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Physiology of stretching
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- 2. Try this out! Musculoskeletal Biomechanics are voluntary actionstriggering a chain of psychological responsesALL of this : without our conscious awareness!
- 3. Physiology of Stretching •Conscious biochemical reactions influence unconscious physiological responses • Moving the body into a yogasana initiates a cascade of these biomechanical and psychological events
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- 5. Spinal Cord ReflexArc • Regulate tension & length of skeletal muscle contractile elements • Automatic response to biomechanical actions Muscle contracts/ stretches Receptors alert CNS CNS signals muscle to respond appropriately Muscle Relaxes/ Contracts • We are unaware of entire process • 3 major spinal cord reflexes discussed: Muscle Spindle, Reciprocal Inhibition, Golgi Tendon Organ
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- 7. Methods of Stretching Ballistic Jumpingtype actions used Helps “reset” muscle length to that attained in previous practice e.g. Sun Salutation Passive Body weight, gravity, agonist/synergist muscle groups used Position of stretch held for long to “acclimate” stretch receptors Affects Muscle Spindle Receptors primarily. Lengthens noncontractile elements of muscle Facilitated Brief contraction of muscle targeted for stretch This stimulates GTO receptors. Spinal cord then signals muscles to relax The “Slack” thus created is taken up by deepening the stretch
- 8. Stretching and Endorphins •Endorphins are responsible for a variety of physiological responses • Including those bringing sense of relaxation and wellbeing after yoga practice • Stretching triggers release of these neuroendocrine factors
- 9. Key Concepts • Agonist– Antagonist • Contraction – Extension • Activation – Inhibition • Excitatory – Inhibitory Nerve Impulses Quadriceps – agonists - contract Hamstrings – antagonists - relax Hamstrings – agonists - contract Quadriceps – antagonists - relax KneeFlexion KneeExtension The nerve impulse resulting in contraction of the quadriceps = excitatoryThe nerve impulse to the hamstrings = inhibitory
- 10. Muscle Spindle StretchReceptor • Muscle stretches > signals spinal cord > Muscle contracts and resists stretch “Spinal Cord Reflex Arc” • Forcing a stretch intensifies firing of spindle causing muscle to contract • This blocks deepening of a stretch. • Instead “dissolve” the blockages slowly by working with the spinal reflexes Detects changes in length & tensionHolding a stretch for 30-60 sec causes the muscle spindle to decrease its firing, and the muscle begins to relax ! Backing part way out of the stretch also decreases its firing, relaxing the muscle and allowing a deeper stretch “Reassure” the Spindle that you are carefully stretching the muscle.
- 11. Padahastasana / Uttanasana Hamstringsstretched Hamstrings Relaxed Activating the quadriceps to stretch the hamstrings
- 12. Stretching the ErectorSpinae Activating the psoas to stretch the erector spinae Relaxing the erector spinae Practice tips: 1) Back off approximately 20% from a full stretch. Make sure you feel a mild stretch so that some of the muscle spindles are still firing. 2) Hold the milder stretch for 3 to 4 breaths to acclimate the muscle spindle and reassure it that you are stretching safely. 3) Then, with control, carefully go deeper into the pose by engaging the opposing muscle group.
- 13. GTO Contraction InhibitsRespondsto Muscle Spindle Receptors Stretch ActivatesMuscleResponds to So, You can activate an inhibited muscle
- 14. Reciprocal Inhibition Key Concepts: •When Agonist Contracts – Antagonist Relaxes • Unconscious Process through primitive spinal cord reflex arc • We can consciously access this reflex arc to deepen & improve our Asanas • Equivalent to Ha/Tha, Yin/Yang, Spanda/Nishpanda: Balanced energy in body
- 15. RI e.g. Paschimottanasana •Quadriceps – agonist, hamstring - antagonists. • Consciously engaging the quadriceps also signals the hamstrings to relax. • This takes place via the spinal cord. • Helps to get a bit deeper in this pose. • Added biomechanical benefits of improved alignment in your pose.
- 16. • Detects changesin tension • Acts like a “circuit breaker” signaling muscle to relax • v/s spindle: signals muscle to contract • Basis of PNF • May seem counterintuitive • Used to “dissolve” blocks and deepen asanas. Golgi Tendon Organ
- 17. Contract the muscleyou want to lengthen Increased tension at the MTJ GTOs recruited ( > in normal stretching) Spinal Cord signals muscles to relax, creating a ‘slack’ in the muscle Move deeper into the Asana Proprioceptive Neuromuscular Facilitation (Facilitated Stretching)
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- 19. Practice tips: 1) Ifnew to yoga, spend a few months conditioning your body first before using these powerful techniques to deepen stretches. 2)Remember, GTO is there to protect the tendon from injury. Never overdo its limits. Never contract the target muscle more than 20% of its maximum force. 3) The force generated by contracting muscles is transmitted to the joints “Joint reaction force”. Thus always protect your joints by maintaining them in natural alignment while stretching. In case of joint pain, back off from the stretch and stop. 4) Focus on one muscle group at a time, limit your PNF stretching to one asana per session. Limit to 2-3 cycles of this technique. 5) Allow 48 hours for recovery before repeating this technique. 6) Always practice under guidance of an experienced and qualified teacher
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- 22. Combining Biomechanics &Physiology in Stretching: JanuSirsasana In final pose, apply moderate stretch to Hams (straight leg) • This stimulates muscle spindle to fire, thus a reflex contraction of the hams Bend knee to lighten the stretch of hams, releasing their insertion on lower leg • Hold for 2-3 breaths as spindle accommodates to lighter stretch Contract Quads to straighten knee & draw Hams out to length, moving the insertion at knee away from origin • This actions signals Hams to further relax
- 23. Attempt to pressthe heel into the ground by contracting the Hams • This increases tension at MTJ & stimulates GTO to fire. Spinal cord then signals Hams to relax Contract Quads to straighten the knee & move the insertion of Hams away from origin. • This takes up the slack created by the relaxation response. Quad contraction creates RI, further relaxing the Hams The Psoas tilts the pelvis forward moving the hams origin away from insertion • Bending the elbows by contracting biceps bends the trunk forward, deepening the asana
- 24. Practice tips: 1) Alwaysbuild contraction of a muscle gently and slowly. This aids to minimize the risk of injury and soreness. 2) Learn to "regulate" the force of muscle contraction, especially those of large muscles like the quadriceps. 3) Combine reciprocal inhibition with the technique outlined for the muscle spindle to attain greater relaxation of the muscles you are stretching. 4) Allow ample time for recovery between practices. 5) Always practice under the guidance of an experienced teacher. 6) Always, in your particular case, consult your health care provider before doing yoga or any exercise program.
