# Optimization of ski jumping in-run posture using computational fluid dynamics

## TL;DR

This paper uses computer simulations to find the best body posture for ski jumpers to reduce air resistance before takeoff.

## Contribution

The study introduces athlete-specific CFD modeling to optimize in-run posture by identifying torso angle as the key factor for drag reduction.

## Key findings

- Torso attack angle (α) is the most influential parameter for aerodynamic resistance during the in-run phase.
- Optimized posture reduces cumulative air resistance by about 5% compared to conventional postures.
- Drag minimization, not lift enhancement, is the primary goal for in-run posture optimization.

## Abstract

While aerodynamic optimization during ski jumping flight phases is well-studied, critical knowledge gaps persist regarding posture-fluid interactions in the in-run phase – particularly the dominance of drag dynamics over lift enhancement for speed maximization. This study establishes an athlete-specific 3D model to investigate posture-dependent resistance through high-resolution CFD simulations. Systematically analyzing four key posture parameters – torso attack angle (α), thigh attack angle (β), ankle joint angle (γ), and hip abduction angle (ε) – reveals α as the governing factor influencing aerodynamic resistance during acceleration. The optimized configuration (\documentclass[12pt]{minimal}
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\begin{document}$$\:\epsilon\:\in\:\left[-2^\circ\:,0^\circ\:\right]$$\end{document}) reduces cumulative air resistance by approximately 5% compared to conventional postures, demonstrating that marginal angular adjustments in torso positioning significantly outweigh other joints’ contributions to drag reduction. Contrary to flight-phase strategies emphasizing lift generation, the results establish drag minimization as the primary in-run optimization objective. These findings provide evidence-based posture guidelines for athletes while advancing a paradigm shift from empirical to physics-driven training methodologies – particularly through computational fluid dynamics with practical sports biomechanics. The work positions CFD as an indispensable tool for quantifying millimeter-scale posture adaptations in winter sports equipment-athlete system optimization.