Importance of Maintaining and Improving Immune Function by Physical Activity During the COVID-19 Pandemic

Gen Li1, Laikang Yu1,2*

1Department of Strength and Conditioning Training, Beijing Sport University, Beijing, China.
2Key Laboratory of Physical Fitness and Exercise, Ministry of Education, Beijing Sport University, Beijing, China

Received Date: 09/02/2022; Published Date: 11/04/2022.

*Corresponding author: Laikang Yu. Key Laboratory of Physical Fitness and Exercise, Ministry of Education, Beijing Sport University, Beijing, China

Mini Review

In early December 2019, a novel coronavirus disease, designated as COVID-19, came into light in Wuhan, Hubei Province of China. With the first pneumonia cases of unknown origin being identified, it has become a pandemic worldwide. The World Health Organization (WHO) has declared it as a potential threat to the world population, and a public health emergency of international concern on January 30, 2020 [1]. Many countries and regions have advised people to reduce traveling and stay at home to avoid human-to-human transmission of the virus. As a result, most work, physical and recreational activities were suspended. However, staying at home can reduce the physical activity of the general population. Sedentary behaviors such as watching television and movies, browsing the Internet, using smartphones, and playing video games are associated with an increased risk of obesity [2-4], hypertension [5, 6], cardiovascular disease [4, 7], and type 2 diabetes mellitus [4, 7, 8]. Evidence showed that individuals with weak immunosuppression or immune defense mechanisms are more susceptible to severe disease [9-11]. However, there are several research suggested that physical activities such as moderate-intensity continuous training (MICT), resistance training (RT), and high-intensity interval training (HIIT) have a significant effect on modulating the immune system. Physical activity-induced immunoregulation has been recognized for more than 30 years, and there are about 5000 peer-reviewed original and review papers in the PubMed database [12].

Effects of MICT has been reported in many studies, i.e. MICT can improve cognitive function in patients with mild Alzheimer's disease [13], Parkinson's Disease [14], and schizophrenia [15], provide comparable reductions in resting blood pressure in adults with pre- to established hypertension [16], induce modest body composition improvements in overweight and obese individuals [17], and improve cardiorespiratory fitness in participants of cardiac rehabilitation [18]. MICT is also considered a preventive measure to bring down the further incidence of COVID-19 [19]. Evidence showed that even a slight increase in baseline maximal oxygen uptake (VO2max) may convert a significant proportion of high-risk patients to low-risk patients [20]. A randomized controlled trial assessed preventive effects of exercise on acute respiratory infection (ARI) illness, the results showed that 8 weeks of MICT contributed to the reduction in ARI illness, and the magnitude of observed benefit was similar to that from accepted medical interventions, such as influenza vaccination [21]. As shown in Table 1, a large number of randomized controlled trials have investigated the relationship between MICT and immune system function. Previous studies suggested that 12 weeks [22], 15 weeks [23, 24], or 12 months [25] of MICT had significant effects on the prevention of upper respiratory tract infections (URI), and the mechanisms were related to the improvement of vaccination responses, T-cell proliferative capacity, neutrophil phagocytic activity, NK cell cytotoxic activity, and leukocyte telomere lengths, and the depression of numbers of exhausted/senescent T cells, circulatory levels of inflammatory cytokines, and inflammatory response to bacterial challenge [26-31].

Table 1: Research on the relationship between MICT and immune function

RT, a form of exercise that actively activates specific skeletal muscle groups against external resistance, has become a popular form of exercise and is recommended by the American Heart Association [32], the American College of Sports Medicine (ACSM) [32, 33], and the American Geriatrics Society [34]. RT has been proven to be an important strategy to improve muscle mass, muscle strength, and power output, as well as functional capacity [35]. And a growing number of studies strongly support the beneficial effects of RT on various aspects of cognitive performance, such as attention [36], memory [37], executive control [38], and mini-mental state examination (MMSE) score [39]. For example, Cassilhas et al. found that 24 weeks of moderate- and high-intensity RT had equally beneficial effects on cognitive functions in the elderly [40], and the mechanism was related to the increase of insulin-like growth factor-1 (IGF-1) [41]. In addition, RT has been shown to have significant effects on immune system function. Table 2 summarizes published evidence from randomized controlled trials on the relationship between RT and immune system function. Previous studies suggested that 10 weeks [42-44], 12 weeks [45], and 16 weeks [46] of RT had significant effects on improving the immunity of elderly people, and the mechanisms were related to the improvement of the resting natural killer cell activity [42], and monocyte and T-cell-mediated immunity [45], and the reduction of the inflammatory reactivity and overall inflammatory milieu [43, 44], and C-reactive protein (CRP) levels [46].

