Disclaimer: This post addresses general immune system health and fitness training. It does NOT address specifically COVID 19 pandemic prevention strategies, such topics are beyond the scope of this post. For information on COVID 19 preparedness and prevention, I suggest you go to CDC.gov.
Everyone knows that exercise is good for you. According to the Centers for Disease Control and Prevention (CDC, 2020a), adults should try to get the following amounts of exercise per week as the minimum standard:
- 2 or more strength training sessions for the entire body each week PLUS
- Moderate exercise such as brisk walking at least 30 minutes per day x at least 5 days per week each week, OR…
- Vigorous exercise such as jogging/ running for at least a total of 1 hour and 15 minutes total per week, OR…
- An even mix of moderate and vigorous exercise at least 2 days per week
While as many as 1 in 3 adults have no leisure exercise activity (CDC, 2020b), there are many of us accustomed to pushing ourselves beyond these recommendations. The CDC notes that additional health benefits can be recognized by exercising above the minimum guidelines. For those of us that push ourselves with heavy physical training, is there a point at which we jeopardize our immunity? If so, what is that point?
What training considerations should we implement so as to get the best exercise has to offer while minimizing our risk for compromised immunity? What does the evidence say? In the first part of this series, I explored research-backed nutritional factors that athletes and heavy exercisers can follow to improve their immune system competence and ability to resist respiratory infections. In this post, I will explore training considerations.
Moderate exercise enhances immune function
Research notes that exercise lasting less than 60 minutes at a time leads to numerous immune enhancing effects (Nieman & Wentz, 2019). Moderate to vigorous aerobic exercise limited to less than an hour:
- Enhances virus and bacteria fighting activity of macrophage immune cells (which ingest and destroy infected cells, clean up debris, and notify other immune cells of invaders)
- Enhances circulation of immunoglobulins (antibodies that bind and neutralize threats as well as make threats easier to destroy or expel)
- Enhances circulation of anti-inflammatory immune cytokines
- Enhances circulation of natural killer cells (which kill virus infected cells and tumor cells), neutrophils (which surround wounds/ damaged tissue to reduce risk of disease spread), cytotoxic T-cells (key fighters of virus infected cells and cancer cells), and B-cells (which activate T-cells and produce antibodies) (National Institute of Allergy and Infectious Diseases, 2014; Nieman & Wentz, 2019)
- Moderate exercise REDUCES your risk of contracting upper respiratory tract infections by 40-50%!!!!!!!!!!!!! (Nieman & Wentz, 2019)
When aerobic exercise is kept to under an hour, stress hormones and inflammatory cytokines do not reach levels at which they negatively impact immune function (Nieman & Wentz, 2019).
What is moderate resistance training?
Moderate resistance training:
- Uses training loads at 60-80% of your 1 rep max
- Multiple sets per exercise
- 4 to 5 days a week (González-Badillo, Gorostiaga, Arellano, & Izquierdo, 2005)
- Generally lasts under an hour
- Is balanced with recovery, thereby preventing feelings of accumulated fatigue, significant pain, or significant delayed onset soreness
- Allows for continued performance improvement (Grandou, Wallace, Impellizzeri, Allen, & Coutts, 2019; Nieman & Wentz, 2019) .
Training repetitions, sets, and rest periods vary widely. Individual response to such also varies widely. However, the above serves as a good guide for training within the moderate range. Staying within the moderate training range is one way to reduce the chances of over-training and non-functional overreach. The goal is to prevent overly large surges in stress hormones, reduced immune system function, and blunting of testosterone to cortisol ratios (Grandou et al., 2019).
What is “heavy training?”
Heavy training and heavy training loads of course are relative to SOME extent base on your fitness level. However, unless your entire life is devoted to training and recovery (such as professional athletes), most people that train to the extent described below will subject themselves to the risks associated with heavy training. In the research various examples are provided. Some of the examples of heavy training include:
- Single events such as exercise exceeding 60 minutes, especially when reaching 90 minutes (1 and a half hours and beyond)
- Competition events
- Consecutive days of heavy training loads exceeding an hour, such as cycling or running 1-3 hours at your 50−70% V̇o2max (Peake, Neubauer, Walsh, & Simpson, 2017)
- Consecutive days of interval training, such as 3 sets of 6-minute maximum-effort rowing two days in a row
- Resistance training with high intensity (weights closer to 1 rep max), high frequency, and lacking exercise variety
- Resistance training with insufficient recovery–detectable when symptoms of NON-FUNCTIONAL overreach occur, such as accumulated fatigue, pain, soreness, and possibly but not always, reductions in training performance (Grandou et al., 2019)
Pushing yourself to improve versus warning signs that you are crossing the line
Exercising at the above intensities quickly lead to states of overreaching in terms of the body’s recovery capabilities. Indeed, heaving training (as opposed to moderate training) has been shown to increase your risk of illness. When prolonged, heavy training loads can cause you to progress into states of over-training (Grandou et al., 2019; Peake et al., 2017). Over-training can take weeks or months for recovery (Grandou et al., 2019). While pushing yourself (or overreaching) to some extent can help boost performance, you know you have crossed the line when the following symptoms begin to manifest:
- Persistent fatigue
- Persistent muscle soreness
- Declines in your training performance, such as reduced sprint, squat, bench, or other performance measures–this sign is not always present!
- Changes in mood
- Possibly worsened sleep–also not always present (Grandou et al., 2019; Peake et al., 2017).
Heavy training negatively impacts your immune system
Researchers have observed that heavy training introduces a stress to the body’s recovery resources and immune system (Peake, Neubauer, Walsh, & Simpson, 2017). Intense exercise, by definition, acts as a significant physical stress (Walsh, 2018). Similar to psychological stress, intense physical stress activates hormones such as cortisol, epinephrine, and norepinephrine (Walsh, 2018). These hormones are essential for health and life, but when elevated at high levels over prolonged periods of time they can impede protective immune functions (McEwen, 2012).
