The purpose of this study was to assess the analysing reaction time (RT) and normalized power when calculated using two different methods: a method using ground reaction forces (GRFs) of only the legs (legs F-based method) and a method using GRFs of arms and legs (whole F-based method). In total, 127 block start motions from fourteen male sprinters were analysed from all participants. The RT of the legs F-based method was not similar to that of the whole F-based method: the mean difference was 7.4 ms and the 95% CI was –45.1–59.8 ms. In contrast, the normalized power of the legs F-based method was similar to that of the whole F-based method. This information will help reconsider the golden standard methods currently used to analyse RT and encourage the use of analysis methods to analyse the performance in block starts