Most competitive athletes follow a stress and recover training program and so should you, even if you don't compete in sports. To make muscles stronger, you need to exercise intensely enough to damage them, and to increase your ability to take in and use oxygen, you need to exercise hard enough to become short of breath. However, several recent studies show that if you don't follow your hard workouts with easy ones, you may suppress your immunity to increase risk for developing infections such as colds and increase your chances of injuring yourself.
This month a study shows that taking intense workouts reduces the immunities of elite soccer players by lowering salivary levels of Immunoglobulin A (IgA), an antibody in your body secretions that prevents germs from entering your tissues and bloodstream (Journal of Strength and Conditioning Research, September 2016;30(9):2460–2469). The same reduction in salivary IgA occurred in football players after games (Journal of Sports Sciences, August 2015). It has also been shown in ordinary exercisers (who are not competitive athletes) when they take intense workouts on consecutive days without allowing time for recovery (Frontiers in Physiology, June 28, 2016). IgA is found in tears, saliva, and secretions in your stomach, intestine, colon, bronchial tubes, and skin as a first line of defense to prevent germs from entering your bloodstream. Having prolonged low levels of IgA can predict infections in the future.
The researchers also found that consecutive intense workouts reduce levels of anti-inflammatory cytokines, which are proteins produced by white blood cells that act to dampen inflammation ("turn down your immune response"). These are the chemicals that control the strength of your immune response to invading germs. Having low levels of anti-inflammatory cytokines increases the chances of your immunity attacking your body in the same way that it tries to kill germs, which can lead to the various "auto-immune" diseases.
Other studies show that consecutive days of intense exercise also reduce the number of white blood cells that defend you against invading germs. All these changes increase your chances of developing an overtraining syndrome in which your muscles hurt and you feel exhausted all the time. Overtraining suppresses your immunity to increase risk for infections, excessive muscle damage and delayed recovery from workouts.
Your immunity is lowered by taking too many consecutive intense or very long-duration workouts, not taking enough rest periods, and not stopping a workout when your muscles burn and hurt or you feel excessively tired.
How Muscles Heal after Intense Exercise
Muscles are made up of hundreds of thousands of individual fibers. To make muscles stronger, you have to damage them. Then when they heal, they become larger and stronger. You can tell that you are damaging a muscle during exercise by the burning you feel in the muscles, and the soreness you feel in that muscle on the next day. If you take an easy workout when your muscles feel sore, your muscle will become stronger. If you take an intense workout on sore muscles, you can tear them and become injured.
The healing of muscles damaged by intense exercise is governed by your immune system:
• The exact same cells and cytokines that kill germs initiate the healing process.
• When you feel sore after intense exercise, your immune system goes into high gear to heal the damaged muscle tissue.
• If you do another intense workout when you feel sore and are trying to heal, your body senses that you are causing further damage, so it reduces the amount of white blood cells and proteins that initiate muscle healing.
• Your body reduces your immune reactions because if your immunity stays active all the time, it can attack your healthy tissues in the same way that it attacks germs. This is called inflammation and can lead to the many "auto-immune" diseases such as chronic fatigue syndrome or inflammatory bowel disease. Inflammation can also lead to a heart attack because your overactive immunity can punch holes in arteries, which starts the formation of plaques. Cancer can be caused by your immunity attacking your own cells to damage the DNA genetic material that controls cell growth. Damaged DNA can cause uncontrolled growth which is cancer.
How Exercise Strengthens your Immunity
When you are exercising properly by taking hard workouts to strengthen your muscles followed by easy workouts to allow your muscles to heal, you are also strengthening your immunity. When you damage muscles with hard exercise, your immunity uses the same white blood cells and proteins that attack and kill germs to start the healing process, so vigorous exercise turns on your immunity in the same way that an infection does. Then to keep your immunity from being too active and using the same chemicals to damage you, you produce anti-inflammatory chemicals to dampen down your immunity. A proper training program of vigorous exercise followed by an easy workout strengthens your immunity by turning it up and down.
Listen to Your Body
After intense exercise, you should expect to feel sore because of the muscle damage, which is good for you. If you do another intense workout when you are trying to heal, your body senses that you are causing further damage. Your body reduces the same white blood cells and proteins that you use to kill germs and heal damaged muscles.
• Try to alternate harder workouts with easy recovery ones on consecutive days.
• If you are training properly, expect to feel sore every morning when you wake up. If your muscles feel better after a 5-10 minute warm up, take your planned workout.
• If you don’t feel better during your warm up, go home because continuing to exercise will only increase your chances of injuring yourself.