Partial reps for muscle growth

Question

I've been thinking about it for some time now and came to the conclusion that chin ups and pull ups are ego-lifting partial repetitions, even when the chin is over the bar or when the chest is over the bar it's not a full repetition because the back muscles are contracted at less than half of their full range of motion.

An actual fully contracted pull up would be with a bar under the belly button and elbows bent completely behind the back like in a dumbbell row. But people just do simple chin over the bar pull ups and get a good back workout out of it. Why doesn't this apply to other exercises, if pull ups build the back muscle with just some partial reps so why don't partial deadlifts or partial squats build muscle too?

Answer 1

Who says they don't?

Partial squats would be something like pin squats.

Partial deadlifts would be something like rack deadlifts.

The pull-ups you described sound something like a stomach pull-up or a sternum pull-up (or in the case of that video, a sternum chin up). Although, if you put your back to a wall and slid your arms down against it, I'd wager your hands would only reach to your shoulders (hence "full ROM").

Sometimes a lot of arguments regarding range of motion are semantic. For example, a pull-up by definition is done from full extension of the arms to where the bar touches your chest. If you manage to go further then that, then it is not a pull-up.

In the case of a competition lift, there is a set rule regarding what is considered a "rep". This is the case of a squat in which the crease of your hip must be below your knee-cap.

Generally speaking, full-range of motion is going to be more effective. The time-under-tension is longer. There's more muscle activation. Though, that doesn't mean partial reps don't have their place. You just need to utilize them for a reason as long as that reason isn't "Because I'm delusional about my physical ability."