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
74 lines
4.5 KiB
Markdown
74 lines
4.5 KiB
Markdown
# MTB / XCO demand profile (and why power governs off-road)
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**Load this doc when:** planning for mountain-bike racing, deciding MTB-specific workouts, or
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questioning whether HR is trustworthy off-road.
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**Data/knowledge split:** MCP gives you the power streams, HR, and interval stats from a ride. This
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doc explains what the *demand profile* is and why, for MTB, **you prescribe and judge from power,
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not HR.**
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---
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## The demand profile: intermittent, explosive, anaerobically shifted
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XCO (Olympic cross-country) racing is **intermittent and explosive**: a hard start followed by
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repeated high-intensity bursts, with roughly **25% of race time spent above maximal aerobic power
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(MAP)** in brief 5–10 s efforts, on top of a hard first-lap start (Hays et al. 2018, *Front Physiol*
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9:1062; PMID 30158873; DOI 10.3389/fphys.2018.01062). A corroborating dataset reports ~30% of time
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in the top zone across 334 efforts averaging ~4.3 s at ~135% MAP (Prinz et al. 2021, *IJSPP*;
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PMID 33848975).
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Contemporary XCO has **shifted toward greater anaerobic contribution while maintaining high aerobic
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demand** — you need both engines (Protzen et al. 2026, *Sports Med Open* 12:16; PMID 41739301;
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DOI 10.1186/s40798-026-00976-4).
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## Both aerobic and anaerobic power independently predict performance
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- **Aerobic:** body-mass–normalized aerobic/threshold indices correlate strongly with XCO race time.
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Reported correlations across the literature sit in the **r ≈ 0.6–0.9** range, but note the classic
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elite-cohort study found raw VO2max/peak power did **not** separate riders — the significant
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correlations were for **mass-normalized threshold** power/VO2 (Impellizzeri et al. 2005,
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*Br J Sports Med* 39(10):747–751; PMID 16183772; DOI 10.1136/bjsm.2004.017236). **Frame the
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0.6–0.9 as "across studies," not one clean value.**
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- **Anaerobic:** maximal power in a 5×30 s Wingate protocol correlated **r = −0.79** (p = 0.006) with
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XCO race time — anaerobic power independently predicts performance (Inoue et al. 2012, *J Strength
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Cond Res* 26(6):1589–1593; PMID 21912290; DOI 10.1519/JSC.0b013e318234eb89). *(The correlation is
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negative because higher power = lower/faster race time.)*
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**Training implication:** develop both. Aerobic base/VO2max (`vo2max-intervals.md`) *and* anaerobic/
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repeated-sprint power and strength (`strength-for-cyclists.md`). Neither alone covers the demand.
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## Fatigue resistance separates the field
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Higher-performing MTB riders decline **less** under fatigue. Across 693 elite male XCO race files,
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power under fatigue fell ~**6–10%** in Top-10 riders vs ~**15–20%** in lower-ranked riders (p from
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0.008 to <0.001) — durability is decisive off-road (Sánchez-Jiménez et al. 2025, *Scand J Med Sci
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Sports* 35(11):e70170; PMID 41285697; DOI 10.1111/sms.70170). Train it via `durability.md`.
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## ⚠️ The HR caveat (read this before prescribing MTB intensity by HR)
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In intermittent MTB racing, **HR, power, and VO2 dissociate**:
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- **VO2 stays high on descents where power drops** — you're still consuming oxygen while barely
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pedaling, so power under-reads true metabolic cost on descents.
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- **HR lags short efforts** — a 5–10 s surge is over before HR responds, so HR under-reads the
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intensity of the bursts that define the sport.
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- In XCO, %VO2max did **not** correlate with %HRmax or %MAP (Hays et al. 2018, PMID 30158873).
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**Therefore: power governs MTB intensity; HR is unreliable for it.** Prescribe intervals, pacing,
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and race targets from power. Use HR only where it is valid — steady-state durability decoupling and
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recovery trends — and always screen the confounds in `data-confounds.md`. Do **not** set MTB
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interval targets or judge burst efforts by heart rate.
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## Discipline nuance: marathon/point-to-point ≠ lap XCO
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A 4-hour marathon MTB has **different performance predictors and pacing** than lap-based XCO
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(Novak et al. 2018, *J Sports Sci* 36(4):462–468; PMID 28406361; DOI 10.1080/02640414.2017.1313999).
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Marathon/point-to-point events (e.g. Iceman) are steadier and more sustained; lap XCO is punchier
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and more repeatedly supra-MAP.
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> ⚠️ **Don't over-transfer.** The XCO numbers above come largely from **small-n elite** samples.
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> A masters marathon rider does **not** inherit an elite XCO rider's ~25%-above-MAP profile or their
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> exact fatigue-decline percentages. Keep absolute numbers **discipline- and level-specific**, use
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> the *principles* (both engines matter; power governs; durability decides), and **track the
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> individual's own race files** via the MCP data rather than importing elite constants.
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