The human body is amazing and it never ceases to amaze – with the
ability to learn new techniques and adapt over time in order to survive – however,
there is one thing that it gradually ceases to do: be flexible.

A human fetus (unborn baby developing in the mother’s
womb) spends whole of its time floating and somersaulting in amniotic fluid
(water that breaks before a woman goes into labor). This could explain the
smooth flexibility of babies. One can often see an infant suckling their big
toe or tumbling left and right in their cots and cradles. This flexibility only
increases during childhood when they get the hang of their bodily functions.
The newly acquired skills of walking, running and jumping add to the mayhem as
kids are seen playing everywhere. However, this privilege starts to decline as
they get older.

The first slump in a kid’s
flexibility is during their teenage years or adolescence. In this age, kids are
having a rage in hormones and a lot of bones and joints are reaching
ossification (bones become rigid and strong). The second slump occurs in their
twenties – when they have reached their prime and are now regressing slowly to
a degenerative phase of their life.

The question is : why does this happen? Why don’t
we remain as flexible as when we are born? What factors affect this change?

1. Connective Tissues

Growth is a natural process. It happens to everyone. It is
inevitable. No elixir in the world can prevent it from happening. We grow
taller and more mature. We grow smarter and acquire new skills. Different
organs and systems in our body contribute in growth. To the naked eye, it would
appear that only our bones and muscles are getting bigger and longer. In
reality, our entire body is made up of congregations of cells. Connective
tissue is one of the most abundant kind of tissue present in the body. It holds
various structures and fluids in place.

As we grow, our connective tissues
also adapt to the surrounding conditions, environmental stress and genetic
predisposition. The cells grow bigger and multiply into various progenies
(families) until they can do no more. Their lifespan is spent and waste
products accumulate as a result of it. Common among these inclusions
(substances that are found suspended in cells) are lipids and pigments, eg
lipofuschin, which is a fatty brown pigment. ^[1]

The impact of these wastes makes cells
acquire a stiffer arrangement. Not only the vasculature (blood vessels like
arteries, veins and capillaries that carry blood) or airways, tissues also have
great trouble getting sufficient oxygen and nutrients. Thus, they end up
getting stiff. This change, however, is not sudden.

2. Joint Structure Formation

When we are born, we are very small
and flexible  This is because majority of
the structures in our body have not undergone complete development. The bones
have not been completely fused and hasn’t acquired complete length either.

Aging leads to ossification (becoming
rigid) of bones and development of joints. As these elements fix, our body
loses flexibility. It has also been observed in cases of immense stress that
our muscles tend to become taut. Acute or chronic stress can directly injure
muscle tissue by increasing damage by reactive oxygen species (ROS) and a
greater rate of accumulations in the cells 
This cell damage leads to apoptosis (cell death) of muscle cells, and
thus, contributing to increased rigidity and decreased mobility. ^[2]

3. Bone and Muscle Hardening

It is apparent that the body undergoes various changes with time.
Our bones are initially soft and our movements more swift. However, it is our
habits that shape how our body transforms. For example, how pelvic joint fuses
and bones of the body become harder as we get involved in various day to day
activities. Whether we are active or sedentary also determines the fate of our
flexibility. The more active someone is, the more likely he or she is to be
swift in their movements. It has also been noted that activities like
stretching directly contributes to ease in mobility, whereas weight training
and heavy duty activities decrease it.

But it is essential to note that activities are performed during
a certain time frame. It is the long-term position of our body that ultimately
determines our state. Just like prolonged collision with a water stream can
form rivers or even crack open rocks, repetitive movements – or lack thereof – can
leave lasting effects. Good posture is key.

Everyone must have heard phrases like “don’t
make that face or it will stick that way” in their childhood. Well, there is
some truth in it. How you stand or sit affects the alignment of your body. If
you continuously cock your head forward near a screen or perhaps bend your neck
to get a closer view of your phone every other minute, you might see a hump
forming in some time. This is the effect of posture.

Other than the position we maintain while we’re
wide awake, our sleeping positions also matter. On average, we sleep 6 to 8
hours a day, and some even 9 or 10 hours. The posture we maintain during this
time can affect the mobility of our joints and the tautness of our muscles and
fasciae (the connective tissue sleeves that cover muscles and associated
structures in place, fitting like a glove).

4. Race

It is undeniable that our genetic makeup plays a major role in determining our adaptation in every aspect of life. Whether it is contributing to our intelligence or our physical characteristics. It has been observed that most Asians with have soft connective tissues as compared to the people of the West. ^[3]

5. Use It or Lose It

There is a simple theory called “use it or lose it”.
According to this, if you keep on using your joints and performing everyday
activities, you will remain able to move swiftly. It is seen that kids move
around a lot and thus are immensely flexible but as they start to age, pain and
inflammation, and a sedentary lifestyle prevents them from practicing and
exercising their joints at the rate they used to. This leads to a disuse
atrophy and joints become hypoflexible (less flexible). ^[4]

Thus, it can be summed up that healthy lifestyle modifications early on in life can contribute to a healthier and easier adulthood, with lesser obstacles in movement. Eating healthy foods, regularly exercising, and good posture can set you up for a flexible life.

References

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2147307/

[2] https://www.apa.org/helpcenter/stress-body

[3] https://academic.oup.com/rheumatology/article-abstract/26/1/9/1781943?redirectedFrom=fulltext

[4] https://arapc.com/maintaining-flexibility-with-aging/