Representatives of the hadza tribe is carried out in an inactive state as much time as typical inhabitants of first world countries, reported in the Proceedings of the National Academy of Sciences. However, they squat down or kneel — and in these positions, the load on the muscles more than the sitting chair. Apparently, the “nature” of man is to load the muscles during maintenance of static postures.
It is assumedthat in the course of evolution the ancestors of humans have adapted to long periods of moderate (aerobic) physical activity — slow running or at least walking. A sedentary lifestyle combined with food, is subjected to intensive treatment, with provokes arterial hypertension and probably other diseases. One of the reasons is that when sitting on the chairs and such objects, muscle activity is lower than during walking and standing — and that level is clearly insufficient.
However, sitting and long periods of inactivity in General, help to save energy and therefore can be beneficial to the body. From this position it is not clear why a sedentary lifestyle must be unhealthy.
David Raichlen (David Raichlen) from southern California University in Los Angeles and his colleagues from several universities in the United States and Tanzania have suggested that ancient people — hunters and gatherers — time spent in relative inactivity, straining more muscles than modern humans sitting on a chair. Thanks to this “sedentary lifestyle” helped the ancestors of the present inhabitants of the globe to save power without significant negative consequences for the condition of the body.
To test this hypothesis, they assessed physical activity 28 the representatives of the African hadza people, who still mainly a hunting and gathering — that is, lead a lifestyle similar to the one that was the ancient people. 12 women and 16 men for 8 days to the thighs attached accelerometers to keep track of what position the person is at a given time.
Muscle activity (quadriceps, soleus and tibialis anterior) was assessed using electromyography (EMG). In addition, the volunteers took blood on the analysis — revealed the presence of biomarkers of increased risk of cardiovascular diseases.
It turned out that men and women of the hadza spend without moving (not standing and not walking and running) an average of nearly 10 hours a day. For comparison, the modern inhabitants of the Netherlands are sitting or are in a similar level of activity poses 9 hours and 20 minutes a day, and the citizens of the United States — 9 hours a day.
But if people from developed countries generally sit in the chair, the hadza much more time sitting or squatting on a small stone, that is, in the positions when the pelvis is lowered low enough. (Another common variant is kneeling.) Apparently, therefore, the muscles of their feet even “no movement” work harder.
While biomarkers of increased risk of cardiovascular diseases in the blood hadza virtually no. It turns out, formally a sedentary lifestyle in the case of this nation does not pose a threat to health. The authors suggest that the human body imprisoned under large static load of muscles than when sitting on the chair, but from the seat as such, he does not suffer. Probably this information will be used to reduce the harm from a sedentary lifestyle to people from developed countries — for example, to modify their jobs to not have to stand, and the load on the muscles of the legs increased.
Interestingly, in 2015, the researchers from Exeter University, using data on more than 5,000 people, found that the proportion of time spent sitting, is not associated with risk of death. However, this does not mean that long periods of sitting does not harm health: about the risks of various diseases in the work nothing was said.