"Gluteal Muscle Activation During Common Therapeutic Exercises"-JOSPT 7-09
Be careful about choosing exercises for conditioning or rehab based on EMG studies. The authors conclude their study by dividing the exercises into "tiers" based on the level of muscle activation. It would not be surprising then that a sagittal plane exercise like a SLB & reach to the toes would be the nominated as best exercise for activating the glute max. The same for frontal plane side lying adduction & the glute medius.
Every muscle has a 3D function, and the most obvious one may not be the most important with regards to joint function. For instance, let's say our athlete has patellofemoral dysfunction with running. While the SLB c/ toe reach may indeed create MVIC >60, the exercise is not consistent with gait, and may not be useful in this case.