Introduction
In order to maintain a meaningful Performance Management Chart it is necessary to measure Training Stress Score. My Powertap is on my training wheels. My race (TT) bike does not have the ability to properly measure power. In order to keep the PMC up to date I therefore need to estimate TSS.Methods of TSS Estimation
Training Stress Score can be defined as:
(Intensity Factor)^2 x duration (hours)
I’ve tried several estimation methods:
·
Fixed multiple
·
Perceived Exertion
·
Energy Expenditure
·
Estimated Intensity
·
Heart Rate
Fixed Multiple
Based on the average TSS/hr achieved on a
number of rides. Estimate is simply (Hours Ridden) x (average TSS/hr).
Perceived Exertion
Joe Friel on Training Peaks quotes the
following table:
Energy Expenditure
Based on average TSS/Kj of work. Estimate
is simply
(Total work done on ride)/(Average TSS/Kj
of work)
Estimated Intensity
Based on personal assessment of intensity
%. Estimate is:
(Intensity Factor)^2 x duration (hours)
Heart Rate
Strava and others propose using HR to
estimate TSS. In principle this would be better. However I’ve not been
comfortable with the results as the HR estimates appear to be much lower than
power based measures for very similar rides.
Test Data
In order to compare these methods I took a
selection of 6 rides of varying distance, intensity and terrain, where I used
my Powertap:
Conclusion
Estimating TSS is clearly inaccurate. Using
a Fixed Estimate is quite weak – especially when intensity varies. RPE
estimates both too high and too low. Energy seems to be the most reliable of
the methods. For me, dividing Energy by 8 gives an approximation of TSS. The estimate tends to be a little high on very low intensity rides.
