Jakarta –
The limbs of the human body usually have unconscious movement reflexes. One example is when you run, subconsciously your arms will swing with your elbows bent.
How did this movement happen and what are the actual benefits? This was revealed through a research by Dr Andrew K Yegian from the Department of Human Evolutionary Biology, Harvard University, United States et al which was published in The Journal of Experimental Biology by title Straight arm walking, bent arm running: gait-specific elbow angles.
Researchers investigated how arm position affects energy efficiency, and they found that walking with bent arms was actually less energy efficient than walking with straight arms.
Arms Will Naturally Bend When Running
As quoted from the page Live Science, the bent arm has a shorter arc than the straight arm. This causes the bent arm to require less energy to swing back and forth.
The researchers had an initial hypothesis that this movement should be more efficient for both running and walking. However, if it is more efficient, when walking, humans will also bend their arms naturally.
In fact when walking the human arm tends to be straight. Why is that?
Researchers then examined the movements of eight people, four men and four women, above treadmill. As the subjects walked and ran they performed both activities with their arms straight and then with their arms bent.
Infrared cameras and software are used to capture motion. This camera is used to record the movement of the subject and create a 3D digital model of their body.
After two weeks, the subjects repeated the session treadmill while wearing a respirator mask. This allowed the researchers to collect metabolic data that represented the energy use of the participants.
When the subjects ran with their arms straight, they reported that it felt awkward. However, the researchers reported that there was no marked difference in energy efficiency, whether their arms were bent or straight.
Expends More Energy When Moving Slower
Scientists found that when subjects walked with their arms bent, the energy released increased by about 11%. This is because it requires more effort to keep the arm bent while moving at a relatively slow speed.
This experiment provides an explanation for why humans naturally keep their arms straight when walking. However, why running with your arms bent naturally remains unclear.
A 2014 study found that swinging arms consumes energy while running, but keeping your arms straight requires more energy. That’s because the arm swing will reduce the movement of the upper body.
Relation to Human Evolution
Additionally, the relationship between arm movement and stride can help explain how arm proportions evolved in the human family tree.
In contrast to modern humans, ancient humans of the species Australopithecus dan Habilis Homo who lived millions of years ago, had arms that were much longer than the legs.
Lower arm Australopithecus and A handy man also longer compared to their upper arms. However, shorter arms and shorter overall arms are known to sway less.
Shorter arms would have benefited modern humans in running long distances. Selection for this trait could shape the evolution of the length of the human arm bone. Therefore, modern arm proportions emerged with the evolution of long-distance running Standing man.
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2023-08-03 02:30:00
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