The Effects of Age and Height on Gait Smoothness in Adolescent Athletes †

(1) Background: Despite evidence of increased rates of sports injury during the years surrounding peak growth in adolescents, little is known regarding the relationship between adolescent growth and gait stability. The aim of this study was to gain a better understanding of how chronological age and height relate to gait stability in both male and female adolescents. (2) Methods: Participants (N = 67; females: n = 34, ages 8.7–15.9 years; males: n = 33, ages 10.0–16.7 years) completed two trials of treadmill walking at varying speeds: the preferred walking speed and 30% above and below. Trials were separated by a bout of fatiguing exercises. HarmonicRatios of the trunk, calculated from acceleration signals taken during walking, were used to quantify gait stability. Data were separated by sex and relationships between height and chronological age, and HarmonicRatios were assessed using multiple linear regression. (3) Results: Females’ HarmonicRatios improved with chronological age both before and after fatigue. Males’ HarmonicRatios increased with chronological age before fatigue; however, this effect was eliminated post-fatigue. Females’ height was negatively associated with HarmonicRatios post-fatigue. Males’ height was positively associated with HarmonicRatios pre-fatigue. (4) Conclusions: The study findings suggest sex differences in the effects of fatigue on gait stability during adolescence. In both sexes, HarmonicRatios increased with chronological age. These improvements were eliminated for males and altered for females with fatigue. The results of this study indicate the need for the reevaluation of sports progression based on chronological age in adolescents.