The limbs of the human body usually have unconscious motor reflexes. For example, when you run, subconsciously your arms will swing by bending your elbows.
How did this movement come about and what is its real use? This was discovered in a study by Dr. Andrew K. Yeghian of the Department of Human Evolutionary Biology, Harvard University, USA, et al., which was published in Journal of Experimental Biology by name Walking with straight arms, running with bent arms: gait-specific elbow angles.
The researchers studied how hand position affects energy efficiency and found that walking with bent arms is actually less energy efficient than walking with straight arms.
Your arms will naturally bend as you run.
Quote from the page live science, the bent arm has a shorter arc than the straight arm. This results in the bent arm requiring less energy to swing back and forth.
The researchers had the initial hypothesis that this movement should be more efficient for both running and walking. However, if it is more efficient, people will also naturally bend their arms when walking.
In fact, when walking, a person’s arm tends to be straight. Why is this?
The researchers then studied the movements of the eight people, four men and four women, above. Treadmills. During walking and running, the subjects performed both actions with their arms straight and then with their arms bent.
Infrared cameras and software are used for motion capture. This camera is used to record the subject’s movement and create a digital 3D model of their body.
The subjects repeated the session two weeks later. Treadmills when wearing a respiratory mask. This allowed the researchers to collect metabolic data reflecting the participants’ energy intake.
When the subjects ran with straight arms, they reported feeling uncomfortable. However, the researchers reported that there was no noticeable difference in energy efficiency regardless of whether their arms were bent or extended.
Consumes more energy when moving slowly
The scientists found that when the subjects walked with their arms bent, the energy released increased by about 11%. This is because more effort is required to keep the arm flexed while moving at a relatively low speed.
This experiment explains why people naturally keep their arms straight when they walk. However, why it is natural to run with bent arms remains unclear.
A 2014 study found that swinging arms consumed energy while running, but holding arms straight required more energy. This is because arm swings will reduce upper body movement.
Relation to human evolution
In addition, the relationship between hand movement and step may help explain how hand proportions have evolved in the human family tree.
Unlike modern people, ancient people of the species Australopithecus and Homo habilis who lived millions of years ago had arms that were much longer than their legs.
Forearm australopithecine AND skillful man also longer compared to their shoulders. However, shorter arms and shorter arms are known to sway less in general.
Shorter arms would have helped modern humans in long-distance running. Selection for this trait could have influenced the evolution of the length of the human hand bone. Thus, the modern proportions of the hands appeared with the development of long-distance running. Homo erectus.
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