fix(vo2max): rebalance rep-length conflict, correct overstatements

Review of the VO2 conflict section against primary sources (verified via
PubMed + search):

- Rønnestad & Hansen 2016 (PMID 23942167) confirmed: 13 cyclists, 30s vs
  50%/80% Tmax at 2:1 work:rest, measured time >=90% VO2peak, 30s won. Table
  row corrected to reflect the actual comparison.
- Yang 2025 optimum ~140s is a MEDIUM rep (~2.3 min), between the poles.
  Section reframed from binary short-vs-long to an inverted-U with a
  modality/protocol-dependent peak. 'Weighted toward running' softened to
  match what the abstract actually supports.
- Removed the overstatement 'best-controlled evidence favors short 30/15
  intervals'. Added two caveats: (1) cycling short-interval superiority is
  largely one research group; (2) effort-matched work (total-work-matched)
  reportedly nulls the advantage (Seiler group; unpublished/secondary,
  flagged low-tier, not cited as fact).
- Practical menu now defaults to medium (~2-4 min, near the pooled optimum)
  rather than short; short/long presented as goal-dependent options.
- citations.md: added single-group caveat on Ronnestad body of work and an
  explicit NOT-VERIFIABLE entry for the effort-matched replication.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TqrhBhC3GEcKyaw8RTk8G6

references/citations.md

@@ -152,6 +152,19 @@ Rønnestad BR, Øfsteng SJ, Zambolin F, Raastad T, Hammarström D. *Superior Phy
 After a Microcycle of Short Intervals Versus Long Intervals in Cyclists.* Int J Sports Physiol
 Perform. 2021;16(10):1432–1438. **PMID 33735833 · DOI 10.1123/ijspp.2020-0647.**
 
+> **Caveat on the cycling short-interval body of work (Rønnestad 2016/2020/2021 + Almquist 2020):**
+> the short-interval superiority comes chiefly from a **single research group**, and its adaptation
+> claims are challenged by effort-matched work: when **total work duration** is matched, the
+> advantage reportedly disappears (attributed to a Seiler-group study — **unpublished /
+> secondary-source, low evidence tier, not cited as fact**). Present short-interval superiority as a
+> *lab-consistent but not independently settled* finding, not a cycling consensus. See
+> `vo2max-intervals.md`.
+
+**❌ "Effort-matched cycling replication, no difference" (Seiler group)** — **NOT VERIFIABLE as a
+primary source.** Referenced only via secondary/coaching sources as an unpublished master's thesis
+(~30 cyclists, VO2max ~64, total-work-matched, no short-vs-long difference). Used only to *temper*
+overconfidence in the short-interval side; **do not cite as established evidence.**
+
 ---
 
 ## Distribution / periodization philosophy

references/vo2max-intervals.md

@@ -22,43 +22,63 @@ a **work-to-recovery ratio of ~0.85**, with ~3×/week over 3–6 weeks as an eff
 Wang & Guan 2025, *BMC Sports Sci Med Rehabil* 17(1):156; PMID 40605061;
 DOI 10.1186/s13102-025-01191-6).
 
-> **Caveat — modality.** This meta-analysis is weighted toward **running-based** HIIT. The ~140 s /
+> **Caveat — modality.** Yang 2025 describes its *optimal protocol* as running-based; the abstract
-> 0.85 optimum is a strong starting anchor, but see the cycling-specific conflict below before
+> does not give a cycling-vs-running breakdown across the 51 studies. Treat ~140 s / 0.85 as a
-> treating "longer is better" as settled *for cyclists*.
+> cross-modal anchor, not a cycling-specific verdict — and note that **~140 s is a *medium* rep
+> (~2.3 min): longer than 30s, shorter than the classic 5-min "long" interval.** The pooled optimum
+> sits *between* the two poles people usually argue about.
 
-## ⚠️ Genuine conflict: rep length in cycling vs running
+## ⚠️ Rep length is unsettled and protocol-sensitive — not a solved short-vs-long question
 
-The claim that **longer reps (3–5 min) accumulate more time ≥90% VO2max than 30/30s** is
+A common coaching claim is that **longer reps (3–5 min) accumulate more time ≥90% VO2max than short
-**supported in running but contradicted in cycling.** Do not present it as settled.
+(30s) intervals.** The evidence does not settle this cleanly: it flips by modality, depends heavily
+on how the protocols are built, and can wash out when total work is matched. Do **not** present
+either "go long" or "go short" as established.
+
+**The direct time-at-VO2max studies disagree by modality:**
 
