Rising performance-efficiency demands in female junior tennis: A longitudinal analysis of ITF World Tennis Tour Juniors rankings, 2004–2025

Long-term changes in ranking-point production efficiency among female players on the ITF World Tennis Tour Juniors were examined between 2004 and 2025. Year-end ranking data comprised 8,510 player-year observations from 5,919 players aged 12–18 years. Elite status was defined annually using a two-stage data-driven knee-point procedure: players were ordered according to Total Ranking Points (TRP), the knee percentile was identified from the smoothed Total Singles Points profile across this TRP-based ordering, and the threshold was applied to the same percentile scale. Performance efficiency was assessed using Singles PPE, Doubles PPE, and Total PPE, with Total PPE defined as TRP divided by total competitive event exposure. In pooled descriptives excluding 2020–2021, median Singles PPE was 64.62 in elite versus 26.56 in non-elite players; corresponding values were 48.57 versus 29.00 for Doubles PPE and 40.38 versus 17.71 for Total PPE. Positive Year × elite-status interactions were identified in linear player-year models adjusted for age, discipline-specific competitive event exposure, COVID-disrupted seasons, and repeated player observations, corresponding to additional average annual increases of 10.81%, 8.97%, and 9.25%, respectively. However, non-COVID natural-spline models showed that temporal differentiation was non-linear and did not support uniform monotonic widening across 2004–2025. In lagged sensitivity analyses, prior-year elite status was associated with higher subsequent PPE, but Year × prior-year elite-status interactions were not significant in the strict non-COVID specification. Forecasts based on 20 non-COVID annual elite medians projected higher PPE through 2030 under continuation of the observed linear trend, while event-exposure scenarios indicated fewer competitive event exposures associated with fixed TRP benchmarks at higher projected efficiency. These projections should be interpreted as conditional ranking-system scenarios rather than measures of physiological load or individual participation requirements. Overall, structurally defined elite players were characterised by persistently higher ranking-point production efficiency and significantly different, non-linear historical trajectories.