The musculoskeletal system provides structural support, enables movement, and protects internal organs. It consists of bones (the skeleton), skeletal muscles (the motors), and the connective tissues that link them (tendons, ligaments, cartilage, fascia). This is the organ system that somatics works with most directly — and the system whose dysfunction produces a significant proportion of chronic pain.
Bones
The human skeleton contains 206 bones. Bones provide:
- Structural support — the rigid framework that holds the body upright against gravity
- Protection — the skull protects the brain, the ribcage protects the heart and lungs, the vertebral column protects the spinal cord
- Movement — bones serve as levers that muscles pull on to produce movement
- Mineral storage — bones store calcium and phosphorus, releasing them into the blood as needed
- Blood cell production — red bone marrow (inside certain bones) produces red blood cells, white blood cells, and platelets
Bones meet at joints — the points of articulation that determine the range and type of movement possible. Joint types include hinge joints (elbow, knee), ball-and-socket joints (hip, shoulder), pivot joints (atlas-axis at the top of the spine), and gliding joints (wrist, ankle). The range of motion at a joint is determined by the bone shapes, the ligaments (connective tissue bands connecting bone to bone), and the tone of the muscles crossing the joint.
Skeletal muscle
Skeletal muscle is the tissue that produces voluntary movement. Each muscle is composed of bundles of muscle fibers (individual muscle cells), each fiber containing contractile proteins (actin and myosin) that slide past each other when the muscle contracts.
Contraction occurs when a motor neuron releases acetylcholine at the neuromuscular junction (the synapse between the motor neuron and the muscle fiber). Acetylcholine binds to receptors on the muscle fiber, triggering an action potential that leads to calcium release inside the fiber, which enables the actin-myosin sliding that shortens the muscle. This entire sequence — from motor cortex command to dorsal horn relay to motor neuron to neuromuscular junction to muscle contraction — is the motor pathway that somatic practices seek to refine.
Muscle tone — even at rest, skeletal muscles maintain a baseline level of contraction (tone) that keeps the body ready for movement and maintains posture. Tone is regulated by the nervous system through a feedback loop involving:
- Muscle spindles — sensory receptors embedded in the muscle that detect stretch. When a muscle is stretched, spindles send signals to the spinal cord, which triggers a reflexive contraction (the stretch reflex) to resist the stretch. This reflex maintains posture and protects against overstretching. Proprioception — the sense of body position and movement — is mediated largely by muscle spindles.
- Golgi tendon organs — sensory receptors in tendons (where muscles attach to bones) that detect tension. When muscle tension is too high, Golgi tendon organs trigger a reflexive relaxation (the autogenic inhibition reflex) to protect the muscle and tendon from damage.
Thomas Hanna’s sensory-motor amnesia describes what happens when the cortex loses the ability to voluntarily control muscle tone. Muscles become locked in habitual contraction patterns — held by reflexive circuits that the cortex can no longer override. Pandiculation restores cortical control by engaging the same motor neurons that drive the habitual contraction, then slowly releasing, retraining the nervous system’s control over the muscle.
Fascia
Fascia is a continuous network of connective tissue that envelops, separates, and connects muscles, organs, bones, and nerves throughout the body. It is not an inert wrapping but a dynamic tissue with contractile properties, sensory innervation, and mechanical significance.
Structural Integration (Rolfing) works primarily with fascia, treating it as a continuous tension network. The tensegrity model describes this: bones are compression elements floating in a continuous tension network of fascia. Force applied at any point distributes through the network — which is why a restriction in the thoracic fascia can affect hip mobility, and why fascial manipulation at one location can produce effects at distant sites.
Movement
Movement is produced by muscles pulling on bones across joints. But useful movement — coordinated, efficient, adaptive movement — requires the nervous system to integrate sensory feedback (proprioception, vision, vestibular input) with motor output in real time.
The Feldenkrais Method works with this integration explicitly. By reducing effort and increasing sensory attention during movement, Feldenkrais exploits the Weber-Fechner law (reducing signal intensity increases the nervous system’s ability to detect differences) to improve proprioceptive resolution. The result is movement that is more refined not because the muscles are stronger but because the nervous system’s coordination is better.
Musculoskeletal pain
The musculoskeletal system is the most common source of chronic pain. Low back pain, neck pain, shoulder pain, knee pain, and headaches (often driven by cervical and cranial muscle tension) collectively affect hundreds of millions of people worldwide.
The critical insight from modern pain science is that musculoskeletal pain, especially chronic musculoskeletal pain, is often not proportionate to the structural findings. Disc herniations are present in many asymptomatic people. Degenerative joint changes are universal with aging and do not reliably correlate with pain. Muscle tension patterns (Hanna’s sensory-motor amnesia) can produce significant pain without any structural pathology visible on imaging.
This does not mean musculoskeletal pain is imaginary. It means the source is often in the nervous system’s processing of musculoskeletal information (central sensitization, altered motor patterns, habitual muscle tension) rather than in structural tissue damage — and therefore the treatment must address the nervous system, not just the tissue.