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IcuSync is a subscription service that connects Claude (by Anthropic) to your Intervals.icu training account. Once connected, Claude can read your training history, build structured workouts using your zones and threshold data, and push those workouts directly to your Intervals.icu calendar, which then syncs automatically to your Garmin, Coros, Wahoo, Suunto, Polar, or other connected device.

You need three things:

1. A free Intervals.icu account with at least one sport configured and your threshold pace or power set in your sport settings.
2. An IcuSync account. Connecting to Intervals.icu takes one click via OAuth, no API keys needed.
3. A Claude account. A paid Claude plan (Pro, Max or Team) is recommended as it gives you access on web, mobile, and desktop with higher usage limits. A free Claude plan works too but limits you to one custom connector.
4. An IcuSync subscription, $20 USD per year.

No. Both connection methods work on a free Claude plan. The MCP URL method works on any plan but limits free users to one custom connector. The desktop extension method works on any plan via Claude Desktop.

A paid Claude plan (Pro, Max or Team) is recommended as it removes the one-connector limit and gives you higher usage limits overall.

If you use the desktop extension method, no, it works with a free Claude plan but only on Claude Desktop.

Both methods are covered in the setup guide included with your IcuSync account.

Intervals.icu is a free training platform for endurance athletes. It handles fitness and fatigue tracking, structured workout scheduling, and automatic sync to Garmin, Coros, Wahoo, Suunto, Polar, or other connected device. It is free to use, no paid tier is required to use IcuSync with it.

If you are new to Intervals.icu, see our guide: What is Intervals.icu?

Most people are up and running in under ten minutes. The steps are:

1. Create your IcuSync account and subscribe
2. Click Connect with Intervals.icu in your IcuSync dashboard and approve the connection. No API keys needed
3. Connect Claude using the MCP URL or the desktop extension
4. Open Claude and start talking

IcuSync is built on MCP, Model Context Protocol, the open standard that lets AI assistants connect to external tools and take real actions like reading your training data and pushing workouts to your calendar.

Claude is the recommended AI for IcuSync because it follows structured workout instructions precisely and reliably. When you ask it to add a Zone 2 run, it creates the correct format first time, no correction needed. That matters when the output is going straight to your training calendar and syncing to your watch.

Claude also handles ongoing, context-heavy training conversations well. It remembers your goals and preferences within a Project, reasons carefully about your data, and gives considered responses rather than generic advice.

IcuSync already works with ChatGPT via Developer Mode, which added full MCP support in late 2025. You can connect IcuSync the same way you would any remote MCP server.

That said, the experience is noticeably different. In testing, ChatGPT tends to over-interpret workout instructions and add its own formatting instead of following the structured format that intervals.icu requires. Getting a simple Zone 2 run added correctly took multiple correction rounds, whereas Claude does it right first time.

For now Claude is the recommended platform. If you already use ChatGPT and want to try it, it does work, just expect to be more hands-on with corrections.

No. You connect IcuSync once during setup and after that it is invisible. You just open Claude and have a conversation about your training. IcuSync handles everything in the background, you never need to think about the technical layer underneath it.

These are the two ways to connect IcuSync to Claude.

The MCP URL is a web address you paste into your Claude account's customize section. You can add it in Claude web or Claude Desktop (Customize → Connectors). Once added, IcuSync is available across Claude web, mobile, and desktop. Free plan users can use this method but it will use their one custom connector slot.

The desktop extension is a single .mcpb file you open in Claude Desktop. It configures Claude Desktop to connect to IcuSync automatically. It works on any Claude plan but only on Claude Desktop.

If you are on a paid Claude plan, use the MCP URL as it is simpler and works everywhere. If you are on a free plan, use the desktop extension to keep your one connector slot free for other tools.

Yes. If you use the MCP URL connection method, add the custom connector on Claude web or Claude Desktop (Customize → Connectors) and it will automatically appear in the Claude mobile app. This works on any Claude plan. If you use the desktop extension method, IcuSync is only available on Claude Desktop.