Table 2: Research on the relationship between RT and immune function.

HIIT can be described as “a short interval of vigorous activity interspersed with periods of low activity or rest”, which can cause a strong acute physiological response [47]. A growing number of studies suggested that HIIT had effects on promoting cognitive function [48, 49], glucose and lipid metabolism in skeletal muscle [50], the expression of genes related to endogenous antioxidant enzyme activity and inflammation [51], the insulin sensitivity [52], the cardiopulmonary function [53], the aerobic capacity [54, 55], anaerobic capacity [56, 57], and the vascular endothelial function [58], and on reducing the oxidative stress level [59]. In addition, HIIT can provide comparable reductions in resting blood pressure in adults with pre- to established hypertension [16], induce modest body composition improvements in overweight and obese individuals [17], and improve cardiorespiratory fitness in participants of cardiac rehabilitation [18]. In addition to MICT and RT, HIIT has also been shown to have significant effects on immune system function. Table 3 summarizes published evidence from randomized or controlled trials on the relationship between HIIT and immune system function. Previous studies suggested that one single session [60, 61], 3 weeks [62], and 10 weeks [63, 64] of HIIT had significant effects on improving the immune function, and the mechanisms were related to the improvement of the potential anti-inflammatory benefits [60], the number of antimicrobial proteins in the saliva [62], and the innate immune functions [64], and the reduction of monocyte [63] and IFN-γ/IL-4 ratio [61].

Table 3: Research on the relationship between HIIT and immune function

In conclusion, different types of physical activity have significant effects on immune function, and maintaining physical activity levels during the current situation initiated by the COVID-19 pandemic will have significant physical health benefits.


Gen Li was supported by the Graduate Students’ Innovative Scientific Research Program of Beijing Sport University (20212011); Laikang Yu was supported by the Chinese Universities Scientific Fund (2021QN001).

Conflict of interest

The authors declare no conflict of interest.


