Physiological Adaptation Analysis of Adolescent Athletes to a Training Program Based on Internal and External Load Monitoring

Abstract

Background: Adolescent athletes are in a critical period of physiological development, making appropriate training load management essential to optimize performance while minimizing injury risks. The monitoring of both internal and external training loads has emerged as a fundamental approach in contemporary sports science to ensure training effectiveness and athlete well-being. Objective: This study aimed to analyze the physiological adaptations of adolescent athletes following a structured training program based on systematic internal and external load monitoring at the Faculty of Sport and Health Sciences, Universitas Negeri Makassar. Methods: A quasi-experimental design with a pre-test and post-test approach was employed, involving 30 adolescent athletes aged 14-17 years selected through purposive sampling. Internal load was measured using the session Rating of Perceived Exertion (sRPE) and heart rate monitoring (HRmax and TRIMP), while external load was assessed through GPS-based metrics including total distance covered, sprint distance, and training volume. Physiological parameters including VO2max, resting heart rate, blood lactate threshold, and muscle strength were evaluated at baseline and after 12 weeks of intervention. Results: Significant improvements were observed across all physiological parameters. VO2max increased from a mean of 42.3 ± 3.1 mL/kg/min to 48.7 ± 2.9 mL/kg/min (p < 0.001). Resting heart rate decreased significantly from 74.2 ± 5.3 bpm to 62.8 ± 4.7 bpm. Blood lactate threshold improved by 18.4%, and muscle strength indices showed a mean gain of 22.6%. Internal and external load data confirmed progressive overload adherence throughout the intervention period. Conclusion: A systematically monitored training program integrating internal and external load parameters produces significant physiological adaptations in adolescent athletes, supporting enhanced aerobic capacity, cardiovascular efficiency, and muscular performance. These findings underscore the importance of individualized load monitoring in youth athletic development