Durability of parameters associated with endurance running in marathoners

Physiological markers of endurance performance include the maximal oxygen uptake (V̇O 2peak), its fractional utilisation at lactate threshold (FU LT), and running economy (RE), which are closely tied to the speed eliciting the lactate threshold (sLT). These parameters deteriorate during prolonged exercise, and the ability to resist such declines (i.e., durability) is now also considered a marker of marathon performance. This study investigated the durability of markers of endurance performance (V̇O 2peak, FU LT and RE), and whether the durability of these markers was associated with marathon performance. Eighteen participants of the 2024 London Marathon (11 males, age: 41 ± 12 years, marathon finish time: 3:17 ± 0:32 h:min) completed two separate visits to determine V̇O 2peak, FU LT, RE and sLT in a ‘fresh’ state (PRE) and following a 90-min run at sLT (POST). Reductions in V̇O 2peak (PRE: 56.7 ± 7.2 mL·kg −1·min −1 vs. POST: 53.4 ± 6.3 mL·kg −1·min −1, p < 0.001) and sLT (PRE: 12.8 ± 2.0 km·h −1 vs. POST: 12.1 ± 2.2 km·h −1, p < 0.001) were evident, but RE and FU LT were unchanged (both p > 0.05). The percentage change in sLT between POST and PRE (r = 0.680, p < 0.01) was significantly associated with marathon performance, whereby small deteriorations of sLT were associated with faster marathon times. Prolonged running impairs key physiological markers of endurance performance, and the degree of this deterioration, that is, durability, is associated with marathon performance. Marathon runners and practitioners should consider quantifying durability to complement existing physiological markers.