Short Intense Efforts Affect on Form

Sorry, another question. This time about form/tireness. Probably asked before but I can’t find any topic similar.

I’m in my build phase for GC Specialist focus training. In the build phase the hard interval workouts are very hard for me and I need to be fresh. I’m planning to do one such workout tomorrow. As Joe Friel says, hard interval workouts should be something you fear, and I do just that with the harder prescribed Xert workouts.

Question, why do short hard efforts impact tiredness much more than longer zone2/3? Example:

Today Xert is proposing a 90 minute ride in zone 2/3 (eg. Save Yourself - 90 @ 99 xss). This means intervals in zone 3 and the rest in high zone 2. This for me will actualy be tiring, I did this yesterday and I was tired. However, if I do this then Xert projects I’ll be ‘fresh’ tomorrow.

Instead I did a recovery ride, 60 mins in zone 1, but with a single 20 second sprint at the end (zwift group ride), 45 xss. With this short sprint it has now put me as tire/yellow for tomorrow.

Where my body doesn’t seem to agree with Xert is in these recovery days, Xert seems to continually think I can do 90-120 minutes zone 2/3 and be recovering, whereas other platforms would probably prescribe much lower intensity recovery rides. I’m not sure why it is, I’m not sure if Xert overestimates my training status when it gives me 4 stars. Four stars is ‘elite’ and I’m probably not even competitive, I just spend quite a lot of time on the bike… is there a way to tell Xert that I’m not an elite athlete? or to get it to understand that 90 mins zone 2 with zone 3 efforts is tiring?

Elite is simply the label assigned to that level training load (4 stars 110-150). Top riders typically need to reach that level of commitment to achieve their goals. Pros (5 stars 150+) even more so.
Long hours in the saddle, however, don’t necessarily translate to peak fitness without diligent block periodization and progressive overload that includes the right mix of intensity at focus durations required for your events. Even so, that doesn’t mean those of us who like to ride a LOT are going to be competitive. Fitter within our means and potential, yes. Podium placements, not so much. :slight_smile:

Xert doesn’t use traditional zones but relies on a 3-level strain model (low, high, peak) along with a hybrid polarized approach. The closest thing to zones in Xert is focus duration points along your power curve that roughly fall into these quadrants.

While the points are labeled, they aren’t exact numbers but a range. Climber, for example, is an activity that results in a focus duration of around 10 minutes.

Any activities that remain at and below TP are classified endurance level with low strain.
SMART - Save Yourself - 90 is an over/under LTP workout with low strain XSS as shown in this chart and table you can view when you Open in Designer. Example:

You can check your recovery ride XSS table to see how much high/peak strain resulted from that sprint effort.
Xert endurance workouts include “easy” endurance, at or below LTP, and “hard” endurance with intervals in tempo/SS territory up to threshold.
You will certainly tire yourself riding over/under LTP for long periods as seen by the rising difficulty (shaded portion in the chart above). However, most riders will handle that well so 24 hours later their calculated form has returned to Fresh. If not, use your discretion and adjust the FF slider or simply select lower strain/difficulty options from the list of daily recommendations.

The over-riding factors to reach your top fitness are consistency and progressive overload. No need to micro-manage by traditional zones although you can certainly factor that in if you prefer.
As to your readiness to train you have final say on a day-to-day basis. For details see this article which includes this chart.


I rely on RHR and a simple stairs test in the morning to gauge my readiness. Then weigh that against XATA and what I really want to do today especially when a nice day to ride outdoors. Or gauge when to take the day off which at my age can mean two days off in a row. Once I reach 4 stars during the season, I always come back feeling stronger when I do that. YMMV

Reference –
Sweet Spot, Threshold and Polarized Training … By the Numbers – Xert (
Personalizing Xert’s Training Algorithms by using Freshness Feedback – Xert (
Stress, Focus, Specificity and Strain – Xert (

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Brilliant, thank you.

A few things for me to learn about readiness. My watch doesn’t give HRV but does provide RHR, so I might use that.

Today is an example where I did an hour at 90% yesterday morning, followed bay a 40 min Zwift race in the evening. Xert has me as fresh, but I may need to use my own judgement… your info will help me. Also, it may be that this morning I’m not ready, but by evening I may be closer, noting tomorrow is my easy day, so if I don’t train today then it’ll have to wait a few days.