Is it just me or is the double with the knee to the ground extremely rare in mma? As far as I can tell, the blast double seems to be the more popular variant - what are the reasons for this, risk of getting kneed in the face?
The knee to the ground isn't necessary in mma, because of the striking the stance is higher, where as in wrestling/pure grappling the stance is lower. So in order to take someone down in a grappling match you need to get lower, hence the knee to the ground. At least this is my understanding of it.
Normal doubles happen about 90% more than blast doubles. Not sure where you are observing your wrestling, but hitting a knee to a double is far and away the most utilized skill in wrestling no matter what the venue of competition is.
The blast double is not more popular than head outside in any venue. Blast doubles are getting more popular generally since the most popular wrestler in the country's signature move is a blast double, and people are seeing its effectiveness. I imagine it leaves you less likely to get guillotined as well, although I don't have any BJJ experience. Still, I would say 80%+ of doubles in MMA are head outside. As someone said before, peoples levels are generally much higher in MMA, so you don't need to lower your level as much. This makes snatches, or no knee contact, more common and practical.
You should learn the double against a wrestling stance and by touching your knee. Hitting a double, either normal or blast in MMA will feel easy as pie.
There are a few outliers, but outside of the upper 2 weights, most guys are shooting to a knee with their head outside on their doubles, not head up the middle with very little elevation change. Watch all of the fights, not just a few of the top tier elite wrestlers, and you see the double leg that gets used is a traditional wrestling double, not a blast double.
To succeed in the double you have to get your hips under the person, in MMA we stand more upright for effective striking therefore the level change typically puts you low enough to take the opponent off their feet. By not having to do a complete drop step the transition between grappling and striking is more smooth. My coach used to say, "it's not the speed of the techniques, but rather the time between them". In wrestling the stance is lower and the opponent is primed and ready for a shot. Dropping to the knee allows you to get under a lower opponent and enables you to pivot on the knee often called turning (or cutting) the corner. Additionally, counters such as sit throughs, sucker drags, dumps and re-shots are best executed from the knee(s). For me I always felt more comfortable with the blast double - head in the center and blast away. My shot was never super technical, but I was powerful and had decent timing so for me shooting a high double made more sense. Just before the 30 second mark is a double leg montage, most of them in MMA https://www.youtube.com/watch?v=YaIQ6_dDW5I
