Pulmonary rehabilitation has been proven to benefit COPD patients in terms of quality of life and functional capabilities. The effects of pulmonary rehabilitation (exercise) on immune function are unclear despite clear benefits of exercise on immune function in healthy individuals being identified. Moderate-intensity and frequency of exercise has been shown to decrease the risk of upper respiratory tract infections in healthy individuals in comparison to sedentary individuals. Respiratory infections, also known as exacerbations, in COPD are the main cause of hospitalisation and mortality. Therefore, if exercise can modulate immune function in COPD, it can be encouraged further in COPD to reduce hospitalisation risk. However, it is important to compare the effects of exercise amongst different phenotypes as frequent exacerbators are known to have elevated inflammatory markers, and may consequently respond to exercise differently to infrequent exacerbators, paving a rationale for a different approach to this subset of patients.