CXCL8 and chronic obstructive pulmonary disease: Finally, a 6-month walking program performed at 80% of maximal capacity with a daily frequency showed improvements in upper and lower limb strength, as well as a decrease in serum C-reactive protein and interleukin-8, which is associated with a reduction in systemic inflammation in COPD individuals [37] because interleukin-8 is an oxidant-sensitive protein and a proinflammatory cytokine [44].