Let us consider how the chronic shortening of just one muscle, which happens to be a core muscle, can impede performance and cause imbalances that lead to injuries.
The rectus abdominis is a good example of an over worked muscle. As this muscle is overworked, the other core muscles are often ignored. Crunches, leg raises and exercises using abdominal machines all work only in the sagittal plane, therefore limiting “benefit” to muscles that produce hip and trunk flexion (note that repetitive trunk flexion places increased injury-causing stress on the intervertebral discs of the lumbar spine).
It is imperative to train the core in a multi-planar fashion, especially the transverse plane, in order to create stabilization in the trunk, and in effect more optimal posture, strength and motion in the entire body.
The following is a common example of the result of overworking the rectus abdominis. A tight rectus abdominis, when creating tension, or pull, on its upper and lower attachments, including the anterior pelvis, anterior ribs and inferior sternum, produces a flexion force in the trunk. This has consequences beyond the immediate structures affected.
These consequences include a chain of effects that begin with shortening and tightening of the pectoral muscles. These muscles will exert an inferior tension on the clavicle, superior ribs and the anterior scapula and will assist in internally rotating the humerus. The force of gravity also contributes to the internal rotation of the glenohumeral, or shoulder joint, as the trunk flexes forward. Internal rotation of the humerus tensions and lengthens the external rotators of the shoulder which in combination with the tension exerted on the anterior scapula by the pecs, will bring the scapula into protraction, lengthening and weakening the middle and lower trapezius and rhomboid muscles (note that a tight latissimus dorsi can also be a primary contributor to internal rotation of the humerus). The internally rotated humerus and protracted scapula will place the rotator cuff muscles at a biomechanical disadvantage in dynamically stabilizing the glenohumeral joint. The cuff will not function effectively, increasing the risk of injury.
The reaction of the cervical spine is two-fold. The lower segments of the cervical spine follow the forward and downward movement of the trunk, and they themselves flex, causing lengthening and weakening of the deep cervical flexor muscles. This can also stress the outer layer of the intervertebral discs, which over time, may lead to injury.
Of course, if the lower cervical spine flexes forward, the head will follow, and if this force is not countered, gravity will cause the head to fall forward. In order to prevent this from happening, tension will develop in the cervical extensors, including the upper trapezius, splenius, semispinalis, spinalis and sub-occipital groups, which attach to the base of the skull. The upper cervical segments including the base of the skull are extended, shortening the sub-occiptal muscles. This extension will allow the skull to remain somewhat level as it rests on the atlas, or the uppermost cervical vertebra.
The overworking of the upper trapezius muscle and lengthening and weakening of the middle and lower trapezius and the rhomboids will also contribute to early elevation of the scapula with shoulder motion. This will worsen the position of the glenohumeral joint and will further stress the rotator cuff.
Although this example has been limited to the rectus abdominis, it is important to understand that single muscles are rarely the isolated culprits in postural distortions and biomechanical dysfunction. An exception would be an acute specific muscle injury that has not healed correctly and has caused compensatory overloading in other areas. Because muscles act synergistically and as agonists and antagonists, there is usually more than one contributor. There are also connections between muscles through tough fascial connective tissue, which help to transmit forces between tissues. These cases of dysfunction can be rooted in other parts of the body, as the musculoskeletal system functions as a whole.
Not only will these faulty positions and compensatory biomechanics cause an athlete to move inefficiently. Over time they may lead to degenerative processes in the soft tissues and joints that will lead to further injury and impairment. The neurological system also adapts to these changes, applying muscle memory, as it controls the musculature. Training this system is essential in developing healthy neurological pathways and muscle firing patterns. This is achieved through the methods mentioned above – using medicine balls, balance boards and stability balls and challenging the neuromuscular system.
Any of the muscles mentioned above may be the source of dysfunctional patterns. However, it will most likely be a combination of them that will be the cause. For this reason, it is important to follow the entire kinetic chain when assessing and treating these conditions.
1. McGill, S, Ultimate Back Fitness and Performance: Ontario. Wabuno Publishers. 2004.
2. Kendall FP, McCreary EK, Provance PG. Muscles: Testing and Function. 4th ed. Philadelphia: Lippincott Williams and Wilkins. 1993.
About the Authors
Charles DeFrancesco is the owner of the education program at Westchester Sports and Wellness (www.fitandfunctional.com). He is also a consultant for Pure Fitness Group, LLC and Fit and Functional, LLC. He is certified by the National Academy of Sports Medicine (NASM) and by the National Federation of Professional Trainers (NFPT). He is also USAW Olympic lifting certified and Equinox Fitness Group Prenatal certified. Charles has completed specialty courses for Functional Exercise Specialist, Cardiac Conditions (AFPA), attended EFTI, and has over 5,000 hours of clinical experience. He is the NFPT workshop coordinator for the Northeast region, and currently sits on the NFPT Board of Education. He is also a board member of the Ethics and Safety Compliance Standard for personal trainers. Charles is the main author of the Principles of Functional Exercise manual and A Squash Player’s Training Handbook.
Dr. Robert Inesta is a Certified Chiropractic Sports Practitioner and a Certified Strength and Conditioning Specialist. His extensive post graduate training consists of functional rehabilitation, functional soft tissue therapy and biomechanics, clinical neurophysiology and electrodiagnosis and nutrition. He is a certified provider of Active Release Techniques, Graston Technique and Kinesiotaping. Dr. Inesta’s main goal is to help his patients to reach their goals in the most efficient and effective way. He has lectured on topics including sports medicine, functional training, biomechanics, injury prevention and nutrition and has co-authored articles on functional training. He is also a co-author of the training manuals of the National Federation of Professional Trainers.