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Using our skeleton to combat gravity

Comparing a human and an ape skeleton to understand how our body is designed to stay upright.
Gravity is a constant challenge to our balance. As humans walking on two feet, we have had to evolve over millions of years to fight the effects of gravity. In fact, we have placed one of our most precious organs right at the top of our body and encased it within a protective but very heavy skull. Because our head is so heavy, evolution has altered the position of our skull. On an ape skeleton, we can see how the skull is inserted onto the spine at the back. Yet as our spine is vertical, our skull is positioned more centrally to avoid pulling us forward. Our spine has also evolved to cope with our upright posture and supporting our heavy heads.
You can see the almost S-shape of the spine to distribute the weight of our upper body directly above our hips. In comparison, the ape’s spine has a single gentle curve.
Our hipbones are deep and curved to support our organs sitting above them. This distributes our upper body weight over a broader base. When an ape walks on two legs, its knees stick outwards and are unable to straighten. This makes it hard work on the muscles and explains why they can only walk short distances. Our thigh bones actually point inward from the hip to our large knee joints. This focuses our centre of gravity above our feet to help maintain our balance. But unlike the ape, we have also very powerful muscles around the hip joints to keep our legs stable. You can feel these muscles come into action when standing on one leg.
Right at the bottom of our skeleton, we have our feet. We have larger and stronger ankle joints and an arch in our feet to provide stronger support and stability. So understanding the importance of the skeleton in maintaining our upright balance, it becomes clear why conditions such as arthritis or joint replacements can increase our risk of falls. Similarly, we can see how muscle weakness, especially around the hips, can increase our risk of falling.
In the next two videos we will discover how our bodies are designed to help keep us upright. Learning how our body is supported and how it combats the effects of gravity will help us understand the importance of ageing healthily. It will also improve our understanding about the risk factors which we will explore in Week 2.
This first video explores how our skeleton helps to support our upright posture and maintain our balance. In the following step we will learn about how our organs and senses help keep us upright, preventing us from falling.
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