Meliora.
Performance lab

Measuring effort without being ruled by the numbers.

The Performance Lab explains the common ways of tracking training, from perceived effort to heart rate and power, and how adults aged 35 and over can use them without over-reading a single reading.

Man in his forties running on a treadmill in a physiology laboratory with a monitor showing a heart rate trace

The lab in four numbers

These figures describe how the page is organised. They are not results or performance claims.

4

common measures compared side by side

6

steps in the self-observation routine

3

reading guides linked below

2026

year of the most recent review

Four ways to describe effort

No single measure is complete. Each captures a different slice of what is happening, and each has conditions under which it misleads. Used together, they provide a more balanced picture than any one alone.

Measure What it reflects Strengths Common pitfalls
Perceived exertion How hard the effort feels Needs no equipment and responds to heat and fatigue. Influenced by mood, motivation and sleep.
Heart rate Cardiovascular response to effort Continuous and easy to record. Lags behind effort and shifts with heat, caffeine and hydration.
Pace or speed Output over distance Familiar and comparable between sessions. Affected by terrain, wind and traffic.
Power Mechanical work per unit time Immediate and independent of conditions. Requires equipment and regular calibration.
Close view of a fitness watch on a wrist beside a notebook with handwritten training notes

Devices estimate; they do not diagnose

Wearable devices have made measurement easy, and the volume of data can feel like precision. In practice, wrist-based sensors work best in steady conditions and can drift during intervals, in heat or with loose straps. Readings such as heart rate variability or sleep stages are modelled estimates, produced by proprietary algorithms that differ between brands.

A sensible approach is to treat devices as note-takers. Trends across weeks are more informative than any single reading, and a number that conflicts with how you feel is a prompt for curiosity rather than alarm.

  • Compare like with like: same device, same time of day, similar conditions.
  • Review weekly patterns instead of reacting to each morning.
  • Discuss persistent concerns with a qualified professional, not with an app.

A six-step self-observation routine

The routine uses a simple notebook or note app. It takes about five minutes after each session, and it helps connect what you did with how you responded.

  1. Step 1

    Record the session

    Write the activity, duration and conditions, such as heat, terrain or time of day.

  2. Step 2

    Rate the effort

    Choose a number from one to ten that reflects overall effort, before looking at any device.

  3. Step 3

    Add a device reading

    Note one measure only, such as average heart rate or pace, to keep the record readable.

  4. Step 4

    Note how you feel later

    Add a line in the evening and another the next morning describing energy, soreness and mood.

  5. Step 5

    Review weekly

    Once a week, read the entries together and look for patterns rather than single days.

  6. Step 6

    Adjust gently

    Change one thing at a time, and give it a few weeks before judging whether it helped.

A working rule

A measurement is a question put to the body. The answer is only useful if the question was clear and the conditions were stable.

Many readers find that fewer measures, recorded consistently, tell them more than a dashboard full of metrics. A page of handwritten notes that includes how the session felt will often hold more information than an export from a device, because it contains the context the device cannot see.

Related reading guides

Glossary

Definitions for heart rate variability, training load, aerobic threshold and related terms, each with a stated limitation.

Open the glossary

Research notes

How we describe the strength of evidence when a study discusses wearable devices or testing methods.

Open research

Training plans

Example weekly structures that show where measurement fits within a broader routine.

Open training plans

Interpretation needs context

Nothing on this page assesses your fitness or your health. If a reading concerns you, or if you are unsure how to read a result, talk with a qualified professional who can consider your history. Our health check preparation page offers prompts for that conversation.

Send a question to the editors