Claudius the Cycling Coach

A set of Claude Code skills that turn Claude into a cycling coach and training logger, powered by Intervals.icu training data.

Claudius reads your workout data, generates charts, classifies your sessions, gives coaching feedback, and logs your weight training — all from the command line.

What It Does

Six slash commands, each a different coaching interaction:

Command	What it does
/review	Analyze a specific workout — generates a 6-panel chart, classifies the session type (intervals, endurance, race, etc.), and assesses execution quality
/weekly-review	Review recent training load, intensity distribution, and progression over the last 30 days
/status	Quick check: current fitness (CTL/ATL/TSB), recovery readiness, and what to do today
/plan	Prescribe the next 3-5 days of workouts based on current fitness and fatigue
/science	Look up training science topics with evidence-based explanations
/log-weights	Describe your gym sessions conversationally and save them as completed activities in Intervals.icu

Workout Review Example

> /review last Wednesday's ride

## Workout Review — Cycling (2026-03-25)
Classification: 6x5min threshold/VO2max intervals on climbs with ride-out/ride-home

W'bal structure: 6 depletion cycles detected, each reaching 0-2% W',
spaced ~8min apart. Classic interval pattern.
...

The /review skill generates a 6-panel workout chart showing power, zone distribution, heart rate, cadence, elevation, and W' balance:

Weight Training Logging Example

> /log-weights Monday I did squats 3x10 at 60lb each side, leg press
  180lb each side. Wednesday was upper body — pull-ups 12, 8, 7 reps,
  lat pulldown 3x10 at 170lb, seated row 3x10 at 190lb.

### Mon Mar 30 — Heavy Leg Day

| Exercise          | Sets × Reps | Weight              | Notes         |
|-------------------|-------------|---------------------|---------------|
| Barbell Squats    | 3×10        | 60 lb/side (~165 lb)| Executed well |
| Leg Press         | 3×10        | ~180 lb/side        |               |

### Wed Apr 1 — Upper Body

| Exercise          | Sets × Reps | Weight    | Notes      |
|-------------------|-------------|-----------|------------|
| Pull-ups          | 12, 8, 7    | Bodyweight|            |
| Lat Pulldown      | 3×10        | 170 lb    |            |
| Seated Cable Row  | 3×10        | 190 lb    |            |

Does this look right? I'll save these to Intervals.icu.

> yes

Saved 2 weight training activities to Intervals.icu:
- Mon Mar 30: Heavy Leg Day (id: i137051310)
- Wed Apr 1: Upper Body (id: i137051324)

How It Works

Intervals.icu API  -->  MCP Server  -->  Claude Code  -->  Coaching Skills
    (your data)        (48 tools)       (CLAUDE.md)      (/review, etc.)

• intervals-icu-mcp provides 48 MCP tools covering activities, streams, wellness, performance curves, calendar, and sport settings
• CLAUDE.md defines the coaching persona, athlete reference data (FTP, zones, HR zones), and training science frameworks
• Slash command skills (.claude/commands/) are structured prompts that orchestrate the MCP tools into coaching workflows
• chart.py generates workout visualizations from stream data (power, HR, cadence, elevation, W'bal)

Setup

Prerequisites

• Claude Code CLI installed
• uv for Python package management
• An Intervals.icu account with API access

1. Clone and install the MCP server

git clone https://github.com/richardkiss/intervals-icu-mcp.git
cd intervals-icu-mcp
uv sync

2. Configure your MCP connection

Copy the example config and fill in your credentials:

cp .mcp.json.example .mcp.json

Edit .mcp.json with your Intervals.icu API key and athlete ID. You can find these in your Intervals.icu settings.

3. Customize CLAUDE.md

Update the Athlete Reference section in CLAUDE.md with your own thresholds:

- **FTP:** 325W | **W':** 25kJ | **LTHR:** 171 bpm | **Max HR:** 189 bpm

Replace with your values. The power zones and HR zones will need updating too.

4. Install chart dependencies

pip install matplotlib numpy

5. Run

claude
> /review yesterday's ride
> /status
> /plan

Project Structure

.
├── CLAUDE.md                    # Coaching persona, athlete data, training science
├── .claude/
│   └── commands/                # Slash command skills
│       ├── review.md            # Workout review
│       ├── weekly-review.md     # Training block review
│       ├── status.md            # Daily fitness check
│       ├── plan.md              # Workout prescription
│       ├── science.md           # Training science lookup
│       └── log-weights.md       # Weight training logger
├── scripts/
│   └── chart.py                 # 6-panel workout chart generator
├── memory/                      # Project context and learnings
└── .mcp.json.example            # MCP server config template

The Weight Training Logger

The /log-weights skill lets you describe gym sessions in plain language. It:

1. Parses your conversational description into structured exercises (names, sets, reps, weights)
2. Shows you a table to confirm before saving
3. Creates manual activities in Intervals.icu via the API — these show as completed workouts on your calendar, just like device-recorded rides
4. Flags any injuries or pain prominently

It handles natural language like "the thing where I pull down a bar" (lat pulldown), calculates total barbell weight from per-side descriptions ("60 lb each side" → ~165 lb total), and marks unknown weights as "not recorded" rather than guessing.

The Workout Review Skill

The /review skill is the most developed. It:

1. Fetches activity streams from Intervals.icu
2. Computes W'bal depletion cycles to classify the workout structure
3. Generates a 6-panel chart (power, zones, HR, cadence, elevation, W'bal)
4. Classifies the session type from the depletion pattern
5. Fetches supporting metrics (best efforts, TSS, IF)
6. Presents a coaching review with assessment and recommendations

The classification uses W'bal depletion cycle counting as its primary signal:

Depletion cycles	Classification
0	Endurance or recovery ride
1	TT or sustained threshold effort
4-8 with similar spacing	Structured interval session
9+ irregular	Race or group ride

License

MIT