--- title: "AIFitnessAPI — blog" canonical: "https://aifitnessapi.com/blog" type: "blog-index" pages: "23" last_reviewed: "2026-09-01" publisher: "AIFitnessAPI" --- # AIFitnessAPI — blog > 23 posts. Findings are derived from this site's own published datasets. ## The Fitness API Cost Your Users Pay - HTML: https://aifitnessapi.com/blog/wearable-api-user-side-cost - Markdown: https://aifitnessapi.com/blog/wearable-api-user-side-cost.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 5 of 24 products bill your end user, not you. All five are direct wearable integrations, and the hardware requirement, not your budget, sets your reach. ## Ten Health Metrics, Two Platforms - HTML: https://aifitnessapi.com/blog/ten-metrics-two-platforms - Markdown: https://aifitnessapi.com/blog/ten-metrics-two-platforms.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 We checked 10 metrics against Apple's and Google's own docs. Every one exists on both. The shapes don't match, and that is the part that costs you. ## Your HealthKit Bridge Last Shipped in 2024 - HTML: https://aifitnessapi.com/blog/react-native-health-stale - Markdown: https://aifitnessapi.com/blog/react-native-health-stale.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 The main React Native HealthKit bridge last released in October 2024. Its Android counterpart cut five versions in one week this August. ## 'No Data' Means Four Different Things - HTML: https://aifitnessapi.com/blog/no-data-means-four-things - Markdown: https://aifitnessapi.com/blog/no-data-means-four-things.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 An empty health read has several causes and only one is 'connect your device'. Here is the order to rule them out before you write that empty state. ## HRV Is SDNN on iOS and RMSSD on Android - HTML: https://aifitnessapi.com/blog/hrv-sdnn-vs-rmssd - Markdown: https://aifitnessapi.com/blog/hrv-sdnn-vs-rmssd.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 Apple stores heart rate variability as SDNN. Health Connect stores RMSSD. Different statistics, no conversion factor, and one chart that quietly misleads. ## How We Verify, and What a Stamp Can't Say - HTML: https://aifitnessapi.com/blog/how-we-verify - Markdown: https://aifitnessapi.com/blog/how-we-verify.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 341 pages, 1188 FAQ entries, 283 resolving citations, median stamp age 36 days. What those numbers prove, and the larger thing they do not. ## 64 Cumulative, 53 Discrete: Sum or Average - HTML: https://aifitnessapi.com/blog/healthkit-sum-or-average - Markdown: https://aifitnessapi.com/blog/healthkit-sum-or-average.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 64 HealthKit quantity types state cumulative aggregation, 53 state discrete. Choose wrong and nothing errors, no test fails, and the chart still renders. ## Nutrition: HealthKit's Biggest Group at 39 - HTML: https://aifitnessapi.com/blog/healthkit-nutrition-is-biggest - Markdown: https://aifitnessapi.com/blog/healthkit-nutrition-is-biggest.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 Nutrition is HealthKit's largest group with 39 identifiers, ahead of Activity at 37. It is also the group almost nobody fills. Your food database is why. ## Apple's Newest HealthKit Types Are a Roadmap - HTML: https://aifitnessapi.com/blog/healthkit-newest-types-roadmap - Markdown: https://aifitnessapi.com/blog/healthkit-newest-types-roadmap.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 Apple ships the data type years before most apps ship the feature. The additions since iOS 16 are a public preview of what the platform expects to matter. ## HealthKit's 9 Mobility Types, Barely Used - HTML: https://aifitnessapi.com/blog/healthkit-mobility-types-unused - Markdown: https://aifitnessapi.com/blog/healthkit-mobility-types-unused.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 HealthKit's Mobility group is 9 identifiers the system derives from ordinary walking. No workout to start, no extra hardware, and almost nobody reads them. ## The HealthKit Error That Never Fires - HTML: https://aifitnessapi.com/blog/healthkit-error-that-never-fires - Markdown: https://aifitnessapi.com/blog/healthkit-error-that-never-fires.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 HealthKit defines 17 error cases. The authorization-denied one is documented for saving, not reading — which is why an empty read is so hard to debug. ## 58 HealthKit Types Apple Never Explains - HTML: https://aifitnessapi.com/blog/healthkit-58-silent-types - Markdown: https://aifitnessapi.com/blog/healthkit-58-silent-types.