How many times do we have to learn this? While "at rest" is a meaningful thing for a biological system to be in, it pretty much never equates to "no activity/changes", if ever. Everything in your body is always up to something; you can't press pause on chemistry. If nothing appears to be happening, that just means that the processes that do X and the processes that do opposite-of-X are currently in balance or homeostasis, not that they are not happening at all.

Another example: Many people have the mental model of fat cells as mostly sitting there doing nothing, grabbing energy when in excess and only letting out energy when needed. Radio-tagged water studies have shown that in fact they are always taking in energy and always releasing energy (I'm glossing over the exact forms of "energy" since they don't matter to my point here), and what changes is not whether they are sitting there idle, but the difference in intake vs. outflow rates. They are not passive bags, but things constantly in motion.

It still boggles my mind how many stories we get coming out like this, amazed that yet another process is never really "stopped". The amazing thing is when processes really do stop. (I can think of a few cases where this might happen, like when those anti-freeze blood frogs freeze, but I wouldn't care to bet that there isn't still some processes going on anyhow...)