Stretching is good for you. The benefits of stretching include pain reduction, improvements in posture and overall cardiovascular and physiological health. In this article, I will provide an overview of the biology of stretching, the types of stretches, and the suggested amount of time and frequency of stretching that are shown to result in improvements in flexibility.
Pandiculation – the immediate urge to stretch
The immediate urge to stretch the body is quite common upon waking. Yawning is also common. You see this in cats and dogs in the morning, with the classic outstretched paws lengthening the front of the body (ie ‘downward facing dog’). This is known as ‘pandiculation‘.
Pandiculation is an involuntary reflex stretching mechanism that occurs during cyclical transitions such as waking up in the morning. In other words, it helps to prepare the body for movement. So the benefits of stretching are immediately apparent every day.
The biology of stretching
When understanding how stretching occurs, the first point to note is that your nervous system controls your muscles. Within the spinal cord, there are a category of neurons called ‘motor neurons‘. Upon muscle activation, the motor neurons will send an electrical impulse to the muscle and will meet at the ‘neuromuscular junction’.
At this point, the motor neuron releases an electro chemical (‘acetycholine’) which causes the muscle to contract. This results in movements in the muscle fibres causing them to temporarily shorten or lengthen as well as surrounding tendons and ligaments.
Connective tissue wraps around muscle fibres on three levels (an outer level, which wraps around individual muscles (the ‘epimysium’), an intermediate level which wraps around groups of muscle fibres (the ‘perimysium‘) and a deeper level which wraps around each individual muscle fibre (the ‘endomysium‘).
Within those individual muscle fibres comprise filaments called sacromeres. Within the sacromeres are thin filaments called myocin and actin, which interact with each other. It is the activation of the sacromeres and the interplay of the myocin and actin which results in muscle contraction.
Within the spinal cord there is another type of neuron called ‘sensory neurons‘. These sensory neurons extend from the spinal cord to the muscles and wrap around the muscle fibres (known as ‘spindles’). The spindles sent an electrical signal to the motor neurons which send an electrical signal to the muscle to the contract.
So, the purpose of spindles is protective. It detects changes in muscle length and the speed of that length change – when muscle spindles sense that a muscle is being stretched, it works to control the activation of that muscle within a safe range of motion by causing the motor neurons to fire. The result? The muscle fibres to contract. This is known as the ‘stretch’ or ‘myotatic stretch reflex‘.
Golgi tendon reflex
In addition, around the tendons of muscles are sensory receptors known as ‘Golgi Tendon Organs’ (GTO). They operate to sense where the body is in space. They also sense the amount of load a muscle is under. If the GTO senses that the load is too much for the muscle, it sends a signal that shuts down the motor neurons to prevent contraction of the muscle fibres.
The image below visually represents how muscle activation works. Visualise the GTOs, which are located where the muscles and tendons meet (the ‘myotendinous junction’).
The benefits of stretching
According to the Huberman lab, the benefits of stretching include:
“In addition to alleviating general feelings of “tightness,” increasing flexibility can also contribute to improvements in overall general health: balance/stability, improved posture, smoother gait and elevated physical performance; and it can reduce pain. Stretching can also reduce inflammation — some data in animal models suggest it may even potentially reduce the risk of cancer.”
There is no doubt that stretching is good for you. Although traditional models of longevity may not consider the benefits of stretching, there is no doubt that the relaxation inducing effects of stretching help to bring about a state of calm. Flexibility begins to decrease from the age of 20, at an estimate of about 10% every 10 years. Regular exercise helps to offset that flexibility as you age.
Stretching and changes in brain volume
Regular stretching may also have an effect upon brain structure volume. Within the cerebral cortex (the front part of the brain), there is a part of the brain called ‘insula‘ which has a sensory motor processing function within the body. I.e., it interprets what is coming into the body externally where the rest of the brain processes that information (eg sight, smell).
It also has a function where it senses what is going on inside the body and the amount of pain that the body is experiencing. Furthermore, it works to increase pain tolerance if the exercise is functional or otherwise has a distinct purpose.
“Yogis, as opposed to controls, used cognitive strategies involving parasympathetic activation and interoceptive awareness to tolerate pain, which could have led to use-dependent hypertrophy of insular cortex. Together, these findings suggest that regular and long-term yoga practice improves pain tolerance in typical North Americans by teaching different ways to deal with sensory inputs and the potential emotional reactions attached to those inputs leading to a change in insular brain anatomy and connectivity.”
Such cognitive strategies involve attitudes of acceptance without resisting the pain as well as particular methods of yogic breathing, which led to increases in pain tolerance. In other words, by practising yoga, you learn to control your neuromuscular system, which has all sorts of benefits in ordinary life, such as stress management, resilience, pain tolerance as well as increases in flexibility.
