Why Do Muscles Ache After Exercise?

The human body has 639 muscles, each with its own name! If all the muscles arc the put together, they make up the flesh of the body.
Most muscles are fastened firmly to the bones of the skeleton. The skeleton forms the framework, and the muscles move the parts of the body. Without them a person could not live. Not only would it be impossible to eat, breathe, and talk, but the heart would stop because its beating is a muscular action.
All muscle is made up of long, thin cells called "muscle fibres". But muscles differ in what they do and how they do it. They also differ in shape, appearance, size, and in other ways.
When a muscle is contracted, it produces an acid known as lactic acid. This acid is like a "poison". The effect of this lactic acid is to make you tired, by making muscles feel tired. If the lactic acid is removed from a tired muscle, it stops feeling tired and can go right to work again!
But, of course, lactic acid is not removed normally when you exercise or work. In addition, various toxins are produced when muscles are active. They arc carried by the blood through the body and they cause tiredness—not only in the muscle, but in the entire body, especially the brain.
So feeling tired after muscular exercise is really the result of a kind of internal "poisoning" that goes on in the body. But the body needs the feeling of tiredness so that it will want to rest. Because, during rest, waste products are removed the cells recuperate, nerve cells of the brain recharge their batteries, the joints of the body replace the supplies of lubricant they have used up, mid so on. So while exercise is good for the body and the muscles. rest is just as important!

It's funny how so many people still believe that lactic acid is the reason for pain in your muscles.  Finally enough studies have been done to show that it's not the lactic acid that causes pain (even though it is definitely a by- product of working out) it's the small tears in your muscles that occur when you put more stress on them then usual.  Same with your bones.  That's how you get stronger.  Your body realizes the the unusual stress it was put under and heals the micro-muscle tears and builds them up stronger so they are better able to handle stress.  This is the same reason why walking is good for your bones, because when you put them under stress, your body responds by rebuilding you stronger.

Well, if you just started to exercise your body muscles are getting used to being "worked" out.
They will eventually get used to the exercise as they tone-up and the fat turns to muscle. Have some rest while exercising. Exercise every 2 days. So you have a day of relaxation for your muscles. :) hope I helped.

During the stress of exercising the muscles, tiny microscopic tears are made in the muscle fibers. This is the source of the pain in your muscles....not the lactic acid build-up. The lactic acid is a by-product of your muscles running out of a source of energy (glycogen) during high demands, so lactic acid is diffused from the muscles into the bloodstream where it can facilitate the production of glycogen without the presence of oxygen. It is a relatively short term effect, as compared to the long term pain (normally 2-5 days) felt by tearing the fibers. The pain/tenderness from rigorous exercise lessens as the muscles adapt. The desired result of tearing these muscle fibers, is that they do repair themselves through diet and rest, and they will grow back bigger and stronger with continued exercise.

Imagine your muscles as people.            You're making them work when they don't want to and making you hurt is the only way to tell you off.