  1. Guan WJ, Ni ZY, Hu Y, et al. Clinical Characteristics of Coronavirus Disease 2019 in China. N Engl J Med, 2020, 382(18): 1708-1720.
  2. Angoorani P, Heshmat R, Ejtahed HS, et al. The association of parental obesity with physical activity and sedentary behaviors of their children: the CASPIAN-V study. J Pediatr (Rio J), 2018, 94(4): 410-418.
  3. Keane E, Li X, Harrington JM, et al. Physical Activity, Sedentary Behavior and the Risk of Overweight and Obesity in School-Aged Children. Pediatr Exerc Sci, 2017, 29(3): 408-418.
  4. Carbone S, Del Buono MG, Ozemek C, et al. Obesity, risk of diabetes and role of physical activity, exercise training and cardiorespiratory fitness. Prog Cardiovasc Dis, 2019, 62(4): 327-333.
  5. Lee PH, Wong FK. The association between time spent in sedentary behaviors and blood pressure: a systematic review and meta-analysis. Sports Med, 2015, 45(6): 867-880.
  6. Bakker EA, Sui X, Brellenthin AG, et al. Physical activity and fitness for the prevention of hypertension. Curr Opin Cardiol, 2018, 33(4): 394-401.
  7. Patterson R, Mcnamara E, Tainio M, et al. Sedentary behaviour and risk of all-cause, cardiovascular and cancer mortality, and incident type 2 diabetes: a systematic review and dose response meta-analysis. Eur J Epidemiol, 2018, 33(9): 811-829.
  8. Hills A P, Arena R, Khunti K, et al. Epidemiology and determinants of type 2 diabetes in south Asia. Lancet Diabetes Endocrinol, 2018, 6(12): 966-978.
  9. García L F. Immune Response, Inflammation, and the Clinical Spectrum of COVID-19. Front Immunol, 2020, 11:1441.
  10. Tufan A, Avanoğlu Güler A, Matucci-Cerinic M. COVID-19, immune system response, hyperinflammation and repurposing antirheumatic drugs. Turk J Med Sci, 2020, 50(Si-1): 620-632.
  11. Mckechnie JL, Blish CA. The Innate Immune System: Fighting on the Front Lines or Fanning the Flames of COVID-19?. Cell Host Microbe, 2020, 27(6): 863-869.
  12. Leandro CG, Ferreira ESWT, Lima-Silva AE. Covid-19 and Exercise-Induced Immunomodulation. Neuroimmunomodulation, 2020, 1-3.
  13. Yang SY, Shan CL, Qing H, et al. The Effects of Aerobic Exercise on Cognitive Function of Alzheimer's Disease Patients. CNS Neurol Disord Drug Targets, 2015, 14(10): 1292-1297.
  14. Altmann LJ, Stegemöller E, Hazamy AA, et al. Aerobic Exercise Improves Mood, Cognition, and Language Function in Parkinson's Disease: Results of a Controlled Study. J Int Neuropsychol Soc, 2016, 22(9): 878-889.
  15. Shimada T, Ito S, Makabe A, et al. Aerobic exercise and cognitive functioning in schizophrenia: A pilot randomized controlled trial. Psychiatry Res, 2019, 282:112638.
  16. Costa EC, Hay JL, Kehler DS, et al. Effects of High-Intensity Interval Training Versus Moderate-Intensity Continuous Training On Blood Pressure in Adults with Pre- to Established Hypertension: A Systematic Review and Meta-Analysis of Randomized Trials. Sports Med, 2018, 48(9): 2127-2142.
  17. Wewege M, Van DBR, Ward RE, et al. The effects of high-intensity interval training vs. moderate-intensity continuous training on body composition in overweight and obese adults: a systematic review and meta-analysis. Obes Rev, 2017, 18(6): 635-646.
  18. Hannan AL, Hing W, Simas V, et al. High-intensity interval training versus moderate-intensity continuous training within cardiac rehabilitation: a systematic review and meta-analysis. Open Access J Sports Med, 2018, 9:1-17.
  19. Dixit S. Can moderate intensity aerobic exercise be an effective and valuable therapy in preventing and controlling the pandemic of COVID-19?. Med Hypotheses, 2020, 143:109854.
  20. Ahmed I. COVID-19 - does exercise prescription and maximal oxygen uptake (VO(2) max) have a role in risk-stratifying patients? . Clin Med (Lond), 2020, 20(3):282-284.
  21. Barrett B, Hayney M S, Muller D, et al. Meditation or exercise for preventing acute respiratory infection (MEPARI-2): A randomized controlled trial. PLoS One, 2018, 13(6): e0197778.
  22. Nieman DC, Henson DA, Gusewitch G, et al. Physical activity and immune function in elderly women. Med Sci Sports Exerc, 1993, 25(7): 823-831.
  23. Nieman DC, Nehlsen-Cannarella SL, Markoff PA, et al. The effects of moderate exercise training on natural killer cells and acute upper respiratory tract infections. Int J Sports Med, 1990, 11(6): 467-473.
  24. Sloan CA, Engels HJ, Fahlman MM, et al. Effects of exercise on S-IGA and URS in postmenopausal women. Int J Sports Med, 2013, 34(1): 81-86.
  25. Chubak J, Mctiernan A, Sorensen B, et al. Moderate-intensity exercise reduces the incidence of colds among postmenopausal women. Am J Med, 2006, 119(11): 937-942.
