Explosives performances (jumps, sprint running, throws…) have been often related to athlete’s power output capability. Maximal power output can be improved by increasing the ability to develop maximal force and/or muscle contraction velocity qualities, the best strategy continuing to be an everlasting source of interest and debate. Recently, a biomechanical model has been validated to simply and individually evaluate these qualities in field conditions and to determine the optimal balance between these two qualities for each athlete, be it for explosive push-offs (jumping, sprint starting), sprint accelerations or throwing. These concepts and methods will be presented and supported by examples of practical applications on high levels sportsmen (track and field, soccer, rugby, basket-ball), thus underlining their interest in the performance optimization and in the individualization of training loads and kind of exercises in strength and conditioning. The contraction velocity qualities will be especially focused.