RELATIONSHIP BETWEEN MUSCLE-FIBER COMPOSITION AND FUNCTIONAL-CAPACITYOF BACK MUSCLES IN HEALTHY-SUBJECTS AND PATIENTS WITH BACK PAIN

Back muscles are important to the stability oi the lumbar spine. Muscl e fiber composition may give some indication of the functional capacit y of these muscles. This review explores the relationship between musc le fiber composition and functional capacity of back muscles. The refe rence values for the type and size of the muscle fibers found in the b ack musculature of healthy subjects and patients with back pain are al so presented. A high percentage of type I fibers, which are larger in size than type II fibers, has been found in back muscles at the thorac ic and lumbar levels. This is in accordance with the postural function of these muscles. The diameter of type II fibers is smaller in female s than males, which may partly explain the lesser strength and greater endurance capacity of back muscles in females. Due to the limited amo unt of pertinent data, no conclusive evidence is available regarding a ge-related changes in muscle fiber composition in the musculature of t he back. In patients with lumbar disorders, pathological changes and s elective atrophy of type II fibers are seen, and these can be changed with adequate exercises. Further research is suggested to address issu es related to gender, age, back pain, and exercise and their effects o n the apparent back muscle fiber composition.