How to Read Your Cycling Training Data — a Beginner's Guide
After your first ride with a power meter you see a screen full of numbers: WAP, RI, TSS, cardiac drift, zone breakdown. What does it all mean? Which numbers actually matter? Here's a guide so you don't have to Google it after every ride.
Basic metrics — during the ride
| Metric | What it measures | What to watch for |
|---|---|---|
| Power (W) | How much force you're putting into the pedals | Keep it in your target zone |
| Heart rate (bpm) | How hard your heart is working | Rises with a lag, drifts over time |
| Cadence (RPM) | Pedal revolutions per minute | 85–95 RPM is the optimal range for most riders |
Power is "what you're doing", heart rate is "how your body is reacting". Power responds instantly, heart rate with a 30–60 second lag.
Metrics after the ride
Weighted Average Power (WAP / NP)
A better measure of effort than plain average power. It accounts for the cost of variability — a ride averaging 150 W but with many spikes to 300 W is harder than a steady 150 W. WAP reflects that.
Relative Intensity (RI / IF)
RI = WAP ÷ FTP. It tells you how hard the ride was relative to your capability:
- RI < 0.75 — recovery, Z1–Z2
- RI 0.75–0.85 — moderate training, Z2–Z3
- RI 0.85–0.95 — hard training, Z3–Z4
- RI 0.95–1.05 — at the limit, race pace
- RI > 1.05 — above threshold, sustainable only briefly
Training Stress Score (TSS)
TSS combines intensity and duration into a single number. The higher the TSS, the bigger the training dose. It's used to track your load over a week and to build the PMC chart.
Cardiac drift
Cardiac drift is a rise in heart rate at constant power over the course of a ride. High drift (> 5%) means your aerobic system was under stress — typical after long rides or with dehydration.
Zone breakdown
How many minutes you spent in each of the 7 power zones. It helps you check whether the session had the character it was meant to — if the plan said Z2 and you spent 40% of the time in Z3, you rode too hard.
Which data should you track regularly?
You don't need to analyse everything. For beginners, the most important are:
- Weekly TSS — is your load stable, rising or falling?
- CTL on the PMC — your fitness over a scale of weeks. Rising = good.
- RI of individual rides — are you riding at the target intensity?
The rest comes with time. After a few months you'll start intuitively connecting the data with how you feel — and that's when the data really starts to help.
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