How to Improve Flexibility Through Stretching

TL;DR

Flexibility depends on coordinated activity across the nervous system, muscles, and connective tissue. Stretch-sensitive muscle spindles and load-sensitive Golgi tendon organs protect the body, while brain circuits can reduce alertness, increase relaxation, and help a person tolerate productive discomfort during stretching. Effective practice also requires choosing suitable stretching methods, intensity, frequency, warm-up, and timing relative to exercise.

Transcript

Welcome to Huberman Lab Essentials, >> [music] >> where we revisit past episodes for the most potent and actionable science-based tools for mental health, physical health, and performance. I'm Andrew Huberman and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today we are going to discuss the science and practice ... Read More

Key Insights

• Flexibility is governed by the combined behavior of the nervous system, muscles, and connective tissue. These components are interwoven rather than independent, so changes in range of motion reflect more than the physical length or mechanical properties of a single muscle.
• Motor neurons are nerve cells in the spinal cord that cause muscles to contract. They release acetylcholine onto muscles, enabling muscular contraction and limb movement through changes involving muscle length and the function of connective tissues such as tendons and ligaments.
• Muscle spindles are sensory connections that wrap around muscle fibers and detect stretching. When a muscle elongates because a limb's range of motion increases too much, spindle signals can activate motor neurons, contract the muscle, and return the limb toward a safer range.
• Golgi tendon organs are sensory neurons associated with tendons that detect how much load is placed on a muscle. When force could damage muscles, tendons, joints, or ligaments, these organs can inhibit motor neurons and make continued muscular contraction impossible.
• Interoception is the nervous system's ability to sense conditions inside the body, including organ discomfort, pain, and feelings arising from the gut. The insula interprets much of this internal information and helps classify bodily experiences as desirable or aversive.
• The posterior insula is primarily concerned with internal bodily experience. It helps evaluate whether a sensation, movement, environment, or activity should be continued or avoided, connecting somatic information with approach and withdrawal responses.
• Von Economo neurons integrate information about body movement, pain, discomfort, and motivation. These unusually large neurons can support persistence when a person decides that discomfort serves a specific goal, and they connect with brain regions capable of changing internal physiological state.
• Relaxing into a stretch involves shifting from sympathetic alertness or stress toward parasympathetic relaxation. Higher brain circuits can influence spinal and muscular mechanisms, especially the spindle response, allowing controlled decisions and internal state changes to affect how stretching discomfort is experienced.

Questions & Answers

Q: What determines flexibility and range of motion?

Flexibility and range of motion depend on three major components: the nervous system, muscles, and connective tissue. The nervous system activates muscles and receives sensory information about stretch and load. Muscles generate force and movement, while tendons, ligaments, and other connective tissues participate in that movement. These components are woven together and jointly regulate how far a limb can move.

Q: How do motor neurons make muscles contract?

Motor neurons in the spinal cord cause muscles to contract by releasing a chemical called acetylcholine onto the muscles. That chemical signal activates contraction. Contracting muscles contribute to limb movement by changing muscle length and affecting connected structures, including tendons and ligaments. This motor pathway works alongside sensory pathways that continually report muscle stretch and tendon load back to the spinal cord.

Q: What are muscle spindles, and how do they affect stretching?

Muscle spindles are sensory nerve connections that wrap around muscle fibers and detect how much those fibers are stretching. If a muscle elongates excessively as a limb moves through a greater range, the spindles send electrical signals to the spinal cord. Those signals activate motor neurons, causing the muscle to contract and bringing the limb back toward a safer range of motion.

Q: What do Golgi tendon organs do during muscular effort?

Golgi tendon organs are sensory neurons closely associated with tendons, and they detect the load placed on a muscle. If someone tries to move a load that could rip muscles or tendons, disrupt joints, or tear ligaments, these organs can send signals into the spinal cord that inhibit motor neurons. This shutdown prevents the threatened muscle from continuing to contract.

Q: What is the difference between muscle spindles and Golgi tendon organs?

Muscle spindles sense stretching within muscle fibers and can activate motor neurons so the muscle contracts when a limb moves beyond a safe range. Golgi tendon organs sense load near the tendons and can inhibit motor neurons when muscular force becomes dangerous. Both operate as protective sensory mechanisms, but one primarily responds to stretch while the other responds to load.

Q: How does the insula influence the experience of stretching?

The insula is a brain region associated with interpreting internal bodily conditions. Its posterior portion is especially concerned with somatic experience and helps evaluate sensations as desirable experiences to continue or aversive experiences to stop. During stretching, this system processes information about limb position, pain, and discomfort, helping shape whether a person relaxes, persists, or withdraws from the sensation.

Q: What role do von Economo neurons play in tolerating discomfort?

Von Economo neurons are exceptionally large neurons in the posterior insula that integrate body movement, pain, discomfort, and motivation. They can help a person continue through discomfort when that sensation is judged useful for a specific goal. Their connections to other brain areas also allow internal state to shift between sympathetic alertness and parasympathetic relaxation, influencing responses to stretching.

Q: What does it mean to relax into a stretch?

Relaxing into a stretch means reducing relative alertness or stress and increasing parasympathetic activation. Brain circuits involving the insula and von Economo neurons can evaluate bodily discomfort and influence lower-level neural mechanisms, especially muscle spindle responses. This top-down control can help a person remain calm and intentionally tolerate a controlled stretch instead of automatically reacting to every uncomfortable sensation.

Summary & Key Takeaways

• Flexibility and range of motion emerge from three interconnected components: the nervous system, muscles, and connective tissue. Motor neurons release acetylcholine to make muscles contract, while sensory neurons monitor what happens within muscles and tendons. These interacting systems regulate movement and help keep the limbs within safe operating ranges.

• Muscle spindles detect the stretching of muscle fibers and can initiate muscle contraction when a limb moves too far. Golgi tendon organs perform a different protective function by detecting muscular load. When a load threatens muscles, tendons, ligaments, or joints, these sensory neurons can inhibit motor neurons and prevent further contraction.

• The brain can influence protective reflexes and the experience of discomfort during stretching. The posterior insula evaluates internal bodily sensations, while von Economo neurons integrate movement, pain, motivation, and physiological state. By shifting from sympathetic alertness toward parasympathetic relaxation, higher brain circuits may help a person relax into a controlled stretch.