User data collection is best done using a trusted forum to which only app users have access.  Like Stack Exchange, only private, it will provide a means of discussing use of the app, experiences applying its features, goals and strategies for achieving them, and can be a source of downloadable workout templates.  Rather than spying on users, collecting cell phone and other sensor data, acting ostensibly as their agent developing wonderful new technology, provide a means for users to share the information they want to share without fear of the usual "use this and you consent" webpage and app privacy policies which permit almost unlimited use of data collected in commerce.  Further, the user is engaged and knowingly contributing to the software's development.  Those that are so engaged form a core of supporters will benefit more, gaining more value from use of the software.

This is relevant to the design of a social media component into the exercise designer and tracker app so that users with a common constructive purpose can interact, share material, find support, etc.

The following is a comment I posted responding to this blog article:
How Social Media Shortens Your Life, 
URL: https://www.gurwinder.blog/p/how-social-...-your-life


Your discussion of the problems with the current status quo of social media platforms is excellent and detailed, and as a software engineer I've both experienced the feeling of futility or lack of purpose that their "engagement" tactics produce, and spent a lot of time thinking about designing better. There are technology redesign solutions to the profitable and powerful social media platform designs prevalent on the Internet today, just a there are cooking and dining solutions to the prevalence of fast food and other convenience addictions. Governance of the user is the main problem since their rewarded goal generally is to attract attention with the most relevant or compelling content posts, and this frequently involves bending or breaking the ordinary rules of constructive restraint in social interaction.
By facilitating communities with constructive purposes, rather than collecting as many users as possible, with any motives or intentions possible, and mixing them all together into the same inflammable pot, you get an inherent governance from the users themselves. They are also not structurally motivated to attract the greatest number of followers or greatest amount of attention, but can if they like, and can simply be ignored, unlike algorithm driven attention grabbing scrolling machines. Search-ability by the user is key to finding content and other members with similar interests, and should be possible with user selected or provided criteria. This capability is crippled in profit driven or social manipulation driven algorithm control of content and ad delivery. Restore agency to the user and you restore civilization.

My proof of simultaneity (which Einstein argued was unprovable):
Pick one point in time. Prove two things happened.

Things might be much simpler than the experts on top would like us to believe.

Social interaction is impossible without common purpose, and prevalent social media designs create an algorithm driven statistical interaction control machine taking purpose out of our control.  This is justified as the normal way to enhance the user experience with relevant content, membership connections, and advertising.  Conveniently for the social media company's power, there is no search capability implemented allowing the user to do this for themselves, nor are they allowed to review what the sentiment analysis and other algorithms are basing their decisions on.