Stature is the key: a systematic review and Meta-analysis on the role of body mass and stature in physical fitness through Allometric modeling

Objectives: To evaluate how stature and body mass influence youth physical fitness performance across different test modalities using allometric modeling, and to quantify domain-specific allometric exponents for stature and body mass. Design: Systematic review and meta-analysis. Methods: A comprehensive literature search was conducted in PubMed and Web of Science (July 2024;CRD420251030848). Sixteen cross-sectional studies involving youth populations (aged 7–19 years) met inclusion criteria. Extracted allometric exponents for stature and body mass were synthesized across four fitness domains: cardiorespiratory fitness, upper-limb strength, lower-limb explosive strength, and speed–agility. Random-effects meta-analyses were performed using Restricted Maximum Likelihood estimation. Heterogeneity was assessed via I2 and Cochran's Q. Results: Stature showed a consistently positive association with performance across all domains, with allometric exponents ranging from 0.40 to 1.39 (p < 0.001). Body mass demonstrated divergent patterns: negative exponents for cardiorespiratory fitness (boys: − 0.24; girls: − 0.22), explosive strength, and speed–agility; but positive associations for upper limb strength (boys: 0.31; girls: 0.30). All models showed high heterogeneity; moderation and sensitivity analyses confirmed test-type-independent results. Conclusions: Stature shows a consistent positive association with physical fitness independently of test modalities, whereas body mass exponents are domain-specific, negative in weight-bearing tasks and positive in upper-limb strength. These pooled estimates suggest clear trends in size-performance scaling, though substantial heterogeneity and the absence of independent model validation limit their generalizability. Allometric modeling remains a useful approach to reduce size-related bias when applied alongside sport-specific and developmental considerations.