No, this is normal and nothing to worry about.

When you add the IcuSync connector in Claude for the first time, or if you remove and re-add it, Claude.ai immediately tries to ping the server to validate the connection. This check can fire before the connection is fully established, which causes a brief warning banner to appear even when the connection is working correctly. It is a timing issue in Claude.ai's own connector flow, not a problem with IcuSync.

The warning will disappear on its own within a few seconds.

If IcuSync appears in your connectors list in Claude's Customize section, you are connected and everything is working. Start a fresh conversation and IcuSync will be available.

Claude has access to thirteen tools through IcuSync:

1. Read your training history, recent sessions, load, metrics
2. Read your fitness metrics (CTL, ATL, TSB)
3. Read your wellness data
4. Read your athlete profile, zones, threshold pace or power, sport settings
5. Read your power curves
6. Read detailed lap-by-lap data for a specific activity, including pace splits, power, and heart rate per lap
7. Push a new workout to your calendar
8. Edit an existing workout on your calendar
9. Delete a workout from your calendar
10. Read your calendar events
11. Read your best efforts for run, ride or swim
12. Read advanced sensor metrics per interval (ground contact time, DFA alpha1, W' balance, core temperature, and more)
13. Summarise training load, zone distribution, and volume across any date range

Claude can read, write, and manage workouts in natural conversation. You review everything before it affects your training.

Once a workout is on your Intervals.icu calendar, it syncs to your connected device automatically, just as any other workout would. IcuSync pushes to Intervals.icu and Intervals.icu handles the sync to your device.

For this to work you need your device connected in Intervals.icu with Upload planned workouts enabled. Without this ticked, workouts will appear on your Intervals.icu calendar but will not reach your watch.

Go to Intervals.icu Settings → Connections and confirm Upload planned workouts is enabled for your device Garmin, Coros, Wahoo, Polar, Suunto or other compatible device.

Yes, always. After Claude pushes a workout to your Intervals.icu calendar, take a moment to review it before you head out.

Check that the duration, intensity targets, and structure look right for where you are in your training. Then confirm the workout has appeared on your Garmin, Coros, or other device after your next sync.

If anything looks wrong or does not feel right for today, tell Claude and it will adjust the workout and update your calendar automatically.

Claude builds, you approve. You are always in control of what goes on your watch.

Yes. Once your Intervals.icu account is connected, IcuSync shows a Calendar Subscription section on your dashboard with one-click buttons for Apple Calendar, Google Calendar, and Outlook.

Click the button for your app and it opens directly with a subscription prompt. Confirm and your planned workouts will appear in your calendar automatically, staying in sync as new workouts are added.

A Copy URL option is also available if you use a different calendar app that supports iCal subscriptions.

This works for all connected users automatically. No need to find the URL inside Intervals.icu yourself.

Claude can access the training data available through your Intervals.icu account via the API. This includes your recent activities, fitness and fatigue metrics, and your athlete profile. It does not access data outside of what Intervals.icu makes available through its API.

Yes. IcuSync includes an activity detail tool that retrieves interval by interval data from any completed activity. Claude can see each effort segment including pace, power, heart rate, and elevation for the full session.

You can ask things like:

• “How did my intervals go in yesterday's run?”
• “Show me my pace splits from this morning.”
• “How much did my heart rate drift across my long run?”

To use it, Claude first needs the activity ID which it finds automatically by checking your recent training history. You do not need to look anything up yourself.

IcuSync works with any sport configured in your Intervals.icu account. Running is the most thoroughly tested. Cycling, swimming, triathlon, and other endurance sports work through the same tools. Claude will use whichever sport settings and zones are configured in your Intervals.icu profile.

Yes, with some extra setup steps compared to Garmin, Coros, Wahoo, Polar, and Suunto.

IcuSync and Claude work the same way regardless of what device you use. You can build structured workouts with Claude, push them to your intervals.icu calendar, and analyse your completed activity data through Claude as normal.

