The influence of ball in/out of play and possession in elite soccer: Towards a more valid measure of physical intensity during competitive match-play.

The physical demands of soccer match-play have typically been assessed using a low-resolution whole match approach ignoring whether the ball is in or out of play (BIP/BOP) and during these periods which team has possession. This study investigated the effect of fundamental match structure variables (BIP/BOP, in/out of possession) on the physical demands, and especially intensity, of elite match-play. For 1083 matches from a major European league, whole match duration, and player physical tracking data, were divided into BIP/BOP, and in/out of possession periods throughout the match, using on-ball event data. These distinct phases were used to derive absolute (m) and rate (m·min This large-scale study utilising >1000 elite level competitive matches found profound differences in rate of distance covered between periods of BIP vs BOP, being 2-fold higher overall and 8- to 33-fold higher for the rates of distance covered within running, high-speed and sprinting speed categories.Consequently, commonly used whole match physical metrics, that incorporate both BIP and BOP, such as distances covered but even rates of distance covered, were not valid indices of physical intensity (rate of distance covered) during BIP.Thus a more valid and direct approach to quantifying physical intensity during elite soccer match-play as the rate of distance covered during BIP is proposed.Utilising a unique within-match analysis the effect of possession (i.e. in vs out) revealed that teams covered ≥30% more running and high-speed distance while out than in possession during BIP.