The adductors(groins) are an area that I often see neglected. That area of the body is often forgotten because people don't think it is crucial in performance. The mindset is that exercises such as the back squat are the only essential ones for performance. But the adductors are crucial in plenty of sports, especially in those containing change of direction movements such as soccer, basketball, football, handball, as well as in swimming(mostly in breaststroke).
Imagine a soccer player that wants to dribble their opponent and quickly has to change direction. The player has minimum time to produce an isometric force great enough to completely stop the energy of the eccentric contraction, loading his quads before reaccelerating concentrically and sprinting in the other direction. This action has to occur faster than their opponents if they want to run them off.
The athlete who can stop the eccentric load quicker will benefit more with an improved stretch reflex and more energy absorbed to use in the stretch-shortening cycle(SSC). Any delay between the eccentric contraction and concentric contraction will result in lost energy from the SSC. Not only are the adductors important for performance, but groin strains are common among both professional and recreational athletes.
It's often caused by straining the adductor muscle while kicking, so it's more common in the athlete's dominant leg. It can also be caused by turning quickly while running, skating, or jumping. Movements that require your muscle to both lengthen and contract at the same time usually cause a groin strain. This puts stress on your muscle and can lead it to overstretch or tear.
If your adductor muscles are too weak, not only will you lose energy put, you are more exposed to injury. Because if a muscle is put under more stress than it can handle and there's no way to get rid of that force, the tissue will tear.
This exercise is great for many reasons, but mostly to teach your neuromuscular components to transfer force. Start by lying on your back. Bring your knees up so that you have a 90-degree angle in both the hips and the knees. Put a ball of any kind between your knees and squeeze it as hard as you can. Start with 3 sets of 5x5 seconds hold. As you progress, you can increase any of the three variables(sets, reps, or time). Try it out and let me know what you think!