Can the twisted pairs used for Ethernet be placed in coils?

Question

Computer networks

Good evening everyone! Tell me, is it permissible to wind the "extra" cable of the Gigabit Ethernet network, left as a reserve, into a coil and place it next to one of the network devices?
I know for sure that this is undesirable for coaxial cables. But what about twisted pairs? I don’t notice the effect, but the boss talks about reducing the speed in this case.