Objectives: This study aimed to determine changes and interrelationships between changes in selected anthropometric growth parameters and motor and physical fitness, among boys over a 2 year period during mid-adolescence. Methods: Speed, agility, hand-eye coordination, explosive power, muscle strength, and aerobic endurance were measured once a year, and the anthropometric measurements (stature, body mass, sitting height, arm span, and sitting height ratio), were measured three times per year, 4 months apart (among 73 adolescent boys). A hierarchical linear model, adjusting for covariates and partial correlation analysis (R2) were used to analyze the data. Results: All anthropometric, motor, and physical measurements improved significantly over the two-year period. Significantly, greater changes were seen between 13 and 14 years in stature, arm span, sitting height and body mass. Changes in muscle strength, speed and agility were mainly significant between 13 and 14 years while the biggest changes occurred in explosive power and upper-body-arm-and-shoulder-strength during year 2 (14-15 years). The majority of interrelationships, indicating moderate to small relationships, were found between changes in stature, arm span, and sitting height, and changing strength, speed, agility, and hand eye coordination over the two-year period, after adjusting for maturity age and physical activity levels. Conclusion: Motor and physical fitness improved significantly from 13 to 15 years, showing definite interrelationships with anthropometric growth during the mid-adolescence period. Awareness and education about these changes are recommended as it can have significant effects on the sport performance and fitness training of boys during mid-adolescence. Am. J. Hum. Biol. 26:617-626, 2014. © 2014 Wiley Periodicals, Inc.
