The hard cup jock serves the vital purpose of keeping your testicles freer of serious injuries when struck by a moving object, such as a ball, a stick, a knee, a foot, a puck, or you falling upon some object like a rail, a tree stump, a board etc. While most struck injuries may be minor in nature the pain never is. Every Dude instinctively knows this.
In earlier years these cups were not very well-shaped and never seemed to quite fit just right. So young men and boys abandoned using them, taking the risk of injury rather the discomfort of wearing one. Today there are lots more and better designed ones available that not only fit into a jock to strap on, but also in a pouched trunk. The pouched trunk design give a more “free floating fit. Yet with all the protection your will need to avoid injury.
The side blow to your groin area is perhaps the most difficult to have because the cup will shift more into a testicle more than if it is a direct frontal or bottom blow. The bottom blow often comes when Skate Boarders fall down on a rail or some similar object between their legs. In any event the other side of the cup will stop the force and spread it out more evenly across a wider area, than if your body part struck has to absorb the forces directly. A lot of newer engineering and testing has gone into these newer flex-cup designs. The newer all metal Titanium hard cup does a good job as well in distributing the forces around your pelvic bone area, rather than directly onto your penis, testicles.
In all cases it has to do with the fit. You should wear a swimmer or some other jock or pouched snug fitting brief first and then fit the hard cup over it, so that there is a space between the two types of supports. That way the forces wont have direct contact with your sensitive and fragile body parts.