History-dependent force, angular velocity and muscular endurance in XXXX genotypes.

@entity1 @entity308 @entity40967 @entity31202
PURPOSE: This study aimed at determining the influence of the @entity31202 @entity40967 polymorphism on muscle strength and muscle endurance in non-athletic young @entity1 . METHODS: 266 healthy young @entity1 were included in this study. Each subject performed maximal isometric, concentric and eccentric contractions of the knee extensor muscles on an isokinetic dynamometer. Force @entity308 , force enhancement and the fatigue index were derived from these data. In addition, handgrip strength, squat jump (SJ) and counter movement jump (CMJ) height were obtained. RESULTS: Our group included 83 RR (31  %), 131 RX (49  %) and 52 XX (20  %) individuals. The muscle bone cross-sectional area of the thigh was 5  % higher in RR compared to XX individuals (P  =  0.033). RR genotypes showed 6  % higher handgrip strength compared to the XX group (P  =  0.047). They also jumped 5  % higher in both the SJ and CMJ tests (P  =  0.029; P  =  0.031). No differences were found in force @entity308 , force enhancement, isometric or eccentric strength. The relative concentric knee torque at 200  /s and at 300  /s was 7 and 8  % higher in RR compared to XX genotypes, respectively (P  =  0.049; P  =  0.048). Also, the fatigue index was found to be 4  % lower in XX genotypes (P  =  0.037). CONCLUSIONS: Our findings are in agreement with the higher prevalence of the RR genotype in power-oriented activities. The better fatigue index of XX genotypes may be beneficial in endurance-type activities.
