This article was originally published in Positive Health PH Online in issue 163 – October 2009
Gravity, the attractive force by which bodies are drawn towards the centre of the earth, has a bad press among both physical therapists and lay persons. Many musculo-skeletal ills affecting human beings have been attributed to it: back ache, herniated discs, hernias, flat feet, prolapses, and bad posture. From this point of view, it would seem that the attainment of an erect posture and a bipedal stance in humans was not a good evolutionary step. In this scenario, gravity is a harmful force that pulls us not only downwards but also forwards under the pretext that there is more weight in front than in the back of the spine. Could it be that we are not fully adapted to life in a gravitational environment?
Faced with such a distorting force, some muscles have been labelled ‘antigravity’ or postural muscles. They are supposed to have the important function of opposing the inimical force of gravity. They don’t seem to do a good job though, judging by the prevalence of slouched and slumped postures, flat feet, and back pains. Seeing how inefficient they are in playing their ‘anti’ action, they are regularly accused of being weak. To remedy this perceived shortcoming, countless generations of physical therapists and fitness instructors have coaxed our gravity-challenged selves into strengthening our anti-gravity muscles.
In spite of a general consensus that tends towards the above hypothesis about gravity, I think it is misconceived. Gravity per se is not the cause of our mal-posture and the pains that ensue. There is therefore no need for antigravity muscles; and the misnamed ‘antigravity’ muscles, far from being weak, always end up tight and short.
If you think that it would be a blessing to live in a zero-gravity field, ask astronauts what they think about it. They will tell you that spending some time in such conditions is a sure recipe for developing terrible backaches. They might also add that any trivial action or movement becomes very complex and requires months of training.
In fact, gravity is necessary for our upright stance. It does not crush down on us but rather provides us with just the right amount of force to keep our feet on the ground. In other words, the upright stance does not need muscle contraction to counteract the force of gravity.
Our bodies are subject to the basic laws of physics. Take equilibrium for example: it is achieved when the centre of gravity is over its base of support (in our case, the area formed by our feet). The state of equilibrium does not require any effort; it’s gravity that does all the work and it is free and tireless. All our bodies have to do is to offer some rigidity provided by our bones, ligaments and muscle tone (not to be confused with muscle contraction). Our upright posture is a very energy-efficient one, inasmuch as it requires very little, if at all, muscular action, only small, intermittent contractions to keep the centre of gravity within its base of support. Electromyography (EMG) has proven this fact again and again. There is even no EMG activity (read no contraction), in the neck muscles of horses in spite of the fact that their head weighs around 10kg and that their neck is about 1m long. Our so-called ‘antigravity’ muscles are not so much to hold us up and constantly fight the battle against gravity, as they are to produce most of our everyday movements.
Take now the common flat-foot condition (another very loosely applied term). It is usually thought that the internal longitudinal arch is maintained by muscles. When these muscles become weak or tired, they can no longer counteract the pulling down effect of gravity and the arch collapses, or so goes the prevalent theory. In the past, strengthening the weak muscles was the treatment of choice; in our high-tech times, it is the wearing of orthotics in all kind of sizes, shapes, and materials that is in favour. Yet, EMG studies reveal that it is ligaments that maintain the longitudinal arches of the foot, not muscles. Ironically, it is the shortening of muscles, not their weakness, which causes the arches of the foot to ‘collapse’. The very muscles that are believed to be too weak to preserve our postural integrity are, in reality, the ones that destroy it due to their tendency to shorten and tighten. The neck and back are the first to suffer from this lack of muscle length. To escape this discomfort, the body finds some slack by distorting the limbs: the knees turn inwards which, in turn, makes the medial longitudinal arches to flatten. To be precise, the arches are still intact – they have only keeled over. The wearing of orthotics, as in most cases of symptomatic treatment, is a misguided choice. Not only do they not remove the cause, but they also prevent the twisting of the leg and foot that was giving the back some relief. Since the cause has not been removed, the distorting influence is sent back upwards to the knees and this is why orthotics and knee pains frequently go together.
The upper limbs have no more need of anti-gravity muscles than the lower ones. According to JV Basmajian, “…the vertically running muscles that cross the shoulder joint and the elbow joint are not active to prevent distraction of these joints by gravity.” They are not even recruited when loads are held unless the carrier chooses to flex the shoulder or elbow joints.
There is really no need to strengthen and tone up the so-called anti-gravity muscles – they are the ones that pull you down in the first place.
JV Basmajian. Muscles Alive, Their Functions Revealed By Electromyography. The Williams & Wilkins Company, Baltimore. 1967.
Lecoeur P. Le muscle, la function musculaire. In Médecine de Rééducation. Grossiord A., Held J. P. Flammarion, Paris. 57. 1981.