Purpose: The purpose of this study was to examine whether the heart rate deflection point (HRDP) in the heart rate - power relationship is concomitant with the maximal stroke volume value achievement (SV_max) in endurance-trained subjects. Methods: twenty-two international male cyclists (30.3±7.3yrs, 179.7±7.2cm, 71.3±5.5kg) undertook a graded cycling exercise (50 watts every 3 minutes) in the upright position. Thoracic impedance was used to measure continuously the heart rate (HR) and stroke volume (SV) values. The HRDP was estimated by the third order curvilinear regression method (D_max). Results: 72.7% of the subjects (HRDP-group, n=16) presented a break point in their HR-work rate curve at 89.9±2.8% of their maximal HR value. The SV value increased until 78.0±9.3% of the power associated with VO_2max (pVO_2max) in the HRDP-group whereas it increased until 94.4±8.6% of pVO_2max in six other subjects (No-HRDP-group, P=0.004). Neither SV_max (mL.beat^-1 or mL.beat^-1.m^-2) nor VO_2max (mL.min^-1 or mL.kg^-1.min^-1) were different between both groups. However, SV significantly decreased before exhaustion in the HRDP-group (153±44 vs. 144±40mL.beat^-1, P=0.005). In the HDRP-group, 62% of the variance in the power associated at the SV_max (pSV_max) could be also predicted by the power output at which HRDP appeared. Conclusion: In well-trained subjects, the pSV_max-HRDP relationship supposed that the heart rate deflection coincided with the optimal cardiac work for which SV_max was attained.