Stryd Running Power Critical Power & W′bal Reconstructor

Stryd Running Power Critical Power & W′bal Reconstructor | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Sports
Input types: select, textarea, file, number
Output type: html
Sample coverage: 4
API ready: Yes

Overview

The Stryd Running Power Critical Power & W′bal Reconstructor calculates your Critical Power (CP) and anaerobic work capacity (W′) from field test data and simulates running sessions second by second. It models real-time W′bal depletion and recovery using the Skiba 2012 integral and Froncioni/Skiba/Clarke differential algorithms, maps training intensity across official Stryd power zones, and provides time-to-exhaustion forecasts alongside dual-panel interactive charts.

When to use

Analyzing a 3-minute all-out running test or multi-trial power/time data to determine accurate CP and W′ values.
Replaying structured interval workouts from .fit, .tcx, or CSV files to identify anaerobic battery depletion and recovery points.
Validating pacing strategies and forecasting time-to-exhaustion for supra-threshold race efforts and repetition sets.

How it works

1Select your CP test method—such as a 3-minute all-out series, power–time trial pairs, distance–time trials, or predefined values—and input your baseline test data.
2Optionally provide a full workout file (.fit, .tcx, or .csv) or paste session power streams along with your body weight and running efficiency.
3Choose your preferred W′ balance algorithm (Skiba 2012 integral, Froncioni/Skiba/Clarke differential, or both) to track anaerobic reconstitution dynamics.
4Generate an HTML report displaying CP/W′ stat cards, time-to-exhaustion projections, Stryd 5-zone distributions, and synchronized power/W′bal charts.

Use cases

Coaches verifying whether an athlete fully exhausted their anaerobic reserve during track repetitions.
Runners calibrating Stryd threshold and interval training zones following a seasonal fitness benchmark test.
Marathoners and middle-distance runners simulating pacing plans to prevent premature W′ exhaustion on race day.

Examples

1. Deriving CP and W′ from a 3-Minute All-Out Test

Competitive Runner

Background

A runner conducted a 3-minute all-out field test using a Stryd footpod to determine their current Critical Power and anaerobic work capacity without lab testing.

Problem

They need to isolate the final 30-second plateau to extract true CP and calculate the exact energy expended above CP.

How to use

Set CP Test Method to '3-min all-out series', paste the time/power stream sampled every 5 seconds into Test Data, and set body weight to 70 kg.

testMode: 3min-allout
testData: 0,430\n5,428\n10,425...175,301
wbalModel: both
bodyWeight: 70

Outcome

Yields a CP of 305.2 W, a W′ of 9.17 kJ, and generates time-to-exhaustion chips for supra-threshold intensities (110%, 120%, and 130% CP).

2. Replaying High-Intensity Interval Depletion

Endurance Coach

Background

A coach wants to check if an athlete's 5×(60s on / 60s off) repetition workout was paced aggressively enough to draw down anaerobic reserves.

Problem

The coach needs second-by-second visibility into how deeply W′bal dropped during each interval and how quickly it replenished during active recovery.

FAQ

What test protocols can I use to determine CP and W′?

You can use a 3-minute all-out test (Vanhatalo model), two or more power–time trials, distance–time trial pairs using ACSM metabolic estimation, or enter known CP and W′ values directly.

What is the difference between the Skiba and Differential W′bal models?

The Skiba 2012 integral model calculates recovery rate based on average power below CP across the session, whereas the differential model dynamically adjusts recovery kinetics relative to the instantaneous depth of W′ depletion.

Which workout file formats are supported for session replay?

You can upload standard binary .fit files, XML-based .tcx files, or plain text .csv and .tsv files containing time and running power columns up to 20 MB.

How are the Stryd training zones defined?

Zones are calculated relative to your CP: Easy (65–80%), Moderate (80–90%), Threshold (90–100%), Interval (100–115%), and Repetition (115–130%).

Why are body weight and running efficiency required for distance–time data?

testMode: known-cp
testData: cp=300 wprime=18000
sessionData: 0,200...1490,180
wbalModel: both

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Deriving CP and W′ from a 3-Minute All-Out Test

2. Replaying High-Intensity Interval Depletion

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