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.

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 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.

In previously trained adults, lifting weights with 0–1 reps left in reserve produces the same total amount of work over five weeks as lifting with 4–6 reps left in reserve, even though the latter feels harder.

Lifting lighter weights many times until you can't do more improves muscle endurance better than lifting heavy weights just a few times, especially for people who already work out.

For healthy adults, certain types of weight training—like lifting moderate weights quickly or doing Olympic lifts—can help improve how fast and powerful your muscles work, according to research reviews.