Moreover, {HEAD ~ the “second leg}” corresponds to {TAIL ~ the standing leg} in the next single leg grounded period 
Moreover , { HEAD ~ the “ second leg } ” corresponds to { TAIL ~ the standing leg } in the next single leg grounded period
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH