Chris Farhood
f6dd9dfc27
Modular cycling-training skill: periodization logic, workout design, and research-backed protocols that companion an Intervals.icu MCP server (the server owns all data + computed metrics; the skill owns knowledge + reasoning). Structure: - SKILL.md router + README (companion-to-MCP architecture, install steps) - references/: durability, mtb-xco-demands, strength-for-cyclists, vo2max-intervals, periodization, data-confounds, citations - assets/: base + build plan templates, durability field-test protocol Every quantitative claim carries an inline citation; citations.md is the single source of truth with PMID/DOI, each verified against PubMed on 2026-07-20. Notable honesty flags baked in: - VO2 rep-length: running (Fleckenstein 2025) vs cycling (Ronnestad) conflict documented rather than asserted; cycling evidence favors short intervals. - 'Yu et al. 2025' (frequency > distribution) could not be found; not cited. - Under-researched doses (durability, taper TSB, CTL ramp) flagged 'track response'. - HR-confound doc forbids naive decoupling<5% / RHR+5 rules. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01TqrhBhC3GEcKyaw8RTk8G6
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VO2max interval optimization
Load this doc when: designing high-intensity interval sessions, choosing rep length or work:rest, or trying to rebuild sustained aerobic power.
Data/knowledge split: MCP gives you the power/HR streams and interval stats to check whether a session did what you intended (was power sustained across reps?). This doc gives the design logic.
The target: maximize time spent ≥90% VO2max
The organizing principle of VO2max interval design is accumulating time at or above 90% of VO2max — that's the stimulus, not simply "going hard." Design sessions to spend the most quality minutes in that band that the athlete can repeat and recover from.
What a large meta-analysis found (dose-response)
A systematic review with pairwise and network meta-analysis (51 studies, 1,261 athletes) found inverted-U dose-response relationships and identified an optimum around ~140 s work duration and a work-to-recovery ratio of ~0.85, with ~3×/week over 3–6 weeks as an effective pattern (Yang, 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 / 0.85 optimum is a strong starting anchor, but see the cycling-specific conflict below before treating "longer is better" as settled for cyclists.
⚠️ Genuine conflict: rep length in cycling vs running
The claim that longer reps (3–5 min) accumulate more time ≥90% VO2max than 30/30s is supported in running but contradicted in cycling. Do not present it as settled.
| 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 |
| 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 (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, PMID 32267032) and a microcycle shock-block (Rønnestad et al. 2021, PMID 33735833).
Why they might differ: protocol construction differs (cycling short-interval work is typically 30/15 s series to exhaustion; the running comparison used fixed-volume intensified 30-s reps), so part of the divergence may be design, not pure modality. Either way, for cyclists the best-controlled evidence favors short 30/15-style intervals for accumulating time ≥90% VO2max, which cuts against a blanket "bias toward longer reps."
⚠️ 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 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):
- Short intervals: 30/15 s (≈13 reps × 2–3 series) — strong for time ≥90% VO2max and adaptation in cyclists (Rønnestad 2020/2021).
- Longer intervals: ~3–5 min reps at ~0.85 work:rest — the meta-analytic optimum region (Yang 2025); useful for sustained aerobic power and for riders who tolerate short intervals poorly. If rebuilding sustained power specifically, longer reps have a rationale — but this is a reasoned choice, not a proven superiority in cycling.
- 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 target across reps. Fading power = too much intensity or too little recovery; adjust work:rest.
Frequency vs distribution
For how often to do hard sessions and how they fit the week/season, see periodization.md — the
argument there (after Seiler 2024) is that the long-term integration of frequency, intensity,
and duration matters more than chasing the acute maximum of any single session.