The adductors work to both flex and extend the hip when sprinting and also play a major role in change of direction and lateral movement during sports. Because of this poor tissue quality or mobility of the adductors can play a role in groin strains.
A good place to start when stretching your adductors is the kneeling adductor dip.
Set up with a straight line knee to your heel, keep your ribs down and hips forward, and dip your lead knee out. If you have trouble staying in a good position with your spine and hips you can also use a light dumbbell or kettlebell in a goblet hold as a counterbalance.