Since the pandemic began, many of us are now reframing how we approach our health. You might still be suffering the mental and physical effects, or have a new understanding of the importance of a strong immune system. But what does that mean, and what can we do to help our immune system function better?
To help boost the immune system, moderate workouts are best. Too much or too little exercise can have negative effects, making us more susceptible to harmful organisms, chemicals, and preventable disease.
What is the Immune System?
The ‘immune system’ refers to the network of organs, hormones, and cells that help react to the environment and produces chemicals to circulate around the body. We are born with an innate immune system in the lining of the cornea, respiratory tract, and gut with special cells called ‘phagocytes’ that surrounds and kills foreign material.
We then have the ability to develop the ‘adaptive’ immune system, cells made in the body in response to the environment, known collectively as white blood cells due to their light pink color under a microscope and smaller size (about 1% of blood cells) when compared to red blood cells (99%). One type of white blood cell referred to as ‘leukocytes’, originate and mature in the bone marrow (eosinophils, neutrophils, and basophils), whereas the ‘lymphocytes’ also originate in the bone marrow but mature in the spleen, lymph nodes, and thymus (B and T lymphocytes).
Immune cells are like the body’s army, building up their forces in response to invaders, then mobilizing and attacking by producing antibodies to kill them. The white blood cells, including T cells have memory, keeping an exact record of particles they encounter.
What is Inflammation?
‘Inflammation’ refers to the body’s natural response of sending this army of cells to fight off invaders such as bacteria or viruses, or repair an injury. ‘Acute’ inflammation occurs in response to an injury and can cause pain, redness, swelling, and bruising.
Chronic inflammation occurs when the body continues to send immune cells even though there is no continued danger. Effectively it ‘learns’ this response if it continues over time. The effect can be localized as with rheumatoid arthritis, or can affect organs and tissues throughout the body, as in type 2 diabetes and prolonged stress.
Exercise and the Immune System
The research shows exercise can have both harmful and beneficial effects, and that moderation is where health benefits occur. For example, in studies done with runners, exercise shows a ‘J’ curve with respiratory tract infections, with too little exercise and too much exercise having a negative effect, but moderate* giving you a boost (see this article for review).
One foundational study done in 1983 with South African runners in a 56-km ultramarathon showed a 33.3% increase vs 15.3% in the incidence of respiratory infection in the 2-week period following the race. Subsequent studies have shown a similar result, due to increased levels of stress hormones, epinephrine*, and cortisol. However, exercise must be longer than 40 minutes and moderate-high intensity to see raises in cortisol levels in salivary glands.
In contrast, other studies have shown that activity as simple as brisk walking reduced the number of sick days by half over a 12- to 15-week period compared with inactivity, without change in resting immune function (see article* for review). The authors further concluded that there was in effect a ‘summation’ of the acute positive changes from individual exercise bouts that resulted in improved immunity.
Another study from 2008 with 12 moderately trained subjects showed a significant difference of 5% vs. 83% in cortisol levels when comparing the 40% exercise and 80% intensity groups. Further examination controlling for plasma volume and other factors actually showed a decrease in cortisol levels at the lower intensities.
Repeated, Moderate intensity exercise is anti-inflammatory
The beneficial effects of moderate exercise are now well-known, and the protective effect of exercise on the immune system has since been confirmed by subsequent studies (for review). While acute exercise can cause temporary cellular disturbances and raises in cortisol, the body will adapt after repeated bouts, enhancing its ability to respond to pathogens and cortisol in the future. For example, repeated moderate intensity exercise (e.g. 40-60%) improves the immune system response, the efficiency of the oxidative process (i.e. cells burning calories for energy), and increases the efficiency of energy generation*. This in turn allows the body to defend itself against pathogens as well as prevent other chronic diseases related to inflammation such as type 2 diabetes, cardiovascular diseases, high blood pressure, as well as cancer and dementia.
An easy way to think of it is that exercise creates a laboratory for cortisol, so your body can be exposed to a little bit at a time, then have a chance to react. There are many examples of this, including lifting weights to build muscle, practicing music or athletic skills, and studying to improve mental function.
