Not likely, the definition of addiction requires harm. Resistance training has profound wholistic benefits. It's possible that someone can neglect professional or personal relationships to the point of harm, but I don't think there's any reason to assume that's the case here.
My point is simply that just because you do something compulsively, does not make that thing an addiction. E.g. breathing is compulsive, but it's not an addiction.
See: people working out even when injured, people who exercise to be as thin as possible. People doing steroids and other drugs for performance or appearance. These are edge cases.
They exist, and endorphins are using the addiction biological framework.
Feel free to ignore this if it feels like nit-picking, but I'm particularly sensitive to "addiction" language.
We don't have a biological framework for addiction, we have a framework for building routines and healthy habits. The system is incredibly beneficial and we'd do ourselves a great disservice not utilizing that system to improve our health and lifestyle.
Again, I'm fairly sure we all understand what you're saying, but I find there's a great deal of cumulative power in the language/framing we use day-in and day-out and I believe my characterization isn't just optimistic, but more accurate.
No, we don't - we have a biological framework for creating motivation for certain behaviors. This is a well established concept. Motivated behaviors (or habits) are the framework, addiction is when we misuse that framework. We're not born with some defect that gives us negative evolutionary fitness. That makes no sense at all.
Addiction is feeling compelled to do something against your will. Consciously choosing despite circumstances is probably the furthest thing from addiction, and what the OP is referring to.
You can learn to enjoy pushing yourself in this way. To an outsider it can look like you're hooked on it, or that it is easy to make the choice every time.
The reason could be addiction.