How stretching actually changes your muscles – Malachy McHugh

VIDEOSCRIPT:

Here we have an athlete preparing for a game. They’ve put on their gear and done their warmup, and now it’s time for one more routine—stretching. Typically, athletes stretch before physical activity to avoid injuries like muscle strains and tears. But does stretching actually prevent these issues? And if so, how long do the benefits of stretching last?

To answer these questions, we need to know what’s actually happening in the body when we stretch. There are two kinds of stretching our athlete might be doing: dynamic stretches, which are controlled movements that engage a range of muscles throughout the motion, and static stretches, where the stretcher holds a position to keep specific muscles at a fixed length and tension. Our athlete is currently doing a static hamstring stretch—a 30-second interval where he pulls his hamstring beyond its usual range of motion.

However, while we often think of stretching a muscle like stretching a rubber band, muscles are actually comprised of various tissue types, which interact to make a complex material. Rubber is elastic, meaning it resists being stretched and then returns to its original shape. But muscle is viscoelastic. This means that, in addition to those elastic qualities, muscle changes under the stress of being stretched.

Let’s see this in action. At the large scale, this hamstring stretch is pulling on layers of protective tissue surrounding the muscle fibers, as well as the tendons that connect this muscle to nearby bones. These tissues contain elastic proteins like collagen and elastin, which allow them to slightly elongate over the duration of the stretch. At the smaller scale, these skeletal muscle fibers are comprised of millions of sarcomeres—the smallest contracting unit of muscle tissue. Sarcomere’s long, fibrous proteins can relax to elongate muscle fibers or contract to shorten them, pulling on tendons and protective tissue to create the force propelling our athlete’s body.

When those tissues have been stretched out, they retain their strength at longer lengths, allowing our athlete to take full advantage of his improved range of motion. Unlike a rubber band, this muscle’s resistance to stretching decreases with each 30-second stretch, allowing our athlete to continually elongate his hamstring. This improved flexibility likely decreases the chance of incurring certain muscle injuries. But due to muscle’s elastic properties, this effect will be gone in just 10 minutes without further activity.

The exercise from his match should elevate his muscle’s temperature and continue elongating the muscle, maintaining his increased flexibility throughout the game. But once he gives his hamstrings a break, they’ll retract back to their previous state. So if all this is just temporary, how can you permanently improve your flexibility?

For skeletal muscles, improved flexibility comes from additional sarcomeres, which allow you to maintain strength at even greater lengths. Sarcomeres are added and subtracted to muscles depending on how frequently they’re used, so improving overall flexibility requires a comprehensive stretching regimen. Plus, you need to stretch often—very often. Current research suggests at least 10 minutes a day for roughly two months.

Since it’s unsafe to hold any stretch for too long, it’s recommended that you break up your stretching within any given session. Frequent stretching also makes lasting changes to your brain. The more you stretch a muscle, the higher your pain threshold becomes, allowing you to stretch further and further. Long-term improvements to your flexibility can provide a better range of motion for your joints, potentially reducing your risk of muscle injury in the short and long-term.

However, it’s also possible to stretch too much, as flexible people can move their joints in potentially dangerous ways. Stretching also isn’t helpful for every kind of movement, especially those where muscle injuries aren’t very common. For example, long-distance running only involves a small range of motion for the joints involved, so stretching is unlikely to prevent that sport’s most common injuries.

In the end, different lifestyles require different kinds of mobility, and no single stretching regimen is flexible enough to fit every situation.

VOCABULARY:

