Natural bodybuilder and power lifter Tuan Tran explains single leg squats: "The bases for this movement is to bring better understanding to the biomechanics for a proper squat. Also, to increase your ability to activate you legs with greater effect and build up stronger and my stable joints. 3 sets, 10 reps each leg."
In the second video Tuan Tran performs the "Rev. Glute/Hamstring Raise":