Fifteen young adult males participated in leg and arm ergometry with CO measured throughout incremental workloads. No significant difference exists for COabs (L·min-1) during leg ergometry between larger (14.34±4.93) and smaller (12.68±4.47) leg musculatures (P=0.067). During arm exercise, COabs was greater in participants with larger (20.25±9.60) versus smaller (13.73±4.89) arm musculatures (P\u3c0.01). During both exercise modalities, no difference exists between the subjects with larger and smaller musculatures for COrel (ml·kg-1·min-1). We conclude that differences exist in the CO response to matched submaximal exercise between larger and smaller muscle mass