Yes youll slap your arm. I started off w/o one and a nice bruise came up. At first it was a slap here and a slap there, but after time, it became painfull. In the late summer and early fall when its hot especially. During the winter (cold) you may get by w/o one because of the long sleeves but also an arm guard will hold tight the sleeves.

everything else has been covered.

have fun!