  26. Nieman DC, Wentz LM. The compelling link between physical activity and the body's defense system. J Sport Health Sci, 2019, 8(3): 201-217.
  27. Zbinden-Foncea H, Francaux M, Deldicque L, et al. Does high cardiorespiratory fitness confer some protection against pro-inflammatory responses after infection by SARS-CoV-2?. Obesity (Silver Spring), 2020, 28(8):1378-1381.
  28. Nieman DC, Gillitt ND, Sha W, et al. Metabolic recovery from heavy exertion following banana compared to sugar beverage or water only ingestion: A randomized, crossover trial. PLoS One, 2018, 13(3): e0194843.
  29. Simpson RJ, Lowder TW, Spielmann G, et al. Exercise and the aging immune system. Ageing Res Rev, 2012, 11(3): 404-420.
  30. Turner JE, Brum PC. Does Regular Exercise Counter T Cell Immunosenescence Reducing the Risk of Developing Cancer and Promoting Successful Treatment of Malignancies?. Oxid Med Cell Longev, 2017, 2017:4234765.
  31. Simpson RJ, Kunz H, Agha N, et al. Exercise and the Regulation of Immune Functions. Prog Mol Biol Transl Sci, 2015, 135:355-380.
  32. Nelson ME, Rejeski WJ, Blair SN, et al. Physical activity and public health in older adults: recommendation from the American College of Sports Medicine and the American Heart Association. Med Sci Sports Exerc, 2007, 39(8): 1435-1445.
  33. Kraemer WJ, Adams K, Cafarelli E, et al. American College of Sports Medicine position stand. Progression models in resistance training for healthy adults. Med Sci Sports Exerc, 2002, 34(2): 364-380.
  34. American Geriatrics Society Panel on Exercise and Osteoarthritis. Exercise prescription for older adults with osteoarthritis pain: consensus practice recommendations. A supplement to the AGS Clinical Practice Guidelines on the management of chronic pain in older adults. J Am Geriatr Soc, 2001, 49(6): 808-823.
  35. Lopez P, Pinto RS, Radaelli R, et al. Benefits of resistance training in physically frail elderly: a systematic review. Aging Clin Exp Res, 2018, 30(8): 889-899.
  36. Liu-Ambrose T, Nagamatsu LS, Graf P, et al. Resistance training and executive functions: a 12-month randomized controlled trial. Arch Intern Med, 2010, 170(2): 170-178.
  37. Perrig-Chiello P, Perrig WJ, Ehrsam R, et al. The effects of resistance training on well-being and memory in elderly volunteers. Age Ageing, 1998, 27(4): 469-475.
  38. Quintero AP, Bonilla-Vargas KJ, Correa-Bautista JE, et al. Acute effect of three different exercise training modalities on executive function in overweight inactive men: A secondary analysis of the BrainFit study. Physiology & behavior, 2018, 197:22-28.
  39. Ozkaya GY, Aydin H, Toraman FN, et al. Effect of strength and endurance training on cognition in older people. J Sports Sci Med, 2005, 4(3): 300-313.
  40. Cassilhas RC, Viana VA, Grassmann V, et al. The impact of resistance exercise on the cognitive function of the elderly. Med Sci Sports Exerc, 2007, 39(8): 1401-1407.
  41. Tsai CL, Wang CH, Pan CY, et al. The effects of long-term resistance exercise on the relationship between neurocognitive performance and GH, IGF-1, and homocysteine levels in the elderly. Front Behav Neurosci, 2015, 9:23.
  42. Mcfarlin BK, Flynn MG, Phillips MD, et al. Chronic resistance exercise training improves natural killer cell activity in older women. J Gerontol A Biol Sci Med Sci, 2005, 60(10): 1315-1318.
  43. Phillips MD, Flynn MG, Mcfarlin BK, et al. Resistive exercise blunts LPS-stimulated TNF-alpha and Il-1 beta. Int J Sports Med, 2008, 29(2): 102-109.
  44. Phillips MD, Flynn MG, Mcfarlin BK, et al. Resistance training at eight-repetition maximum reduces the inflammatory milieu in elderly women. Med Sci Sports Exerc, 2010, 42(2): 314-325.
  45. Hagstrom AD, Marshall PW, Lonsdale C, et al. The effect of resistance training on markers of immune function and inflammation in previously sedentary women recovering from breast cancer: a randomized controlled trial. Breast Cancer Res Treat, 2016, 155(3): 471-482.
  46. Brooks N, Layne JE, Gordon PL, et al. Strength training improves muscle quality and insulin sensitivity in Hispanic older adults with type 2 diabetes. Int J Med Sci, 2006, 4(1): 19-27.
  47. Cassidy S, Thoma C, Houghton D, et al. High-intensity interval training: a review of its impact on glucose control and cardiometabolic health. Diabetologia, 2017, 60(1): 7-23.
  48. Bell KE, Fang H, Snijders T, et al. A Multi-Ingredient Nutritional Supplement in Combination With Resistance Exercise and High-Intensity Interval Training Improves Cognitive Function and Increases N-3 Index in Healthy Older Men: A Randomized Controlled Trial. Front Aging Neurosci, 2019, 11:107.
