A new energetics model for the assessment of the power-duration relationship during over-ground running

We evaluated the reliability of an over-ground running three-minute all-out test (3MT) and compared this to traditional multiple-visit testing to determine the critical speed (CS) and distance > CS (<i>D</i>'). Using a novel energetics model during the 3MT, critical power (CP) and work > CP (<i>W</i>') were also evaluated for reliability and compared to the multiple-visit tests. Over-ground running speed was measured using Global Positioning Systems during fixed-speed trials on a 400 m track to exhaustion, at four intensities corresponding to: (i) maximal oxygen uptake (V̇<i>O_2max</i>) (V_max), (ii) 110% V̇<i>O_2max</i>(110%<i>V_max</i>), (iii) Δ70% (i.e. 70% of the difference between gas exchange threshold and V_max) and (iv) Δ85%. The participants subsequently performed the 3MT across two days to determine its reliability. There were no differences between the multiple-visit testing and the 3MT for CS (<i>P</i> = 0.328) and <i>D</i>′ (<i>P</i> = 0.919); however, CP (<i>P</i> = 0.02) and <i>W</i>′ (<i>P</i> < 0.001) were higher in the 3MT. The reliability of the 3MT was stable (<i>P</i> > 0.05) between trials for all variables, with coefficient of variation ranging from 2.0–8.1%. The current over-ground energetics model can reliably estimate CP and <i>W</i>′ based on GPS speed data during the 3MT, which supports its use for most athletic training and monitoring purposes. The reliability of the over-ground running 3MT for power- and speed-related indices was sufficient to detect typical training adaptations; however, it may overestimate CP (∼ 25 W) and <i>W</i>′ (∼ 7 kJ) compared to multiple-visit tests.