Rebuild Log · Week 1: Five Sessions, CTL Off Zero

Quick housekeeping before the numbers: this is the first entry in a new weekly series. Every Sunday-ish, I pull my real training data — no rounding, no cherry-picking — and Cosmo (my AI coach, the one I argued with and lost to last time) tells me straight what it means. Same format every week, so if you’re rebuilding something yourself — a body, a business, whatever — you can watch the pattern instead of just one post.

This week’s headline: my training platform’s fitness score went from a flat zero to 4.3 in seven days. That sounds tiny. It is tiny. It’s also the first real data point of the whole comeback, and I want you to see exactly what “starting from scratch” looks like on a chart, not just hear me say it.

The numbers

A fast note before the table, because I’m not going to make you learn jargon to read your own comeback story:

CTL — think “fitness in the bank.” It’s a rolling ~6-week average of how much training you’ve done. A fit age-group athlete usually sits around 60–80. Mine was flat-out zero until this week — meaning TrainingPeaks had nothing logged for almost two months. That’s not a metaphor. The bank account was empty.
ATL — think “how tired you are right now.” A ~1-week average of recent effort. It moves fast.
TSB — think “fitness minus fatigue,” your bank balance minus this week’s spending. Negative means you’re carrying some fatigue. For someone with a real fitness base, a moderately negative number is normal and even good. For someone with almost no base (me, right now), the same negative number means something different — I dug into exactly why in the last post.
TSS — “training stress score.” One number per workout for how hard it hit you. A hard hour scores more than an easy hour.

Metric	Start of week (Jul 13)	Now (Jul 20)
CTL — fitness	0.0	4.3
ATL — fatigue	0.0	17.1
TSB — form	0.0	−15.5
Weight	199.1 lb	191.2 lb

This week’s training: 5 sessions, 198 total stress-score points, 5 hours 17 minutes, 18.5 miles — a mix of 3 short runs and 2 brisk walks, all in the 1-hour range.

Day	Type	Distance	Time	Stress score
Jul 13	Run	3.70 mi	1:04	28.9
Jul 14	Walk	3.70 mi	1:06	27.8
Jul 16	Run	3.68 mi	1:01	51.3
Jul 17	Walk	3.71 mi	1:08	27.8
Jul 19	Run	3.69 mi	0:59	62.6

The graphs

Fitness vs. fatigue, since late May. The flat line at zero for almost two months, then the jump — that’s not a rendering glitch, that’s the real gap between “recovering from illness, nothing logged” and “first week of actual training.”

Weight, since May 31. Two reference lines on this one worth knowing: the amber line at 180 lb is the point where Cosmo and I agreed I can start building real running mileage (below that, ground-impact forces on 64-year-old knees get punishing — short easy runs are fine now, piling on miles isn’t yet). The blue line at 165 is the longer-term target.

What the data says (Cosmo’s read)

Let’s start with what’s real and good here, because there’s genuine good news: you logged five sessions in a week where three months ago you couldn’t climb stairs without your lungs complaining. That’s the actual headline, not the CTL number. Consistency — showing up five times — is the entire game at this stage. You did that.

Now the honest part. Look at the stress-score column: 28.9, 27.8, 51.3, 27.8, 62.6. That’s not a smooth ramp — it’s two big spikes (the two runs on the 16th and 19th) sitting almost twice as hard as everything around them. Think of it like a bank account with $4 in it: you can technically make a $62 withdrawal, but you’re borrowing against a foundation that isn’t there yet. That’s exactly what that −15.5 form number is telling us — not “you’re overreached,” but “you spent hard against almost no savings, two days apart, right out of the gate.” I’d rather see next week’s hardest day sit closer to 40–45 than 60+, so the effort curve looks more like a gentle staircase and less like a saw blade.

On weight: down 11.2 lb since May 31, and that trend line is real and it’s good — steady, mostly one direction, right through a stretch where you were also getting back into training. I do want to flag one thing plainly, because burying it wouldn’t be honest coaching: the jump from 194.1 lb on the 19th to 191.2 lb on the 20th — nearly 3 lb in one day — is very likely water weight and hydration, not fat loss. Bodies don’t lose 3 lb of actual tissue overnight. Don’t bank that single number; watch where it settles over the next several days. The real story is the slope from 202→191 over seven weeks, not any one dot on the line.

