BBC: Man vs beast: Who is more efficient?

Whether it's salmon swimming upriver to lay  their eggs or cheetahs running faster than a car, animals can do incredible things with thier bodies. 

Human bodies are no less incredible- just think of Olympic swimmers and sprinters. 

Our bodies work using just the energy provided by what we eat. This means that the human body has to be incredibly efficient, using as little energy as possible to do what it needs to.

Yet even with our efficient bodies, no-one can run as fast a cheetah, not even Olympic champions!

In this programme, we'll be asking exactly how efficient is the human body?

We'll be comparing human bodies' performance against each other, and against some animals too. And, of course, we'll be learning some new and useful vocabulary as well. 

But before that I have a question for you, Roy. Efficiency involves an input and an output. It's abouth the relationship between the amount of energy coming in- in other words, the food we eat- and the amount of the energy going out- the usual movements and activities of day-to-day life. So, according to this definition, which animal is the most efficient? Is it:

a) an ant    b) a whale    or  c) a human?

Humans are the most efficient animal. 

OK, Roy. I'll reveal the answer later in the programme. To find out more about how the human body works it' helpful to know how our species evolved. Here's Herman Pontzer, professor of evolutionary anthropology at Duke University, speaking with BBC World Service programme, CrowdScience. 

Humans are remarkably efficient. We walk on two very straight legs, if a human stands next to a dog, for example, the dog has got that funny bent classic dog leg shape, right? And that crouched posture is really typical of most animals. Humans have a very straight leg, and so because of that, and because our legs are pretty long for our body size- humans are part of the ape family- we're are efficient. 

Humans are apes and evolved fromt he same origin as gorillas and chimpanzees. One big difference  however is that humans walk upright on straight legs, whereas most animals are couched- bent over at the knee and leaning forwards to the ground. This crouched posture is not an efficient way to move. 

Other animals, like dogs, have flat backs and move on four bent legs called doglegs- something bent in the shape of a dog's leg. The word dogleg can also mean a sharp bend in a road or path. 

So, the design of the human body makes it efficient compared to some other animals- but how do humans compare with each other? How do Kenyan athletes break long-distance running records, while many of us struggle to run for the bus? The main reason, according to Loughborough University physiologist, Rhona Pearce, is training. But there may be other factors too, as she explained to BBC World Service's, CrowdScience. 

Age probably comes into it in that there's probably an optimal age for tendon elasticity- that drops off as you get older, s probably there's a sweet spot in age for running economy. So, in terms of weight, it depends what you weight is made up, if you've got more muscle  mass that's goign to help you, whefreas if it's more fat then you've got to carry it. 

Efficient running depends on having flexible muscles and tendons, and this flexibility drops off, or decreases, as we get older. This means that, in terms of running, the body has an optimal age- the best age, or the age at which you are most likely to succeed.