Editor's Notes
- #12 For fig 1: Carefully bend forward until you feel a moderate stretch. The muscle spindles of the hamstrings and erector spinae will fire in response to this stretch and send a signal to the spinal cord. This is the first part of the reflex arc. The second part is the outgoing signal from the spinal cord to the muscle. This involves the motor nerve and stimulates the muscle to engage. This contraction of the hamstrings and erector spinae is part of what may prevent deepening of the posture. Fig 2: "Dissolve" reflex contraction of stretched muscles by slightly relaxing the stretch. This decreases the firing of the muscle spindle stretch receptors. You can do this for the hamstrings by slightly bending the knees. Hold this milder stretch for a few breaths. Fig 3: Once the muscle spindle acclimates to the milder stretch, activate the quadriceps to straighten the knees and deepen the pose. Engaging the quadriceps inhibits the reflex contraction of the hamstrings caused by the muscle spindle. It may seem counter-intuitive, but we can actually deepen a stretch by first backing off on the stretch.
- #13 For fig 1 : Here the same reflex arc goes into action for the erector spinae muscles. The muscle spindle signals that the erector spinae are stretching and the spinal cord signals them to contract. Fig 2: As with the hamstrings, you can dissolve the reflex contraction of the erector spinae by slightly relaxing the stretch. This decreases the firing of the muscle spindle stretch receptors. Do this for the erector spinae by lifting the back slightly from the hips. Hold this milder stretch for a few breaths. Fig 3: Once the muscle spindle of the erector spinae acclimates to the milder stretch, contract the psoas and rectus abdominis to flex the hips and torso and deepen your pose. Engaging the psoas inhibits the reflex contraction of the erector spinae.
- #19 Base position: First take the position out to length. This establishes the “set length”, the point which brain recognizes as the end of stretch Fig 1- Facilitated stretching involves contracting a muscle that you are lengthening. This increases the tension at the muscle-tendon junction and recruits more Golgi tendon organs than does stretching a muscle alone. Facilitated stretching causes the spinal cord to signal the muscle to relax, in essence, creating "slack" in the muscle. You can then take up the slack to move deeper into the pose. For example, in Paschimottanasana, slightly bend the knees and squeeze the trunk against the thighs. Then gently press the heels into the mat as if you are trying to flex the knees further. This engages the hamstrings and stimulates the Golgi tendon organs at the muscle-tendon junction. Hold this steady contraction for five to eight breaths before releasing it. This produces relaxation and increased length in the hamstrings. Then contract the quadriceps to straighten the knees and take up the slack created by the reflex arc. This has the added effect of producing reciprocal inhibition, which further relaxes the hamstrings into the stretch. Fig 2 - Follow the same steps in this pose with the quadratus lumborum and erector spinae. First, bend forward to stretch these back muscles. Hold the stretch by bending the arms, and then attempt to arch the back. This increases tension at the muscle-tendon junction of the erector spinae and quadratus lumborum, stimulates the Golgi tendon organs, and ultimately relaxes these muscles. Hold the arch of the back for five to eight smooth breaths. Then engage the abdominals and use the arms to draw yourself deeper into the pose, taking advantage of the new length created by the reflex arc. Activating the abdominals also produces reciprocal inhibition of the back muscles, relaxing them into the stretch.
- #21 This Scientific Key focuses the drishti on the lower arm in Gomukhasana and uses a facilitated stretch of the infraspinatus, teres minor, and posterior portion of the deltoid to allow deepening of the pose. A belt connects the upper and lower arms. 1. Gently drawing the lower arm up the back creates a mild stretch of the infraspinatus, teres minor and posterior deltoid in the lower arm. 2. Pulling down on the belt while pressing the back of the hand on the lower arm into the back creates an eccentric contraction of the stretching muscles. This activates the Golgi tendon organs of these muscles and creates a “relaxation response” that frees the muscles to lengthen. (For more on the Golgi tendon organ please see “The Key Poses of Hatha Yoga”). 3. Relaxing the rhomboids frees the scapula to move away from the midline, allowing the lower arm to be drawn further up the back to stretch the target muscles. The hand is then held in place by the upper arm.
- #22 4. The rhomboids then activate to draw the scapula back towards the midline, accentuating the stretch. These steps are repeated once to deepen the stretch. Do not attempt to attain your maximum in one practice. Rather, build your flexibility over time with consistent, gentle practice.