Two. That’s the number of millions of years – slightly more actually, according to the latest findings – of existence of Genus Homo on our planet. Evolution has manifested itself in our species with incredible improvements in reasoning skills, has caused our somatic features to lighten and for us to become over time less similar to the remaining primates, but has left virtually intact in our bodies one of the features that has enabled our survival: the structure of the Achilles tendon.
This extremely strong joint component is able to withstand high intensity stresses and allows our bodies to stand and move, especially to move for a long time.
In fact, researchers agree that the association between having such a thick Achilles tendon and proportionately longer legs than in other animals allowed our species to develop endurance over long distances. In particular – but this is a technical-medical detail that is greatly simplified – it is the ratio of tendon thickness to muscle fiber length that is in favor of the tendon and allows the whole complex to provide a return of energy close to 20 percent of that which the foot discharges to the ground.
Said in very poor, very poor words, assuming that to make your foot move forward you spend 100, once it touches the ground, activation of the elastic part of the tendon gives you back almost 20, so it is as if by moving you spend only 80. Added to this saving are the conformation characteristics of the shoulders, head movements, and arm sway, all of which contribute to making the human machine an example of adaptation to movement, particularly running.
Today we “use” the body differently
What for our ancestors was a necessity (running meant doing it to hunt or to escape from a predator), for us – as we have twisted the use of our bodies – has become a complementary activity to do during leisure time (professionals excluded, of course). This sedentarization is – again according to the researchers – the biggest risk factor for the occurrence of injuries, especially for people who fail to maintain an adequate weight and for those who do not exercise consistently throughout their lives.
The prevalence of long-distance running has fortunately had noticeable increases in recent decades, and running for the sheer pleasure of it has become a very popular activity. The numerous studies of significant samples of runners show how running activity can prevent a wide variety of problems, including even obesity and depression and, of course, weakening of the bone component.
Researchers conclude that a healthy lifestyle, balanced diet and physical activity – even low-intensity physical activity – for at least a few times a week will bring us closer to our ancestors capable of moving dozens of miles every day and enable us to live longer. It is not that difficult, just try.
Ispirato da “Endurance running and the evolution of homo.” di Bramble DM and Lieberman, 2004.