Previously, @xertedbrain described how to handle weight training workouts in Xert, especially when doing leg exercises. The idea was that they would increase your peak power because of training your torque. It would also make your peak power system tired.
For running, there will be some cross training effect to cycling as you utilize partly the same leg muscles and heart/lungs. In addition, you utilize your upper body, which is less relevant for cycling. Thus, for a given heart rate you will presumably have a lower load on your leg muscles while running than while cycling. The load on the heart/lungs should be similar.
For XC skiing the effect is similar to running, but as you also utilize your arms to move forward I assume the load is even more skewed towards the upper body (for similar effort levels).
What is your take on the best way to handle this? Assume the effect is 0 XXS? Use the same XSS as in the running sub account? Add a fraction (e.g. 80%) of the XSS?