I workout 2-3 days a week but I don't see a need for an app for that. I don't even record what I did because it's pretty much the same every week and I only need to increase the weight maybe every 2-3 months.

Just my 2 cents. This may not be the answer you want because the question seems to target people who used such apps before.

Maybe your app could target the trainers, especially the private ones who do not have the support from a facility? They definitely need something to record their clients' progress.

I'm going to guess that the drop-off is mostly because of the traditional pattern of fitness efforts, not so much the app. Most people who get very interested in fitness programs of any sort lose their interest in a couple of months.

But, and I think I may be in the minority here, I've never found value in fitness apps, so never used them beyond a trial period to see if they're useful to me. The reason is because they don't address any need that I have. I don't need them to motivate me (I'm already motivated), and the data is pretty and all, but in the end it doesn't inform my fitness efforts and so I begin to ignore it. That renders any app pointless.

i hate all apps related to fitness. i don't look at apps when i am working out. my gym switched to an app QR code key to enter the gym and I hate it. Before i didn't even take my phone with me. I look at screens all day at work, why do i need a screen in the gym or going for a run or walk or a bike ride? the answer is, i do not need a screen during that time. the one fitness app that i have loved was the couch to 5k running app because it just told you exactly what to do and didn't do anything else. So next run, it tells you exactly when to run, when to walk, when to start, when to stop. then it does that until you get done with the program. i stopped using the app because i switched from android to iphone and stopped running to ride my bike instead.

I go to gym regularly and have for decades so I have experience of all kinds of bookkeeping. During 2022-2024 I tried many different fitness apps (for Android) but they all failed to do the single thing I was interested in: log my workout. Instead ALL of the apps (I tried about a dozen before giving up) either wanted to sell me things, suggest me workouts, pretend that they know more about my body than I do (I'm over 50 and I know my body quite well by now) and basically just annoyed they hell out of me instead of being a working logbook.

All I want from a fitness app is to specify my A/B-day routines ONCE and then during gym I just wanna hit some button which means "I completed this set plz give me next one", but I also need a way to mark if I couldn't do a full set or if for one reason or another I had to do the set with lower weights (again, I'm over 50 and trust my body more than my routine). Also would be nice to have a comment box so I could write down the reason why I had to lower weights "shoulder was acting up again".

Anyway, it's 2025 now and I use a paper notebook and a pen and I don't even carry my phone to gym. Like another reply here mentioned I still have phone with me because the gym door only opens with an app (which is incredibly annoying). Paper notebook fulfulls all of my requirements above: I can mark sets with weight, I can cross over a number if I failed to complete a set, I can write down a lower number if my body can't handle the set weight that day, and I can always write down an explanation what was wrong.

Basically this is what I need (imaginary numbers for example):

  Day A
  Squat    200   200   200   200   180   
  Bench    100   100   100   -     -     (left shoulder)
  ...

  Day B
  Deadlift  50   100   150   200   250
  OHP       70    70    70    60   -     (left shoulder)
  ...

The downside of paper notebook is that I have to write down a number after every set, I would prefer for an app just to give me a button for "Done" and then something else for exceptions. The reason I need to OK every set is once you get into higher weights it becomes really hard to keep count as blood from your brain goes to muscles and you feel kinda lightheaded.

EDIT: When I come home from gym I now have to copy my numbers from paper to computer so I can do graphs and stats and that's a bit annoying. If I was using an app I would need to have a way to automatically submit the workout results to MY OWN SYSTEM/API - forcing me to subscribe and use someone elses database is totally out of the question.