Why are my Muscles sore 48 hours later?

Most people, if training properly, especially beginners or if you've had a long layoff, should experience muscle soreness 24 hours to 48 hours after working out. There is actually a term for this. It's called Delayed Onset Muscle Soreness, or DOMS.

This pain is caused by microscopic tears in your muscle during a good workout. After the workout, the muscle starts to rebuild itself (provided it is allowed enough time and nutrients to recover). This rebuilding process helps creates new muscle, stronger than before. Keep in mind that your muscles grow when you  rest - not when you're at the gym. When you start looking at yourself in the mirror all the time, keep in mind that's called a pump and it's the blood rushing to the muscles. It goes down a few hours later. So remember rest is important. And when you feel that muscle soreness you can rest assured that you had a great workout. If you are not sore, you may need to increase the amount of weight you are using during that particular workout. NOTE - muscle soreness is very different than injury pain. For example if you are doing bench press and your elbow pops out of its socket because you lifted too much weight, that's actualyl an injury not muscle soreness. Forget looking in the mirror and go get an x-ray.

Should you workout when your muscles are sore?
You are always going to rest the bodyparts you have just made sore so chances are by the time they come around again in your routine you should be ok. However, if you are still so sore, you should rest a little more. In other words of you are having trouble sitting on the toilet from your leg workout, do not squat that day. Be smart. If your body is telling you it is not ready then do not be a hero. Chances are you will not have a great workout and you will be in a lot of pain during the workout.

To help offset the soreness, drink a lot of water, perform stretches for the sore bodyparts and if it is really bad take aspirin if you can stomach them.