Age- and sex-associated variation in neuromuscular capacities of adolescent distance runners

The main aim of this study was to examine the age- and sex-associated variation in neuromuscular capacities of young distance runners. A secondary aim was to compare the magnitude of sex differences in young athletes in the same sport compared with the general population. Twenty-seven male and 27 female distance runners were enrolled in the study, whose ages ranged from 8.0 to 15.1 years at initial visit. Twenty males and 16 females were followed at approximate annual intervals for 4 or 5 years. Seven neuromuscular capacities were measured: quadrant jump, figure 8 run, standing long jump, vertical jump, flexed arm hang, sit-and-reach and sit-up. Age- and sex-associated variation was analysed by two-way analysis of variance. There were significant main effects for age for quadrant jump, figure 8 run, long jump, vertical jump, sit-and-reach and sit-up. There were significant main effects for sex for figure 8 run, long jump, vertical jump, flexed arm hang and sit-and-reach. The interaction between age and sex was statistically significant for long jump and vertical jump. In general, differences in neuromuscular agility (figure 8 run, quadrant jump) and explosiveness-power (long jump, vertical jump) between the sexes were attenuated before 13 years of age in young distance runners. However, during the adolescent growth spurt, differences in agility and power between the sexes emerged as a result of a continued increase in males and a plateau in females. Differences between the sexes in upper body neuromuscular endurance (flexed arm hang) and sit-and-reach persisted throughout the age range. The magnitude of sex differences between the runners and the general population varied by age and neuromuscular capacity.