The effect of 90 and 120 min of running on the determinants of endurance performance in well-trained male marathon runners

The combination of maximal oxygen uptake (V̇O₂max), fractional utilization at lactate threshold (FU_LT), and running economy (RE) is considered to largely determine/predict marathon performance, which is also closely associated with the speed at lactate threshold (sLT). Although these determinants are considered to deteriorate during prolonged running, except for RE, their temporal changes with fatigue remain largely unknown. This study aimed to measure the changes in V̇O₂max, FU_LT, RE, and sLT after running for 90 and 120 min in the heavy-intensity domain. Fourteen trained marathon runners (V̇O2max 63.1 ± 5.8 mL·kg⁻¹·min⁻¹; marathon time 2:46:58 h:mm:ss) completed three separate visits to determine sLT, FU_LT, and V̇O₂peak in the following conditions (sessions): unfatigued, and after two prolonged runs of 90 and 120 min at a fixed speed (10% Δ between LT and lactate threshold 2). During the runs, respiratory gases were collected at 15 min intervals to quantify RE. Decreases in V̇O₂peak (−3.1%, p = 0.04 [post-90]; −7.1%, p < 0.001 [post-120]) and subsequent increases in FULT (+2.8%, p = 0.03 [post-90]; +4.9% p = 0.01 [post-120]) both occurred at an increasing rate with run duration, with FULT changes linked to the decreased V̇O₂peak, while RE (mL·kg⁻¹·km⁻¹) deteriorated more linearly with time (by 4.2% [post-90] and 5.8% [post-120], p < 0.001). sLT also showed a nonlinear decrease, from 14.0 to 13.5 (p = 0.01 post-90), to 13.0 km·h−1 (p < 0.001 post-120). In conclusion, performance determinants and sLT changed following 90 min, and particularly 120 min of prolonged running. These dynamic changes have strong implications for running performance and would particularly affect longer duration events such as the marathon.