Workout Builder

Build a swim, bike or run workout block by block and see its training load, intensity factor and time in zones.

Workout Builder

Adjust each zone’s upper bound. Adjacent zones adjust automatically.

Z1Recovery0%138 W
Z2Endurance56%188 W
Z3Tempo76%225 W
Z4Threshold91%263 W
Z5VO2max106%300 W
Z6Anaerobic121%375 W
Z7Neuromuscular151%378 W+
50%100%0:0015:0030:0045:0060:00

❤️ Red line = estimated heart rate response, including lag and upward drift.

  • Rampmsfrom%(113 W)to%(175 W)rpm
  • Interval× times
    1ms-%(250 W)rpm
    2ms-%(125 W)rpm
  • Rampmsfrom%(150 W)to%(100 W)rpm

Training Metrics

Load Score
73
Intensity Factor
0.83
Duration
63 min
Z10-55%
20 min
Z256-75%
7 min
Z491-105%
36 min

How it’s calculated

Intensity Factor (IF)

How hard the effort is relative to your threshold (FTP, threshold pace, CSS…). 1.00 means right at threshold; ~0.75 is easy endurance, ~1.10 is above threshold. Each block’s IF is simply its target as a fraction of your reference.

IF = intensity / threshold

Load Score

Combines how hard and how long. One hour at threshold = 100. Doubling the time doubles the load, but harder efforts count much more because IF is squared (an hour at 110% scores ~121, not 110).

Load = duration(h) × IF² × 100

Session IF is the intensity of the whole workout: the square root of the time-weighted average of IF², i.e. √(Σ(IF²×time) / total time).

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