There are two gaps to bridge with Apple Watch that do not exist with Garmin, Coros, Wahoo, Polar, and Suunto.

Yes it matters a lot. If your threshold pace or power is not set in Intervals.icu Settings → Sport Settings, Claude cannot calculate your zones correctly. Workouts will still generate but the intensity targets will be blank or incorrect. Set your threshold values before asking Claude to build workouts.

This is not an IcuSync issue. Response speed depends entirely on Claude and Anthropic's servers, which can slow down during peak usage periods such as weekday business hours and Friday evenings.

If you are on a free Claude plan you are more likely to experience slowdowns as free plan users have lower priority during busy periods.

A few things that help:

• Try again outside peak hours. Early mornings and weekends are typically faster.
• If you use Claude regularly for training, upgrading to a paid Claude plan (Pro, Max, or Team) gives you higher priority access and significantly better response times.

IcuSync itself has no usage limits or throttling on our side. If Claude is responding slowly, the issue is with Claude's servers, not the connection to Intervals.icu.

Claude shows a generic connection failure message when something goes wrong during setup. The two most common causes are:

No. Your athletes hold the IcuSync subscription. You connect through a token they grant you. There is nothing to sign up for and nothing to pay on your end.

Yes, you need a Claude account to use the connector. Claude's free plan includes one custom connector slot which is enough for IcuSync coach access. Paid Claude plans (Pro, Max, Team) give you additional connector slots if you use other connectors alongside it.

If multiple athletes invite you to the same email address, they all connect to your single MCP URL automatically. You do not need a separate connector for each athlete. One URL, your entire roster.

You work with one athlete per conversation.

Start a chat, ask Claude to list your athletes, then use select_athlete to choose who you want to work with. Switch athletes by starting a new chat.

It depends on what each athlete grants when they send the invite. Read access covers training history, fitness metrics, wellness data, power curves, best efforts, activity detail, athlete profile and planned events. Write access covers pushing workouts to the calendar, editing and deleting them. Each athlete sets this individually.

Yes, at any time from their IcuSync dashboard. If an athlete revokes your access, you will no longer be able to retrieve their data or push workouts to their calendar. Your access to any other athletes you coach is not affected.

Visit the For Coaches page, enter your coach email in the Resend my MCP URL section, and a confirmation link will be sent to your inbox.

Clicking it resends your existing URL. Your token does not change.

Use the Regenerate my token section on the For Coaches page.

Enter your email, confirm via the link sent to your inbox, and a new MCP URL will be issued. Your old token is immediately invalidated. Update your Claude connector with the new URL to continue. All your athletes stay linked automatically, no action needed from them.

Yes. Add the connector once on the Claude web or desktop app and it syncs automatically to the Claude mobile app.

Yes. Sign up for your own IcuSync account, then send a coach invite to your own email address from your athlete dashboard.

Replace your athlete connector URL in Claude with your coach token URL. Your coach token covers both your own training data and all your coached athletes in one connector.

Use select_athlete in Claude to move between yourself and your athletes.

Your athletes grant access to specific tools only and can revoke at any time. Their intervals.icu credentials are never exposed to you and never leave IcuSync's backend. You interact with their data only through the tools they have permitted.

Payment is processed securely by Stripe. Your subscription renews automatically each year. You will receive a reminder email before renewal. You can cancel at any time from your account settings.

We do not offer refunds for partial billing periods. If you cancel, your access continues until the end of the period you have paid for.

If something is not working and you feel you have not been able to use IcuSync at all, email us at [email protected] and we will look at it on a case by case basis.

Log in to your IcuSync account, go to account settings, and cancel from there. Your access will continue until the end of your current billing period. You will not be charged again after that.

If you have trouble cancelling, email [email protected] and we will sort it out for you.

No. Unlike a typical app, there is no interface to evaluate. IcuSync runs in the background connecting Claude to your Intervals.icu account. The value is immediate, the first time Claude reads your training data or pushes a workout to your watch you will know if it works for you.

