Our purpose was to compare the effect of a periodized preparation consisting of power endurance training and high-intensity power training on the contractile properties of the quadriceps muscle and functional performances in well trained male sprinters (n = 7). After 4 weeks of high-intensity power training, 60-m sprint running time improved by an average of 1.83% (SD = 0.96; p less than 0.05). This improvement was inversely related to an increase in maximal voluntary contraction torque (r = -0.89, p less than 0.05) and poorly correlated with changes in the contractile kinetics of the quadriceps muscle (r range from 0.36 to -0.46). These findings suggest that sprint performance is poorly predicted by muscle intrinsic properties and that a neural adaptation appears to explain most of the observed functional adaptations. (Contains 2 tables and 1 figure.)