Why your muscles feel sore
No matter how often you exercise, you're still vulnerable to muscle soreness afterward. It's easy to assume soreness simply means a workout “worked,” and there's some truth to that, pushing your body to a new level, especially when you move from one routine to another, causes microscopic tears along the muscles and nearby tissue. This is known as DOMS, or delayed onset muscle soreness: discomfort that typically peaks 24 to 72 hours after exercise, leaving muscles tender to the touch and tighter than usual.
Telling soreness apart from an injury
There's a fine line between ordinary soreness and pain from an injury, and understanding the difference matters, mistaking one for the other can turn temporary discomfort into lasting damage, or keep you from noticing a real injury. The clearest signal is time. Normal soreness doesn't last more than a few days: it comes on quickly during or shortly after exercise, then decreases gradually rather than getting sharper or more intense as the days pass.
If discomfort goes beyond a few days, or feels sharper or stronger the longer it continues, that's a sign something more serious may be going on in the muscles, bones, or tissues. Everyone experiences pain differently, but persistent or worsening pain is reason enough to see a medical practitioner for a full assessment before it causes further damage.
Using ice and heat therapy
Once you've assessed whether you're dealing with soreness or an injury, ice and heat therapy can offer relief, depending on the severity. Ice therapy reduces swelling and pain and works best on acute or new injuries, such as a muscle or joint sprain, limit sessions to 20 minutes to avoid damaging the skin or tissue.
Heat therapy is better suited to chronic pain, old injuries that have gone untreated, or general muscle stiffness. Heat relaxes blood vessels and increases circulation, the opposite effect of ice, and should also be limited to 20-minute sessions to avoid blisters or burns.
When it's time to see a physical therapist
Most injuries from physical activity improve with consistent ice and heat therapy applied at the right time. But if pain persists or doesn't ease up after a week or two of consistent care, the next step is a visit to a physical therapist, who can identify the problem and take the right action to improve your condition. A physical therapist can help you understand what led to the injury, manage the pain, and build a plan around your body's specific condition, one that still gets you the results you're working toward.