Exercise and resistance to infection.

The influence of exercise on resistance to infection has been debated for decades. Part of this controversy is due to the complex interactions between pathogens and host defense mechanisms as well as to the mutable nature of exercise. Psychological influences and normal temporal variations in immune mechanisms have also complicated the issue. An understanding of how each of these factors affects host defense should help in the design of new experimental approaches to the problem as well as in the interpretation of previously published results.