Strength and Flexibility: Our Amazing Hands and Feet

Our hands and feet are biomechanical marvels. More than any other piece of anatomy, they are what made us into such a successful species, enabling early humans to walk out of Africa to colonise the globe and master the natural world. Together with the brain, our hands and feet coordinate and control much of what we do daily – standing, sitting and moving around with such grace and flexibility that we rarely give a thought to these marvels of nature’s engineering.

THE HAND

Both the human hand and foot represent a triumph of complex engineering, exquisitely evolved to perform a range of tasks. Photo: Science Photo Library

The hand is one of the most complex and beautiful work of nature in the human body. Not only does it give us a powerful grip, it also allows us to manipulate small objects with great precision, a versatility that sets us apart from virtually every other creature on Earth. At the same time, the human hand has one of the strangest arrangements of muscles in the body. Most of its movements are controlled by muscles that aren’t located in the hand at all, but in the forearm. The muscles of the forearm connect to the finger bones via long tendons that pass through a flexible wrist. This remote musculature gives our fingers strength and flexibility that wouldn’t be possible if all of the muscles had to be attached directly to them. In effect, the hand is simply a bony puppet, lashed together by ligaments and controlled by the forearm.

What gives our fingers their dexterity? For that, you have to thank the muscles within the hand called intrinsic muscles. Some of these muscles specifically control the thumb and little finger while others such as the lumbricals are not directly attached to bones but to tendons and allow a wonderful subtlety of movement.

You should also thank the thumb, which is the most important digit of all. The thumb accounts for 40% of the hand’s capabilities and unsurprisingly, if you lose one, surgeons will happily amputate your big toe and use it to create a new thumb, sacrificing one body part for the greater good.

Which finger could you most afford to lose? At first glance, you may think it is the little finger. But as a hand surgeon will tell you, the little finger is second only to the thumb in importance. Oddly, the finger you can lose with minimum inconvenience is the index finger. It can be included or excluded from everything we do with our hands.

THE FOOT

Our feet are equally complex. Each foot contains 26 bones, 33 joints, 19 muscles and 57 ligaments that connect bone to bone. So in terms of complexity, it is on par with the hand.

Why this complexity? Being bipedal creatures, our feet must be strong enough deal with some of the greatest forces experienced by the body, whilst also capable of movements as exquisite as a ballerina’s pirouette. In fact, you could say that it is due to our feet that we have evolved such extraordinary hands because the ability to walk upright over great distances efficiently frees our hands to develop their unique anatomy and capabilities as mentioned.

To do all that it needs to do, the foot must be optimally designed. First, the skin of the foot is thick and tough. Moreover, under the heel of the foot lies a pad of specialised fat, packaged up like bubble wrap to absorb shock and spread the load of our body weight. Second, the core of the foot is the arch which creates the space for a tough web of muscles and ligaments that play a vital role in absorbing the forces created when you walk or run. But the arch also acts as a spring; storing and releasing energy when you push off with your toes. Even the simple act of standing would be clumsy were it not for the design of the foot. A lot happens just to keep us upright. In particular, there is a continuous feedback system between foot muscles and the brain so that tiny changes can be detected that allow us to keep our balance while standing.

So the next time you go for a brisk wall, or a run, or go grocery shopping with your hands full, spare a little thought for those marvels of nature’s engineering that are yours hands and your feet.

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