Gravity and the Body
“Gravity is a habit that is hard to shake.” (Terry Pratchett). In fact, the very activity of that shaking is dependent upon gravity. It is the law our bodies cannot break. Gravity demands our adherence to it. All biological processes on earth evolve in response to it. Even in space, we are subject to its absence. We suffer losses in bone density and muscle mass. Our heart muscles atrophy when no longer called to beat against its undeniable force. But instead of working against it, in this series on gravity and the body, we will consider the benefits and joys of working with it.
Take a look at our beginnings. We start life floating blissfully in a sea of amniotic fluid, but as we grow our buoyancy changes. In the last trimester of gestation, the cardiovascular system, the spine, the extensor muscles, and muscles of the lower extremities develop and strengthen as they oppose gravitational forces. Thus begins our dance with gravity, a relationship that has an impact upon all of our activities for the duration of our lives. This early relationship to gravity later influences our acquisition of the gross motor skills that enable us to get where we need to be in life. Activities such as sitting, standing, and walking are not possible without gravity. Even the movement of the jaw as we speak depends upon gravity.
When we stand up to gravity, blood flow easily moves to areas of the body below the heart. Have you ever had swollen feet at the end of a long workday? Blame gravity. Such a pooling of blood below the heart (called orthostatic stress) challenges blood supply to the brain. The heart rate and blood pressure change to meet the challenge, ensuring sufficient blood flow to the head.
However, certain circulatory demands such as mountain climbing or standing up too quickly from a reclined position can upset this balance and result, especially for those more prone to dizziness, in symptoms such as headache, fatigue, visual disturbances (seeing spots), anxiety, tremulousness… These symptoms are immediately, or at least very quickly, relieved when we lie down or faint, a reflex of the autonomic nervous system that equalizes blood circulation within the body, essentially giving in to gravitational forces.
Luckily our bodies evolved for motion, thus reducing the impact of orthostatic stress. We love to move. As infants or octogenarians, our bodies crave the increased circulation, sensory perception, and blood flow that result from even the most gentle movement. Imagine the person in front of you in line at the grocery store soothing a baby. The parent will gently bounce or rock the baby invoking a calming response. (As you observe, you may very well start bouncing or rocking, too.) In this baby dandling, motion and gravity conspire to soothe the vestibular system, that part of the body that balances and orients us in our environment. By rocking in rocking chairs, we comfort ourselves in a similar way at the other end of our lifespan. Weight-bearing exercises such as walking, Tai Chi or Yoga take our work with gravity up a notch. Exercises such as weight lifting or Crossfit turn it up even further.
Dr. Joan Vernikos, former NASA Director of Life Sciences, explains in her book Sitting Kills, Moving Heals, that “In weightlessness, astronauts, who are far fitter than the average adult, seem to rapidly age; their muscles, bones and overall health degenerate to levels usually seen in elderly people. Vernikos found that keeping subjects resting and immobile — an extreme form of the typical American lifestyle — caused the same health problems as extended weightlessness.” (http://www.joanvernikos.com/pages/sitting-kills-moving-heals.php) Despite hours of aerobic exercise in space, the astronauts she studied still aged at greater rates than those of us engaged in our constant gravity dance here on earth. She suggests that gravity exerts such a healing force on the human body; we need simply rise against it at least once every twenty minutes.
In this series on Gravity and the Body, we’ll recommend some activities you can add to rising every twenty minutes. We will explore the effect of gravity on the mind, balance, tissues, and digestion. We’ll also take a look at turning this relationship with gravity on its head in the form of inversions in the yoga practice.
Gravity is an essential component to wellness. Don’t let it get you down; join us in the dance.
References:
Sekulić, Lukac, and Naumović (2005). The fetus cannot exercise like an astronaut: gravity loading is necessary for the physiological development during second half of pregnancy. https://www.ncbi.nlm.nih.gov/pubmed/15607544
Amrit Naam Nidhaan Hai (2003). Effects of gravity on the cardiovascular system. http://sikhsangat.com/index.php?/topic/2435-effects-of-gravity-on-the-cardiovascular-system/
Christopher Bergland (2013). The Neuroscience of calming a baby. https://www.psychologytoday.com/blog/the-athletes-way/201304/the-neuroscience-calming-baby
Image http://maxpixel.freegreatpicture.com/Levitation-Girl-Forest-Weightlessness-In-The-Forest-1333635