  49. Costigan S A, Eather N, Plotnikoff R C, et al. High-Intensity Interval Training for Cognitive and Mental Health in Adolescents. Med Sci Sports Exerc, 2016, 48(10): 1985-1993.
  50. Davis R H, Halbrooks JE, Watkins EE, et al. High-intensity interval training and calorie restriction promote remodeling of glucose and lipid metabolism in diet-induced obesity. Am J Physiol Endocrinol Metab, 2017, 313(2): E243-E256.
  51. Tucker PS, Briskey DR, Scanlan AT, et al. High intensity interval training favourably affects antioxidant and inflammation mRNA expression in early-stage chronic kidney disease. Free Radic Biol Med, 2015, 89:466-472.
  52. Søgaard D, Lund MT, Scheuer CM, et al. High-intensity interval training improves insulin sensitivity in older individuals. Acta Physiol (Oxf), 2018, 222(4): e13009.
  53. Klonizakis M, Moss J, Gilbert S, et al. Low-volume high-intensity interval training rapidly improves cardiopulmonary function in postmenopausal women. Menopause, 2014, 21(10): 1099-1105.
  54. García-Hermoso A, Cerrillo-Urbina AJ, Herrera-Valenzuela T, et al. Is high-intensity interval training more effective on improving cardiometabolic risk and aerobic capacity than other forms of exercise in overweight and obese youth? A meta-analysis. Obes Rev, 2016, 17(6): 531-540.
  55. Xie B, Yan X, Cai X, et al. Effects of High-Intensity Interval Training on Aerobic Capacity in Cardiac Patients: A Systematic Review with Meta-Analysis. Biomed Res Int, 2017, 2017:5420840.
  56. Arazi H, Keihaniyan A, Eatemadyboroujeni A, et al. Effects of Heart Rate vs. Speed-Based High Intensity Interval Training on Aerobic and Anaerobic Capacity of Female Soccer Players. Sports (Basel), 2017, 5(3):57.
  57. Moghaddam M, Estrada CA, Muddle TWD, et al. Similar Anaerobic and Aerobic Adaptations After 2 High-Intensity Interval Training Configurations: 10 s: 5 s vs. 20 s: 10 s Work-to-Rest Ratio. J Strength Cond Res, 2019, 35(6):1685-1692.
  58. Chuensiri N, Suksom D, Tanaka H. Effects of High-Intensity Intermittent Training on Vascular Function in Obese Preadolescent Boys. Child Obes, 2018, 14(1): 41-49.
  59. Poblete ACE, Russell Guzmán JA, Soto Muñoz ME, et al. Effects of high intensity interval training versus moderate intensity continuous training on the reduction of oxidative stress in type 2 diabetic adult patients: CAT. Medwave, 2015, 15(7): e6212.
  60. Durrer C, Francois M, Neudorf H, et al. Acute high-intensity interval exercise reduces human monocyte Toll-like receptor 2 expression in type 2 diabetes. Am J Physiol Regul Integr Comp Physiol, 2017, 312(4): R529-R538.
  61. De Souza DC, Matos VF, Dos Santos VOA, et al. Effects of High-Intensity Interval and Moderate-Intensity Continuous Exercise on Inflammatory, Leptin, IgA, and Lipid Peroxidation Responses in Obese Males. Front Physiol, 2018, 9:567.
  62. Born D P, Zinner C, Sperlich B. The Mucosal Immune Function Is Not Compromised during a Period of High-Intensity Interval Training. Is It Time to Reconsider an Old Assumption?. Front Physiol, 2017, 8:485.
  63. Bartlett DB, Shepherd SO, Wilson OJ, et al. Neutrophil and Monocyte Bactericidal Responses to 10 Weeks of Low-Volume High-Intensity Interval or Moderate-Intensity Continuous Training in Sedentary Adults. Oxid Med Cell Longev, 2017, 2017:8148742.
  64. Bartlett DB, Willis LH, Slentz CA, et al. Ten weeks of high-intensity interval walk training is associated with reduced disease activity and improved innate immune function in older adults with rheumatoid arthritis: a pilot study. Arthritis Res Ther, 2018, 20(1): 127.
  65. Nieman DC, Nehlsen-Cannarella SL, Henson DA, et al. Immune response to exercise training and/or energy restriction in obese women. Med Sci Sports Exerc, 1998, 30(5): 679-686.
  66. Barrett B, Hayney MS, Muller D, et al. Meditation or exercise for preventing acute respiratory infection: a randomized controlled trial. Ann Fam Med, 2012, 10(4): 337-346.
  67. Rakel D, Mundt M, Ewers T, et al. Value associated with mindfulness meditation and moderate exercise intervention in acute respiratory infection: the MEPARI Study. Fam Pract, 2013, 30(4): 390-397.
  68. Shimizu K, Suzuki N, Imai T, et al. Monocyte and T-cell responses to exercise training in elderly subjects. J Strength Cond Res, 2011, 25(9): 2565-2572.
  69. Abd El-Kader SM, Al-Shreef FM. Inflammatory cytokines and immune system modulation by aerobic versus resisted exercise training for elderly. Afr Health Sci, 2018, 18(1): 120-131.