anatomyrefocused

(b) A proprioceptive feedback loop lets a muscle fiber calibrate its length to optimize its ability to control eccentric movement. When external forces are higher, such as during running, the sarcomere length is reduced to give more leeway for the fiber lengthening that occurs during the eccentric phases. By recalibrating itself, the muscle becomes more efficient and helps protect the tissues by reducing the possibility of going over the peak of the force-length curve and becoming too weak to control the eccentric movement. The operating range is now adjusted to fully focus along the ascending limb of the curve and does not cross over the peak of the curve. The readjustment allows the muscle fiber to lengthen without handicapping its ability to create force—it remains strong. (Based on M. Ishikawa, J. Pakaslahti, and P. V. Komi, “Medial Gastrocnemius Muscle Behavior during Human Running and Walking,” Gait and Posture 25, no. 3 (2007): 380–84) from going over the top of the forcelength curve. If muscle fibers lengthen beyond the top of the curve, they rapidly weaken and are therefore less able to control the movement. A fiber recalibrating its length to get stronger as it lengthens makes sense for tissue protection. Think of the difference between kicking a ball for a child to catch and propelling the same ball across a soccer pitch. When we need more force, we tend to go further toward the end of joint range—we get more leverage for the intended movement, but we also put ourselves in easily compromised positions (yet another example of cost/benefit). Thankfully, the body has more than one defense mechanism—as the tissues strain, lengthen, and expand they also become stiffer.

JAMES EARLS

James has been a dedicated manual therapist for almost 30 years. During the last 20 years he has have specialized in myofascial approaches to bodywork and co-authored ‘Fascial Release for Structural Balance’ and ‘Born to Walk’.

While teaching myofascial anatomy around the world he encountered many interesting models and became especially interested in the functional movement work of Gary Gray. After being awarded the highly regarded GIFT Fellowship from the Gray Institute he managed to blend my understanding of myofascial anatomy and functional movement into his second book –‘Born to Walk’ – which has been translated into numerous languages with an updated second edition released in 2020.

His work combines my interests in functional, evolutionary and comparative anatomy to explore the ‘truths of movement’. He firmly believes that by understanding normal, everyday movement we are better able to understand the limitations our clients may experience and thereby develop appropriate, fun and individualised movement practices for them.