Physiological characterization using standardized submaximal treadmill responses in professional male soccer players

Submaximal treadmill variables are increasingly used in professional soccer, but their practical interpretation remains limited. Therefore, we aimed to determine whether standardized submaximal treadmill-derived variables provide a more informative characterization of positional differences than maximal exercise variables and to examine their associations with maximal exercise performance.

In this retrospective cross-sectional study, professional adult male soccer players (n = 206), including midfielders, defenders, and forwards performed an incremental treadmill test until exhaustion, with enhanced speed-dosing above 4 mmol·L⁻¹ blood lactate (4L). Absolute and relative heart rate (HR) and speed variables at 4L and exhaustion, together with their associations were analysed during this incremental treadmill test.

Midfielders reached the highest 4L-related values, including speed (V_4L: 15.6 ± 1.3 km/h, p < 0.005 vs others), HR (HR_4L: 177.2 ± 9.0/min, p < 0.05 vs others), V_4L as % of maximal speed (V _4L/Max ratio: 77.6 ± 4.9%, p < 0.005 vs. forwards), and HR_4L as % of HR reserve (HR _4L/Res ratio: 87.1 ± 4.9%, p < 0.05 vs. others). Positional differences at maximal exercise were inconsistent. V_4L correlated moderately with HR_4L in all players (r = 0.364, p < 0.001), largely with HR _4L/Res ratio (r = 0.609, p < 0.001) and while HR _4L/Res ratio correlated very largely with V _4L/Max ratio (r = 0.795, p < 0.001), without positional differences. Between 4L and exhaustion, correlations were larger for HR, than for speed, being very large for HR in all (r = 0.739, p < 0.001), while large in forwards (r = 0.661, p < 0.001), and for speed large in all (r = 0.575, p < 0.001), across playing positions. After adjustment for age, BMI, club, competitive division, testing phase, and testing year, positional effects remained significant for V_4L (p = 0.003) and HR_4L (p = 0.007), but not for V_Max (p = 0.077) or HR_Max (p = 0.147).

Submaximal treadmill-derived variables differentiated playing positions more consistently than maximal exercise variables, while remaining strongly associated with maximal treadmill performance. These findings highlight 4L-related heart rate and running speed variables as informative submaximal markers for the physiological characterization of professional soccer players.