Integrating Biological Maturity into Fitness Assessment and Physical Activity Interventions in Children and Adolescents: A Narrative Review

Background: Childhood and adolescence represent critical developmental periods characterized by rapid somatic growth, endocrine changes, and the progressive attainment of biological maturity. These maturational processes substantially influence the development of physical fitness, yet are often overlooked when evaluating performance in youth populations. This structured narrative review aims to synthesize current knowledge regarding the relationships between somatic growth, biological maturity, and physical fitness in children and adolescents. Methods: A structured narrative review was conducted by systematically searching PubMed, Scopus, and Web of Science databases for peer-reviewed articles published up to February 2026. Keywords included ‘biological maturation’, ‘physical fitness’, ‘youth’, ‘adolescence’, ‘peak height velocity’, and ‘bio-banding’. Studies were eligible if they examined relationships between biological maturity indicators and physical fitness outcomes in children and adolescents aged 8–19 years. No publication date restrictions were applied, although priority was given to articles from the past 15 years. Results: Evidence consistently indicates that biological maturity substantially influences muscular strength, power, and speed in males; findings among females and for cardiorespiratory fitness are more nuanced and context-dependent. Early-maturing boys typically exhibit superior strength and power performances, whereas findings among girls are more variable. Earlier maturation in girls is frequently associated with increased adiposity, which may attenuate performance in weight-bearing activities. When maturity status is ignored, physical fitness evaluations may misrepresent the capabilities of late-maturing youth and potentially discourage long-term participation in physical activity. Conclusions: Integrating biological maturity into youth fitness evaluation frameworks is essential for accurately interpreting performance data and for providing developmentally appropriate interventions. Three implementation strategies are recommended: (i) adoption of maturity offset or percentage of predicted adult stature as standard covariates; (ii) development of maturity-stratified normative standards; and (iii) implementation of bio-banding in youth sport development.