My hoops collapse into four arcs/sections.   I run thick bungie cord through them which serves to add weight,

keep the sections together when collapsed, and make the hoops spring open when going from collapsed to expanded/whole. I also use spring clips to tightly hold the sections together so that no twisting occurs at the connector sites.  The tubing is flexible, so it doesn't hurt your neck or hipbones, yet is very sturdy and durable. 

Please see the picture below to get a better idea of the construction.