If you’re lifting weights and have goals of getting stronger and building lean muscle mass, you want to ensure that the lifts you’re doing are provide enough stimulus to signal your muscles to grow back stronger.
How do you know if what you’re doing is providing enough stimulus? A simple way to tell is if your last few reps in a set slow down. Let’s say you’re doing incline dumbbell chest press for 3 sets of 10. Reps 8, 9, and 10 should move at a slower pace than reps 1-7. Meaning the difficulty got to the point where there’s a little struggle in those last reps. Those last 3 reps that moved more slowly are the reps that provided the stimulus the body needs to tell those muscles to grow back stronger.
So if you’re doing a lift and the weight is moving the same speed for every rep, you probably need to add additional weight or add more reps.