Similarly, the body reacts to cortisol slowly over time, enhancing immunity and responding more quickly when confronted with other foreign invaders, from stress, overexertion, or the environment.
Check out a few moderate intensity workouts to boost your Immune system.
WORKOUT #1
Core:
• Plank on Elbows x 60’’ (seconds)
• Modified Side Plank x 30’’ each side
• Single Leg Bridge, Hold Knee x 10-20 each side
• Body Weight Squat x 10-20
• Plank to Push-up x 5 each side
• X 1-2 sets
Cardio:
• Walk or jog @ 40% of effort
• Continue for 10-15 minutes
WORKOUT #2
Core:
• Body Weight Squat x 10-20
• Plank on Hands x 60’’
• Single Leg Bridge x 10 each side
• Side Plank x 30’’ each side
• Leg Raises x 10-20 each side
• X 2-3 sets
Cardio:
• Walk or jog @ 50% of effort
• Continue for 10-15 minutes
WORKOUT #3
Core:
• Overhead Squats x 10-20
• Push-up x 10-20
• Bridge March x 10 each side
• Side Plank, Arm Extended x 30’’ each side
• Full Sit-ups x 20
• X 2-3 sets
Cardio:
• Walk or jog @ 60% of effort x 2 minutes
• Walk or jog @ 40% of effort x 1 minute
• Continue for 10-15 minutes
WORKOUT #4
Core:
• Squat jumps x 10-20 reps
• Push-up position Jumping Jacks x 30’’ (or 30 reps)
• Full sit-ups x 20
• Double Leg Lifts x 10 each side
• Side plank, Leg Lifted x 30’’ each side
• X 3-4 sets
Cardio:
• Walk or jog @ 60% of effort
• Continue for 10-15 minutes
WORKOUT #5
Core:
• Squat Thrust x 10-20
• Overhead Squats x 10-20
• Push-up, Arm Opener x 10 each side
• V-ups x 10-20
• Seated Twists x 20-30 each side
• X 4-5 sets
Cardio:
• Walk or jog @ 60% of effort x 3 minutes
• Walk or jog @ 40% of effort x 2 minutes
• Continue for 15-20 minutes
Katy Harris, MSPH, CSCS
Katy Harris, MSPH, CSCS is a master of Public Health, Certified Strength & Conditioning Specialist, health and fitness studio owner, and ultimate Frisbee athlete who runs WellLife Consulting, LLC in Chapel Hill, North Carolina.
References:
• Campbell, John P., and James E. Turner. “Debunking the Myth of Exercise-Induced Immune Suppression: Redefining the Impact of Exercise on Immunological Health across the Lifespan.” Frontiers, Frontiers, 16 Jan. 2018, https://www.frontiersin.org/articles/10
• Elmer, Jamie. “Understanding Inflammation: Causes, Symptoms, Diagnosis, Treatment, & Takeway.” Healthline, Healthline Media, 19 Dec. 2018, https://www.healthline.com/health/inflammation.
• “Evidence That the Effect of Physical Exercise on NK Cell Activity Is Mediated by Epinephrine.” American Physiological Society, The American Physiological Society, 1 June 1991, https://journals.physiology.org/doi/epdf/10.1152/jappl.1991.70.6.2530.
• Hill, E. E., et al. “Exercise and Circulating Cortisol Levels: The Intensity Threshold Effect – Journal of Endocrinological Investigation.” SpringerLink, Springer International Publishing, 22 Mar. 2014, https://link.springer.com/article/10.1007/BF03345606
• “How Your Gut Affects Your Immune System: A Symbiotic Relationship.” GilbertLab, GilbertLab, 8 June 2021.
• “Immune System Explained.” Better Health Channel, Department of Health, State Government of Victoria, Australia, 17 Dec. 2017, https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/immune-system.
• “The Immune System.” Johns Hopkins Medicine, The Johns Hopkins University, https://www.hopkinsmedicine.org/health/conditions-and-diseases/the-immune-system#:~:text=What%20is%20the%20immune%20system,and%20proteins%20that%20work%20together.
