{HEAD ~ a first leg ZMP restraint condition} restricts {TAIL ~ the first leg ZMP position} to the first leg ZMP permissible area, 
restricts
{ HEAD ~ a first leg ZMP restraint condition } restricts { TAIL ~ the first leg ZMP position } to the first leg ZMP permissible area ,
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH