Arm muscle pain is most commonly caused by injury, such as muscle strains, muscle tears or ruptures, and direct trauma to the muscle. Other common causes of arm muscle pain include overuse of the muscles and even a lack of conditioning of the muscle. In some cases, a pain that may feel like arm muscle pain may actually be caused by something else entirely, such as tendon pain, ligament pain, and even nerve pain. A doctor's visit may be in order to obtain a proper diagnosis, especially if the pain persists for more than a few days or if the pain worsens over time.
Muscle strains are perhaps the most common causes of arm muscle pain. Such an injury occurs when the arm muscles bear a burden they are not prepared to handle, or the muscles are twisted beyond their means. The result is tearing in the tiny fibers that make up the muscle, leading to pain, soreness, or tenderness. Minor muscle strains can be treated with the RICE treatment — Rest, Ice, Compression, and Elevation — and are considered a fairly minor injury that does not necessarily require the sufferer to cease all physical activity. More severe strains, however, may be more painful and should be treated with caution to avoid worsening the injury. If the pain is intense, the sufferer should cease all physical activity and attempt to treat the injury with the RICE treatment.
A muscle rupture occurs when a muscle separates entirely from the tendons connecting it to bone, or from itself. This is a painful injury that will be readily apparent because not only will the pain be intense, but also the appearance of the arm will change; the muscle can sometimes bunch up at one end of its length, and bruising and swelling is likely to occur quickly. This is considered a serious injury and anyone suffering from such an injury should seek medical attention immediately. A surgery may be necessary to repair the ruptured muscle.
More common arm muscle pain causes include overuse and underuse of the muscles. People who are very active will experience soreness or tenderness when the muscles have been overused; this is common during long athletic activities or when one is attempting to build muscle. Such arm muscle pain often goes away within a day or two, and rest and stretching usually speeds the recovery process. Not using the muscles enough can also lead to pain, since weaker muscles are more likely to become tired quickly, and tired muscles are more likely to tighten, thereby leading to pain or discomfort.