In vitro quantification of the resistance force properties of a hydraulic resistance device designed for sprinting

Abstract

The hydraulic resistance device (HRD), a state-of-the-art device developed primarily for resisted sprint training, lacks exploration of its force-generating properties. This technical note aims to evaluate these properties in vitro. In a laboratory experiment, the HRD was pulled with a motorised winch at four speeds (1–4 m s⁻¹) and 12 different HRD resistance levels (low, medium and high). The resistance force induced by the HRD was measured using a force plate mounted under the device, and calculated as mean horizontal force produced at a constant pulling speed. Resistance force repeatability between pulling speeds at specific resistance levels was assessed using the coefficient of variation (CV) whereas the intraclass correlation coefficient (ICC_3,1) was calculated to determine the consistency. A linear regression model quantified resistance force as a function of HRD resistance level. Accuracy of the model was assessed using root mean square error (RMSE). Across 12 resistance levels, the HRD produced resistance forces ranging from 22.57 ± 4.84 to 164.57 ± 4.84 N. The CV decreased from 21.5% at the lowest resistance to 0.4% at the highest. The HRD produced resistance force with high consistency (ICC_3,1 CI = 0.990–0.999). The linear regression model showed a near-perfect fit (R² = 0.99) and predicted resistance force more accurately at medium and high resistance (RMSE range = 0.97–4.57 N). The HRD provides favourable force-generating properties for resisted sprint training and testing, warranting further studies on its exploration in vivo.