How it works
How GYMKC sets your weight
Log a set and the weight and reps for your next set are recalculated on the spot. It changes during your workout, not after it ends. The engine inside the app does that calculation, and it works the same without an internet connection. The AI's job is to explain why.
1. One set gives you an estimated 1RM
It estimates from three things: the weight, the reps, and your reps in reserve (how many more reps you could have done). That's the most weight you could lift once for that exercise, and it's the starting point for setting your next set.
A single set that jumps way up isn't used right away; your next set has to confirm it. When reps plus reps in reserve come to 11 or more, the estimate gets shakier, so it's lowered by 2%.
2. The target is reps in reserve, not failure
Every set has a target reps in reserve. If you're new, the lowest target is 2 reps. Muscles grow without pushing to failure. As you get more experienced, the target comes down little by little.
Being a little off your target reps doesn't change the weight. This range is called the deadband: 2 reps if you're new, 1.5 reps if you're experienced. When the weight is adjusted during a workout, it never changes by more than 5% at a time.
3. Reps go up first, then the weight goes up one step
Each exercise has a target rep range. For example, with 8 to 12 reps, reps go up until you hit 12, then the weight goes up one step. The equipment sets the size of a step: 2.5kg (5 lb) for a barbell, 5kg (10 lb) for a machine, and for dumbbells, the gap between the dumbbells you own.
- If one equipment step is more than 10% of your current weight, reps go up first instead of the weight. Adding 2.5kg to an empty 20kg bar is a 12.5% jump, which is too steep.
- If you beat your target by 2 or more reps on every set, the weight goes up right away, even if your last set was hard. That's a clear sign the weight is too light.
- For bodyweight exercises, once you reach the top of the rep range, the app adds 2.5kg (5 lb) of extra weight at a time.
- When you reach the heaviest step your equipment has, the app adds a set or widens the rep range instead.
4. Your last set sets your rest
Rest time isn't fixed. If your last set was harder than the target, it gets longer, and if it was easier, it gets shorter. While you rest, the weight and reps for your next set show on screen.
Extra reps you do after an unusually long rest count as a benefit of the rest, not as strength. Those extra reps aren't used to set your next weight.
5. Plateaus and deloads
For the same exercise, if your best estimated 1RM over your last 3 workouts has barely gone up, your average reps per set haven't gone up either, and you pushed hard enough at least once, it counts as a plateau. Then instead of telling you to add more weight, the app suggests a variation or a different way to train it.
In a deload week, only the number of sets is cut in half. The weight and reps stay the same, so the logs from your light week don't blur your next prescription. If you're new, there's no scheduled deload week. One is suggested only when your weekly check-in on sleep, motivation, and pain shows a high level of fatigue.
6. Safety rules come first
- If you're under 19, the weight cap drops to 85%, the lowest target reps in reserve is 2 reps, and adjustments during a workout are capped at 5%.
- If you're 60 or older, intensity stays the same, but deloads come a week earlier and the app leaves more room when adding sets.
- In pregnancy and postpartum modes, the app avoids sets close to failure and screens exercises and positions separately.
- 97.5% of your estimated 1RM is the absolute cap. Experience and age caps apply on top of it, so in practice it's lower: 90% is applied if you're new, and 85% if you're under 19.
- A set you stopped on purpose, as planned, isn't read as a drop in strength. That keeps the app from wrongly cutting your workout short on a day you feel good.
7. It checks left-right balance too
For exercises that work one side at a time, the app asks after your last set which side was harder. As signals build up, it adds a check set that measures each side separately. When the difference holds, it lets you know. It doesn't lower your weight for you.
8. Every value has a recorded source
For values like when to add a set or how much to cut back after a break, we record the evidence. We look in peer-reviewed papers and expert knowledge and record it for each item. When the evidence is weak, we record it as weak, and when a paper disagrees with our call, we record that too and review it again.
This page explains how the calculation works and does not replace medical advice. Everything you do yourself is free, and what your trainer does for you is the Pro plan. Details are in Pricing.