Apple: Health Privacy Overview (PDF)
Spotify is now working on Apple Health integration in their app to improve playlist quality. Spotify's approach is find songs that motivate users and improve their fitness results.
Using workout and health data might help improving communication with users and adjust features if app could affect user's workout performance or health in general (like, sleep, heart rate and so on).
Apple published new report that focuses on role of iOS and watchOS ecosystem in helping users accessing their health information.
Report focuses on role of iPhone and Apple Watch in gathering and accessing health information. Report also highlights APIs available for third-party developers and opportunities to participate in health data exchange.
All health related applications and APIs are built with privacy-first principle and user is in full control on who has access to data.
Apple Newsroom: How Apple is empowering people with their health information
Report: Empowering people to live a healthier day (PDF)