Oxidative stress, post-training inflammation and muscle damage from heavy training require restorative processes that appear to shift immune resources away from virus monitoring and protection (Nieman & Wentz, 2019; Peake et al., 2017). These stresses on the immune system combine with other factors such as life stress, nutrition deficiencies, and sleep disruption to further impact our immune system function. Travel across time zones and environment extremes (such as winter time outdoors training) add additional challenges for some people (Walsh, 2018). Heavy training raises your risk of upper respiratory infection by 2 to 6 times the average population!!!!
Heavy training against the background of our lives
While it would be nice for many of us exercise fanatics to have lives that centered around our physical endeavors, the reality is that many of us juggle full time career demands and exercise serves as a recreational activity. Our perception of our life stressors can have significant impact on how such stressors impact us at a physiological level (McGonigal, 2015; Walsh, 2018). However, it is fair to say many of us have lost sleep at various times over work or life concerns.
Sleep is at times therefore less than optimal. Our work lives, even home lives at times, can contribute to our physical and mental stress burden. Keep this in mind if you still desire to train at the “heavy training” level. The truth is, for many of us, heavy training should be kept to short spurts during low risk times (if ever), with the majority of our training falling within the “moderate” range.
Additional research-backed immune-friendly training tips
The following tips are provided by the European Journal of Sport Science (Walsh, 2018) to assist athletes and exercisers in maintaining immune health while enjoying their physical training pursuits:
- Adjust training volumes and training intensities so as to permit adequate recovery (auto-regulating your intensity according to your body’s recovery abilities)
- Manage volume /intensity increases no greater than 5-10% each week
- Frequent, shorter bouts of training are preferable to fewer, longer sessions of training
- Recognize winter training as a particularly high risk time to perform heavy training sessions/ or loads
- If training heavy, follow a heavy training session by several light or moderate training sessions
- Consider a lighter, recovery week every 2nd or 3rd week of your training cycle
- Allow for several weeks of active recovery after competition or season completion
- Pursue recovery activities immediately post intense training sessions
Interestingly, many of these principles can be found in the popular 5-3-1 training protocol by Jim Wendler!! The basics of the program can be found here.
I will admit that I was skeptical in the past regarding moderate training. I felt heavy training would be the only training my body would respond too. I quickly altered the 5-3-1 program so as to continue my heavy weight training sessions. My sessions plus cardio would extend to an hour and a half to two hours at times on the weekend. However, I also got frustrated with the multiple respiratory illnesses I experienced each year (along with training set backs and minor injuries).
After diving into the research referenced above, and re-reading Jim Wendler’s works on the 5-3-1 program, I can see the value of “starting too light,” very gradually increasing the weights, having frequent deloads, and auto-regulating (where at times accessory exercises are skipped based on time or how your body feels, or resetting weights back by 10% or so if plateauing). In particular, staying FOR THE MOST PART in the 60-80% range of the 1 rep max will be an adjustment! Nonetheless, after reviewing the above, this seems to be the wisest way to train–limiting the heavy training to very short time frames when risk of illness is low.
Thanks for reading, I hope you enjoyed the post and learned something new! Feel free to leave a comment, sign up for my e-mail list, or share with friends! Sincerely, Donovan
Centers for Disease Control and Prevention. (2020a). How much physical activity do adults need? Retrieved from https://www.cdc.gov/physicalactivity/basics/adults/index.htm
Centers for Disease Control and Prevention. (2020b). Percent of adults who who engage in no leisure-time physical activity. Retrieved from https://chronicdata.cdc.gov/Nutrition-Physical-Activity-and-Obesity/Percent-of-adults-who-who-engage-in-no-leisure-tim/6nef-e823
Grandou, C., Wallace, L., Impellizzeri, F. M., Allen, N. G., & Coutts, A. J. (2019). Overtraining in resistance exercise: An exploratory systematic review and methodological appraisal of the literature. Sports Medicine. Retrieved from file:///C:/Users/test/AppData/Local/Temp/Grandou2019_Article_OvertrainingInResistanceExerci.pdf
González-Badillo, J. J., Gorostiaga, E. M., Arellano, R., & Izquierdo, M. (2005). Moderate resistance training volume produces more favorable strength gains than high or low volumes during a short-term training cycle. Journal of Strength and Conditioning Research, 19(3), 689-697. doi: 10.1519/R-15574.1
McEwen, B. S. (2012). Protective and damaging effects of stress mediators. The New England Journal of Medicine, 338(1), 171-179. Retrieved from https://pdfs.semanticscholar.org/ee3c/1a87d21b1865abe72157226e38103b0d95cf.pdf
McGonigal, K. (2015). The upside of stress: Why stress is good for you, and how to get good at it. New York, NY: Penguin Random House
National Institute of Allergy and Infectious Diseases. (2014). Immune cells. Retrieved from https://www.niaid.nih.gov/research/immune-cells
Nieman, D. C. & Wentz, L. M. (2019). The compelling link between physical activity and the body’s defense system. Journal of Sport and Health Science, 8(3), 201-217. https://doi.org/10.1016/j.jshs.2018.09.009
Peake, J. M., Neubauer, O., Walsh, N. P., & Simpson R. J. (2017). Recovery of the immune system after exercise. Journal of Applied Physiology, 122(5), 1077-1087. https://doi.org/10.1152/japplphysiol.00622.2016
Walsh, N. P. (2018). Recommendations to maintain immune health in athletes. European Journal of Sport Science, 18(6), 820-831. https://doi.org/10.1080/17461391.2018.1449895