• Jacks, Dean E, et al. “Effect of Exercise at Three Exercise Intensities on Salivary Cortisol.” Journal of Strength and Conditioning Research, 2022, 16(2), 286-289, National Strength & Conditioning Association, https://www.gfe-ev.de/onnews/2011/d2011_04_t0
• Kappel, M., et al. “Evidence That The Effect of Physical Exercise on NK Cell Activity Is Mediated by Epinephrine.” Journal of Applied Physiology, 1 June 1991, https://journals.physiology.org/doi/abs/10.1152/jappl.1991.70.6.2530.
• Knight, Joseph A. “Physical Inactivity: Associated Diseases and Disorders.” Annals of Clinical & Laboratory Science, The Association of Clinical Scientists, Inc., 2012, http://www.annclinlabsci.org/content/42/3/320.full.pdf+html.
• Kubaszek, Agata, et al. “The C-174G Promoter Polymorphism of the IL-6 Gene Affects Energy Expenditure and Insulin Sensitivity.” PubMed.Gov, U.S. National Library of Medicine, https://pubmed.ncbi.nlm.nih.gov/12540635/.
• Lipski, Elizabeth. “The Gut-Immune System.” SpringerLink, Springer International Publishing, 1 Jan. 1970.
• Murray, David R., et al. “Sympathetic and Immune Interactions During Dynamic Exercise.” AHA Journals , July 1992, https://www.ahajournals.org/doi/pdf/10.1161/01.CIR.86.1.203.
• Nieman, David C., and Bente K. Pedersen. “Exercise and Immune Function – Sports Medicine.” SpringerLink, Springer International Publishing, 23 Sept. 2012, https://link.springer.com/article/10.2165/00007256-199927020-00001.
• Pedersen, Bente K, and Helle Bruunsgaard. How Physical Exercise Influences the … – Springer. Adis International Limited, https://link.springer.com/content/pdf/10.2165%2F00007256-199519060-00003.pdf.
• Peters, EM, and ED Bateman. Ultramarathon Running and Upper Respiratory Journal. SA Medical Journal , 1 Oct. 1983, https://journals.co.za/doi/10.10520/AJA20785135_9804.
• Peters, EM. Altitude Fails to Increase Susceptibility. Preventative Sports Medicine , https://journals.co.za/doi/10.10520/AJA10155163_964.
• Peters, EM. Exercise and Upper Respiratory Tract Infections: A Review. https://journals.co.za/doi/pdf/10.10520/AJA10155163_1132.
• Petersen, Anne Marie W., et al. “The Anti-Inflammatory Effect of Exercise.” Journal of Applied Physiology, The American Physiological Society, 1 Apr. 2005, https://journals.physiology.org/doi/full/10.1152/japplphysiol.00164.2004.
• Radák, Zsolt, et al. “The Effect of Exercise Training on Oxidative Damage of Lipids, Proteins, and DNA in Rat Skeletal Muscle: Evidence for Beneficial Outcomes.” Free Radical Biology and Medicine, Pergamon, 23 July 1999, https://www.sciencedirect.com/scie
• Scheffer, Débora da Luz, and Alexandra Latini. “Exercise-Induced Immune System Response: Anti-Inflammatory Status on Peripheral and Central Organs.” Biochimica Et Biophysica Acta (BBA) – Molecular Basis of Disease, Elsevier, 10 Oct. 2020, https://www.scie
• Suardi, Carlotta, et al. “Link between Viral Infections, Immune System, Inflammation and Diet.” International Journal of Environmental Research and Public Health, MDPI, 2 Mar. 2021.
• Ticinesi, Andrea, et al. Exercise and Immune System as Modulators of Intestinal Microbiome: Implications for the Gut-Muscle Axis Hypothesis. Microbiome Research Hub, University of Parma, Italy, 2019.
• Vighi, G, et al. “Allergy and The Gastrointestinal System.” Wiley Online Library, British Society for Immunology , 2008.
• “White Blood Cells: What Are They, Normal Ranges, Role & Function.” Cleveland Clinic, Cleveland Clinic, https://my.clevelandclinic.org/health/body/21871-white-blood-cells.