A comparison of manual and automatic force-onset identification methodologies and their effect on force-time characteristics in the isometric midthigh pull.

The aim of this study was to assess the agreement of three different automated methods of identifying force-onset (40 N, 5 SDs, and 3 SDs) with manual identification, during the isometric mid-thigh pull (IMTP). Fourteen resistance-trained participants with >6 months experience training with the power clean volunteered to take part. After three familiarisation sessions, the participants performed five maximal IMTPs separated by 1 min of rest. Fixed bias was found between 40 N and manual identification for time at force-onset. No proportional bias was present between manual identification and any automated threshold. Fixed bias between manual identification and automated was present for force at onset and F₁₅₀. Proportional but not fixed bias was found for F₅₀ between manual identification and all automated thresholds. Small to moderate differences (Hedges g = -0.487- -0.692) were found for F₉₀ between all automated thresholds and manual identification, while trivial to small differences (Hedges g = -0.122--0.279) were found between methods for F₂₀₀ and F₂₅₀. Based on these results, strength and conditioning practitioners should not use a 40 N, 5 SDs, or 3 SDs threshold interchangeably with manual identification of force-onset when analysing IMTP force-time curve data.