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Tuesday's intervals did not happen. Work ran late, the weather turned, or the legs were simply not there. The plan still has four days left in the week, and the decision you make now matters more than the session you lost.
The short answer
One missed session costs very little fitness: fitness (CTL) is a slow average of several weeks of load, so a single empty day moves it by a point or two for most amateurs, and your form improves because fatigue falls. Do not squeeze the session into tomorrow on top of what was planned. If it was an easy ride, let it go. If it was the week's key session, move it to a later day of the same week with enough time, ideally after an easy day. If you missed it because you were ill, do not make it up at all.
What one missed session costs
In the Performance Manager model of Allen, Coggan and McGregor, fitness (CTL) is a slow exponentially weighted average of your daily training load (TSS) and fatigue (ATL) a fast one, with conventional time constants of about 42 and 7 days. Any single day is a small part of fitness, while fatigue reacts quickly in both directions. Take a rider at a CTL of 60 and an ATL of 65 who misses an 80 TSS session:
| The day | TSS | CTL | ATL | Form next morning |
|---|---|---|---|---|
| Session done | 80 | 60.5 | 67.1 | −6.6 |
| Session missed | 0 | 58.6 | 55.7 | +2.9 |
Illustrative, computed with the published model's conventional constants, not Summit's internals. Form (TSB) is the day's CTL minus its ATL, read the next morning.
The missed day costs this rider under two points of fitness, roughly a forty-second of the session's TSS, and leaves them almost ten points fresher the next morning. Nothing about one empty day undoes a training block. What can undo it is the attempt to win those two points back before Sunday.
The mistake: catching up
The instinct is to put the lost session somewhere it does not fit: on top of tomorrow's ride, or as a double day at the weekend. Load added that way lands almost entirely in fatigue, because the fast average responds within days while the slow one barely registers it. The second session is also ridden on legs that are already tired, which is the quickest way to turn a good session into a mediocre one, and it pushes the next key session into a tired body too.
Fitness is built in the recovery after a session, not during it, as the base, build, peak piece puts it, and a crammed week takes away exactly that recovery. The more useful question is which session you missed, because they are not worth the same.
Which session did you miss
An easy or endurance ride
- Let it go: it was the cheapest session of the week
- If the week has room, add a little time to another easy ride
- Do not turn it into intensity
The week's key session
- Move it to a later day of the same week with enough time
- Leave an easy day before it if you can
- Drop an endurance ride to make room, never the next key session
Missed because you were ill
- Do not make it up
- Come back with easy riding before any intensity
- Treat the week as a different week, not a late one
Several days in a row
- Stop counting what was lost
- Re-plan from today, starting easy
- Keep the event; adjust the weeks before it, not the date
In all four cases the week's load is spread across the days that remain instead of being stacked onto one of them, so a missed session becomes a reason to rearrange the rest of the week and never a reason to double a day.
How Summit handles it
Summit, on Elite
- After your midnightThe session is marked missed, in your own time zone
- The week keeps its loadWhat you missed is spread across the days still open
- The key session movesTo a later training day of the same week
Summit detects a missed session shortly after your own local midnight, in your time zone, and re-plans the week around it. The weekly load budget is kept, and what you missed is spread across the days still open instead of disappearing, so the week does not quietly under-load. Spread is the operative word: the load goes to several open days, not onto one.
A missed key session is promoted onto a later training day of the same week. It never goes onto a day already past, a day you marked to ride your own way, or a day without enough time, and a missed race is not replaced by a training session.
The miss re-plans the current week and the next one, and it does not rebuild your season: the phases and your event date stay where they were, and later weeks are planned as they come into range. If you reopen a day you cancelled, the exact same workout comes back, and the rest of the week is rebalanced around it.
Each remaining day still goes through the morning reading. If your recovery is poor on the day the key session lands, it is capped, swapped for an easier type or turned into rest, as on any other morning. And when the reason was illness, marking it in the morning check-in cancels today's session and the plan rearranges the days that follow. How the recovery side decides is in How HRV should change today's ride.
All of this is the adaptive plan, which is Elite and is described in full on the adaptive training page. Imported rides and the daily recovery score are free, permanently, and fitness, fatigue and form are Pro. The prices and their caveat are on the pricing page.
Questions
Will I lose fitness if I miss one training session?
Very little. Fitness (CTL) is a slow average of roughly six weeks of training load, so one empty day moves it by a point or two for most amateurs, and your form improves slightly because fatigue falls.
Should I do two sessions the next day to catch up?
No. Doubling up raises fatigue quickly for a negligible gain in fitness, and the second session is ridden on tired legs. Move the key session to a later day of the same week with enough time, and let an easy ride go.
What does Summit do when I miss a session?
On Elite, the week keeps its load: what you missed is spread across the days still open, and a missed key session moves to a later training day of the same week, never to a day already past or one without enough time. The current week and the next are re-planned; your season is not rebuilt and your event date does not move.
What happens if I reopen a day I cancelled?
Summit brings back the exact same workout and rebalances the rest of the week around it.
Sources, in the app's own sources sheet
- Allen, Coggan & McGregor (2019), Training and Racing with a Power Meter, 3rd ed.: the Performance Manager model, TSS and the fitness and fatigue averages used in the table above.
This is training guidance, not medical advice. It does not replace the advice of a healthcare professional or a certified coach.
Let the week rearrange itself.
On Elite, a missed session is spread across the days still open and the key session moves to a later day of the same week, without rebuilding your season. Your recovery score is free, permanently. No model decides anything.
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