Massage Therapy Journal Winter 2024

Winter 2024 • 75

How Spindle-Stim Techniques Can Help Many manual and movement therapies reduce chronic muscle hypertonicity and improve muscular balance and posture. However, a regularly overlooked issue is the lack of tone in neurologically inhibited muscles. In these cases, the massage therapist may need to manually stimulate tone in chronically weakened or atrophied muscles to “relink” the body-mind connection. Spindle-stim techniques are valuable for waking up muscles. Exploiting the stretch reflex. Spindle-stim techniques work through muscle spindles and the stretch reflex. Massage therapists know that muscle spindles are embedded within skeletal muscles and are responsible for detecting changes in muscle length, as well as the rate of those changes. They provide critical feedback to the central nervous system, enabling the body to maintain muscle tone, posture and coordinated movement. At the core of muscle spindles are intrafusal fibers, which are different from the main contractile muscle fibers known as extramural fibers. Intrafusal fibers include nuclear bag fibers that are sensitive to the rate of stretch, as well as nuclear chain fibers, which are responsive to static muscle length. Sensory endings wrap around these fibers and relay information about muscle stretch to the spinal cord and brain. Gamma motor neurons innervate intrafusal fibers, adjusting their sensitivity. By causing intrafusal fibers to contract, gamma motor neurons maintain tension within the spindle, ensuring it remains sensitive to changes in muscle length during muscle contractions. This interaction helps maintain a smooth length-tension balance between intrafusal and extrafusal fibers. How Do Spindle-Stim Techniques Work? Spindle-stim techniques cause rapid length changes in the agonist muscle’s extrafusal fibers, triggering intense firing of the intrafusal fibers. The intrafusal fibers work hard to maintain a constant length-tension relationship with the

a reflex is absent, our muscles stop contracting, and the body comes to rest. However, the nervous system is designed to optimize efficiency. Repeatedly performing the same movements or postures prompts the nervous system to streamline these actions, reducing the cognitive load required for their execution. As a result, when the brain learns a muscle pattern, it begins to keep the muscles involved in that pattern partially contracted all the time, even when the muscles should be at rest. The Downside of Muscle Memory While the efficiency gained through muscle memory has many benefits (you don’t have to think about brushing your teeth or your tennis serve), it also has drawbacks because we’re developing facilitated muscle patterns every time we slump in front of a computer or TV, carry a bag on one shoulder, or stand with an arched back and locked knees. Just like the tennis pro, we’re training ourselves. But instead of a championship trophy, we get stiffness, restricted movement, compensation and pain. Over time, the brain regards the continuous contractions of certain muscles as normal, impairing the proprioceptive feedback loop between muscles, joints and the brain. The sensory-motor cortex, which controls voluntary muscle actions, loses its ability to accurately sense and control muscle tone and movement. The brain “forgets” how to relax and contract muscles properly. As a result of this body-mind disconnect, affected muscles become weak because they are either constantly contracted (and therefore fatigued) or inhibited (and therefore underutilized). Disruptions to the normal firing patterns of the motor units within these muscles result in poor synchronization of motor neuron activity. Some motor units become overactive, while others remain underactive, leading to a lack of coordinated muscle action, loss of fine motor control and decreases in strength.

We use the term muscle memory as an analogy because it captures the sense that our muscles are performing tasks in a coordinated way without

requiring conscious thought.

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