At $20 USD per year, with both Intervals.icu and Claude free underneath it, the total cost of trying IcuSync is $20 USD.

If you are not sure about anything or something is not working, please contact us. We are here to help.

Your Intervals.icu data is yours and stays on Intervals.icu. IcuSync does not store it. We hold only your email address, subscription status, and your encrypted Intervals.icu OAuth token. When you disconnect your Intervals.icu connection, your token is automatically removed.

Yes. Australian customers are charged an additional 10% GST on top of the $20 USD subscription price, in line with Australian tax law. This is added automatically at checkout by our payment processor Stripe. You will see the GST amount itemised on your receipt.

No. When Claude requests your training history or pushes a workout, that request passes through IcuSync to Intervals.icu in real time. We do not retain your training data. See our Privacy Policy for full details.

IcuSync connects to Intervals.icu via OAuth. You authorise access directly through Intervals.icu without sharing any passwords or API keys with IcuSync. The OAuth token is stored encrypted in our database and is never exposed in plain text or shared with any third party.

IcuSync passes your training data to Claude during a conversation so Claude can read and respond to it. What Anthropic does with conversation data is governed by their privacy policy: anthropic.com/privacy. IcuSync does not control how Anthropic handles data processed through Claude.

Zone-based pace targets (e.g. Z2 Pace) render a coloured zone chart for swim workouts when swim pace zones are configured in your Intervals.icu sport settings. Absolute pace targets (e.g. 1:45/100m) do not render a zone chart but always work regardless of settings. To use zone-based swim workouts, go to Intervals.icu Settings then Sport Settings and configure your swim pace zones.

Using the edit function on an existing workout can strip zone rendering in some cases. If zones disappear after an edit, delete and re-push the workout to restore correct zone colours.

When a structured run workout is synced to Garmin and executed at high intensity, Garmin may classify the activity as "Other" rather than "Run" on the device. This is a Garmin classification limitation and does not affect the workout data or how it is recorded. The activity will still sync correctly back to Intervals.icu.

Power watt targets in structured workouts do not display on the Garmin Connect app calendar view. However the power targets are present in the workout and will appear correctly as target fields on your Garmin watch during the session. This is a Garmin Connect display limitation.

Activities that reach Intervals.icu through Strava are blocked from the Intervals.icu API due to Strava's terms of service. The Intervals.icu web app can still display them because it has direct database access, but the API that IcuSync uses cannot.

To fix this while keeping your existing Strava history, go to Intervals.icu Settings → Connections and uncheck Download activities under Strava. Then connect your device directly to Intervals.icu — Garmin, Wahoo, Coros, Suunto, and Polar all support native sync. New activities will sync natively and be fully accessible to Claude, while your existing Strava history stays intact.

If you use TrainerRoad, enable Dropbox sync in TrainerRoad settings and connect Dropbox in Intervals.icu under Settings.

A few things to check:

If using the MCP URL:

• Confirm the URL is correctly added in your Claude account settings under Connections or Integrations
• Try starting a fresh conversation, new tool connections sometimes require a new session to appear

If using the desktop extension:

• Confirm Claude Desktop is fully closed and restarted after installation
• Check the extension install completed without errors
• Make sure you are using Claude Desktop, not the Claude web app

If still not working, email [email protected] with a description of what you see and which connection method you used.

This usually means one of:

• Your Intervals.icu connection has been revoked. Go to your IcuSync dashboard, disconnect, and click Connect with Intervals.icu to reconnect
• Your Intervals.icu account has no data yet, connect a device or upload an activity first

This is an Intervals.icu sync issue, not an IcuSync issue. Check the following in your Intervals.icu account:

• Your device is connected under Settings → Connections
• Auto-sync is enabled for your device
• The workout date is today or in the future, past-dated workouts may not sync to some devices

For device-specific sync issues, the Intervals.icu community forum is the best resource.

Email [email protected] with as much detail as you can, what you asked Claude, what happened, and what you expected to happen. Screenshots help. We will look into it and get back to you.