Gym training log: what to write, and why

A gym training log doesn't need to be more than one line per exercise. But that line has to hold the right thing: not just what you lifted, but how hard it was. Here's what to write, three ways to keep the log depending on what kind of person you are, and how to read it so it actually tells you something.

Your memory lies about last time

Without a note, every session starts with a guess. Was it twelve kilos or fourteen? Did you get all ten reps, or was it eight in the last set? Your memory answers, but it answers with what feels likely, not with what happened. It's usually too kind to a good day and too harsh on a bad one.

A log takes the guesswork away. You look up last session, see that you managed all the reps with twelve kilos and had plenty left in the tank, and know it's time for fourteen. The decision takes three seconds instead of becoming a feeling. It's the same principle as in a gym workout schedule: increase one thing at a time, when you've earned it. The log is what shows you when that is.

Tracking what you actually do is among the better-supported tools for changing a habit. The research behind it, and why it's the tracking and not the streak of days that makes the difference, is in tracking your habits.

A number for how hard it was

Weight and reps tell you what you did. They don't tell you whether it was easy or right at your limit. Ten reps with forty kilos can be a warm-up one day and everything you've got another. That's why the line needs one more number.

The simplest is reps in reserve: how many more reps could you have done with good technique? A zero means you couldn't have done another one, a three means you had three left. In 2024, Bastos and colleagues reviewed 31 studies that used the scale and found that it works for choosing and adjusting how heavy you train. In 2025, Russo and colleagues showed in a systematic review that the estimate gets more accurate the closer the set is to your limit and the heavier the weight.

For your log, that means two things. Write the number after your last set, when you're closest to your limit and your estimate is most accurate. And expect the number to get better over time: in the first few weeks it's a rough estimate, and after a few months it's a tool.

So a line can look like this: Squats 40 kg, 3 × 10, 2 in reserve. That's all you need for your next session to start with a decision instead of a guess.

Three ways to keep it

No method is best for everyone. The best one is the one you're still actually using three months from now.

Paper, one line per exercise. For you if you want it to be fast and don't want your phone out at the gym. A small notebook in your gym bag, the date at the top and one line per exercise. It's the method that most often lasts, because it never needs charging or updating. First step: put a notebook and a pen in your gym bag tonight.

An app. For you if you want to see graphs and skip doing the math yourself. An app remembers last session for you, shows it when you open the exercise and charts how your weights develop. The downside is that it tempts you into more fields than you need. Use weight, reps and a number for how hard it was, and ignore the rest. First step: enter your last session in the app and check that you can find it again in ten seconds.

A detailed log. For you if you like data and want to understand why some weeks go better. Add sleep, energy before the session and a short comment if something stood out. After a few months you can see patterns no single line shows, such as sessions feeling heavier after short nights. It's the most demanding method, and it only works if you read the log, not just fill it in. First step: add a column for how you slept and start filling it in next session.

Read it once a week

A log you only write in is just an archive. Reading it is what turns it into a tool, and the best pace is once a week, not after every session. After a single session, you see a bad day. After a week, you see a direction.

Ask three questions when you read. Has any exercise been stuck for three weeks? Then it's time to switch to a different variation, or lower the weight and build back up. Has your number for how hard it was crept downward in several exercises at once? Then it may be your sleep, stress or too little rest, not your strength. And have you missed sessions? Count them, without judging. It's your pace that builds strength, not any single record.

If you want to raise the difficulty, the log is what shows you when that makes sense: when most exercises have three or more reps in reserve in the last set, week after week, your schedule is too easy.

When the log becomes a problem

A log should make training easier, not harder. If you notice you're avoiding the gym because you don't want to write down a worse number, or pushing through pain so the line looks good, the log has switched roles. Then it's better to write less for a while, or just check off that you showed up.

And if the numbers start being about punishing yourself, for what you've eaten or how you look, talk to someone you trust or to a doctor. The numbers are there to keep your training going, not to judge you.

A first step today: write down your last session as best you remember it, with a number for how hard it was.

If you want to add cardio to your week, the next part of the series is about walking as exercise.

This is the understanding and a way to start. Atlas is where it becomes a habit. You log every time you train and see your pace week by week, and with Rested? you rate how rested you woke up, so you can put your sleep next to your training and see the pattern after a few weeks. Try Atlas free for 7 days, and cancel whenever you want.