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https://curvefit.app https://curvefit.app it's a weight-training app that helps you train along your "pareto frontier" of weight vs reps. The idea is to train

https://curvefit.app https://curvefit.app it's a weight-training app that helps you train along your "pareto frontier" of weight vs reps. The idea is to train at lower weight-higher rep, medium weight medium reps, and higher weight, lower reps for every movement. I tried to develop my own weight training program following bits and pieces of advice from bodybuilding forums and ended up injuring several tendons in my first year. So I did a bunch of research on tendon strengthening as well as what's most effective for hypertrophy (reps near failure) strength (reps near maximal load) and injury-prevention/frequency (not bringing yourself to failure too often) and designed an app to automatically prescribe and advance weights and reps based on your learned strength curve (Brzycki-like, with an added shape parameter) The app is designed to make use of the free Cloudflare tier, so I can support thousands of athletes for just the cost of the domain name. I'm primarily interested in understanding the "Fatigue curve" - right now I have some basic per-set fatigue modeling (basically a log-linear strength dropoff) but I think it could be much better characterized with more data. I could go on and on about the modeling but my intention is to keep it free (maybe add some non-intrusive ads on content pages if it ever starts costing me a few pennies a month) but my primary interest is to be able to do statistical analysis on the data.

Bishonen88 12d ago
Gave it a quick go as I'm looking to adopt some sort of fitness app. There's too much text/complexity for my taste. The website could use some images/simplification to get going and then have more details and whatnot later on. It seems that you let the LLM generate the content itself (em dashes, emojis) - Personally I'd be skeptical of a fitness app that has most of its content LLM'izied. On step 3 of the tutorial, it's not clear that you can scroll down and there's more there on a mac 16''. I was confused what to do. It didn't allow me to change to metric system either (which I later found in the user-settings). You can't 'esc' from the tutorial popup either.
- jerkstate 12d ago
  yeah, it's a difficult balance to explain why this app doesn't work like every other weightlifting app and not inundate people with too much information. It actually is pretty simple once you start using it. I'll look at the tutorial scrolling issue, and eventually rewrite the content. The tutorial can't be escaped because it requires a liability waiver checkbox at the end.
Akranazon 12d ago
Interesting, this reminds me of my workout planning tool, which I've been working on. https://grademyworkout.com/ https://grademyworkout.com/
- jerkstate 12d ago
  This is really awesome! I used to have an movement to tissue mapping in an earlier version of app but I opted to focus more on the weight-reps curve it because the tissue volume calculations added too much complexity to the interface, and it just encouraged me to do too many different movements. So exercise selection and tissue coverage is something I actually think about outside my app. I had coefficients mapping each exercise to its tissue impact but it was kind of arbitrary and unscientific - even between athletes you will have different techniques on the same movement that will impact tissues differently. I do think that workout design is a super important area and I hope you crack it, it was too hard for me to do a good job on.
teiferer 12d ago
> a bunch of research What exactly is your "research"? Is it reading more bodybuilder forums (bro science) or is it physiological studies (actual science)?
- lemming 12d ago
  Check here: https://curvefit.app/methodology https://curvefit.app/methodology
- jerkstate 12d ago
  physiological papers. My main interest is contributing to the research by developing a fatigue model. My hypothesis is that athlete recovery factors like accrued fatigue in-day and cross-day can be used to predict workout log outputs of total tonnage, combination of weight and rep count, and proximity to failure. Eventually I hope to be able to link these recovery factors directly to provide targeted advice about your overall program's effectiveness, deload planning, etc. in order to most efficiently achieve strength, endurance, and hypertrophy goals.
