Exclusive: Strava just sued Garmin, demanding the company stop selling all their fitness devices (watches and bike computers), due to infringing on a patent. I dive into what's being said, a whole lot of history, what it means, and much more: www.dcrainmaker.com/2025/10/stra...

100 years ago this month, AV Hill published 3 papers summarising a lecture on the physiology of athletic records he gave at the British Association for the Advancement of Science. They gave birth to exercise physiology as we know it today. physoc.onlinelibrary.wiley.com/doi/10.1113/...

Apparently Garmin added OAuth2 to their Connect API: New apps can already use it, existing apps can't migrate yet. More info "this fall". As a developer, this makes me very happy (maybe more than it should, but OAuth1 really is a pain to work with). Docs: developerportal.garmin.com/sites/defaul...

You can see exactly where Wightman’s tank emptied, about 5-10 m from the line (by the Honda sign). If you calculate his critical speed and D’ from his outdoor PBs, D’ was gone 6 m before the line.

Intervals.icu uses pretty much the same method to find max efforts. Doesn't do any pre-smoothing of the power data. I never tried smoothing.

So there you have it. This was our proposed solution to interrogate real-world (messy) MMP data, identify maximal values in that data, and use (only) those to derive CP.

@james-spragg.bsky.social Hey James. Is it possible to share the code or detailed explanation of the "shoulder method" in your "An improved methodology..." paper from 2023? I'm considering making a paper playground (paperplayground.app) for it.

This comment/thread made me realize I had some gaps in my intuition around regression methods for power-duration models. New blog: gssns.io/posts/same-m...

I'm building a new Paper Playground for this paper: arxiv.org/abs/2503.14841 This gives me a chance to revisit asymmetric loss functions for fitting the 3-parameter CP model (following up on my earlier blog here: gssns.io/posts/asymme...)

New blog: Mean-max sampling gssns.io/posts/mean-m...

New tutorial: "One-Off Analysis Scripts: Cycling Torque Example" developer.sweatstack.no/tutorials/on...

Friday Vibe Coding

New blog: Asymmetric loss for power duration models gssns.io/posts/asymme...

Amazing!: fpca.paperplayground.app From @aartgoossens.bsky.social a Paper Playground paperplayground.app implementation of the FPCA model. It's a great concept to interactively showcase research results. cc @drphilipskiba.bsky.social

New paper with @drphilipskiba.bsky.social is now out: journals.humankinetics.com/view/journal... We took a new approach to modeling the power duration curve in cyclists using functional principal component analysis.

GitHub Codespaces provides a free web-based development environment backed by a Linux container... and it turns out it also includes a GITHUB_TOKEN environment variable that provides free API access to the GitHub Models collection of LLMs ... here it's running my LLM CLI utility

COROS has confirmed a substantial set of security vulnerabilities, impacting not just the watch, but COROS online account as well. These were initially spotted by security researcher Moritz Abrell, and I've confirmed they impact all devices. Full details: www.dcrainmaker.com/2025/06/coro...

If you're interested in the nascent field of context engineering (the new, more cromulent alternative to prompt engineering) Drew's piece here provides some excellent nomenclature for some of the challenges you might face...

Feature request for sonnet/claude 5: please unlearn everything about pip, pipenv, requirements.txt. Go all in on uv :P

Apparently I'm adapting to my 3-year-old's sense of humor a little too well 😅 ``` git stash poop fatal: subcommand wasn't specified; 'push' can't be assumed due to unexpected token 'poop' ```

Agent says no.

📊 New Publication! We analyzed 5000+ cycle ergometer tests (ages 14-64) to create reference standards of lactate thresholds for health studies and clinical practice. Full text: doi.org/10.1080/0264... #Exercise #SportsScience 🧪

📊Looking to re-decorate your #dataviz office? Y ou need Boxplot Shelves!

FPCA paper with @drphilipskiba.bsky.social accepted at IJSPP so that’s a nice way to start the week.

This is one of a few demo projects I'm working in preperation for the Science & Cycling 2025 conference. (anyone else here going?...)

New paper out in Scand J Med Sci Sports! 
We tested the reliability of running economy (RE) and other physiological parameters during 90 min of running.

