In {TAIL ~ this case}, {HEAD ~ the first single leg grounded period} corresponds to the current single leg grounded period 
In
In { TAIL ~ this case } , { HEAD ~ the first single leg grounded period } corresponds to the current single leg grounded period
REL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH