Surfing is a hell of a lot of fun, but if you’re looking to compete at a professional level it can be hell on your body. Few sports tax the sense of balance quite like it, and pro surfers have to do some fairly unusual exercises to stay in top form. Recently ESPN checked in with Paige Alms, the Canadian-born self-taught female surfer who just brought home her second consecutive win at the Pe’ahi Challenge in Hawaii.

Pro surfing requires incredible body control, and you can’t always be out on the water. So surfers develop inside techniques to train the important core muscles and reflexes. Alms met with a writer to show off the one methodology that she claims to hate the most but delivers insane results.

It starts with Alms standing on top of a balance ball. This in itself is a difficult task that you need to work up to, but then she ramps it up even farther. A partner stands on the floor in front of her and throws a weighted ball at her, first in a predictable pattern and then more erratically. It not only tests core strength and balance but split-second decision making that surfers need to challenge big waves.

Read more at ESPNW.