When people lift weights until they're almost too tired to continue, especially with arm exercises, they get better at guessing how many more reps they could do. It's like training your body to feel its limits more accurately.

When people do more reps in a row during weight training, they become worse at guessing how many more reps they could do. This means longer sets make it harder to judge your own effort accurately.

When people lift lighter weights compared to their max, it's harder for them to accurately guess how many more reps they could do, making it less reliable than when lifting heavier weights.

Whether you're new to lifting weights or have been doing it for years, you're just as good at guessing how many more reps you can do before your muscles give out.

People who lift weights regularly are pretty good at guessing how many more reps they could do during bench press, usually only off by less than one rep, and they tend to guess a bit too low.

People aren't very good at guessing how close they are to muscle failure when doing many reps of weightlifting.