Official book companion

Put the science
into practice.

The index, glossary, references, appendices, runnable code, and continuing updates for The Endurance Code—collected in one place.

First edition · Resource release 1.8.2 · Updated August 2026

The Endurance Code by Alan Couzens
Reference249 index entries
Explore9 notebooks

Start with your goal

From reading to doing.

Use the quick references in the field, download a planning tool, or open a notebook and explore the models with real data.

Online appendices

Field-ready references.

View all appendices
APDF + HTML

Field Testing and Benchmark Protocols

Repeatable field protocols for assessing the qualities that matter, tracking change, and making better training decisions.

  • Aerobic efficiency
  • Critical power & pace
  • Durability
  • Readiness
BPDF + HTML

Training Zone and Readiness Quick Reference

A practical field guide to intensity zones, morning signals, warm-up decisions, and matching load to readiness.

  • Zones 0–7
  • Morning checklist
  • Warm-up rule
  • Load matching
CPDF + HTML

Athlete Planning Templates

A complete set of prompts and templates for turning athlete context, race demands, and readiness into a coherent plan.

  • Athlete profile
  • Annual plan & benchmarks
  • Weekly plan
  • Post-race review

Code library

Make the models tangible.

Every notebook runs with sample data first, so you can understand the method before adapting it to your own training.

Chapter 1

Daily Heart-Rate Distribution

Compare the shape of a full day of heart-rate data with a generated demonstration dataset.

Download notebook
Chapter 3

Swim-Data Analysis

Recreate the chapter’s swim-block analysis and predict a missing 100 m performance from training-zone distribution.

Download notebook
Chapter 5

Specialization Analysis

Explore the performance relationships behind the book’s discussion of specialization.

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Living companion

The book stays in print.
The resources keep moving.

Check corrections, clarifications, and resource changes against the edition on your shelf.

View updates and errata