Yesterday I worked on an app to keep track of my gym progress. I've done it for a couple of years in my notebook, developing a personal syntax along the way.
The first logs are mostly digits + text
Pretty soon progress slopes begin appearing, but these are for stoking the ego. They don't register well the progression, you need to register both repetitions and total weight carried.
More slopes
The gym is about progressive resistance training. When you start going to the gym you will gain muscle, no matter what diet and what training method you use. This is because your body has an introductory genetic potential, to call it someway, and our current life is so sedentary that any minimum amount of strength training will yield good results.
But, after the beginner gains comes a tough slope which is training your body to become stronger, and this is done through progressive increasing of weight/resistance in your workouts.
Gym trackers focus on pampering the ego. The most important task is: how much should I lift in the following exercise, and how do register it in the most simple way possible.
Say you want to register you lifted a 120 pound bar for 12 repetitions. A well designed app will be able to register that in seven taps: "1•2•0•↵1•2↵". I'd like to resolve that in a single press + drag + release. I had already programmed a widget for this.
For the day I was happy to view my progress in my homegrown syntax, but in pixels:
I shall improve it in the upcoming weeks.