Translation
The wife does not have authority over [her] own body, rather the husband does; and likewise also, the husband does not have authority over [his] own body, but rather the wife does.
Paraphrase
The wife’s body is intended to satisfy her husband’s needs, therefore he can decide when to benefit from her body to meet his sexual needs (as long as he keeps other principles in mind, such as putting her needs before his own and not forcing his will on her without proper consideration). Likewise, the husband’s body is intended to satisfy his wife’s needs, therefore she can decide when to benefit from his body to meet her sexual needs (as long as she keeps other principles in mind, such as respecting her husband).
THIS IS NOT AS EASILY ABUSED AS IT MAY SEEM
It seems to us like this verse can be easily abused by the spouse that has the more insatiable sex drive. However, this statement does not give either spouse freedom to do whatever is desired at any time. There are limiting principles provided by the rest of Scripture; I strive to include a few of those in my paraphrase column. Although other spiritual and relational principles are not mentioned in this verse, all of Scripture works together to give us a full picture of what our life in Christ should look like. It is obvious that other principles the Bible teaches should be kept in mind, not just what is being said here. There should be balance. He is also making clear that the spiritual principle of selflessness should also be applied to the use of our bodies to meet our spouse’s sexual needs. That is the way it is supposed to work, and other considerations are supposed to be kept in mind.