Training energy systems using Xert

The more I read about training and racing it seems that the systems that need to be trained boils down to PCr, anaerobic (glycolytic) and aerobic. The classic table in training and racing with a power meter relates training zones to adaptions (central and peripheral) and Tom Bell @ High North Performance (The Physiological Demands Of Cycling Disciplines — High North Performance) has published this useful table regarding the demands of events. It would seem that you need to balance training and adaptions that occur to the demands of your event.

There are different philosophies as to how this may be achieved. Some I am familiar with include:

  • Balance VLamax and Fatmax (Sebastian Weber @ INSCYD) the argument here centres on peripheral adaptions that include increased mitochondrial density and more importantly converting intermediate fibres to slow twitch
  • Tim Cusick extensive to intensive (classic periodisation model). I think the Xert model seems to adopt this with progressive transition from extensive to intensive interval; the Cusick approach is a little more stepwise
  • Steve Neal raising LT1 through extensive tempo work (but strict definition of tempo zone) this then raises LT2. VO2 max work once no longer seeing an increase to raise the ceiling. To me there are similarities in this approach to the Inscyd approach (Tom Bell again [How To: Fine-Tune Your Max Glycolytic Rate — High North Performance]). He then gets his athletes race sharp by adding in a few really hard, specific interval sessions prior to racing. He has talked about using Xert (and an up to date signature) to construct workouts that are just achievable or will focus on efforts that will be similar to ‘selection points’ in a race to get his athletes race sharp. He also has described B/C races and zwift racing.

My reading of Xert is that it tends to focus on training for your goal event by by moving from extensive sections of the MMP curve (i.e. 3 hour to 1 hour to 20 min power, etc) until it arrives at the point of the curve that it feels is required for your event (e.g. 5 minute power). You can also use the star system to assess ability to cope with difficult (again useful to use historic data to identify this at key selection points.

There are 2 aspects to my question:

  1. It would be good to start a discussion around how people use Xert to build blocks of training based on more classic descriptions for example VO2max, threshold, LT1, etc. Do they use the challange feature and set the athlete type based on the point on the MMP curve (e.g. threshold = MMP @40-60min, VO2 = MMP @ 5-6min or classic Ronnestadt). For LT1 the tempo suggestions are pretty close for me. I test using the talk test method (Tom Bell again…[5 Ways To Assess Fitness Progression Without Maximal Efforts — High North Performance]. Are there alternative methods that are used?

  2. How do people periodise their training? How have they found the Xert approach?

I suppose my concern is that the evidence base has tended to focus on training blocks focused on metabolic thresholds rather than the MMP curve; different points of the MMP curve have a different proportion of aerobic:anaerobic contribution based on power selected and duration (VO2 slow component). It doesn’t mean it is wrong I just mean, to my knowledge, it has not been tested. I appreciate there is overlap between systems but for me my glycolytic system requires very little training so the Steve Neal approach seems to make more sense for me personally. I also wonder that having clear separation between intervals selected (session to session) enables you to focus more on specific adaptations.

Sorry about the length and if this has been discussed elsewhere. Apologies if I have butchered training philosophies as well!?

I will post this on the fast talk forum also. So apologies if you see this twice.

I focus on CX in the winter and MTB marathon / gravel in the summer.



I would add that I really like the Xert platform. The learning support has really accelerated my understanding. Final question:

  1. How often do people refresh their profile? Does this improve accuracy of training predictor in goals tab. I have found that it tends to underestimate improvement. In order to make any significant gains I would have to put in 20+ hours but I can often make similar gains with 10-14 hours.
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You undoubtedly do! You brought pertinent points that grab my attention. Will be interesting to see the replies.

Lots to unpack here and not sure I’m able to do it all justice.

I don’t race so don’t have target events or use any formal periodisation. I just shift focus at different times depending on what I feel like I need… I use continuous and change athlete type as needed. One of the time trialist types for base / threshold, climber for long VO2, Rouleur for shorter VO2 etc.

Re comparison to other approaches, some aspects of Xert workouts don’t fit ‘traditional’ models e.g. endurance under fatigue (perhaps lactate shuttle? I think probably hitting multiple energy systems), or hard start VO2 workouts (which have been researched). But then a lot of base is traditional enough endurance / tempo, and they use micros a lot (on their own, or to create fatigue before longer efforts).

They do try and polarise, but at least for me, a lot of endurance is actually tempo, so above what Seiler would call easy. But that’s easily dealt with.

Xert also tries to capture the training impact of unstructured riding, which no other systems really do. How the results compare to a stricter structured approach I’m not sure, but it reflects the real world way that many ride (eg group rides, varied terrain) and creates more options / flexibility. It also means you can’t kid yourself that that group ride was an easy day.

I feel like structure also has its place, and probably has other benefits than just the strain on different energy systems though

I’m not sure what you mean re refreshing profile? If it’s athlete type then it’s as needed… if it’s signature I’m mostly on no decay, but may try for a BT every month or so

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Great topic! I’m still digesting this myself - I’ll come back with a lengthier response soon!

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Thanks. Really helpful response. I probably didn’t articulate it very well but I agree changing the focus can change the energy system targeted from aerobic to VO2 to anaerobic to PCr. Lactate shuttling workouts are easy enough to build and tempo workouts are a good option for low cadence workouts to try and reduce VLamax/increase proportion of slow twitch fibres. Your response reassures me that I am on the right tract. The last podcast with Steve Neal was very helpful (as they all are) in describing how focus can be used close to events where specificity is key.

Some helpful threads on the Fast talk forums also.

I am on optimal decay but need to go back over this. I agree scheduling a breakthrough workout each month would be an easy thing to do towards the end of / immediately following a recovery week.

I am working my way through your videos again. Great series I seem to pick up something new each time I watch them.

I look forward to your response.