➡️ Running economy is highly reliable in a fatigued state, a 👍🏼 implication for testing durability
 🆓📄 onlinelibrary.wiley.com/doi/10.1111/... 🧵1/8

Thoughts? 🤔

Building the sports data app you've been dreaming of just got way easier! ⚡🤓

New: SweatStack Express Login lets you register by simply connecting a data source - no account setup needed. This drastically improves onboarding for 3rd party applications that are powered by SweatStack.

This is so cool! 🤯 Those mind-blowing ChatGPT images we're all generating have a bunch of @fastapi.tiangolo.com underneath 😎🚀 Check this interview with Sulman Choudhry and Srinivas Narayanan from ChatGPT/OpenAI by The Pragmatic Engineer newsletter.pragmaticengineer.com/p/chatgpt-im...

I'm glad somebody out there is brave enough to push back against the "personal ChatGPT usage is terrible for the environment" message andymasley.substack.com/p/a-cheat-sh...

MCP has the same hype signature as GraphQL tbh

Yearly reminder that sports science is not limited to humans: "The Application of the Pyramidal Training Model for conditioning Thoroughbred horses" 🏇 www.sciencedirect.com/science/arti...

ASCII art plots of your activity data, using Python, directly in your browser: 🤓

This has been on my want-to-build-list for a long time. 🤓

Pydantic Evals is a powerful evaluation framework designed to help you systematically test and evaluate the performance and accuracy of the systems you build, especially when working with LLMs. More info here: ai.pydantic.dev/evals/

Garmin Connect+ is here. This new paid subscription offering adds a boatload of features. But are those features actually worth it? I dive into it all hands-on, to see how everything works (or, doesn't): www.dcrainmaker.com/2025/03/garm...

Question to the Pythonistas here: What is your go-to way for automatically generating Python API documentation? My requirements: - Generated from docstrings - Separate from the library repository (because it also contains other types of documentation) - Compatible with MkDocs.

Here's the table of contents for my lengthy new piece on how I use LLMs to help me write code simonwillison.net/2025/Mar/11/...

A good editorial attempting to reconcile expert opinions from a physiological & academic perspective on the popular meme of "zone 2" training What Is “Zone 2 Training”?: Experts’ Viewpoint on Definition, Training Methods, and Expected Adaptations. journals.humankinetics.com/view/journal...

A.V. Hill was a hero, a genius, and the most upright person Bernard Katz ever met. He helped bring exercise physiology into being. Here’s our review of that story, published in @jphysiol.bsky.social. physoc.onlinelibrary.wiley.com/doi/full/10....

TrainerRoad & Zwift integration is now finally live! I dig into how it works after a bit of usage, including some of the new features being debuted here. Full details: www.dcrainmaker.com/2025/02/trai...

A trio of SQLite nerdery on my blog today: - simonwillison.net/2025/Feb/6/s... about a neat tool for exploring SQLite's binary file format - simonwillison.net/2025/Feb/7/a... is a tool I built for playing with APSW via Pyodide - simonwillison.net/2025/Feb/7/s... lets you back a SQLite DB with S3

Playing around with the data from this paper about running economy: link.springer.com/article/10.1...

It's been a while since we've had a solid Garmin Connect platform outage. Seems like it's been about two hours thus far. Without GC, you can't seamlessly sync workouts to Strava, get routes to your watch, or do any of the other features listed on Garmin's status site. Hopefully it's fixed soon.

How can an energy budget be used to inform a training process? Smart training starts with understanding the demands of your race & thinking of the specific capacity you need to build! The key is knowing what you need to WORK (😉) on! Read more👇 open.substack.com/pub/sherzog/...

Finally got around to dealing with one of those "DeprecationWarning: datetime.datetime.utcnow() is deprecated" warnings, so I wrote it up as a tiny TIL: https://til.simonwillison.net/python/utc-warning-fix

Wrote up some notes on Limbo, the newly announced rewrite-it-in-Rust fork of SQLite simonwillison.net/2024/Dec/10/...

This is a neat new variant on RAG - no vectors, not even full-text search, instead showing the model a header hierarchy and giving it a tool to read the relevant sections My notes here: simonwillison.net/2024/Dec/6/r...

PydanticAI is here! An Agent Framework designed for production, from the team who created and maintain @pydantic.bsky.social. As some of you will know, I've been working on this for some time, can't wait to see what people build with it. ai.pydantic.dev