How it felt

The chart shows five clean sessions. What it doesn’t show is that five is a number I couldn’t have hit a few months ago — not because my legs wouldn’t go, but because my lungs wouldn’t let me. That’s still the governor on this whole thing. The legs are ex-hockey legs; they’ve got decades in them. The lungs are the ones deciding how far I get. [Say what the lungs actually did this week — steady? one bad day? better than expected?]

The two harder runs — Cosmo’s right that they were spikes, and I felt it. [What did those two runs feel like in the moment vs. the easy days — where did you notice the ceiling?] The walk days weren’t a consolation prize. They were the plan: throttle back before anything complains, not after. Forty years of sport taught me the difference between tired and warning, and at 64 I finally listen to it. [Anything twinge — knees, ankles — or did backing off keep it quiet?]

The weight coming off helps more than the number suggests — [how does moving feel different eleven pounds down? lighter on the climbs, or too early to tell?]. Mostly, week one felt like [one honest line — proud? impatient? both?]. I’ll take it. It’s a start, and a start is the hardest part to earn back.

The lesson

Here’s the shareable bit, and it applies whether you’re rebuilding a training log or anything else in public: the number by itself isn’t the story — the number plus the plain-language “here’s what that actually means” is. A CTL of 4.3 means nothing to almost anyone reading this. “Basically starting from a fitness bank account of zero, and a fit age-grouper carries 60 to 80” — that means something to everyone, including future-me scrolling back through this series in six months. If you’re documenting your own comeback anywhere, translate every metric into a plain-life comparison the first time you use it. It’s also, not coincidentally, exactly what makes a post worth citing instead of skimming past.

Quick answers (the stuff you actually searched for)

How fast does CTL (fitness) rise when you’re starting from zero? Slowly, by design — and that’s the point, not a flaw. CTL is a rolling ~42-day average, so it can only climb as fast as you can sustainably log training stress day after day. Going from a flat zero to 4.3 in one week, like this week’s numbers, is a big relative jump but a tiny absolute one — a fit age-grouper’s CTL sits around 60–80. Expect the first month of a real comeback to look like almost nothing on the chart. That’s the system working correctly, not slowly.

How much weekly training stress (TSS) is right for a beginner or someone rebuilding a base? There’s no universal number, but the pattern matters more than the total. This week logged 198 TSS across 5 sessions — reasonable as a total, but two of those sessions (51 and 63 points) were nearly double the other three. For a true rebuild, especially with almost no fitness base underneath, it’s safer to keep every single session’s TSS close together — a gentle staircase, not spikes — even if the weekly total ends up similar. Consistency of effort beats size of effort at this stage.

Is it normal to lose several pounds in one day? No — and it’s worth knowing so a good week doesn’t get oversold. A 3 lb single-day drop, like the one in this week’s data, is almost always water and hydration shifting, not fat loss; the body doesn’t burn that much tissue overnight. The number worth trusting is the slope over several weeks, not any single morning’s reading. If a big one-day drop shows up, let it sit a few days before believing it.

Next week

Keep the session count — five is a good, repeatable number right now. But flatten the effort curve: aim to keep every single day’s stress score under about 45, even the “good” days, so no one workout is standing alone against almost no base. Keep the run/walk mix — it’s working. And let the weight number breathe for a few more days before trusting the new low; if it holds in the 190s rather than bouncing back to 194+, that’s confirmation, not the single low reading itself.

— running solo, gray on top, green on purpose. X60 SOLO.

This is Week 1 of the Rebuild Log — a real-numbers series documenting a 64-year-old’s return to endurance sport after a serious respiratory illness. New entry every week, same format, real data every time.

About the author — David Presland is a 64-year-old returning endurance athlete and former avionics engineer, rebuilding his aerobic base in public after illness. X60 SOLO is his log of the comeback: solo endurance, gray on top, green on purpose, and no sponsor deciding what he’s allowed to say.

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Next → WK 02

Does the line keep climbing?

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