Incorporate MTB into Road/Crit Training Without Blowing Up?

The past couple years I’ve had a lot of success following the mid-volume crit plan. I generally replace the Wednesday endurance ride with a 90 minute weight training session, and add another 90 min weight training session on Friday. Monday is my dedicated rest day.

I’m fortunate to live in an area with access to great MTB trails right outside my front door. I bought an XC bike last year and I’ve been trying to improve my skill set on the trails (fitness is good, bike handling is poor). I would like to do at least one MTB ride per week to try and build some of those skills and maybe sign up for some MTB races at some point. I’m struggling to figure out the best way to approach this without totally destroying myself under my current training load. I’ve learned that doing intervals on the trails, or trying to go out for a “mellow” trail ride, doesn’t really work out. There are always climbs, rocks/obstacles that are just going to require threshold/Vo2 efforts to get over. So basically, these are just fun, freeform MTB rides without any real structure. From what I can tell, it seems like I have three options:

  1. Continue what I’m doing on the mid-volume crit plan and replace the Sunday Sweet Spot/Endurance ride with a MTB ride. This seems like a great way to blow myself up in the long run.

  2. Switch to a low volume plan and add in the MTB ride. This seems feasible, but from what I’ve seen this would just increase the intensity of the three structured rides per week to compensate for the “lower volume”. I’m putting that in quotes because, with the added MTB ride, I don’t think the actual volume would be any lower than the option above, and the intensity/TSS might actually be higher?

  3. Use Train Now for the structured workouts 2-3 times week plus the MTB ride.

Of course, racing during the Spring/Summer adds another layer of complication (Crits and Road Races), but I think I’d have to deal with that on a week by week basis and just feel it out. Anyway, I would imagine I am not the only person trying to balance fun MTB rides with structured training plans. I’m curious what you guys have had success with in the past, and I am hoping to hear your ideas/suggestions based on my thoughts above!

I mix road, gravel, and mountain. But, I’m not a road racer, so take this all with a massive grain of salt.

I used Plan Builder and picked LV for most blocks. Most of my big races are longer (4-6 hours), and usually 1/month, sometimes with shorter B/C races in-between, so I my week ends up looking like…
M - off
T - structured intervals, 60-90 min
W - group mountain bike ride, B pace average, 120 min
Th - either a group road ride or structured intervals, 60-90 min
F - off
S - select a long alternate to the prescribed ride, usually 2-3 hours, free-ride it but try to follow the general intent of the workout (at this length, it usually ends up being fairly steady endurance pace). This could be road, gravel, or mountain depending on weather, friends, etc.
Su - longer structured intervals, 90-120 min

Would I get fitter faster sticking to the plan? Probably. But, I enjoy mountain biking and gravel. And using mostly LV lets me swap out some of the rides for harder/longer rides without burning out.

If was serious about crits, I’d stick to a MV plan more closely. But even when I raced on the road, at best I was an average masters racer.