I would say that giving your body up for somebody else to manipulate (pardon the awkward expression, can't express this properly in English) is inherently submissive, or at least I strongly feel it to be so.
The problem I see is that we've (by "we" I mean both the patriarchal and feminist worldviews) started seeing all kinds of submission as something to be shunned. But not all kinds of submission are created equal. I think that it pretty obviously boils down to whether the act is voluntary. There are few experiences that can compete with willingly surrendering yourself to someone else, if you do it in love and trust, while the same (if viewed mechanistically) act is traumatizing if imposed upon us.
So, in terms of sex, I think that being a bottom in STRONGLY submissive (you're being penetrated, for God's sake), so men will tend to be more dominant in this sphere of life (also taking into account the vast discrepancy in size and strength), but:
a) it's not a bad thing,
b) it's not true 100% of the time (we can chose to be submissive and it's much more fun if we do from time to time),
c) it does not have to carry over to all the other aspects of life, as some more patriarchally-minded people would like it to.