EGF, and ErbB receptor, signaling was first identified from pathway analysis of mouse data before a consistent negative association between quadriceps EGF transcripts and ST fiber proportions was demonstrated in healthy elderly humans and in COPD patients, and EGF expression was found to be higher in patients than controls, and higher in patients with an abnormally low ST fiber proportion compared to patients with a ST fiber proportion within normal range. This evidence concerns the gene EGF and chronic obstructive pulmonary disease.