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 58 of HealthKit's 240 identifiers carry zero words of discussion prose, and the median across all 240 is 15 words. What to do when the docs say nothing. ## HealthKit: 127 of 240 Types Are iOS 8.0 - HTML: https://aifitnessapi.com/blog/healthkit-240-types-ios-8 - Markdown: https://aifitnessapi.com/blog/healthkit-240-types-ios-8.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 HealthKit has 240 type identifiers and 127 of them shipped in iOS 8.0. None is marked deprecated. The full version histogram, and what it costs you. ## Google Fit: The Signal Came in 2024 - HTML: https://aifitnessapi.com/blog/google-fit-timeline - Markdown: https://aifitnessapi.com/blog/google-fit-timeline.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 Google closed Fit API sign-ups on 2024-05-01 and documented support ends in 2026-12. Both confirmed. The first date was the one that mattered. ## Four Fitness APIs Are Free and Expensive - HTML: https://aifitnessapi.com/blog/free-fitness-apis-are-expensive - Markdown: https://aifitnessapi.com/blog/free-fitness-apis-are-expensive.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 12 of 24 products cost the developer nothing, and four of those are rated high engineering effort. The API price is the smallest term in the integration. ## Four Ways an API Says Contact Sales - HTML: https://aifitnessapi.com/blog/fitness-api-talk-to-sales - Markdown: https://aifitnessapi.com/blog/fitness-api-talk-to-sales.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 4 of 24 products list contact-sales, and their gate text describes four different waits. What to ask for, and what to have ready before the call. ## Integrate Fitness APIs in Risk Order - HTML: https://aifitnessapi.com/blog/fitness-api-integration-order - Markdown: https://aifitnessapi.com/blog/fitness-api-integration-order.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 Three directory columns decide your build order: approval gate, engineering effort, user-side cost. Start the clocks you cannot compress on day one. ## 12 of 24 Fitness APIs Have an Approval Gate - HTML: https://aifitnessapi.com/blog/fitness-api-approval-gates - Markdown: https://aifitnessapi.com/blog/fitness-api-approval-gates.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 Half the directory makes you get approved before production, and the gates are six different obstacles. Which ones start clocks you cannot compress. ## 6 Confirmed, 7 Reported: Grade Your Dates - HTML: https://aifitnessapi.com/blog/confirmed-vs-reported - Markdown: https://aifitnessapi.com/blog/confirmed-vs-reported.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 We track 13 dated ecosystem changes. Only 6 come from a primary source. A confirmed date is a plan; a reported one is a rumour with a number on it. ## One Field, Three Tries, Two Honest Nulls - HTML: https://aifitnessapi.com/blog/building-the-healthkit-dataset - Markdown: https://aifitnessapi.com/blog/building-the-healthkit-dataset.md - Published: 2026-09-01 - Last reviewed: 2026-09-01 Resolving which value enum decodes a HealthKit category type took three attempts. The first resolved 29 of 30 and was wrong in the worst way. ## The Health App That Never Touches HealthKit - HTML: https://aifitnessapi.com/blog/health-app-without-health-data - Markdown: https://aifitnessapi.com/blog/health-app-without-health-data.md - Published: 2026-08-31 - Last reviewed: 2026-08-31 Most health apps read data before they do anything. A whole category skips it — no OAuth, no entitlement, no PHI. Here's when that's the right call. ## Welcome to AIFitnessAPI - HTML: https://aifitnessapi.com/blog/welcome-to-aifitnessapi - Markdown: https://aifitnessapi.com/blog/welcome-to-aifitnessapi.md - Published: 2026-07-08 - Last reviewed: 2026-07-08 Why we're building a hub for the people shipping the next generation of health, wellness, and fitness products — and what you can expect to find here. ## How to Choose a Fitness API in 2026 - HTML: https://aifitnessapi.com/blog/how-to-choose-a-fitness-api - Markdown: https://aifitnessapi.com/blog/how-to-choose-a-fitness-api.md - Published: 2026-07-08 - Last reviewed: 2026-07-08 A practical framework for evaluating fitness and workout APIs: exercise data, motion tracking, AI coaching, pricing, and the questions that matter.