TSS calculation query



GettingFaster

New Member
Apr 27, 2005
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Hi

I'm busy reading 'Training and racing with a power meter' and I find myself a bit confused by the concept of TSS. I get the impression that TSS is supposed to be used as a measure of the overall training load from a workout, and 100 TSS points corresponds to an hour at FTP.

Now suppose I decide to do 3 x 20mins at FTP, with 20' rest after each one - the rest can be at zero power (or close enough to approximate it so.) This workout will last 2 hours in total and SURELY has less training effect than if I ran all three reps together to do a straight hour at FTP. But unless my calculations are wrong, the workout will give a TSS of about 140 points?

My calculations were simply that the NP is going to be [1/2 * FTP^4]^1/4 = FTP/(2^0.25) - therefore the IF is 1/(2^0.25) - and 2 hours at an IF of 1/(2^0.25) has a TSS of 2 x 1/(2^0.25)^2 x 100 = 200/SQRT(2) ~ 140 (apologies if this isn't well written out!) Have I done something wrong?

If I haven't made a mistake then I'm not sure what I'm meant to do to calculate the TSS of my training sessions, as it would seem that the TSS algorithm is misleading when there is time at very low/zero power in the session. A typical session for me would be 2 x 20' at FTP on the turbo, taking a total of an hour including the warm up and cool down and rest inbetween reps. If I just downloaded the power file afterwards and calculated the NP and IF for the whole hour would I end up overestimating the TSS? Should I just pick out the 20' intervals and calculate the TSS from these?

Any help much appreciated please:)
 
Your math is right, but garbage-in-garbage-out, I suppose.

Your typical 2x20' workout in 60 minutes (incl w/u and c/d) seems pretty typical, but including 60 minutes of 0w rest into the calculation doesn't seem to make much sense. For my workouts: 1) the rest periods tend to be much shorter than the work periods, for work around FTP, and 2) I still pedal during my rest periods at ~.5FT. In that case, the TSS calculation is pretty reasonable, and seems to be based pretty squarely around the work portion of the workout and less influenced by the rest portion.

One more thing, TSS does not indicate how 'effective' a training session has been, it just gives a measure of the 'stress' placed on the body. Just because the TSS for 3x20 at FT is higher than 60-min straight at FT, doesn't mean that one has greater training effect than the other.