How does strava calculate fitness and training load based on heartrate for cyclists?

Question

Hello,

I’m wondering how Strava calculates the two above mentioned metrics.
I performed exactly the same endurance training, separated by 8 days. Suprisingly, in exactly the same time, so exactly the same average speed, denivelation (1060 m), distance (131 km). However, heartrates of course were different. First and second workout are summarized below.

AVG HF : 120. 4 min in zone 2, 232 min. in Zone 3, 143 min in zone 4, 2 min in zone 5. It resulted in training impulse of 388, and an fitness increase from 136 to 142
AVG HF : 12 min in zone 2, 152 min in zone 3 and 66 min in zone 4. It resulted in training impulse of 304 and increase from 136 to 142

How are the time spent in the different zones factored in? Is the AVG HF factored in? And are increase/decrease of fitness derived from the training impulse values?

Thanks for clarifying!

Jan_Mantau · Accepted Answer

The Relative Effort depends on how long you spent in each heart rate zones. The exact formula is a trade secret. The avg. heart rate and other stats aren’t incorparated.

And yes, the increase/decrease of fitness is derived from the training impulse value.

jdevos · Answer

So, if you spend x minutes i?n the low-end of the zone (e.g. 122 for Zone 4 in my case) or x minutes in the high-end of the zone (e.g. 132 in Zone 4 in my case), the calculated training load value is exactly the same?

If so, I find this a too coarse-grained approach.

Sign up

Login to the community

Scanning file for viruses.

This file cannot be downloaded