If you thought shooting on high school football fields was bad, try a badly lit indoor high school gym. Here, athletes can be found sprinting across the field to shoot a basket, slamming a ball over a net, or even taking an opponent to the ground across a wrestling matt. Similar to shooting at nighttime football games, you will need to drastically increase ISO sensitivity in order to capture an action shot.
To begin, determine what shutter speed is necessary to stop the motion in the specific sport you are shooting. In general, volleyball will require the highest shutter speed. I would recommend trying to get it around nearly 1/800 due to the high speed at which players hit the ball and because players jump regularly. Basketball will normally be around the range of football at 1/640. In the case of wrestling, the competitors are not moving very fast. For this reason you can drop the shutter speed down to 1/400 and even lower at certain times.
From here, increase ISO sensitivity depending upon your shutter speed. As a guide, the wrestling picture below was at a shutter speed of 1/400, f/2.8 and ISO 1600. In this case, if I were to retake the photo, I would most likely slightly increase ISO sensitivity as I did have to increase the exposure while editing.