Establishing reliable acceleration-speed profiles: Minimum data requirements in rugby union matches

The aim of this study was to determine the minimum playing time in matches required to produce reliable acceleration - speed (AS) profiles from global navigation satellite system (GNSS) data. The playing time of 25 professional rugby union players was recorded using GNSS technology and segmented into four sections from 40, 80, 120 and 160 minutes of play. For each interval, the impact of integrating new match data on the AS profile was assessed, aiming to identify the saturation point where additional data did not induce significant changes in the profile outputs. A repeated measures ANOVA and Bonferroni post-hoc tests were applied to examine the variations of AS profile between time intervals. This led to identify the saturation point for assessing "robust" values of theoretical maximum acceleration (A0) and maximum speed (S0). A substantial lack of significant effect was observed for A0 (<i>p</i> = 1.00) and S0 (<i>p</i> = 0.99) in the section of 160 minutes, with an intra-subject variability of 1.50 and 1.20% for A0 and S0, respectively. Determining AS profiles for rugby players is essential for monitoring performance in training and match contexts. Our findings indicate that an equivalent of two full rugby union matches is required to generate a reliable AS profile.