Yo-yo intermittent recovery test thresholds to determine positional internal match loads of semiprofessional soccer players

The aim of this study was to use heart rates and Yo-Yo Intermittent Recovery test level 1 (Yo-Yo IR1)-derived thresholds to determine the positional internal match loads of semi-professional soccer players. Players completed a Yo-Yo IR1 while wearing a portable gas analyser. Heart rates (HR) that corresponded to the first and second ventilatory thresholds were used to classify internal loads into low- (LI HR zone), moderate- (MI HR zone) and high-intensity zones (HI HR zone). During 12 soccer matches it was found that attackers (n = 17) spent more time in the LI HR zone (3386 s; 62%; P < 0.05) than defenders (2155 s; 40%; n = 36) and midfielders (2425 s; 42%; n = 41). The attackers spent less time in the HI HR zone (260 s; 4%; P < 0.05) than the defenders (964 s; 15%). Midfielders (2444 s; 44%) and defenders (2364 s; 41%) spent more time in the MI HR zone than attackers (1854 s; 44%). This study is the first to show that the Yo-Yo IR1 test can be used to determine individual, physiologically defined intensity zones to determine positional differences in the internal match loads of soccer players