esperent 12d ago
It looks interesting but as someone else noted, it needs more images and animations, way less walls of text. There's a huge database of licensable animations that several apps I've seen use. E.g. take a look at the animations in Hevy. I forget the name of it now but you should be able to find it easily.
- jerkstate 12d ago
  yeah, point taken, I do need to rewrite the user-facing documentation to be more accessible (and less obviously LLM-assisted, heh - although I did review and edit all of it). Workout design (including teaching a user how to do an exercise) and logging are two legitimately different tasks in a workout app and I wanted to focus on being the best logger. Maybe this is paranoid but I felt that saying "here's how you do a workout" introduced a little more potential liability than punting to "if you don't know how to setup a workout and learn to do the movements, hire a personal trainer to help you figure out movements appropriate for your fitness level."
codeatlass 12d ago
hjh
maerF0x0 12d ago
Ok, presuming this is going to be a monetized thing aiming to compete in the market. (if not what follows should be ignored). What about your app is better than what already exists from https://macrofactor.com/workouts/ https://macrofactor.com/workouts/ , https://rpstrength.com/pages/hypertrophy-app https://rpstrength.com/pages/hypertrophy-app , and maybe https://biolayne.com/workout-builder/ https://biolayne.com/workout-builder/ ? All 3 incorporate some form of RIR progression, varying rep ranges, program builders, and (at least in RP) some form of feedback mechanism to tell how impactful the last training stimulus was on recovery. Not trying to bash it, but to either 1.) help you think through your offer or 2) help you realize there's already a lot in the market. If you're really just doing this for you, and your interests then glhf :)
- jerkstate 12d ago
  I don't intend to monetize, I only want to compete for data. I think it's an interesting field and I'd like to be able to contribute back to the science by using the data gathered. I think these workout apps try to be opinionated about what an effective program is, but they try harder to make money, so they generally bend over backwards to accommodate whatever program the paying customer wants to do. Mine is more opinionated. I think this is the best way to lift weights for a wide range of athletes who are interested in getting stronger and bigger with the least amount of wasted effort and lowest chance of injury, the simplest way to record it, and the best way to get a statistically defensible understanding of how your strength is changing over time. If you want to do something different, as you mention, the space is crowded with apps.
  - maerF0x0 12d ago
    Ok, so if I'm synthesizing your words correctly, other apps are "Bring your program, any program" and you're really leaning on "We'll tell you exactly what to do based on Pareto frontier modeling" ?
    - jerkstate 11d ago
      I'm not trying to say that other apps don't also provide great advice (especially RP, I love watching Dr Mike and have learned a ton from him), but I think that a lot of the flexibility in the programs in these apps are primarily for marketing purposes (like are you really gonna look like Black Adam after following the Black Adam program? unlikely..) My marketing is for a different niche - people who lift weights, see that they have variability set to set and day to day, and want a program that will help them quantify that variability and understand what it means. One thing that works really well in my program is detecting when you need a rest or deload, because the baseline comparison is rigorous and sensitive - if you have one bogey set, it might not mean much, but when you see that even your opening sets are at or below baseline after a stretch of workouts, that's a pretty good signal, and that's hard to get with most apps.
shuvrojit 5d ago
you need a more intuitive and easy to use interface, so people can get accustomed to your app in less than 2 minutes.

