Causes of Sore Muscles

Sore muscles have more than one cause and are typically part of any exercise regimen. However, extensive muscle damage can also cause sore muscles and may require medical treatment. The three main causes of sore muscles are lactic acid, delayed onset muscle soreness and muscle strains.
Lactic Acid Burn
Lactic acid forms when there is not enough oxygen to complete the energy conversion process. As blood flows through muscle cells, it carries away lactic acid and waste products while delivering oxygen and nutrients. Strenuously exercised muscles do not have adequate blood flow to remove lactic acid at the rate it is produced. This build up of lactic acid inflames muscles and causes soreness.
Delayed Onset Muscle Soreness
Muscles are usually sore the day after a strenuous workout. This soreness is caused by exercising muscles beyond the their normal limits. Vigorous exercise causes micro tears and bleeding in and near the z-band filaments that keep muscles together. When enough muscles and filaments are damaged, it causes muscles to feel sore.
The repair process begins 8 to 24 hours later, as satellite cells are attracted to the muscle fibers. Additionally, white blood cells and other fluids and nutrients collect around the damaged fibers; this causes swelling. The swelling, in turn, causes sore muscles. Some of the satellite cells fuse to the muscle fibers, causing muscle cells grow in thickness and in number. The process is called delayed onset muscle soreness or DOMS. This muscle soreness, however, means that the muscles are being repaired and growing stronger.
Muscle Strains
Rapid muscle soreness can occur during exercise. However, if the muscle aches when resting, there is pain when stretching the muscle or the muscle weakens, it could be severely torn. If the pain is accompanied by a popping sound or becomes severe, go to the emergency room.
You can treat moderate muscle soreness caused by exercise at home. Reducing these causes of muscle soreness requires the PRICE method. You must "Protect" the muscle from further injury and "Rest" the muscle. Apply "Ice" to the injured area. Apply slight "Compression" with elastic bandages, and "Elevate" the sore muscle to prevent avoidable swelling. If this home treatment does not decrease muscle soreness within a few days, go to see a doctor.
Stretching before a workout, setting limits and building up a tolerance will help prevent muscle strains. Please note that any new sport you take up will probably require you to use underdeveloped muscles; you should build these muscles up slowly to prevent injury. Mild muscle soreness caused by exercise is a healthy response to a strenuous work out. However, you should monitor your soreness to avoid a potential injury.