To elucidate the effect of in-phase chest wall vibration (IPV) during exercise, 17 COPD male patients performed two constant-load exercise tests on a cycle ergometer with and without IPV. The Borg dyspnea score significantly decreased from IPV (-) to IPV (+) (from 13.6+/-2.9 to 12.5+/-2.9, P<0.01). IPV elicited a significant increase in V(O(2)) (P<0.005) and significant decreases in both VE/V(O(2)) (P<0.05) and respiratory frequency (P<0.05), but it did not elicit any changes in VE. The change in Borg score between IPV (+) and IPV (-) showed a significant positive correlation with % predicted V(O(2),max) (r=0.71) and FEV(1)/FVC (r=0.69). Patients in the responsive group (n=11) showed significantly lower FEV(1) (P<0.05) and higher DeltaN(2)/L (P<0.01) than patients in the non-responsive group (n=6). We conclude that IPV reduces dyspnea and improves respiratory efficiency during aerobic exercise in severe COPD.