To make muscles stronger, you need to exercise intensely enough to damage the muscles. You can tell that you are damaging muscles when you exercise vigorously enough to feel soreness in those muscles eight to 24 hours later, which is called Delayed Onset Muscle Soreness or DOMS (Strength & Conditioning Journal, October 2013;35(5):16–21).
Muscles are made of thousands of muscles fibers. Each fiber is made up of blocks called sarcomeres lined end-to-end with each block touching at the Z-lines. To make a muscle stronger, you have to exercise hard enough to damage it at the Z-lines. Then when the Z-lines heal, the muscle is stronger than it was before your intense workout. Biopsies of intensely-exercised muscles show bleeding and disruption of tissues at the Z-lines. You should then take easy workouts until the Z-line damage heals or you will put yourself at high risk for injury. To protect yourself from tearing muscles, you should wait until the DOMS is gone before you take your next intense workout.
Healing from Delayed Onset Muscle Soreness
When you damage tissue by exercising very intensely or through trauma , the healing process is directed by your immune system using the same biological mechanisms that your body uses to kill germs. When germs get into your body, your immune system sends cells and proteins into the infected area to kill the germs. When muscles and other tissues are damaged, your immune system sends the same kinds of inflammatory cells to the damaged tissue to promote healing (Journal of American Academy of Orthopedic Surgeons, Vol 7, No 5, 1999). The inflammatory cells called macrophages release a hormone called Insulin-like Growth Factor (IGF-1) into the damaged tissues, which helps muscles and other injured parts to heal (FASEB J. Jan, 2011; 25(1):358–369).
Applying ice to sore muscles can ease the pain but it delays healing by decreasing the healing immune response (Knee Surg Sports Traumatol Arthrosc, Feb 23, 2014; American J of Sports Medicine, June 2013). Anything that reduces inflammation delays healing: cortisone-type drugs, most pain-relieving medicines, such as non-steroidal anti-inflammatory drugs like ibuprofen (Pharmaceuticals, 2010;3(5)), immune suppressants that are often used to treat arthritis, cancer or psoriasis, and anything else that blocks the immune response to an injury.
What to Do When You Have DOMS
You can stop exercising when you have DOMS if you want, but you will become stronger if you take easy recovery workouts while your muscles are still sore. Athletes do not usually plan to take off workouts during recovery, even though resting when the muscles feel sore will allow muscles to heal faster than exercising at a low intensity. If you exercise at low intensity during recovery, your muscles will become more fibrous and resistant to injury when you stress them in the next intense bout of exercise. If you are a runner, run faster two or three times a week and much more slowly when you feel soreness on the days after running fast. If you are a weightlifter, lift heavy weights once or twice a week and much lighter ones on the following day or days when your muscles feel sore. If you are a basketball player, scrimmage hard for several hours on one day, then run plays and practice shooting on the next days when your muscles feel sore. If you play golf, practice your long drives on one day and practice putting on the following days when your muscles feel sore.
What Does Not Relieve DOMS
• Stretching: Reviews of the scientific literature show that stretching neither prevents nor treats DOMS (Cochrane Database Syst Rev, July 6, 2011;(7):CD004577; Br J Sports Med, 2011;45:1249-1250). It did not prevent the muscle-damage-induced rise in blood creatine kinase, muscle pain, muscle strength or the PCr/P(I) ratio test for muscle damage (Scand J Med Sci Sports, Aug 1998;8(4):216–21). Stretching does not prevent sports injuries (Clinical Journal of Sports Medicine, March 2005) or lengthen muscles (Clinical Biomechanics, June 2014;29(6):636-642).
• Massage: Some studies show that massage decreases pain, but nobody has shown convincingly that massage hastens muscle recovery or increases contraction strength (J Athl Train, 2005 Jul-Sep; 40(3): 174–180). Massage did not hasten short or long-term recovery and was less effective for recovery than light exercise (J Orthop Sports Phys Ther, Feb 1997;25(2):107–12).
• Heat does not reduce DOMS (J Strength Cond Res, Feb 2004;18(1):155–61).
• Icing offers pain relief but delays recovery from DOMS (J Strength Cond Res, May 2013;27(5):1354–61), weakens muscles and impairs training (Eur J Appl Physiol, Mar 2006;96(5):572–80). See Why Ice Delays Recovery
• Nonsteroidals (NSAIDs, such as ibuprofen) can decrease muscle soreness but do not hasten muscle recovery (J Strength Cond Res, Feb 2003;17(1):53–9). In many studies, nonsteroidals did not even decrease muscle soreness (Brain Behav Immun, Nov 2006;20(6):578–84), or offered no benefit whatever (J Sports Sci, Mar 1999;17(3):197–203). See NSAIDs May Block Gains in Endurance and Strength.