Neutrophils not only play a critical role in host defense by migrating to the site of infection and producing reactive oxygen species (ROS), but also mediate pathological processes involved in tissue destruction. Therefore, it is important to assess and modulate neutrophil activities. Exhaustive exercise facilitates neutrophil activity, suggesting their involvement with muscle damage [1-4]. However, at that time, we needed to separate neutrophils from whole blood, and great care was needed to do this. Also, it took at least 1 h to adjust a fixed cell concentration of neutrophils for the functional analyses, and some researchers criticized the method, saying that the recovery rate was low and the neutrophil functions were altered from the in vivo environments. Because we observed complex phenomena centered on neutrophils following exercise, some novel technology was required to examine the neutrophil dynamics and functional modulation. Thus, I would like to share some of our research on neutrophils in relation with exercise and muscle damage. I will begin with my early studies on neutrophil functional analyses and a newly developed measurement system [5-7]. Then, some key data about effects of exercise, antioxidant modulation, mechanisms of exercise-induced muscle damage, and possible preventive countermeasures such as functional foods targeting pathogenesis will be described [7-10].

1.Suzuki K, et al. (1996) Capacity of circulating neutrophils to produce reactive oxygen species after exhaustive exercise. J Appl Physiol 81: 1213-1222.
2.Suzuki K, et al. (1996) Effects of exhaustive endurance exercise and its one-week daily repetition on neutrophil count and functional status in untrained men. Int J Sports Med 17: 205-212.
3.Suzuki K, et al. (1999) Endurance exercise causes interaction among stress hormones, cytokines, neutrophil dynamics, and muscle damage. J Appl Physiol 87: 1360-1367.
4.Suzuki K, et al. (2003) Impact of a competitive marathon race on systemic cytokine and neutrophil responses. Med Sci Sports Exerc 35: 348-355.
5.Suzuki K, et al. (2012) Effect of green tea extract on reactive oxygen species produced by neutrophils from cancer patients. Anticancer Res 32: 2369-2375.
6.Suzuki K, et al. (2017) Exhaustive exercise-induced neutrophil-associated tissue damage and possibility of its prevention. J Nanomedine Biotherapeutic Discovery, 7 (2), 1000156.
7.Suzuki K. (2018) Involvement of neutrophils in exercise-induced muscle damage and its modulation. Gen Int Med Clin Innov 3(3): 1-8.
8.Kanda K, et al. (2013) Eccentric exercise-induced delayed-onset muscle soreness and changes in markers of muscle damage and inflammation. Exer Immunol Rev 19: 74-87.
9.Sugama K, et al. (2015) Changes of thioredoxin, oxidative stress markers, inflammation and muscle/renal damage following intensive endurance exercise. Exerc Immunol Rev 21: 130-142.
10.Kawamura T, et al. (2018) Involvement of neutrophil dynamics and function in exercise-induced muscle damage and delayed-onset muscle soreness: effect of hydrogen bath. Antioxidants 7(10): 127.

Professor, Faculty of Sport Sciences, Waseda University, Japan
Department of Life Sciences, Graduate School of Human Sciences, Waseda University (MS: 1993). Hirosaki University School of Medicine (MD: 1999). General Physician Training Course, Internal Medicine, Hospital, International Medical Center of Japan (1999-2001). Professor, Cooperative Major in Advanced Health Sciences, Tokyo University of Agriculture and Technology and Waseda University (PhD course only: 2010-2013); Adjunct Professor, Institute of Biomedical Innovation, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Australia (2013-2014); President, International Society of Exercise and Immunology (ISEI) (2015-2017); Guest Editor, "Exercise and Inflammation" of Antioxidants (2017-2018); Guest Editor, "Anti-inflammatory and Antioxidant Effects of Dietary Supplementation and Lifestyle factors" of Antioxidants (2019-2020); and Guest Editor, “Anti-inflammatory and Antioxidant Effects of Exercise and Training with the Mechanisms and Modulations”: https://www.mdpi.com/journal/antioxidants/special_issues/exercise_training