Bishonen88 12d ago

Gave it a quick go as I'm looking to adopt some sort of fitness app. There's too much text/complexity for my taste. The website could use some images/simplification to get going and then have more details and whatnot later on. It seems that you let the LLM generate the content itself (em dashes, emojis) - Personally I'd be skeptical of a fitness app that has most of its content LLM'izied. On step 3 of the tutorial, it's not clear that you can scroll down and there's more there on a mac 16''. I was confused what to do. It didn't allow me to change to metric system either (which I later found in the user-settings). You can't 'esc' from the tutorial popup either.

jerkstate 12d ago
yeah, it's a difficult balance to explain why this app doesn't work like every other weightlifting app and not inundate people with too much information. It actually is pretty simple once you start using it. I'll look at the tutorial scrolling issue, and eventually rewrite the content. The tutorial can't be escaped because it requires a liability waiver checkbox at the end.

Akranazon 12d ago

Interesting, this reminds me of my workout planning tool, which I've been working on. https://grademyworkout.com/ https://grademyworkout.com/

jerkstate 12d ago
This is really awesome! I used to have an movement to tissue mapping in an earlier version of app but I opted to focus more on the weight-reps curve it because the tissue volume calculations added too much complexity to the interface, and it just encouraged me to do too many different movements. So exercise selection and tissue coverage is something I actually think about outside my app. I had coefficients mapping each exercise to its tissue impact but it was kind of arbitrary and unscientific - even between athletes you will have different techniques on the same movement that will impact tissues differently. I do think that workout design is a super important area and I hope you crack it, it was too hard for me to do a good job on.

teiferer 12d ago

> a bunch of research What exactly is your "research"? Is it reading more bodybuilder forums (bro science) or is it physiological studies (actual science)?

lemming 12d ago
Check here: https://curvefit.app/methodology https://curvefit.app/methodology
jerkstate 12d ago
physiological papers. My main interest is contributing to the research by developing a fatigue model. My hypothesis is that athlete recovery factors like accrued fatigue in-day and cross-day can be used to predict workout log outputs of total tonnage, combination of weight and rep count, and proximity to failure. Eventually I hope to be able to link these recovery factors directly to provide targeted advice about your overall program's effectiveness, deload planning, etc. in order to most efficiently achieve strength, endurance, and hypertrophy goals.

esperent 12d ago

It looks interesting but as someone else noted, it needs more images and animations, way less walls of text. There's a huge database of licensable animations that several apps I've seen use. E.g. take a look at the animations in Hevy. I forget the name of it now but you should be able to find it easily.

jerkstate 12d ago
yeah, point taken, I do need to rewrite the user-facing documentation to be more accessible (and less obviously LLM-assisted, heh - although I did review and edit all of it). Workout design (including teaching a user how to do an exercise) and logging are two legitimately different tasks in a workout app and I wanted to focus on being the best logger. Maybe this is paranoid but I felt that saying "here's how you do a workout" introduced a little more potential liability than punting to "if you don't know how to setup a workout and learn to do the movements, hire a personal trainer to help you figure out movements appropriate for your fitness level."

codeatlass 12d ago

hjh

maerF0x0 12d ago

Ok, presuming this is going to be a monetized thing aiming to compete in the market. (if not what follows should be ignored). What about your app is better than what already exists from https://macrofactor.com/workouts/ https://macrofactor.com/workouts/ , https://rpstrength.com/pages/hypertrophy-app https://rpstrength.com/pages/hypertrophy-app , and maybe https://biolayne.com/workout-builder/ https://biolayne.com/workout-builder/ ? All 3 incorporate some form of RIR progression, varying rep ranges, program builders, and (at least in RP) some form of feedback mechanism to tell how impactful the last training stimulus was on recovery. Not trying to bash it, but to either 1.) help you think through your offer or 2) help you realize there's already a lot in the market. If you're really just doing this for you, and your interests then glhf :)

jerkstate 12d ago
I don't intend to monetize, I only want to compete for data. I think it's an interesting field and I'd like to be able to contribute back to the science by using the data gathered. I think these workout apps try to be opinionated about what an effective program is, but they try harder to make money, so they generally bend over backwards to accommodate whatever program the paying customer wants to do. Mine is more opinionated. I think this is the best way to lift weights for a wide range of athletes who are interested in getting stronger and bigger with the least amount of wasted effort and lowest chance of injury, the simplest way to record it, and the best way to get a statistically defensible understanding of how your strength is changing over time. If you want to do something different, as you mention, the space is crowded with apps.
- maerF0x0 12d ago
  Ok, so if I'm synthesizing your words correctly, other apps are "Bring your program, any program" and you're really leaning on "We'll tell you exactly what to do based on Pareto frontier modeling" ?
  - jerkstate 11d ago
    I'm not trying to say that other apps don't also provide great advice (especially RP, I love watching Dr Mike and have learned a ton from him), but I think that a lot of the flexibility in the programs in these apps are primarily for marketing purposes (like are you really gonna look like Black Adam after following the Black Adam program? unlikely..) My marketing is for a different niche - people who lift weights, see that they have variability set to set and day to day, and want a program that will help them quantify that variability and understand what it means. One thing that works really well in my program is detecting when you need a rest or deload, because the baseline comparison is rigorous and sensitive - if you have one bogey set, it might not mean much, but when you see that even your opening sets are at or below baseline after a stretch of workouts, that's a pretty good signal, and that's hard to get with most apps.

shuvrojit 5d ago

you need a more intuitive and easy to use interface, so people can get accustomed to your app in less than 2 minutes.