What’s in you on race day?

As accurate as what you tell us. A single distance-and-time entry says a lot about your current level, but nothing about your form on race day – that also depends on training, fuelling, weather and course. So we don’t show a single number. We show a range, and we tell you per discipline how confident the estimate is.

In two steps. First we convert your entry into your threshold values: threshold pace for running, threshold power for cycling, critical speed for swimming. For running we use the VDOT model developed by Jack Daniels and Jimmy Gilbert, for swimming the Critical Swim Speed concept, and for cycling the physical power-velocity equation including air resistance and rolling resistance. In the second step we translate those threshold values into a race time for your distance.

That the sustainable fraction of your threshold falls with race duration is well studied. Péronnet and Thibault showed in 1989 that sustainable aerobic power declines with the logarithm of race duration beyond roughly seven minutes – not linearly. That is why stepping up from middle to long distance costs more than doubling the distance suggests. How high you sit within that decline depends on your training level: Joyner described in 1991 how well-trained runners race the marathon close to their lactate threshold pace, while untrained runners stay well below it. For swimming we use critical swim speed, which Wakayoshi and colleagues confirmed in 1992 as a field measure of the maximal lactate steady state.

The specific numbers per level and distance are framed by this work, not derived from it: we calibrate them against real race results and keep refining them. On the bike we also follow established power-meter practice – around 70 % of threshold power over the long distance, correspondingly more over the short ones. That is practical coaching knowledge rather than a single study, and we won’t pretend otherwise.

Péronnet & Thibault, J Appl Physiol 67(1):453–465, 1989 · Joyner, J Appl Physiol 70(2):683–687, 1991 · Wakayoshi et al., Eur J Appl Physiol 64(2):153–157, 1992

How much endurance performance improves depends mostly on training age. In beginners, double-digit gains within a few months are well documented (Bacon et al., PLOS ONE 2013). In long-term trained athletes progress is far slower and comes through different adaptations – in marathon world record holder Paula Radcliffe, maximal oxygen uptake stayed flat across twelve years while her running economy improved by 15 % (Jones, 2006). That gradient is what we model, scaled by the training volume you plan to do. The same research also shows how differently people respond to identical training – which is why you get a range and not a single number.

Because step 1 has to assume what step 2 knows. Without your training volume and experience we assume a mid-level athlete, and without a specific race we assume a neutral course. Once you add both, not just the race-day projection gets sharper – so does the read on where you stand today.

No. One distance and the matching time is enough. If you already know your threshold values you can enter them directly – then we skip the conversion and the projection gets more precise.

No. This page tells you where you stand and what’s realistically within reach. Getting you there is the app’s job: a plan that adapts to your volume, your recovery and your race, and readjusts after every session.