We all want a healthy immune system, one that’s balanced. A balanced immune system is one that fights foreign invaders, like bacteria and viruses, without overreacting and damaging normal tissue, as happens with autoimmune diseases and chronic inflammation. A variety of factors can impact immune function. For example, lack of sleep and stress can temporarily suppress the immune system. But, what about exercise, more specifically, weight training?
A number of studies have looked at the impact of aerobic training on the immune system. The consensus is that moderate aerobic exercise has a beneficial impact on immune function and may even lower the risk of developing an upper respiratory infection, like a cold. Yet, intense exercise or exercise of long duration, like a marathon has the opposite effect. It decreases the body’s defenses against infection and may increase the risk of catching a pesky case of the sniffles or, even worse, the flu. The greatest harm to immune function is training exhaustively without giving your body time to recover.
There’s a cumulative effect whereby an exhaustive workout followed closely by another exhaustive workout compounds the negative impact training heavily has on the immune system. Overtraining without adequate recovery suppresses the activity of natural killer cells, cells that fight viruses and helps keep tumor cells from gaining a foothold in the body. You don’t want them to fall down on the job! With aerobic exercise, it’s a J-shaped curve. Moderate exercise benefits the immune system and the activity of natural killer cells while overtraining interferes with the immune system’s ability to fight off infection.
So much for aerobic exercise. What about weight training? Training your body against resistance causes a different set of adaptations to take place and has a different impact on the body. But, how does lifting weights impact the immune system and the ability of the immune system to fight off infection?
Weight Training and the Immune System
Not surprisingly, most of the studies looking at the effect exercise has on the immune system have focused on endurance exercise. Immune health is an issue of concern, especially for people who do exhaustive exercise, like running marathons or ultra-marathons. However, few studies have focused on the effect weight training has on immune cell activity- but there are a few. One of the earliest studies was published in 1996.
In this small study, 22 subjects took part in a weight training program. Half of the participants were young, in their 20’s and 30’s and the rest were older, between the ages of 65 and 80. Some of the participants were healthy while others had rheumatoid arthritis. The weight training program consisted of lifting at 80% of one-rep max, 8 reps per set, and 3 sets per session. They lifted three times per week for 12 weeks. There was also a control group who didn’t exercise.
What did they find? When the researchers measured various markers of immune function, they found no substantial difference between the training group and the control group, regardless of age or whether they had rheumatoid arthritis. Resistance training, using a relatively high resistance, didn’t appear to impact immune function. But, this is only one study.
More recent research shows that resistance training session transiently increases the number of circulating immune cells that help protect the body against infection. These cells are part of the body’s innate immune system and include certain types of white blood cells and natural killer cells. This isn’t surprising since some of these cells, like monocytes & neutrophils, help to repair damaged muscle tissue after a strength workout. This upgraded immune activity is less pronounced in older people due to the impact of aging on the immune system. Our immune systems age, just as the rest of our body does, a process called immunosenescence. One study even suggested the enhanced release of immune cells after weight training might be a way to boost the less robust immune response that older people experience. Yet, there are few studies looking at what form of weight training is optimal. Would lifting heavy and lower reps be more beneficial or would high reps, lighter weights offer greater benefits? There are still too many unanswered questions about weight training and immune function.
Overreaching and Overtraining
Overall, there’s no strong evidence that weight training, among people who do it regularly, decreases the risk of developing an upper respiratory infection or lowers the odds of developing the flu. This despite the increase in immune cells identified in some studies. On the other hand, research in this area is limited. In addition, it may be beneficial for older people who have immunosenescence. On the plus side, aerobic exercise in moderation DOES seem to reduce the number of sick days based on a study published in the British Journal of Sports Medicine. So, exercise in general, as long as you don’t overdo it, may help you avoid the sniffles.
What is clear is that exhaustive weight training or overtraining has a negative effect on immune health. Overreaching and overtraining can boost the release of stress hormones, including cortisol. That’s not what you want! A rise in cortisol reduces the body’s ability to fight infection. When your adrenal glands pump out excess cortisol, it suppresses the activity of white blood cells that fight bacteria and viruses. It also stymies the activity of natural killer cells, those that are most adept at killing viruses. The reality is any type of exhaustive exercise, whether it’s aerobic or weight training, isn’t beneficial to your immune system. Regardless of what type of exercise you do, your body needs rest and recovery time between sessions.
But, that’s not the full story. Adequate nutrition is vital for healthy immune function as well. You need enough calories and a balanced array of macronutrients to support immune health. Micronutrients that play a key role in immune function include vitamin A, vitamin C, vitamin D, and vitamin E. along with zinc, selenium, and iron. You can best meet these requirements by eating a nutrient-dense, whole food diet. So, keep your workouts and your nutrition balanced!
References:
Med Sci Sports Exerc. 1996 Nov;28(11):1356-65.
Psychology Today. “How Stress Affects the Immune System”
Exercise Immunology Review 18:8-41 · August 2012
Journal of Sports Medicine 2011;45:987-992.
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