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44 m a s s a g e & b o d y w o r k j a n u a r y / f e b r u a r y 2 0 1 7 FUNCTIONAL ANATOMY slighter build with longer, leaner muscles, naturally excelling at long duration activities (higher ratio of Type I), and others are more densely muscled with shorter, thicker muscles and excel at activities requiring strength and power (higher ratio of Type II). In addition to fi ber-type dominance differences between individuals, there are also fi ber-type dominance differences between muscles. Large, superfi cial muscles like the latissimus dorsi, pectoralis major, and gluteus maximus have a much higher ratio of fast-twitch fi bers. Smaller, deeper muscles like the supraspinatus, quadratus lumborum, and piriformis are dominated by slow-twitch fi bers. Variations in fi ber-type dominance indicate a difference in function between muscles. The large, superfi cial ones, dominated by fast-twitch fi bers, should be at rest most of the time and recruited for short- duration, powerful movements. Smaller, deeper muscles dominated by slow- twitch fi bers are postural muscles, optimally positioning the joints for long-duration and low-intensity activities. Muscles with a balanced ratio of fi ber types offer variable function. CONTRIBUTION TO DYSFUNCTIONAL PATTERNS AND PAIN Muscle pain and dysfunction can occur when large, superfi cial muscles dominated by fast-twitch fi bers are recruited for long- duration activities. For example, when the head is positioned slightly forward, the upper trapezius is recruited to maintain that unbalanced position. The fast-twitch fi bers fatigue quickly and the chemical remnants of anaerobic energy production increase the acidity of the tissue. More fi bers of this muscle are then recruited, creating a positive feedback loop of pain, hypertonicity, and dysfunction. Issues occurring in the small, deep muscles dominated by slow-twitch fi bers are of a different nature. If recruited to perform quick, powerful movements, they are slow to react and suffer damage, resulting in muscle strain and potential acute injury to surrounding structures. Also, if the superfi cial muscles in the area are hypertonic, these deeper ones may become ischemic, lacking the necessary fuel and oxygen needed for aerobic energy production. This ischemic condition is equally painful and may result in muscle inhibition and eventual atrophy. ADDRESSING FIBER TYPE WITH BODYWORK Understanding the different fi ber-type structure and function helps direct appropriate application of bodywork. Hypertonicity and resulting discomfort It is critical that clients address chronic postural issues. in the large, superfi cial muscles can be effectively addressed using neuromuscular techniques to confuse proprioceptors and reduce excessive tone. Once inhibition of these hypertonic muscles is achieved, apply methods to increase circulation in the deeper, slow-twitch dominated muscles in an effort to increase capacity for aerobic energy production. The combined effort begins to restore proper function in terms of energy production to the various muscles. While this strategy may provide immediate relief, it is critical that clients address chronic postural issues and body mechanics to alter dysfunctional recruitment strategies. It is essential that large, superfi cial muscles be retrained to remain relaxed unless called upon for short-duration, powerful movements. The small, deep muscles are reactivated as posture improves, deep circulation increases, and optimal joint mechanics are reestablished. This may require a combined effort between multiple disciplines. Christy Cael is a licensed massage therapist, certifi ed strength and conditioning specialist, and instructor at the Bodymechanics School of Myotherapy & Massage in Olympia, Washington. Her private practice focuses on injury treatment, biomechanical analysis, craniosacral therapy, and massage for clients with neurological issues. She is the author of Functional Anatomy: Musculoskeletal Anatomy, Kinesiology, and Palpation for Manual Therapists (Lippincott Williams & Wilkins, 2009). Contact her at functionalbook@hotmail.com.