Quadrant training: a simple typology-based approach to improve strength and endurance in youth soccer players.

INTRODUCTION

Youth soccer players show heterogeneous performance profiles, yet individualized conditioning is often impractical outside professional settings. We examined whether a typology-based training allocation into four quadrants ("Quadrant Training"; QT) improves endurance- and strength-related performance compared with regular soccer training alone.

METHODS

Male U16-U17 players from two youth academies completed a non-randomized, longitudinal controlled intervention (academy-level and intervention effects are confounded); one academy served as intervention group (n = 38), the other as control (n = 22). Players were classified into four endurance quadrants, i.e., below and above team mean based on 30-15 Intermittent Fitness Test velocity [vIFT] and velocity at 4 mmol·L⁻¹ blood lactate [V4] and four strength quadrants based on relative isometric mid-thigh pull strength [IMTP] and countermovement jump height [CMJ], completing quadrant-specific endurance training plus one weekly strength session.

RESULTS

Between-group ANCOVA models using heteroscedasticity-robust standard errors showed the most precise effect for CMJ (p = 0.020), with V4 (p = 0.066) and vIFT (p = 0.054, favoring controls) showing smaller effects and IMTP showing no between-group difference (p = 0.490). None of these effects survived correction for multiple comparisons (adjusted p = 0.078-0.490). This CMJ effect was itself baseline-dependent, negligible at low baseline values and more pronounced at higher ones. For descriptive comparison, the intervention group improved significantly in V4, CMJ, and IMTP (all p ≤ 0.05), while controls showed no significant pre-post changes in any outcome. Exploratory individual responder analyses showed the highest proportion of improvers for V4 and IMTP, followed by CMJ.

DISCUSSION: QT proved feasible to implement as an individualized training framework, and effect sizes for V4 and CMJ suggested a beneficial impact on submaximal endurance capacity and explosive lower-body power. These preliminary findings warrant confirmation in adequately powered trials.