What a strength training app should do, and how it picks your next weight
Short answer
A good strength training app does three jobs. It logs every set (weight, reps and how hard it felt) in a few taps, it keeps the history of each exercise so you always know what to beat, and it suggests your next weight from that history instead of a guess. Around those, look for clear demos of each exercise, a way to plan your lifting days in the same week as your runs and rest, and logging that is free. Then use it for two or three weeks of the same workouts before you judge it.
What to look for, and why each part matters
Most apps can show a list of exercises. The difference shows up in week three, when you need to know what you lifted last time and whether to add weight.
| What to check | Why it matters | Quick test |
|---|---|---|
| Fast set logging | If logging a set is slow, you stop doing it mid-workout | Log three sets of one lift between real rest periods |
| History per exercise | Progress needs a last time to compare against | Open a lift you logged last week and find each set |
| A next-weight suggestion you can see the reason for | A number with no reason is still a guess | Check whether it holds when your last session was hard |
| Effort per set (RPE) | Reps alone hide whether a set was easy or a grind | Rate a set from 6 to 10 and see if the suggestion uses it |
| Exercise demos and written steps | Form comes before load | Look up a lift you have never done |
| Lifting in the same week as everything else | Hard leg days and hard runs should not land back to back | Plan a lift and a run in the same week |
| Free to log | You should know it fits before you pay | Check whether history or logging needs a subscription |
How an app can pick your next weight, worked through
The rule matters more than the screen. Here is the rule Kinetic's Next Set Guide uses, so you can check any app's suggestion against it, or do the math yourself on paper.
- Compare like with like. Only sessions of the same exercise count, and only when your heaviest set's reps were within two of today's target. At most the three newest such sessions are used. If the newest is more than 90 days old, the guide holds.
- Add weight only on clear evidence. Every session it looks at must have hit the target reps at an RPE of 6 or 7 (with three sessions, the newest and at least two of the three, with no missed targets and no RPE of 9 or 10).
- Hold when it is unclear. A last RPE of 8, a set with no RPE, mixed results or one hard session all mean the same weight again.
- Reduce only after two hard sessions. Both of the two newest sessions missed the target or felt like a 9 or 10.
- Size the step. An increase is 2.5 percent or one practical jump (5 lb or 2.5 kg), whichever is bigger. A reduction is 5 percent or one practical jump, whichever is bigger.
Worked example. Your target is 3 sets of 8 on the bench press. The last two sessions were both 60 kg for 8, 8, 8, rated RPE 7. Both qualify, so the guide adds weight. 2.5 percent of 60 kg is 1.5 kg, smaller than the 2.5 kg jump, so the next suggestion is 62.5 kg. In pounds, 135 lb times 2.5 percent is about 3.4 lb, under the 5 lb jump, so it suggests 140 lb.
Now say the next two sessions at 62.5 kg go 8, 7, 6 at RPE 9. Both missed the target, so the guide reduces. 5 percent of 62.5 kg is about 3.1 kg, bigger than 2.5 kg, so the suggestion drops by about 3 kg, to roughly 59.5 kg. One hard day on its own would only have meant a hold.
That is progressive overload done from your own numbers: small steps up when the evidence is clear, a hold when it is not.
A simple week to start with
The American College of Sports Medicine recommends that people new to lifting train 2 to 3 days a week with loads they can lift for about 8 to 12 reps, putting bigger, multi-joint lifts before smaller, single-joint ones. The CDC asks adults for muscle-strengthening work on at least 2 days a week that covers the legs, hips, back, abdomen, chest, shoulders and arms. Two alternating full-body workouts meet both.
| Workout A | Workout B |
|---|---|
| Squat, 3 sets of 8 to 10 | Romanian deadlift, 3 sets of 8 to 10 |
| Bench press, 3 sets of 8 to 10 | Overhead press, 3 sets of 8 to 10 |
| Bent-over row, 3 sets of 8 to 10 | Lat pulldown, 3 sets of 8 to 10 |
| Plank, 3 holds | Walking lunge, 3 sets of 10 a side |
Train A and B on two or three days with at least a day between them (for example A Monday, B Wednesday, A Friday, then B, A, B the next week). Keep the same exercises for several weeks, so every session has a last time to beat. If you also run or do HIIT, a workout planner app helps you keep the hard days apart.
Lifting with Kinetic
Kinetic is free to train on iPhone, Apple Watch and Android, and strength logging and progress history are free. The exercise picker opens on a body map: tap one of fifteen regions, from chest and upper back to glutes and calves, to see the exercises that mainly train it first, then the ones that also work it. Every exercise has written steps; the free plan includes two video demos per workout, and Pro adds every demo.
As you log, each set keeps its weight, reps and an optional RPE from 6 to 10, and that history feeds the Next Set Guide above. Before your first working set it suggests a warm-up and a starting weight. During the workout it can hold or lower the next set after a hard one, but never raises it mid-session. It is always advice: your plan or the number you type wins, and it changes a set only when you tap to apply it.
You can plan your lifting days alongside runs, HIIT and rest, and planned strength workouts run on Apple Watch too. Kinetic Pro, US$4.99 a month, adds the AI workout builder for workouts, templates and multi-week plans, every exercise video and history export. See what's free and what Pro adds.
Questions
Is there a free app for strength training?
Yes. Kinetic logs every set and keeps your history per exercise for free on iPhone, Apple Watch and Android, with written steps for every exercise and two video demos per workout. There is no account to create. Pro is optional.
How does an app know how much weight I should lift?
From your own history. A good app compares your recent sessions of the same lift, checks whether you hit your target reps and how hard the sets felt, and suggests a small increase, the same weight or a small decrease. For a first session it can only offer a conservative start, so begin light and let the history build.
How many days a week should a beginner lift?
Two to three days a week is the usual starting point, in line with the ACSM's advice for people new to lifting and the CDC's minimum of 2 days. Full-body sessions with a rest day between them are the simplest way to get there.
What is RPE, and do I need to log it?
RPE (rate of perceived exertion) rates how hard a set felt, from 6 (about four reps left) to 10 (nothing left). It is optional in Kinetic, but the Next Set Guide only adds weight when your recent sets were rated 6 or 7, so without it the guide holds.
Can I track strength workouts on my watch?
In Kinetic, planned strength workouts run on Apple Watch, so you can follow your sets without your phone in hand. Your sets join the same history as the ones you log on your phone.
Sources
Train with Kinetic
