Episode 76: Improve Flexibility With Research-Supported Stretching Protocols| Huberman Lab

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Key Takeaways

  • Two main mechanisms of flexibility: (1) the first senses when stretch is too much and signals muscle contraction back into place; (2) the second senses excessive load and shut down the ability to contract muscles for safety
  • Without intervention, age-related declines in the range of motion (average of 1% per year) are inevitable unless you deliberately work on it
  • A consistent stretching practice can improve range of motion and offset the age-related decline
  • A dedicated range of motion practice increases flexibility and also improves posture, reduces pain, improves gait, etc.
  • Superset exercises of antagonistic muscle groups (e.g., push/pull) will offset muscle fatigue as compared to straight sets (completing all sets of push-ups before moving on to pull-ups)
  • All forms of stretching (dynamic, ballistic, static, PNF) will improve limb range of motion but static stretching post-training session or calisthenics gives the greatest gains
  • Stretching protocol: 2-4 sets of 30-second hold static stretches totaling 5 minutes, 5 days per week  
  • Ballistic and dynamic stretches are useful for improving performance but won’t necessarily increase limb range of motion as much as static stretching


Dr. Andrew Huberman, Ph.D. is a Professor of Neurobiology and Ophthalmology at Stanford University School of Medicine. His lab focuses on neural regeneration, neuroplasticity, and brain states such as stress, focus, fear, and optimal performance.

In this episode, Andrew Huberman explains the science behind a range of motion and flexibility and how to increase them by using science-supported protocols.  

Host: Andrew Huberman (@hubermanlab)

Basic Physiology Of Flexibility

  • Flexibility involves neural (nervous system), muscle, and connective tissue working together
  • The nervous system controls muscles via motor neurons which control the contraction of muscles
  • Muscles (temporarily) shorten when contracted and (temporarily) lengthen when relaxed
  • Muscle spindles wrap around muscle fibers and send information from muscle back to the spinal cord
  • If a muscle is stretched, the muscle spindle will spend information to motor neurons and cause the muscle to contract to avoid overstretching and bring the range of motion into a “safe” zone
  • Mechanism 1 – Stretch via motor and sensory neurons: motor neurons contract muscles, spindles sense stretch within a muscle, and sensory neurons send signals to motor neurons to contract and bring the body back within a safe range of motion
  • Golgi tendon organs (GTOs) sense how much load is on a given muscle and have the ability to shut down motor neurons and accompanying muscle contraction
  • GTOs make it impossible for muscles to contract
  • Mechanism 2 – Load via GTOs: when muscles are overloaded, GTOs will send a signal to shut down motor neurons and prevent muscle contraction to allow muscles to stretch and return to safety
  • Stretching consistently over time will change muscles
  • When we stretch, muscles aren’t literally getting “longer” – the myosin and actin conformation is changed
  • The length of muscle belly and location of insertions relative to connective tissue and limbs is genetically determined

 Neurological Components Of Flexibility

  • Interoception: the ability to sense what’s happening in our own body
  • Exteroception: the ability to sense things in the environment around us
  • The Insula region of the brain is responsible for processing and making sense of the external and internal world
  • Posterior insula: houses a dense collection of neurons (von Economo neurons) concerned with somatic experience, how movement makes us feel, whether to override pain and discomfort and lean in or avoid the movement  
  • Von Economo neurons: connected to brain areas that can shift state internal state from sympathetic activation (alert, stress) to parasympathetic activation (rest)
  • Von Economo neurons allow the brain to override spindle mechanisms and subtly override reflexes that would cause us to contract
  • Von Economo neurons pay attention to what’s happening in the brain and body as well as control the amount of calmness or alertness in response to stimulus
  • Experiment: while standing, try to touch toes and see how far you get, then; try again, this time contracting quadriceps muscles – you should reach farther because these muscles are antagonistic (this is thanks to GTOs)
  • If a muscle is tight, you can leverage muscle anatomy by contracting antagonistic muscle – e.g., for tight quadriceps, contract hamstrings; for tight hamstrings, contract quadriceps

Methods Of Stretching

  • Types of stretching: dynamic, ballistic, static, proprioceptive neuromuscular facilitation (PNF)
  • Dynamic & ballistic stretching involves momentum, as opposed to static stretching where positions are being held for a given time
  • Dynamic stretching: less use of momentum towards the end range of motion
  • Ballistic stretching: swinging of limbs through a full range of motion
  • Static stretching: holding stretch through end range of motion
    • Active static stretching: dedicated effort to put force behind stretch to extend the range of motion
    • Passive static stretching: relaxing into the furthest range of motion
  • Proprioception involves knowledge and understanding of where our limbs are in space and relative to our body
  • PNF example: leverages proprioceptive system – for example, using a strap while laying on back to stretch hamstring then trying the same stretch without the strap
  • To increase limb range of motion, stick to static and PNF stretches
  • Ballistic and dynamic stretches are useful for improving performance but won’t necessarily increase limb range of motion as much as static stretching

Stretching Dos And Don’ts

  • Change in flexibility is dependent on frequency and duration
  • Hold static stretches for 30 seconds to increase limb range of motion over time – more than 30 seconds is not additionally useful according to the research
  • Perform static stretches at least 5 minutes per week per muscle, distributed throughout 5 sessions per week to maintain or improve range of motion over time
  • Improvements in range of motion will take place around 3 weeks
  • Protocol: 2-4 sets of 30-second hold static stretches, 5 days per week
    • Sample protocol: 3 sets of 30-second static stretching for hamstrings x 5 times per week
  • Rest between stretching sets is not as critical as during strength or resistance training, try 1:1 or 1:2
  • It’s best to perform static stretches once core body temperature is elevated (i.e., post-workout or calisthenics)
  • Static stretching can limit performance if done before cardio or strength training workout
  • Key elements of stretching protocol: (1) feel the muscles as you stretch & stretch to the end of a range of motion at that moment (it will vary); (2) low intensity (non-painful/straining) static stretching is at least as effective as more intense stretches (pushing to pain)
  • While static stretching is best reserved for the end of the workout, it does have a place prior to exercise if it will help your body overcome limitations and put your body in a greater position of safety

Potential Benefits Of Stretching For Illness

  • Stretching induces relaxation at a local and systemic level
  • Tumor volume in cancerous mice was 52% smaller in mice in one-month stretch protocol versus control – unlikely due to stretch alone but maybe relaxation allows the nervous system to combat tumor growth more effectively
  • Pain tolerance of yoga practitioners is at least twice as high as non-yoga practitioners – likely related to increased volume of the region of the brain responsible for interoception


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