You've been told to "add weight over time", and that's right. But on a Tuesday, with a barbell in front of you, it doesn't tell you what to do. Add weight when? How much? What if last week's reps felt awful? There is a simple rule that answers all three, and it's called double progression.

The idea: two numbers, one rule

Instead of a single target like "10 reps", you pick a rep range, for example 8 to 12. You choose a weight you can lift at least 8 times for every set. Then you work in two steps:

1. Add reps first. Keep the weight the same and try to do one more rep in at least one set each session.
2. Then add weight. Once every set reaches the top of the range (12), the weight goes up a little and the reps drop back toward the bottom of the range. Then you climb again.

That's it. The range tells you when you're ready, so you never have to guess. It also means a "bad" session isn't a failure: you just repeat the weight and try to match or beat your last numbers next time.

Try it: run your own progression

The tool below plays the role of your training log. Set what you did in each of three sets, press Log session, and it tells you what to do next time. Or use Fast-forward to watch a few weeks play out.

Why it works for beginners

Muscles and tendons adapt in small steps, and your nervous system is learning the movement at the same time. A rep range gives you a lot of room to improve on a single weight before you need more load. Research on resistance training suggests that muscle can grow across a wide range of weights and rep counts, as long as sets finish reasonably close to the point where you couldn't do more good-quality reps. So the exact range matters less than being consistent and finishing sets near the limit.

That's why this works with almost any lift, from a leg press to a dumbbell row. A range of 6 to 10 suits heavy lifts like squats and deadlifts. A range of 10 to 15 suits small, isolated moves like curls or lateral raises.

How hard should each set feel?

A handy check is reps in reserve: how many more good reps you could have done when you stopped. For most sets, aim to finish with about 1 to 3 reps left. Not so easy that you could do ten more, and not a grinding battle where your form falls apart. In your first weeks you may be unsure how close you are, and that's normal; it improves with practice. Stopping a bit early is a better mistake than rushing the weight up and losing control.

Rules of thumb for the jumps

• Form comes first. Only count a rep if it's controlled and you used the full movement you're learning. If form slips, the rep doesn't count.
• Small jumps beat big ones. Try the three jump sizes in the tool above. A big jump on a light lift drops your reps close to the bottom of the range, so progress feels slow. Smaller plates, or magnetic "micro" weights, make this easier. Lower body lifts can usually take bigger jumps than shoulder or arm exercises.
• Stuck for several sessions? It happens. Check your sleep and food first, then consider a lighter week, or try a smaller jump or a slightly different range.
• Don't chase it on every lift every week. Some sessions you'll only match your numbers. That still counts as a good day.

This is general training information, not medical advice. If something hurts in a sharp or worrying way, or you have a health condition or injury, check with a doctor or physiotherapist before you push the weight up.

What to take away

Pick a rep range. Add reps until every set reaches the top. Then add a small amount of weight and start the climb again. Write each session down, even on your phone's notes. A log is the cheapest piece of equipment you'll ever own, and it turns "I think I'm getting stronger" into something you can see.