Stretching & cardiovascular health
In addition, some studies suggest that limited amounts of flexibility in the upper body may be associated with arterial stiffness. Another study suggests that there is a positive relationship between flexibility and atherosclerosis (the build of plaque in the arteries). So it seems that there may be some benefits of regular stretching from a cardiovascular health perspective.
Types of stretching
Broadly speaking, there are two main types of stretching. Those which involve movement (dynamic), and those which do not (static). Within those styles of stretching that involve movement, there are dynamic and ballistic styles. Dynamic styles work by stretching the body through a given range of motion whilst under some form of control. Ballistic styles involve more momentum especially at the end range of motion.
Within the styles of stretching that are generally performed whilst being still, there are those which are active and those which are passive. Passive stretching is what most people are familiar with and involves movement through a joint’s range of motion whilst the muscles relax. The body does not offer any effort or resistance. E.g., if you try and touch your toes.
Active stretching involves using your own muscles to provide resistance. It involves working with the reciprocal nature of muscles where one muscle group is contracting whilst the opposing muscle group is relaxing (ie ‘reciprocal inhibition’). Eg if you lift one leg up, the quadriceps contract in order for the hamstrings to stretch.
Another type of static stretching style is known as ‘Proprioceptive Neuromuscular Facilitation’ (‘PNF’). In PNF, the joint is brought into its end range of motion and then the muscles around the joint contract for a short period. It works by activating the muscle spindles and GTO in order to improve the amount of end range of motion.
What is the most beneficial form of stretching
According to the latest research, the most effective form of stretching is static stretching. The minimum amount of time required in order to produce an increase in range of motion is 30 seconds. What is even more interesting is that beyond this period of time, no increases in range of motion are reported, or if doing stretching regimes more than once a day.
Research also shows that the frequency of stretching is important. It is recommended that stretching for a given muscle group should be performed in aggregate up to 5 minutes per week in order to see an increase in range of motion.
How much stretching is required
The tendency to stretch a muscle is to move to the maximum range of motion. However, research suggests that ‘microstretching‘ (defined as around 30-40% of the potential range in motion) is the most effective. This is opposed to moving into a stretch where significant tension is felt in the muscle group (ie your ‘edge’).
Stretching before exercise or not
The evidence is mixed on this question. A meta-review of all the studies to date concluded that on balance, stretching before exercise is beneficial in terms of reduction of injuries, especially for those activities that involved explosive movements such as sprinting or jumping.
The controversy relates to whether stretching before exercise results in reduction in performance. The same review found that stretching before performance did result in a small and temporary reduction in muscle power, albeit for stretches that are held for longer than 1 minute.
Exercising before stretching
It is generally advisable to warm the body a little before engaging in any stretching practice. The body is visco-elastic means that as the body becomes more warm, the tissues become more elastic (or responsive). That said, practices like yin yoga are generally performed when the body is cool, with the intention of the practice to target the connective tissues of the body.
Suggested stretching protocol
In order to see improvements in flexibility, the following protocol is suggested:
- Perform 2 to 4 sets of static hold stretches, 5 days per week.
- Within each stretching session, do 3 sets, holding for 30 seconds, with rest in between.
- If this is not possible to do stretching every day, holding stretches for up to 60 seconds, every other day.
Performing intense stretches once or twice a week isn’t expected to realise much improvement. What matters is consistency of routine.
Conclusion – stretching is beneficial for you
The physiological basis for stretching is through the nervous system. The nervous system determines the ability of a muscle to stretch through monitoring length change and load. By engaging in a regular stretching practice, you can expect to experience less muscle stiffness, pain reduction and improvements in posture. It may also have other health benefits too.
The most beneficial form of stretching is static stretching. The recommended amount of time to see the benefits of stretching is performing static stretches for a minimum of 30 seconds, with an aggregate of up to 5 minutes per week.
If I can help you become more flexible by developing a regular yoga practice, please feel free to get in touch or email me at firstname.lastname@example.org
Huberman Lab. https://hubermanlab.com/stretching-protocols-to-increase-flexibility-and-support-general-health/ (accessed 29th May, 2023)
PT Direct https://www.ptdirect.com/training-design/anatomy-and-physiology/muscle-spindles-the-stretch-reflex-and-force-generation (accessed 29th May, 2023)
Williams, C (2021). The lowdown on stretching: How flexible do you actually need to be? New Scientist.
Wylde, S. (2017). Moving Stretch. Work Your Fascia to Free your Body. Berkeley, California. North Atlantic Books.