 | Modality | Finding | Source |
 |---|---|---|
-| **Running** | 3-min intervals accumulated **more** time >90% VO2max (~328 s) than intensified 30-s intervals (~201 s), even with 30-s intensity raised | Fleckenstein, Braunstein & Walter 2025, *Front Sports Act Living* 6:1507957; PMID 39835194; DOI 10.3389/fspor.2024.1507957 |
+| **Running (acute)** | 3-min intervals accumulated **more** time >90% VO2max (~328 s) than intensified 30-s intervals (~201 s), even with 30-s intensity raised | Fleckenstein, Braunstein & Walter 2025, *Front Sports Act Living* 6:1507957; PMID 39835194; DOI 10.3389/fspor.2024.1507957 |
-| **Cycling (acute)** | **30-s** work intervals induced **more** total time ≥90% VO2peak than longer intervals in well-trained cyclists — the opposite result | Rønnestad & Hansen 2016, *J Strength Cond Res* 30(4):999–1006; PMID 23942167; DOI 10.1519/JSC.0b013e3182a73e8a |
+| **Cycling (acute)** | **30-s** work intervals induced **more** time ≥90% VO2peak than longer intervals (50%/80% of Tmax) at matched 2:1 work:rest, in 13 well-trained cyclists — the opposite result | Rønnestad & Hansen 2016, *J Strength Cond Res* 30(4):999–1006; PMID 23942167; DOI 10.1519/JSC.0b013e3182a73e8a |
-| **Cycling (adaptation)** | Over 3 weeks, effort-matched **short** intervals (30/15 s) beat long (5-min) intervals — e.g. +4.7% 20-min power — in elite cyclists | Rønnestad, Hansen, Nygaard & Lundby 2020, *Scand J Med Sci Sports* 30(5):849–857; PMID 31977120; DOI 10.1111/sms.13627 |
+| **Cycling (adaptation)** | Over 3 weeks, "effort-matched" **short** intervals (30/15 s) beat long (5-min) intervals — e.g. +4.7% 20-min power — in elite cyclists | Rønnestad, Hansen, Nygaard & Lundby 2020, *Scand J Med Sci Sports* 30(5):849–857; PMID 31977120; DOI 10.1111/sms.13627 |
 
-Reinforcing the cycling short-interval side: effort-matched acute responses (Almquist et al. 2020,
+**The pooled meta-analysis puts the optimum in the *middle* (~140 s / ~2.3 min)** — see the caveat
-PMID 32267032) and a microcycle shock-block (Rønnestad et al. 2021, PMID 33735833).
+above. So the honest shape is an **inverted-U whose peak location shifts with modality and protocol**,
+not a binary short-vs-long contest.
 
-**Why they might differ:** protocol construction differs (cycling short-interval work is typically
+**Two reasons not to over-trust the "cycling favors short" side:**
-30/15 s series to exhaustion; the running comparison used fixed-volume intensified 30-s reps),
+1. **It's largely one research group.** The cycling short-interval superiority comes chiefly from
-so part of the divergence may be design, not pure modality. Either way, **for cyclists the
+   Rønnestad and colleagues (2016 / 2020 / 2021; Almquist 2020, PMID 32267032; Rønnestad 2021,
-best-controlled evidence favors short 30/15-style intervals for accumulating time ≥90% VO2max**,
+   PMID 33735833). Internally consistent, but independent replication is limited.
-which cuts against a blanket "bias toward longer reps."
+2. **Effort-matching is the crux.** When independent cycling work matched **total work duration**
+   across formats, the short-interval *adaptation* advantage reportedly disappeared (attributed to a
+   Seiler-group study; **unpublished / secondary-source — low evidence tier, do not cite as fact**).
+   Much of the apparent edge may be that 30/15 sessions simply pack more total high-intensity work,
+   not rep length per se.
+
+**Bottom line:** acute time ≥90% VO2max favors short intervals *in the Rønnestad cycling protocols*
+and long intervals in the one running study; the pooled optimum is *medium* (~140 s); and
+effort-matched adaptation data are equivocal. Treat rep length as a lever to **individualize**, not
+a solved problem.
 
 > ⚠️ **Under-researched — track individual response.** Optimal rep length for a *given cyclist* is
-> not resolved. Use the MCP interval/stream data to verify what actually keeps power ≥90%-effort
+> not resolved. Use the MCP interval/stream data to verify what actually keeps power in the
-> band across reps for this athlete, and let that — not a rule — drive the choice.
+> ≥90%-effort band across reps for this athlete, and let that — not a rule — drive the choice.
 
 ## Practical prescription
 
-- **Default menu for cyclists** (bias to what the cycling evidence supports, then verify per rider):
+- **Menu for cyclists** (no format is proven superior — pick by athlete and goal, then verify per
-  - **Short intervals:** 30/15 s (≈13 reps × 2–3 series) — strong for time ≥90% VO2max and
+  rider with the MCP data):
-    adaptation in cyclists (Rønnestad 2020/2021).
+  - **Medium intervals (~2–4 min, work:rest ~0.85):** closest to the pooled meta-analytic optimum
-  - **Longer intervals:** ~3–5 min reps at ~0.85 work:rest — the meta-analytic optimum region
+    (~140 s; Yang 2025) and a sensible **default** for most riders — long enough to bank time
-    (Yang 2025); useful for **sustained** aerobic power and for riders who tolerate short intervals
+    ≥90% VO2max, short enough to hold power across reps.
-    poorly. If rebuilding sustained power specifically, longer reps have a rationale — but this is
+  - **Short intervals:** 30/15 s (≈13 reps × 2–3 series) — banks time ≥90% VO2max well in the
-    a reasoned choice, not a proven superiority in cycling.
+    Rønnestad protocols (2016/2020/2021); good for riders who fade on long reps or want more total
+    high-intensity work per session. Not proven superior once total work is matched.
+  - **Long intervals (~4–5 min):** favored by the running time-at-VO2max data (Fleckenstein 2025)
+    and useful for **sustained** aerobic power and race-specific steady demands; a reasoned choice,
+    not a cycling-proven one.
 - **Prescribe from power.** For MTB especially, HR lags and misleads (`mtb-xco-demands.md`,
   `data-confounds.md`).
 - **Verify the session worked:** pull the interval stats/streams from MCP and check power held near