Help me understand Training Impulse for Swimming Activities in Fitness & Freshness

[mskolsky]

I track two types of exercise in Strava, Cycling and Swimming.

On the bike, I simultaneously use a power meter and a Polar H10 heart rate monitor.  My understanding is that Strava uses these two inputs to "calibrate" a Training Impulse estimate based on Relative Effort so that can be used for the times when I ride without a power meter or do something other than cycling.

My Fitness and Freshness page is set up to use both, "Power and Relative Effort."

When I bike, my power-based Training Load (which gets used directly for Training Impulse) is always about 0.7x Relative Effort.

When I swim, I wear a heart rate monitor and Strava calculates a Relative Effort.  I expected Training Impulse to be about 0.7x Relative effort for the swims, because that's what it is when I bike with power meter and heart rate monitor.  TSS is always smaller than RE on the bike.  But I see the opposite result.  From swimming, the "Training Impulse" is always about 1.3xRE.

When I bike, TI<RE, but when I swim, TI>RE (about the same ratio, but inverted).

Should I expect the TI:RE ratio from my cycling to carry over successfully to swimming?  It doesn't

[Jan_Mantau · Accepted solution]

Even for riding with powermeters the formula TRIMP = RE x 1.3 is used in case you switch from "Power and Relative Effort" to "Relative Effort". They must have stopped calculating the relation between Training Load and Relative Effort, I can remember this feature exists in 2019.

[mskolsky]

https://medium.com/strava-engineering/fitness-freshness-updates-5d1057d67fac

Thank you for the reply, Jan.  The article I linked above was from 2014.  Back then, it looks like Strava automatically calibrated TRIMP from RE.  As you said, it looks like they must have stopped doing that.