This study analyzed the contribution of the propulsive and braking phases among different percentages of the one-repetition maximum (1RM) in the concentric bench press exercise. One hundred strength-trained men performed a test with increasing loads up to the 1RM for the individual determination of the load-power relationship. The relative load that maximized the mechanical power output (P(max)) was determined using three different parameters: mean concentric power (MP), mean power of the propulsive phase (MPP) and peak power (PP). The load at which the braking phase no longer existed was 76.1+/-7.4% 1RM. P(max) was dependent on the parameter used: MP (54.2%), MPP (36.5%) or PP (37.4%). No significant differences were found for loads between 40-65% 1RM (MP) or 20-55% 1RM (MPP and PP), nor between P(max) (% 1RM) when using MPP or PP. P(max) was independent of relative strength, although certain tendency towards slightly lower loads was detected for the strongest subjects. These results highlight the importance of considering the contribution of the propulsive and braking phases in isoinertial strength and power assessments. Referring the mean mechanical values to the propulsive phase avoids underestimating an individual's true neuromuscular potential when lifting light and medium loads.