Let's say a Eunuch wanted to maintain their muscle and strength at low T, with proper motivation I assume that could be done. Would they have to go above and beyond the normal prescribed amount of exercise for their muscle level, or just keep going with what they where doing before?

If you are just going for muscle tone, It's possible with low testosterone. However, if you are attempting to gain massive muscle, you will require a testosterone substitute.

Massive muscle defined as? Like would you be able to keep/gain enough for day to day heavy lifting or modest level athletics?

If you plan to be castrated, you should get your self into shape prior to castration. It'll be possible to maintain lean body and some muscles but

it will impossible to build big muscles or maintain them, because you won't be able to work hard enough and you'll get tire more quickly without TRT. You'll have to very careful about your diet.

I suppose my situation may be an endorsement of the notion of biological diversity. I did sometimes sustained strenuous work prior to my orchiectomy, and have continued to do sustained strenuous work. I have not noticed any significant diminution of strength or endurance.

However, I continued to do physical work in the same manner as before the orchiectomy, just as I had done sustained strenuous work from time to time prior to publerty, having started a business when I was ten, and that business required that I be able to do sustained strenuous work. My brain sends nerve impulses to my muscles, and, as before puberty, between puberty and orchiectomy, and since the orchiectomy, I command my muscles to act, and they do.

Yet the profound variations in human biology I observe to be normal give me reason to think that my situation may be different than what many other people encounter.

Nonetheless, using muscles ordinarily builds them.

In my experience, it was possible to maintain muscle for a while even after orchiectomy through rigorous training. But after some months, I had a noticeable decrease in max power, so I had to compensate lesser weight by more reps. Also, regardless of the amount of training, I lost some muscle hardness and definition. While on HRT (E plus low T), training felt easier and muscle hardness increased again.

When I was only on E for a while and neglecting training, muscle mass, strength and hardness dropped rapidly to levels barely above female average, while typical fat deposits appeared. When I again started with intensive training and added some T, I was able to regain some muscle mass, but not to the levels as before.

So, training certainly plays an important role, but sex steroids determine much more about quantity and quality of muscle mass. As a castrate, you will always have it much harder to achieve what you could have as intact male, and your limit will be much lower. This is especially true for the upper body, while leg power is less affected.

Okay, as a person who has both used steroids extensively as well as done chemical castration, I will say that testosterone has a fairly direct effect on strength, drive/aggression, and ability to build muscle. This is personal experience, but also well documented. Any guy or woman who takes exogenous testosterone over a six week cycle is going to get stronger and bigger than if they didn't take the testosterone. I can guarantee that every guy in the gym that you go "wow that guy is strong" or "that guy has big muscles" is taking steroids or at least has much higher testosterone levels.

Now the question though I think people are asking is that if they are not aiming to be a muscly athlete, can they maintain the strength/muscle they have pre-castration. As mentioned by a poster above, if you keep up the exact same exercise/physical work regime then your body should maintain it. However, if you're not forced to keep up the regime (i.e. you have a physical job that demands it) then in my experience your drive to exercise will diminish and you won't keep up the regime. You simply won't feel like "hey I want to go pound the weights today" and when you're at the gym you won't push that extra few reps and heavier exertions.

So I'm saying that while it is technically possible to maintain your shape, it will be psychologically much harder to do the work necessary.

However, in the end you just need to do the best you can. Even diminished exercise will be better than none.

Note though that some hormonal effects have nothing to do with exercise -- fat retention, fat distribution, and water retention are mostly hormonal. So you are very likely to get softer (possibly with breast development) even if you maintain your strength and underlying muscle. Having an estrogen-majority body just does that.

Very true, in every regard! Not just academically, but from first-hand experience also!