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
77 lines
4.6 KiB
Markdown
77 lines
4.6 KiB
Markdown
# Durability / fatigue resistance
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**Load this doc when:** the question is about fatigue resistance, why late-race power fades,
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training the ability to hold power deep into long efforts, or running the durability field test.
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**Data/knowledge split:** the MCP server gives you the kJ, power curves, and fatigued-vs-fresh
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efforts. This doc explains *why fatigued-state power matters* and *how to train it*.
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---
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## Durability is a distinct, trainable quality
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"Durability" is the time of onset and the magnitude of deterioration in physiological-profiling
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variables (thresholds, efficiency, power) over the course of prolonged exercise — a quality that
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should be profiled **separately** from fresh-state numbers, because two riders with identical fresh
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profiles can fall apart very differently after several hours (Maunder et al. 2021, *Sports Med*
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51(8):1619–1628; PMID 33886100; DOI 10.1007/s40279-021-01459-0).
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### Why it matters more than fresh power
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- In professional cyclists across a Grand Tour, **fresh** mean-maximal power did **not** separate
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WorldTour from ProTeam riders — but as work accumulated (0 → 35 kJ·kg⁻¹), WorldTour riders held
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higher power. **Fatigued-state power differentiated performance; fresh power did not**
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(Muriel et al. 2022, *Eur J Sport Sci* 22(12):1797–1804; PMID 34586952;
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DOI 10.1080/17461391.2021.1987528).
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- The **fatigued** power profile varies far more across a season than the fresh profile, and it
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tracks with **training characteristics (accumulated volume/load)** — meaning durability is
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something you build with training, not a fixed trait (Spragg, Leo & Swart 2023, *Eur J Sport Sci*
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23(4):489–498; PMID 35239466; DOI 10.1080/17461391.2022.2049886).
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## The load dependency (the key training implication)
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**Durability depends on maintaining high overall training load, whereas fresh power can be held on
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reduced load.** You can taper volume and keep your 5-min power; you cannot taper volume for long
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and keep your *fatigued* 5-min power. This is the empirical thrust of the Spragg training-
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characteristics paper (PMID 35239466); the crisp "reduced load keeps fresh power, sustained load
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keeps durability" phrasing is Spragg's applied interpretation of that data — cite it as such.
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Physiological correlates of *who* is durable (higher VO2max, better gross efficiency, higher fat-
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oxidation) come from the companion paper (Spragg, Leo & Swart 2023, *Med Sci Sports Exerc*
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55(1):133–140; PMID 35977108; DOI 10.1249/MSS.0000000000003024) — useful for understanding
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mechanism, but the *trainable lever* is sustained load + the practices below.
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## How to train durability
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1. **Long-term consistency and high volume.** Durability is a load-dependent adaptation — it is
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built over blocks and lost when load drops. Protect the long ride.
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2. **Prolonged sessions with hard efforts placed late (fatigued-state intervals).** Put the quality
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work *after* accumulated kilojoules, not at the fresh start of the ride — you are specifically
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training the fatigued state that discriminates performance.
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3. **Glycogen-sparing nutrition.** Fuel long sessions to spare glycogen; the goal is training the
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durable state under realistic fueling, not chronic depletion. (Fatigued power is glycogen-
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sensitive — see the fueling caveat in `data-confounds.md` for why HR is unreliable here.)
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> ⚠️ **Under-researched — track individual response.** The *mechanism* (load-dependent fatigue
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> resistance) is well supported, but the **optimal durability dose** — how much accumulated work,
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> how often, how late to place efforts — is not established. **Do not assume a fixed protocol.**
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> Track each athlete's fatigued-state response and titrate.
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## Measure it: the fatigued-state field test
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Use `../assets/field-test-durability.md`. In brief:
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- Establish a **fresh** 1-min max on a fixed hill.
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- On a separate day, accumulate **~1,500 kJ (~2.5 h)** of mostly-endurance riding, then repeat the
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**same 1-min max on the same hill**.
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- `Durability % = fatigued ÷ fresh × 100`. Track the trend across a block.
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- Hold the hill, gearing, kJ pre-load, and fueling **constant** so the comparison is valid.
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- **Judge from power, not HR** — HR after 1,500 kJ is confounded by drift, heat, and fueling
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(`data-confounds.md`).
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## Discipline note
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Durability matters for both road/TT and MTB, but **keep absolute numbers discipline-specific.** The
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1,500 kJ anchor is a sensible generic default, not a validated cross-discipline constant; a masters
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marathon-MTB rider and an elite road pro do not share a durability dose. See `mtb-xco-demands.md`
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for how fatigue resistance shows up specifically in off-road racing.
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