• warmup /ˈwɔːrmʌp/ – An activity to prepare the body for exercise, increasing blood flow to muscles. SYN: preparation, warm-up exercise.
• stretch /strɛtʃ/ – To extend the muscles to prevent stiffness or injury. SYN: elongate, extend.
• muscle strain /ˈmʌsəl streɪn/ – An injury where a muscle is overstretched or torn. SYN: muscle pull, muscle tear.
• dynamic stretch /daɪˈnæmɪk strɛtʃ/ – A type of stretching involving controlled movements that target a range of muscles. SYN: active stretch, movement stretch.
• a range of muscles /reɪndʒ ʌv ˈmʌsəlz/ – Different groups of muscles activated during exercise. SYN: various muscles, muscle groups.
• static stretch /ˈstætɪk strɛtʃ/ – A stretch where the muscle is held in a fixed position for a period. SYN: held stretch, stationary stretch.
• tension /ˈtɛnʃən/ – A feeling of tightness or stress in a muscle. SYN: tightness, strain.
• hamstring /ˈhæmstrɪŋ/ – A group of muscles located at the back of the thigh. SYN: thigh muscles (in context), back thigh.
• interval /ˈɪntərvəl/ – A period of time during which an exercise is held or repeated. SYN: period, duration.
• elastic /ɪˈlæstɪk/ – Able to return to its original shape after being stretched. SYN: stretchy, flexible.
• resist /rɪˈzɪst/ – To oppose or prevent change. SYN: withstand, oppose.
• viscoelastic /ˌvɪskoʊɪˈlæstɪk/ – A material that exhibits both viscosity and elasticity, allowing it to slowly return to shape. SYN: stretchable, adaptive material.
• at the large scale /æt ðə lɑːrdʒ skeɪl/ – Observing something broadly rather than in detail. SYN: broadly, in general.
• protective tissue /prəˈtɛktɪv ˈtɪʃuː/ – Layers of tissue that safeguard muscles and bones. SYN: shielding tissue, guard tissue.
• tendon /ˈtɛndən/ – A tissue that connects muscle to bone. SYN: ligament (in context), connective tissue.
• collagen /ˈkɒlədʒən/ – A protein that provides structure and strength to body tissues. SYN: structural protein.
• elastin /ɪˈlæstɪn/ – A protein that allows tissues to stretch and return to shape. SYN: stretch protein.
• elongate /ɪˈlɒŋɡeɪt/ – To make longer or stretch out. SYN: extend, lengthen.
• skeletal muscle fibers /ˈskɛlɪtəl ˈmʌsəl faɪbərz/ – Muscle cells attached to bones that help in movement. SYN: muscle cells, fibers.
• sarcomere /ˈsɑrkəˌmɪər/ – The basic unit of muscle tissue responsible for contraction. SYN: muscle unit, contraction unit.
• muscle tissue /ˈmʌsəl ˈtɪʃuː/ – Tissue composed of cells that can contract. SYN: muscle mass, muscle fiber.
• pulling on tendons and protective tissue /pʊlɪŋ ɒn ˈtɛndənz ænd prəˈtɛktɪv ˈtɪʃuː/ – Applying force to connective tissues. SYN: stretching connective tissues.
• propel /prəˈpɛl/ – To move or push forward. SYN: drive, push.
• retain /rɪˈteɪn/ – To keep or hold in place. SYN: keep, hold.
• incur /ɪnˈkɜːr/ – To experience or bring upon oneself. SYN: suffer, experience.
• elevate /ˈɛləˌveɪt/ – To raise or increase. SYN: lift, raise.
• retract /rɪˈtrækt/ – To pull back or return to a previous state. SYN: withdraw, pull back.
• additional sarcomeres /əˈdɪʃənl ˈsɑrkəˌmɪərz/ – New units of muscle fiber added to help increase muscle length. SYN: extra muscle units.
• at even greater lengths /æt ˈivən ˈɡreɪtər lɛŋθs/ – At further extended positions. SYN: further lengths.
• comprehensive stretching regimen /ˌkɒmprɪˈhɛnsɪv ˈstrɛtʃɪŋ ˈrɛʤɪmən/ – A thorough routine of stretching exercises. SYN: complete stretching program.
• hold any stretch /hoʊld ˈɛni strɛtʃ/ – To maintain a position for stretching. SYN: maintain stretch.
• pain threshold /peɪn ˈθrɛʃˌhoʊld/ – The level at which pain begins to be felt. SYN: tolerance level.
• muscle injury /ˈmʌsəl ˈɪnʤəri/ – Damage to muscle tissue due to overstretching or strain. SYN: muscle damage.
• joint /ʤɔɪnt/ – The connection between two bones that allows movement. SYN: articulation.
• mobility /moʊˈbɪləti/ – The ability to move freely and easily. SYN: flexibility, movement capacity.
• no single /noʊ ˈsɪŋɡəl/ – Not just one. SYN: not one, not only one.