Workout Reserve

Athletica Workout Reserve tells you, in real time, how close you are to your performance limit over every duration that matters, from a twelve second sprint to a full hour. It reads from 100%, fully fresh, down to 0%. When it reaches zero you have just produced a maximal effort.

That is the short version. Here is why it works the way it does, and why we built it rather than reusing the models everyone already has.

Most performance models compress you into a single value. Critical Power gives you one threshold and a fixed work capacity above it, the W'. It is a good model, and the ideas behind it run all through Athletica. It is also a simplification, because you do not have one limit. You have a limit at twelve seconds, a different one at five minutes, another at an hour, and they do not rise and fall together. A track sprinter and a marathoner can share the same hour power and live in completely different bodies.

The Athletica Workout Reserve holds all of those limits at once. The model keeps a set of rolling averages of your power or pace, each tuned to a different timescale across the range, twelve seconds out to roughly an hour. Every second, it compares each rolling average against the best you have ever produced over that same timescale. Whichever one is sitting closest to your historical best is the system limiting you at that instant. That is your current bottleneck, and it moves around inside a session depending on what you have already done.

We validated the model on 21 professional cyclists across an eleven day training camp. The first ten days built each rider's individual power profile. On the final day we put them through roughly 2000 kJ of work over three hours to fatigue them, then asked for two maximal time trials, three minutes and twelve minutes.

When those riders went genuinely maximal, the Athletica Workout Reserve hit 0% exactly at the predicted time, and the limiting timescale was not the one that matched the length of the effort: it was a much longer one, close to an hour. Put simply, what they had done earlier in the session set the ceiling more than the effort directly in front of them. Most of us, athletes and coaches both, underrate how much the early part of a session governs what becomes possible later. The data says we should pay attention to it.

Athletica Workout Reserve shows up across the platform. It lives on every session you complete, under “Analysis”, so you can see how deep you went after the fact. It also can run live on a Garmin App, so you can watch your reserve fall during training and racing and know when you are genuinely near the edge. It also drives System Engagement, the feature that takes a finished file and shows which metabolic domain was doing the heavy lifting at each moment.
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You were taught energy systems as three isolated systems; phosphocreatine, lactic and aerobic. What is less known is that they run together, with one usually dominant. But which one dominates shifts according to what came before it. System Engagement is the first time you can watch that happen in your own data in any given context.

The Athletica Workout Reserve was first conceived by Andrea Zignoli at the Department of Industrial Engineering at the University of Trento. He spent four years collaborating with professional cycling coaches and with the Athletica team, so this idea could turn into a peer reviewed, published method. The validation study is in the European Journal of Sport Science. The real time algorithm and its on device implementation are in Sports Engineering.

Zignoli A, Giorgi A, Kolodziej F, Martinez-Gonzalez B, Leo P, Laursen PB. Tracking Performance Limits Using Multi-Timescale Maximal Mean Power Ratios. European Journal of Sport Science. 2026:e70179. doi:10.1002/ejsc.70179

Zignoli A, Whitehurst P. Real-time assessment of exercising maximal mean power and speed in endurance sports: a Garmin Connect IQ App. Sports Engineering. 2025;28:45. doi:10.1007/s12283-025-00528-1

Learn about the science behind Athletica → https://athletica.ai/methodology 

See Workout Reserve in a real race file → https://athletica.ai/blog/how-a-protour-cycling-coach-uses-athletica-workout-reserve

What is the Athletica Workout Reserve? The Athletica Workout Reserve is a real time measure of how close you are to your performance limit, calculated continuously across every duration from about twelve seconds to an hour. It reads from 100%, fully fresh, to 0%, where you have just produced a new maximal effort for that duration. Andrea Zignoli conceived the idea, and it runs inside Athletica and on Garmin devices.

‍How is Workout Reserve different from FTP or Critical Power? FTP and Critical Power describe you with a single threshold and a fixed capacity above it. Athletica Workout Reserve tracks many durations at once, from a sprint to an hour, because your limit at twelve seconds and your limit at twenty minutes are different numbers that change independently. It shows you which of your many ceilings you are closest to at any given moment.

‍What does it mean when my Athletica Workout Reserve hits zero? Zero means you have just set a new maximal mean power or speed for one of the tracked durations. You have not failed. You have redefined your own best over that timescale, and the model updates its reference to match.

‍Is Workout Reserve the same as W' (anaerobic work capacity)? No. W' is a single fixed quantity of work available above Critical Power, tied to one timescale. Athletica Workout Reserve is a multi timescale measure that tracks proximity to your historical best across the whole power duration range, not only the anaerobic portion.

‍How is Athletica Workout Reserve calculated? The model keeps a set of rolling averages of your power or pace, each tuned to a different timescale from roughly twelve seconds to an hour. At every second it compares each average against your historical best for that timescale and finds the one closest to its maximum. That value is converted into a reserve between 0 and 100%. The duration sitting closest to its limit tells you which system is currently constraining you.

‍Does Athletica Workout Reserve work for running, or only cycling? Both. It runs on power for cycling and on speed for running. For outdoor running, the implementation estimates road gradient so that pace is judged fairly on hills as well as flats.

‍Who invented Athletica Workout Reserve? Andrea Zignoli conceived it and he developed the idea together with Paul Laursen, Filip Kolodziej and Phil Whitehurst at Athletica. Andrea Zignoli is a fellow researcher in the Department of Industrial Engineering at the University of Trento. The method is published in the European Journal of Sport Science (2026) and Sports Engineering (2025).