Improve Flexibility with Research-​​Supported Stretching Protocols

Flexibility and Stretching

• Flexibility and stretching are fundamental to how we move, learn new movements, prevent and repair injuries, and reduce inflammation
• Stretching can even impact tumor growth
• Flexibility and stretching can be used to modulate pain tolerance, both emotional and physical

Built-​​In Flexibility

• Our nervous system, muscles, connective tissue, and skeletal system work together to maintain flexibility and restore limb positions
• Two major mechanisms ensure limbs don’t stretch too far and muscles aren’t overloaded with tension or effort: 
  • Neurons communicate with muscles and muscles communicate back to the nervous system to prevent overstretching
  • Mechanisms ensure muscles aren’t overloaded with weight or tension, preventing damage
• Leveraging these mechanisms can help increase flexibility almost immediately
  Biological Mechanisms of Flexibility
• Flexibility involves three major components: 
  • Neural (nervous system)
  • Muscular (muscles)
  • Connective tissue (surrounds neural and muscular components)
• Nervous system controls muscles 
  • Motor neurons in spinal cord cause muscles to contract
  • Sensory neurons in spinal cord sense stretch in muscles 
    • Spindle neurons wrap around muscle fibers and sense stretch
• Two key mechanisms for flexibility: 
  • Spindle neurons sense stretch and activate contraction of muscles when stretch is excessive
  • Golgi tendon organs (GTOs) sense loads and shut down motor neurons when tension is excessive, preventing muscle contraction

Stretching and Flexibility

• Dedicated stretching practice can improve limb range of motion
• Flexibility decreases with age 
  • 10% decrease every ten years from age 20 to 49
  • Continues to decrease after age 49, but not necessarily linearly
    Flexibility and the Nervous System
• Flexibility decreases with age, but can be maintained or improved through practices like yoga, stretching, and resistance training 
• The nervous system plays a role in flexibility and injury prevention
• The spinal cord, muscles, and connective tissue work together to control limb range of motion and load handling

The Brain’s Role in Flexibility

• The insula is a brain region responsible for interpreting internal and external sensations 
  • The anterior insula focuses on external sensations like smell and vision
  • The posterior insula focuses on internal sensations and body movements
• Van Economo neurons are large neurons found in the posterior insula 
  • Uniquely enriched in humans, also found in whales, chimpanzees, and elephants
  • Involved in integrating body movements, pain, and discomfort
  • Can drive motivational processes to overcome discomfort if directed toward a specific goal

Stretching and the Nervous System

• Van Economo neurons can help evaluate whether to relax into a stretch or push through discomfort
• These neurons can also shift internal states from alertness/​​stress to relaxation, allowing for better stretching
• The brain’s upper motor neurons can override lower motor neurons, allowing for control and adaptation in stretching and movement
  Van Economo Neurons and Muscle Spindle Mechanisms
• Van Economo neurons play a role in decision-​​making and body control 
  • Found in deeper parts of the brain
  • Can override reflexes and pain signals
  • Uniquely enriched in humans
• Muscle spindle mechanisms affect flexibility and range of motion 
  • Antagonistic muscles can be used to increase flexibility
  • Example: contracting quadriceps to increase hamstring flexibility
  • Neural activation patterns can restrict or enhance range of motion

Short-​​term vs Long-​​term Flexibility

• Short-​​term flexibility changes are due to neural activation patterns 
  • No significant changes in muscle or tendon length
• Long-​​term flexibility changes involve muscle fiber adaptations 
  • Sarcomeres within muscle fibers can change their confirmation
  • Myosin and actin components within sarcomeres play a role in muscle contraction and flexibility
    Stretching and Muscle Flexibility
• Stretching involves changes in neural and connective tissue 
• Muscles have fibers, sarcomeres, myosin, and actin
• Muscle length and insertion points are genetically determined
• Stretching can change the resting state of a muscle

Types of Stretching

• Dynamic stretching: Controlled movement through a range of motion 
  • Example: Swinging arm up overhead and bringing it down
• Ballistic stretching: Involves more momentum, especially at the end range of motion 
  • Example: Swinging foot out to stretch the hip joint
• Static stretching: Holding the end range of motion, minimizing momentum 
  • Example: Bending over at the waist and touching toes
  • Can be subdivided into active or passive
• PNF stretching (Proprioceptive Neuromuscular Facilitation): Leverages mechanisms like spindle activation to increase flexibility

Interleaving Push and Pull Exercises

• Interleaving push and pull exercises can improve performance
• Antagonistic muscles relax when their opposite muscle group is activated
• Example: Alternating between push-​​ups and pull-ups
• Challenges: May require occupying multiple sites within a gym

Increasing Flexibility and Range of Motion

• Focus on the most efficient stretching methods
• Consider dynamic, ballistic, static, and PNF stretching
• Determine which type of stretching is best for individual goals and limitations
  Stretching Techniques and Their Effects
• Four major categories of stretching: 
  • Static stretching
  • Dynamic stretching
  • Ballistic stretching
  • Proprioceptive Neuromuscular Facilitation (PNF)
• Static stretching can be active or passive 
  • Active: dedicated effort to extend the range of motion
  • Passive: relaxation into a further range of motion
• PNF stretching leverages proprioceptive feedback from sensory neurons in joints, connective tissue, and muscles 
  • Can be done with or without straps, machines, weights, or training partners
• Studies show that static stretching, including PNF, is more effective for increasing long-​​term range of motion than dynamic and ballistic stretching 
  • Dynamic and ballistic stretching can be useful for improving performance in specific movements and sports, but carry more risk due to the use of momentum

