Medical Central: Swimming & Exercise

I mentioned last time that skin is waterproof. Well, the body has some other devices that have to be put into action when swimming... or other stuff!

Swimming & Exercise
Everyone knows we have to exercise to get fit. But how come? The body is a machine... an amazing machine extremely well-put together! But, while it does fine on a day-to-day basis, training can make it work better. The different components will work together smoother, and the muscles themselves will get stronger.
Also, healthy eating will increase the muscles' strength and efficiency. Why? Muscle make energy from oxygen and glucose... which explains why the heart beats faster during exercise time (to transport these items more quickly). But exercise can help make longer-lasting energy supplies, and if the lung muscles are strengthened, they can expand to take even more air (and therefore, oxygen) when needed!
Back to the "machine" part. The body parts can work together in many different ways, and those ways can sometimes be complicated. Take swimming, for example! Our feet can act as flippers... but that starts with an action from higher up our leg! And the hips roll in response to the movement of our arms! And even the propelling motion of our arms are controlled by two different muscles... the deltoid (sp?) shoulder-muscle and one in our arm! The muscle pulls as much as possible, and then it comes back, making a propeller motion.
Plus, there are other factors. The body has to be streamlined in order to get through water less and push against it less. And little kicks are better than big ones! Plus, the head rolls in rhythm with the arms, coming up for air when the arm is down, and going down when the arm comes up (you know, to get out of the way!).
And a lot goes into diving, too! Certain feet have to push off, then the arms off the block, and then the body has to be streamlined too! And the hip has to be hinged in order to enter the least amount of water possible, so there's less resistance! Wow... you've got to be impressed with professional swimmers! And that's just swimming... hurdle jumpers can do some pretty impressive stuff as well. And all those other professional athletes! They can do some amazing stuff too!
Developments can happen over long spaces of time as well... meaning generations! People are healthier and stronger (can run faster and jump higher) than hundreds of years ago. This is due to better food and better exercise gear. But scientists believe that someday we'll hit our stopping point... and won't be able to get faster or jump higher or stronger, even throughout generations.