The effects of intensive training on young national competition gymnasts have not been established with precision. This study analyzed, using an isokinetic dynamometer at speeds 60 o /s and 120 o /s, the concentric and eccentric isokinetic muscle strength of knee flexors and extensors in a population of nine young national caliber gymnasts. Results: eccentric strength is greater than concentric strength, there's no significant difference between dominant and non-dominant limb, and a significant increase of the flexor/extensor peak torque ratio was observed with increasing speed, due to the concentric ratios. These results provide information about the relationship between angular velocity and eccentric muscle strength already reported in previous studies and, in particular, the fact that the knee flexors and extensors behave differently during eccentric and concentric work as the angular velocity increases. Analysis of the flexor/extensor ratio also indicated the absence of specific differentiation of muscle activity despite the intensive level of sports activity and suggests the role of age, or even puberty, in these young gymnasts. This analysis encourages annual follow-up of this population and specific studies concerning the role of hormones and muscle maturation.