Chapter 6: Exercise and the Immune System

OBJECTIVES

By studying this chapter, you should be able to do the following:

1. Describe how the innate and acquired immune systems work together to protect against infection.

2. Discuss the key components that make up the innate immune system, and describe how the major elements of the innate immune system protect the body against infection.

3. Outline the primary components that compose the acquired immune system and explain how they protect against infection.

4. Explain the differences between acute and chronic inflammation.

5. Discuss the effects of moderate exercise training on the immune system and the risk of infection.

6. Explain how an acute bout of intense and prolonged (>90 minutes) exercise impacts immune function and the risk of infection.

7. Discuss how exercise in environmental extremes (heat, cold, and high altitude) influence immune function.

8. Explain the guidelines for exercise when you have a cold.

OUTLINE

• Overview of the Immune System 128

  • Innate Immune System 128

  • Acquired Immune System 132

• Exercise and the Immune System 133

  • Exercise and Resistance to Infection 133

  • High-Intensity/Long-Duration Aerobic Exercise Increases the Risk of Infection 135

• Exercising in Environmental Extremes: Increased Risk for Infection? 137

• Should You Exercise When You Have a Cold? 138

KEY TERMS

B-cells

complement system

cytokines

exercise immunology

immunity

inflammation

leukocytes

macrophages

natural killer cell

neutrophils

phagocytes

T-cells

INTRODUCTION

The concept of homeostasis and the control systems that regulate the internal environment were introduced in Chap. 2. The immune system is a critical homeostatic system that recognizes and destroys foreign agents in the body. Obviously, this is important because the body is constantly under attack from foreign agents (e.g., bacteria, viruses, and fungi) that promote infection. By protecting the body against infection, the immune system plays an important role in maintaining homeostasis in the body.

Everyone has suffered from the unpleasant symptoms (i.e., runny nose and fever) of an upper respiratory tract infection (URTI). These URTIs are commonly referred to as colds and are caused by more than 200 different viruses (16). Currently, URTIs are the most common types of infections worldwide, and the average adult suffers from two to five colds a year (10, 25). Although colds are not usually life threatening in healthy individuals, colds have many negative consequences because of increased healthcare costs and lost days from work, school, and exercise training (12). Because of the high occurrence of colds, these illnesses present a real concern to the health of athletes and the general population. Since exercise and other stresses (e.g., emotional stress, loss of sleep, etc.) are known to influence the immune system, it is important to understand ...