed as an accentuation of the the normal lumbar lordosis and can contribute to pain and injury in the lower back.
Thoracic Stiffness
A common postural deviation known as a forward-head-rounded-shoulder posture can contribute to excessive thoracic kyphosis and decreased thoracic extension, making it a problem for many people. That coupled with an emphasis on pushing motions like the chest press can exacerbate muscle imbalances that perpetuate the problem. There are a number of exercises that promote thoracic extension by counterbalancing faulty postures. These include backward bending over a foam roller, side-lying arm circles and the traditional cat/camel stretch. However, because joint mechanics are complicated and compensatory strategies are hard to identify with an untrained eye, consultation with a skilled professional including a physical therapist, chiropractor or personal trainer may be helpful in identifying and addressing thoracic issues.
References
- Sports Injury Bulletin; Thoracic Spine: Sitting, Slouching and Sport; Mark Alexander
- "Management of Common Musculoskeletal Disorders -- Physical Therapy Principles and Methods, Third Edition"; Darlene Hertling, et al.; 1996
