Duration/TSS for Threshold Workouts?

I’ve got a question related to threshold/Z4 workouts and how long they should be. I’ll give a little background then lay out the question in more detail.

For background, I’ve been training for 2.5yrs consistently now, and regularly do 11-15hr weeks of 600-800TSS. My A race(s) are 1:45:00 mountain bike races, so quite intense. I have the time and am willing to do a threshold workout up to 2hrs long, probably 2-3 times a week.

My question can be divided into two parts: 1 ) How much time in Threshold/Z4 should I be aiming for; and 2 ) how much TSS should I be aiming for per workout?

Obviously I don’t want to fall into overtraining, but I also want to make sure I’m doing enough work to actually be effective. In the past I’ve done shorter threshold workouts and have felt like I lose fitness, so I’m considering trying to do longer ones to prevent this. Then again, maybe I just need to do more workouts instead of longer?

Would be grateful for your thoughts.

I would only do 1 threshold session/week - especially if you mountain bike where I would add a shorter VO2 max workout. I TT so I tend to go for 1 x over under and a VO2 session preseason and then go for 2 threshold sessions in my race build up. (Usually o/u, shorter 5-8mins intervals@102-108&FTP or 10-12 mins@96-100%). I find the best threshold sessions are things like Kaweah, Mount Baldy etc where you do 6x10mins@96-99% FTP …they give you the same benefits but are a bit easier and you can do more work. It’s like SS sessions - 3x30mins@85-88% are better than say 4x15mins@90%…that said I do a lot of 50 TT so am a bit of a diesel…I imagine mountain biking is a bit more explosive.

Your FTP is based on the power you can sustain for about an hour (or rather 40-70 minutes). Many people disagree in the term called FTP and the duration one can hold it for. This post is not to argue the point, but put your question into perspective.

How long can you ride at threshold for; with and without recovery in between. If you can’t hold your FTP power for an hour with recovery intervals in between, your FTP is too high.

You want to build progression into your training, to allow your body to compensate for the increased load. After 2-3 weeks, you would take an easier week. When you start after the “rest” week, it is slightly higher (TSS) than the first week of the previous block.

So your goal for time in threshold zone would be to get to ride for 40-70 minutes without any recovery. You do this by doing progressively longer intervals, or sets or a combination of both.

Example 1:
This block has 4mins recovery intervals (RI).
3x8 mins (24 mins)
4x8 mins (32 mins)
5x8 mins (40 mins)

Next block could have 2 mins recovery intervals, or
Increase the %FTP and keep the RI the same

Another way to progress is purely on the work duration (values in brackets above). So you start on 20 minutes and increase it each week with a recovery week every 4 weeks:
20 (4x5)
24 (4x6 or 3x8 or 2x12)
28 (4x7)
32 (4x8)
36 (4x9 or 3x12 or 6x6)
40 (4x10 or 2x20 or 5x8)
44 (4x11)
48 (6x8 or 8x6 or 4x12)
52 (4x13)
56 (4x14)
60 (3x20 or 5x12 or 6x10)

Ignore TSS and concentrate on getting your weekly threshold session up to 60 minutes or longer of work at Z4. If you can ride 40-70 minutes at your FTP, you start increasing the intensity and start again at 20 mins. The circle keeps turning and your threshold gradually increases.

Sounds easy, and does take time to develop (up to 16 weeks).

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I’m planning on putting in more VO2 work in later, but for my build a few months before the race, I figured I’d do just Z4 instead of VO2 since the VO2 gains will come relatively quickly once I start doing them.
Would I really need to do VO2 work 2-3months before the start of my race season? Not to mention my A race comes at the end of the season.

I figured I could do maybe three Endurance Rides and two Threshold or maybe Sweet Spot rides during my build until a month or so before the first race. Thoughts?

If you want to use racing as training then this is smart.

Doing all this threshold and SS won’t prepare you to race XC MTB because it’s more like a vo2 event with recovery inbetween efforts.

Unless your ftp is poor, I’d personally do one threshold and one 30-30 @ 150%ftp or a 40/20 type workout to train your legs and lungs for actual XC MTB specific stresses (regularly). Otherwise I’d just ride easy between these workouts.

Thanks, that gave me a bit more detail that was helpful. I think I’ll start by doing 3x8 and work on increasing the duration and number of sets.

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I am planning on using the racing as training since my A race comes a full 5 weeks after the first race of the season. I figured that a total of 8-9 weeks of VO2 and Anaerobic training would be plenty to get me into shape for the A race.

You can see gains in 2-3 weeks by doing VO2 and AC / NP work.
Perhaps 3-4 weeks depending on how your body reacts to the higher intensity.

Z5-7 takes long to recover from, which is why the concept of Sweet Spot was made popular.
20/40, 30/30, 40/20 are excellent ways to get the HIT in.

Don’t forget that it takes time to “base/build”, and might seem like you never get there. Patience. Consistency is key: as in add a little bit extra each week, recover after 4 weeks and go again.

In the rest weeks, you can hit a max effort (15s, 1m and 5m) to feed your your power duration curve (Intervals, WKO, Golder Cheetah, etc. have this model). Your base/build will feed the 20m, 60m part of the curve.

Good luck, this is the part of the season I enjoy most; only the workout stress to worry about, and not the racing. Once the base fitness is there, the stress changes to HIT and racing.