by Mark Rippetoe

Training with weights produces muscle soreness. Many people don't like to be sore, and that's why they won't train for strength. Running also makes you sore, but not as bad and not all over the body, like weights, so running is more popular. Other people have noticed that riding a bike doesn't produce sore muscles, so they ride a bike for exercise instead of lifting weights or running. But to some people and this may come as a surprise to most of you getting sore becomes the whole point of exercise. They wear their soreness like a badge of honor, and regard sore muscles as the price they must pay for continued self-improvement.

Read article