Exercise is vital to conditioning your body to have an efficient immune response. Hundreds of studies on exercise and immunity have been conducted. In general, the more fit you are the better your immune system works. At the same time, higher amounts of exercise place increased demands on your immune system. Working out or performing significant exercise at the same time your body is trying to fight off the flu could make you more susceptible to getting sick. Thus, it is a good idea to understand exercise in the context of your immune system.
Muscles as Part of Your Immune System
Muscles themselves are actually part of your immune system and are used as the primary savings account of protein to assist in the proliferation of immune cell troops once a battle is on. It is obvious to anyone who has been through a nasty flu for a week or longer that their muscles are weaker and they have less strength. This is because muscle protein is used to fight infection.
Muscle fitness not only implies better protein reserves, it also signifies a generally better immune response potential. Comparing the muscles of the elderly to younger people finds that the rate of protein synthesis declines in proportion to the baseline amount of inflammatory signals like TNFa and IL6. A baseline elevation of these inflammatory signals reduces optimal immune function, as explained in my article, Using Nutrition to Perceive and Combat Swine Flu.
In other words, the lack of vitality in unfit muscle reflects higher baseline immune-disrupting inflammation - which when added to other forms of existing inflammation (obesity, too much stress, lack of sleep, aches and pains, etc) add up to a reduced immune response. Conversely, twenty minutes of strength training three times a week in elderly individuals helps their muscles respond in a more youthful manner.
A study on centenarians indicated that those who maintained functional numbers of NK killer cells vital to front line immunity against the flu had better muscle mass, thyroid function, and vitamin D status.
The most important calorie for muscles is protein. Elderly women on a low protein diet compared to an adequate protein diet have noticeably lacking muscles with concurrent impaired immune response.
It is generally true that the more muscle mass you have entering a flu season the better your baseline immune response and the greater your ability to sustain a battle against a nasty flu.
How Exercise Can Hamper Immunity
The benefits of exercise occur by conditioning your muscles, aerobic system, and inflammatory system to be fit. The potential risk of exercise is that you break down muscle in the process of conditioning them, a process that requires inflammation in the name of future improvement.
Athletes are known to struggle with immune function, especially those who are really pushing their body to an elite level of fitness. Illness is as common as injury in the athletes who fail to make their bid to be in the Olympics.
Exercise places demands on protein supplies to rejuvenate muscles and the process of exercise uses up antioxidants. Antioxidants and protein are vital keys to immune function. If your reverses are run low by exercising you may not be in a good position to mount a proper immune response.
The amount of dietary protein in general is very important. I recommend ½ your ideal weight in grams of protein per day for an average exerciser, up to ¾ your ideal weight in grams of protein per day for a routine exerciser, and more than that for an athlete.
The failure to have enough dietary protein can send your muscles into a highly inflamed catabolic state, meaning that muscle tissue is breaking down too fast. In an athlete this is caused by overtraining. In the average American this is caused by a lack of use or doing exercise without enough protein and antioxidants.
Amino acids are the building blocks of protein. Numerous studies show that the amino acid glutamine is the vital amino acid that determines whether your muscles will break down excessively (inflammatory and catabolic) or rejuvenate and repair (anabolic and fitness). Glutamine is also the most important amino acid for the rapid production of immune cell troops. It was recently demonstrated that glutamine significantly boosted the function of immune troops within your digestive tract. Remember, the swine flu will incubate in your gut before it moves to your respiratory system.
When scientists induce experimental spinal cord injury it results in lack of muscle (due to a lack of nerve stimulation of muscle), in turn severely compromising immunity. These researchers found that a low level of the amino acid glutamine is a key maker for suppressed immunity.
The loss of muscle mass in well-conditioned astronauts during a long mission occurs in conjunction with depleted cell-mediated immunity (adaptive higher-powered immunity). This is one more example that shows the link between muscle health and immunity. I can think of no example of someone with poor muscle function and superior immunity. Conversely, using glutamine to restore weakened muscles helps immunity.
Overweight individuals are often making an effort to exercise more intensely so as to lose weight. However, new science shows they must have adequate antioxidants because their out-of-shape muscles make free radicals too easily. The baseline inflammation of an overweight person is also a risk factor for the swine flu. Overweight people who get in a good weight loss trend with improving muscle fitness will have better immunity - as long as they get adequate dietary protein for healthy weight loss while taking extra antioxidants so as to get an improved response to the exercise.
It is actually a good thing to push your body a bit with exercise for optimal health results. For example, pushing aerobics releases BDNF and repair signals that build new brain cells and help repair existing problems. Pushing strength training will build muscle. Just do it right and be more careful not to overdue during the flu season, especially if you are on the verge of fighting a bug.
Children on sports teams need to pay special attention to these factors. If your child knows he/she is fighting something off, it is generally better to sit out a practice/game or two than to spend the next two weeks in bed. If you keep your child adequate in protein, antioxidants, and glutamine in particular, the potential problems of lots of exercise to their immune system can be reduced.
What to Do if You are Fighting a Bug
The modification of an exercise program is required as soon as you can sense you are fighting off a bug of any kind, including the flu. Exercise is energy intense and inflammatory. Your immune system is energy intense and inflammatory. Both systems use the same raw materials and many of the same functions (albeit for different reasons). If you make your body perform a higher level output of exercise when you are beginning to feel sick, it will create a handicap in your immune response that is likely to speed the onset of an illness.
It is very clear that the 48-hour recovery period following intense exercise is a time of immune suppression, not what you want if you need to fight a bug during that time. This is most likely a system your body uses to prevent an autoimmune reaction against inflamed tissues following exercise. However, this mechanism will clearly get in the way of the short-term need of fighting a flu bug.
Sometimes the first symptoms of a flu bug are subtle and not even recognized as pending flu. This could be an unusual tiredness (energy already being deployed to immunity), a mild sore throat (a key location for viral flare-up symptoms), or stiffness in the calf muscles (the first sign of excess lactic acid production from viral activity). Other times the symptoms are more obvious and you can tell you are fighting something that has its first toehold in you.
If you feel this way you should not do a significant aerobic workout, strength training, or any excessive output of physical energy. Cut back on your activities, go for a walk, stretch - but do not do a lot even if you are generally conditioned to do so and it is part of your regular exercise routine. This is a good time to really boost up your immune support nutrients.
Other basic tips in this precarious time of initial flare up are to minimize anything stressful, do not eat any sugar (especially between meals), do not eat any junk food (especially chips or fries), do not drink any alcohol, and ensure you get adequate sleep.
Your immune system prefers to work at night so that it is not in conflict with your daily energy activities. However, when you are fighting a bug your immune system must become active during the day to protect you. This process has many inherent conflicts, but is vital to your survival. Give your immune system the chance to do its job by not getting in its way or depleting its function with a round of intensive exercise.
The moral of the story is to cut back at the first signs of fighting a bug, which often means it will be out of your body in a day or two with a very mild visit. If you do it right you can save yourself a week or two of downtime.