Static Stretching Duration and Frequency

• Study by Bandy et al. found that a 30-​​second duration is effective for increasing range of motion 
  • No increase in flexibility occurred when the duration was increased from 30 seconds to 60 seconds, or when the frequency was increased from one to three times per day
• Holding static stretches for 30 seconds appears to be sufficient to stimulate an increase in limb range of motion over time

Sets of Static Stretching

• The issue of sets is important for maximizing range of motion improvement without causing injury or requiring constant stretching throughout the day
• In the context of cardiovascular exercise, doing at least 150–200 minutes per week of zone two cardiovascular exercise is useful for cardiovascular health and other aspects of health
  Stretching for Strength, Hypertrophy, and Range of Motion
• Ideal stretching for strength and hypertrophy: 6–10 sets per week per muscle group 
  • Some direct work, some indirect work (e.g., pulling exercises targeting lats and biceps)
• Maintaining or improving range of motion requires dedicated work 
  • Static stretching with 30-​​second holds is most effective
• Review by Thomas Edwin Thomas and Palma (2018) on stretching typology and duration 
  • Static stretching protocols showed significant range of motion improvements compared to ballistic or PNF protocols
  • At least 5 minutes of stretching per week is necessary for range of motion improvements
  • Performing stretching at least five days a week for at least 5 minutes per week using static stretching is beneficial

Stretching Protocols

• Static stretching: holding a stretch for 30 seconds per set
• Aim for 5 minutes per week of static holds, distributed throughout the week
• Example protocol: 2–4 sets of 30-​​second static hold stretches, five days per week 
  • Holding stretches for 60 seconds per set may allow for fewer days per week
• Rest periods between stretching sets not well-​​defined in research 
  • Possibly double the amount of time for rest (e.g., 30 seconds stretch, 60 seconds rest)

Warming Up for Stretching

• Raising core body temperature before stretching can help avoid injury
• If already warm from other physical activities (e.g., running, weight training), static stretching can be done immediately after those sessions
  Warming Up and Stretching
• Warming up the body with 5–10 minutes of easy cardiovascular exercise or calisthenic movements is ideal before stretching 
• Static stretching is most beneficial after resistance training or cardiovascular training 
  • Some studies suggest static stretching before these activities can limit performance
• Static stretching after exercise or a brief warm-​​up is recommended

Stretching Frequency and Duration

• Minimum of 5 minutes per week to elicit a significant response
• Five days per week is the minimum recommended frequency for significant range of motion improvements
• Longer hold static stretches (e.g., 60 seconds) can be done less frequently (e.g., every other day)

Types of Stretching and Range of Motion Improvements

• All forms of stretching (static, active, passive, ballistic, PNF) can improve limb range of motion
• Static stretching provides the greatest gains in limb range of motion (20.9% increase on average)
• Ballistic stretching and PNF stretching also provide substantial improvements (11.65% and 15% increases, respectively)

PNF Stretching and Autogenic Inhibition

• PNF stretching leverages spindle mechanisms and golgi tendon organ (GTO) mechanisms
• Activation of GTOs in one muscle group can inhibit the spindles in the antagonistic muscle group
• This is called autogenic inhibition and can help improve range of motion

Benefits of Improved Limb Range of Motion

• Reduces age-​​related losses in flexibility
• Improves posture, balance, and physical performance
• Can aid in pain management and headache relief
• Maintaining and improving limb range of motion is essential for overall neuromuscular health and longevity
  Interleaving Training for Better Results
• Interleaving push and pull for strength, hypertrophy, and range of motion training can lead to better results in less time 
• During rest periods, you can stretch the opposite muscle group or use PNF training
• Various protocols can be constructed to suit individual goals

Anderson Method for Range of Motion

• Focus on feeling the stretch in the relevant muscle groups, rather than achieving a specific range of motion each session
• Range of motion may vary day-​​to-​​day due to internal and external factors
• Evaluate range of motion over time as the key parameter

Low Intensity vs. Moderate Intensity Stretching

• A study compared low intensity (microstretching) and moderate intensity static stretching on active and passive ranges of motion
• Low intensity stretching (30–40% of pain threshold) led to greater increases in range of motion than moderate intensity stretching (80% of pain threshold)
• Low intensity stretching may be more beneficial and have a lower risk of injury

Takeaways

• Low intensity static stretching appears to be more effective for increasing range of motion
• Focus on feeling the stretch in the muscles, rather than achieving a specific range of motion
• Interleaving different training methods can lead to better results in less time
  Microstretching and Neural Mechanisms
• Low intensity stretching accesses spindle and GTO mechanisms 
• Can shift activation of sympathetic (stress) and parasympathetic (relaxation) nervous systems
• Data on whether to do ballistic or static stretching before training is inconclusive

Stretching Before Training

• Static stretching can be beneficial if it helps overcome tightness or limitations in neuromuscular connective tissue
• Can improve form and stability during training
• Dynamic or ballistic stretching can warm up neural circuits, joints, connective tissue, and muscles
• Can improve range of motion and performance accuracy

Stretching for Relaxation and Inflammation Reduction

• Study by Dr. Helene Langevin: Stretching Reduces Tumor Growth in a Mouse Breast Cancer Model
• Brief whole-​​body stretching increases activation of the parasympathetic nervous system
• 10 minutes of daily stretching for four weeks reduced tumor volume by 52% in mice
• Possible link between inflammation and immune exhaustion mechanisms

Insular Cortex and Stretching

• Insular cortex plays a role in the perception of bodily sensations, emotions, and homeostasis
• Stretching may have an impact on the insular cortex and its functions