PHYSIOLOGY OF STRETCHING:
Flexibility involves the interaction of the nervous system with muscles and connective tissue. Muscles shorten when they contract and lengthen when they relax.
Muscle contains two key sensory detectors:
1 Muscle spindles are stretch detectors that communicate information from the muscle to the nervous system with the goal of preventing excessive stretching. When a muscle is overstretched the spindle fiber sends information to the nervous system and the muscle contracts to prevent overstretching.
2 Golgi tendon organs are muscle tension detectors. When you lift a weight that is too heavy or contract a muscle, the Golgi tendon organ senses increasing muscle tension and sends information to the nervous system which in turn sends a signal that causes the muscle to relax.
The brain has the ability to modulate our response to information collected by receptors in the body. Part of this ability to modulate response is attributed to special nerve cells called von Economo neurons. These nerve cells play an important role in sensing our body’s internal state including discomfort and allowing us to override information from the muscle spindles.
TYPES OF STRETCHING:
Static Stretching involves stretching your muscles and connective tissue to a challenging but sustainable point and holding that position for 10 seconds or longer.
This is best suited to post-exercise cool down or before bed. Studies indicate that static stretches held for > 60 seconds decrease the capacity of muscle and soft tissue to immediately adapt to dynamic stress (1). If static stretches are held for less than 30 seconds and followed by several minutes of light warm-up movements this negative effect is very small (1-2%) and possibly counterbalanced by decreased risk of injury. Static stretches are ideal for when your body is turning off post-exercise or pre-bed and will likely improve the quality of sleep (2).
Dynamic Range of Motion Stretching (eg hip circles or arm windmills) involves repeated, smooth movements (not bouncing) through a range of motion (10- 20 repetitions). This technique will help you reach the upperlimits of your current range of motion but is less effective than static stretching in increasing flexibility. This is well suited to pre-exercise warmup because it reduces muscle and tendon stiffness and may improve physical performance (3).
BENEFITS OF FLEXIBILITY:
Aging Gracefully: Nothing reminds us more of our age than limitations in our ability to move. Participation in activities of daily living like getting up from the floor and putting on shoes and leisure activities like gardening and playing tennis and golf require flexibility.
Posture Improvement: We can’t force ourselves into perfect posture. Instead, with stretching, we can create balanced connections between muscles and bones that lead to healthier posture.
Injury Prevention: Flexibility improves posture, balance, and biomechanics, thereby protecting our bodies from injury.
Body-Mind Balance: A more pliable body leads to a more relaxed and pliable mind. It is hard to be stressed, anxious, or tired when our body is open.
FACTORS DETERMINING FLEXIBILITY:
Age and Activity: While age plays a major role in flexibility, age-related changes are markedly slowed by an active lifestyle and sped up by a sedentary lifestyle. Consider squatting in Asian versus western countries. While all children easily achieve this posture, adults in Asian cultures still squat frequently and maintain this ability versus western adults who spend most of their days in chairs lose leg flexibility at a faster rate. Bodies are adaptive entities and remodel based on the stresses they regularly engage.
Flexibility Decreases by about 1% per year between the ages of 30 and 70 unless you stretch regularly (4,5).
Connective Tissue: People are born with different muscle lengths and degrees of elasticity in their connective tissue (fascia and tendons). It is not healthy to make an inherently stiff person excessively mobile. It is healthful to mildly extend their range of motion to create more functional movements. An unusually limber person may benefit from increased muscle strengthening to increase joint stability.
BEST TYPE OF STRETCHING
While both dynamic and static stretching will increase the range of motion, static stretching is the most effective tool to increase flexibility. Because it may impair sports performance, a reasonable recommendation is to include dynamic stretching in your warmup and static stretching during your post-workout cool-down (6).
OPTIMAL STRETCHING FREQUENCY
Two sets of 30-second stretches on 5-7 days per week (6,7). There are no clear benefits to holding stretches for more than 30 seconds or stretching individual muscles for more than 1 minute per day. In total, you should aim to stretch each muscle for 5-7 mins per week.
OPTIMAL STRETCHING INTENSITY
Low-intensity static stretching (40% of maximum) may be more effective than high-intensity static stretching (80% of maximum) to increase the active range of motion (8). While this is a single study, it is biologically plausible that more relaxed, low-intensity stretching would be both safer and more effective.
ADDITIONAL TOOLS to Maximize The Benefits Of Stretching:
Warm up the Body with light exercise (ex. 2-5 minutes of walking and biking) before stretching to maximize your benefit from subsequent stretching.
Massage and Foam Rolling (over soft tissue and not over bones):
Spend 1 -2 mins gently rolling particularly tight regions of your body (ex. lower back, glutes, or hamstrings) before stretching. This may increase your stretch by up to 10 degrees. Depending on the area, a tennis or lacrosse ball or foam roller may be best. If a tender point is located, rest on that point for 30 seconds or roll on and off that point for 30 seconds. On subsequent days, that tissue will relax and become less tender.
Sequence Your Stretches: Start with the distal extremities and move to the center. Stretch your feet and calves before your hamstrings. This will help you get a deeper stretch of your hamstrings if the stretch is not restricted by tight distal muscles.
2 sets of thirty seconds each: As recommended above, perform a stretch (static or dynamic) for 30 seconds, rest for 30 seconds, and then repeat the stretch. It is in the second 30 seconds of stretching that you will move deeper into your range of motion.
Mental Approach and Breathing: Soft tissue stretches best when completely relaxed. Our body achieves its deepest relaxation with exhalation. Breath in through the nose and let your body sink deeper into a stretch as you breath out.
Consider The Activity: Stretching Is pivotal to preventing muscle injury with activities that require high acceleration, and forceful movements like tennis or basketball. With cycling or running, light pedaling or speed walking is likely an adequate warm-up.
PNF (Proprioceptive Neuromuscular Facilitation) involves contracting a muscle before it is stretched. The initial contraction causes a reflexive relaxation in the muscle and allows one to achieve a deeper stretch.
Move throughout the day: People commonly spend 50 hours a week sitting at a desk or staring at a screen. Each work hour should include a couple of minutes of stretching or calisthenics to counterbalance the negative impact of sedentary postures. Sitting decreases blood flow to muscles and causes certain muscles to shorten.
The body is like a bag of concrete that hardens unless you keep it in motion.
Bradford Rabin MD is a concierge medicine doctor caring for patients in the San Francisco Bay Area including Palo Alto, Menlo Park, Los Altos, Portola Valley, and Woodside.
1 Acute Effects of Static Stretching on Muscle Strength and Power
2 Effects of resistance exercise training and stretching on chronic insomnia
3 Acute effects of muscle stretching on physical performance, range of motion, and injury incidence in healthy active individuals: a systematic review
4 Flexibility of the shoulder joint measured as a range of abduction in a large representative sample of men and women over 65 years of age
5 Relationships of age and sex with range of motion of seventeen joint actions in humans
6 The Relation Between Stretching Typology and Stretching Duration: The Effects on Range of Motion
7 The Effect of Time and Frequency of Static Stretching on Flexibility of the Hamstring Muscles
8 A Comparison of Two Stretching Modalities on Lower-Limb Range of Motion Measurements in Recreational Dancers