Exercise-induced pain and analgesia? Underlying mechanisms and clinical translation.

An acute bout of physical activity and exercise can increase pain in individuals with chronic pain, but regular exercise is an effective treatment. This review will discuss these two dichotomous findings by summarizing studies in human and animal subjects. We will provide the data that supports the role of physical activity in modulating central nervous system excitability and inhibition, immune system function, and psychological constructs associated with pain. We show evidence that the sedentary condition is associated with greater excitability and less inhibition in both the central nervous system (brainstem inhibitory/facilitatory sites) and the immune system. We further show that exercise and regular physical activity decreases excitability and improves inhibition in both the central nervous system (brainstem inhibitory/facilitatory sites) and the immune system. We will then discuss the clinical implications of these findings, make recommendations for clinical application of exercise, and suggest future research directions.