Workouts resembling MTB XC

I would like to monitor the strain/workload from riding MTB XC along side my road riding. Is there workouts in the library which resembles the strain from riding MTB XC (training or racing)? TrainingPeaks uses HR TSS. But I feel this probably overstates the workload from XC as you use more muscle groups than riding road (or indoor).

What you can do is open one of your MTB activities with power data and examine the Focus (and Specificity Rating too to be even more precise) and find workouts with similar Focus and SR. These will mimic the work effort you’d need to perform for that MTB activity. Hence, the workout would target the same ratio of your three systems - low, high and peak - as what you used during the MTB activity.

That would be ideal for sure. Unfortunately I do not have a PM on my MTB so I have no power data from training/racing. Thus I am looking for a workout where there low, high and peak strain would resemble MTB XC as closely as possible.

I would ask the users on the Facebook users group as there are quite a few knowledgeable folks there that can perhaps provide a bit more guidance for you.