Characterizing Change-of-Direction Demands in Professional Soccer Match Play Using Deceleration and Acceleration Metrics.

PURPOSE: This study characterized change-of-direction (COD) actions in professional soccer players using global navigation satellite systems data, with specific emphasis on COD angle and the associated deceleration (DEC) and re-acceleration (re-ACC) kinematics under match-play conditions. METHODS: Data were collected from 52 professional soccer players (mean [SD]: age: 27.3 [5.2] y; body mass: 72.3 [6.9] kg; height: 178.6 [6.8] cm) across 14 official matches, resulting in 3048 individual COD events for analysis. Events were classified by COD angle (15° bins), and DEC and re-ACC phases were detected to extract kinematic variables. Associations between COD angle and selected variables were examined using contingency analyses, and linear mixed-effects models assessed the effects of angle and playing position. RESULTS: CODs, on average, initiated from moderate entry speeds (14.9 km·h-1) and involved substantial braking demands (-4.2 m·s-2), followed by a short DEC-ACC interval (0.6 s) and a relatively low re-ACC magnitude (1.7 m·s-2). Contingency analyses revealed a significant association between COD angle and DEC entry speed (P = .026), with sharper angles showing a slightly greater proportion of moderate-to-high entry speeds. Mixed-effects identified a significant main effect of playing position on DEC entry speed (P = .035), with higher entry speeds for wide midfielders and forwards compared with central defenders. CONCLUSIONS: During soccer matches, CODs have intense braking and rapid DEC-re-ACC coupling despite predominantly submaximal entry and exit speeds. The results support the need for higher DEC thresholds, reflecting match play demands. Additionally, training strategies should account for both angle and entry-speed demands, while considering the playing position.