In a self defense situation, what kind of groin strikes would be the easiest for a beginner to execute under stress?
For example, In terms of kicks, should the toes be pointed up and the heels be used for contact? Or should the toes point forward while using the instep to make contact?
At close range, is it best to attack with the hands or the knees? And how? If the hands are concerned, should it be a punching motion or a squeezing motion?
Sorry for the comedic fluff in between but the question and possible scenarios just invoked some images...
Given you are an average bloke without much experience in martial arts, you should make contact with your shin or, for close range, your knee or thigh in an upward direction. Add some distraction in form of an upper-body movement as an opener to cover what you are about to do. Squeezing with your hand is a thing of manga and fantasy in any normal fighting situation (except sometimes on the ground, see comment section), and hitting with a punch requires a change of level and accuracy that cannot be expected.
Given your opponent is stupid enough to have an open stance with his front turned towards you, a kick to the groin is the easiest thing in the world: Raise your leg. From farther away, a soccer kick (high kick to and with the ball(s)) is good enough: It is fast, it can barely miss as the inner thighs lead the way, and everybody can reach this height regardless of flexibility. I would recommend hitting with the shin as the chance to miss or hurt yourself when hitting with the toes or instep is just too high. When in close range, you raise your knee as fast as possible, and that's about it. It does not matter much whether you connect with your actual knee or your thigh, your opponent will appear to grow some inches before they welcome the floor.
Trying to hit the groins with a teep kick or the heel from the front is not advisable for two reasons: Firstly, it needs a good amount of accuracy and technique to do so properly and secondly, the balls are hanging freely, so hurting them from the front does not make much sense and hitting them so that they get squeezed (which is the main reason for pain) is not a trivial thing to do from there. You can still connect in the general pubis area (this hurts women just as well, btw, just like the groin kicks described in the last paragraph) but if you have a good teep kick, you aim for the bladder as the pain there can be just as excruciating but it aligns better with the direction of force.
In any case, you should set it up with some jab or boo or whatever to set the attention to your upper body. That way, you make sure that they don't see it coming and instinctively defend against the hit.
The first reason is the same as in my last paragraph: The amount of accuracy and technique needed, as well as the direction of force, just make it lose viability. If anything, a hook punch from behind and below (connecting with your biceps) makes sense.
This leads us to the second reason: if you want to punch from the front, you would have to change levels by squatting or going on your knees (I advise against jumping into a full split) in order to have the correct direction of force and this leaves you vulnerable to knees from your opponent connecting directly with your head.
Because of the premise I made in the very first sentence (of the long answer): This depends on an open stance. As soon as your opponent has a lead leg and is tilted away, it becomes exponentially harder to hit the groins.
Also, depending on the legislature of the place you are in, it can cause legal problems as a groin kick is a pretty harsh escalation of violence with potentially life-long consequences (infertility).
I’ve only been kicked there once but it was the most painful experience I’ve ever had. In HS, grade 10, I picked a fight with a younger kid who evidently knew karate. He feinted a throw to my head, but I dropped backwards and left my legs spread open, just as he wanted. He kicked me in the base of my scrotum, bashing both of my testicles with expert precision, and the pain was immediate and so intense I nearly blacked out. I spent about 5 minutes on the sidewalk dry heaving, and in excruciating agony before I was able to let a couple classmates walk me to the school clinic. The nurse checked my privates, told me I didn’t have a rupture and gave me a Tylenol. Good to know I wasn’t damaged, but my testicles were swollen the rest of the day and the pain lingered for hours. Point of the story is: don’t underestimate a proper kick to the balls, it can be the worst 10 minutes of your life or extremely satisfying if you’re the one delivering the pain.
