Threshold now speaks Norwegian Singles

When we started building Threshold we assumed most runners coming to the app were ready for Marius Bakken's full double-threshold protocol — two threshold sessions on the same day, morning and evening, Tue + Thu. That's the Ingebrigtsen template. It's the one the book is organized around. And it's also a template that scales poorly below ~80 km/week.

Over the last six months a different flavour of the method has taken hold in the online running community: Norwegian Singles, a version popularized on r/NorwegianSinglesRun with a foreword by Bakken himself. Three sub-threshold sessions a week, all singles, no doubles. Mon easy, Tue SubT, Wed easy, Thu SubT, Fri easy, Sat SubT, Sun easy long run. Simple enough that time-crunched hobbyists and masters runners can actually sustain it. The results — a sirpoc-to-sub-16 kind of trajectory — speak for themselves.

Today we're shipping first-class support for the Singles protocol in Threshold.

What's live

A free pace calculator at /calculator

Enter a recent race time, get VDOT, training paces, HR zones, and the three canonical Singles workouts — Short (10×1 km @ 15k pace), Medium (5×6 min @ threshold), Long (3×3 km @ 30k pace) — each with its reps individually pace-adjusted per the book's interval-length table. Try it.

Two calculation modes: VDOT from one race, or Critical Speed from two time trials at different distances (better for middle-distance runners). Both are free, run entirely in your browser, and require no account.

One thing the calculator does that similar tools don't: environmental pace adjustments for temperature, humidity (via dew point), and altitude. It's the kind of detail that matters if you race in Georgia in July or train at 1800 m in Flagstaff.

Singles as a first-class method preference

In onboarding you'll now see three method options: Auto (let the coach pick based on your volume and experience), Singles (never doubles), or Doubles (the elite protocol). Pick Singles and Threshold routes you through a dedicated THREE_SINGLE_SUBTHRESHOLD shape — three threshold days, no same-day AM+PM, canonical Tue/Thu/Sat placement.

The three threshold sessions automatically rotate through Short → Medium → Long across the week, matching exactly what the community recommends. No configuration needed.

Bakken's AMA quotes in the coach's brain

Marius Bakken did an AMA on r/AdvancedRunning in April. We pulled the full thread, curated the dozen quotes that address the Singles method, masters runners, fast-twitch athletes, easy-run HR nuance, 45/15 progression, and HRV-driven deloads, and ingested them into our RAG knowledge base. The coach chat now cites Bakken's own words when answering — not just the book but the more recent guidance he gave directly to hobby runners.

A smarter first 45/15 session

One of the AMA insights we baked into the rules engine: the first 45/15 session a runner ever sees shouldn't be a standalone 20-rep workout. Per Bakken's own gradual-intro protocol, it should be 5–7 reps tacked onto the end of a familiar 5×6-min threshold session, so the legs meet the format in a small dose inside a workout they already know. Threshold now emits this hybrid session automatically the first week a new 45/15 appears in your plan.

Mid-plan time-trial nudges

The Singles method relies on recalibrating paces every 4–8 weeks via a 5K time trial or parkrun. At week 5–9 of any plan, if you don't have a recent race on file, the app now prompts you to do one — and on return you can import it automatically via Strava.

Strava race import

Onboarding and the calculator both accept a one-tap Strava import: connect, pick which races to use, done. We look at 12 months of activities, filter for standard distances (1500m, mile, 3K, 5K, 10K, HM, marathon, etc.), and surface up to 20. No manual entry.

HRV-driven deload banner

Also from the AMA: “Say your 7-day rolling HRV is lower than your 60-day average. Maybe back off and change the training a bit.” We compare those two windows on-device from HealthKit data and surface a banner when the signal agrees with a streak of poor recovery scores. Natural periodization, not programmatic.

Research workflow behind the release

A quick aside on how this got built. The research scaffolding lives in the repo at .claude/research/norwegian-singles/ — the Quarto book from norwegiansingles.run, the testimonials archive, the Bakken AMA parsed from the reddit JSON endpoint, the executive- summary Google Doc exported via /export?format=txt, a LacTrace calculator zone table, a competitive read on sweetspot.run and the cellarmate iOS app, and a Running Writings translation of Kristoffer Ingebrigtsen's once-daily 2021 week (95 km/wk, Tue/Thu/Sat SubT, Sun long — almost exactly the shape our engine now produces).

That research map turned into a tiered implementation plan: copy softening (lead with Norwegian Method, not “Olympic champions”), then knowledge-base content, then the calculator, then the rules-engine changes (new shape, solver relaxation, safety-guardrail split between singles and doubles models, post-deload rebound fix), then iOS parity, then Strava.

What we didn't change

Bakken's book remains our training-science source of truth per CLAUDE.md. We treat Singles as a tier variant — a different wrapper around the same threshold physiology — not a competing scientific authority. The Golden Zone target (2.3–3.0 mmol/L, 80–87% max HR) is unchanged. Peak-phase VO2max intervals are unchanged. The 10% weekly-volume cap is unchanged.

What didchange: safety validation no longer fires a false positive on post-deload volume rebounds (it now compares against a 3-week lookback window, matching the book's “returning to established volume is safe” rule), and the placement solver respects shape-declared threshold-day counts instead of a hard- coded max of 2.

What's next

• Submit the Strava production-ramp application so more than one athlete can connect at a time.
• Apple Watch “send today's session” from the watchOS companion.
• Analytics instrumentation so we can tell which methodology preference correlates with sustained weekly completion.
• A “first plan” onboarding experiment that defaults to Singles for runners at < 60 km/week and Auto for everyone else.

Try it

The calculator is free and live at thethresholdapp.com/calculator. If you want the full plan — with Singles mode, weekly rotation, and the AI coach that can cite Bakken's AMA directly — download the iOS app or start the two-minute quiz below.

And if you're one of the r/NorwegianSinglesRun regulars reading this, I'd love to hear what we got wrong. We're one API-agreement question away from full intervals.icu parity, so if there's a piece of the Singles protocol we're not handling the way the community does, tell us.