Willem has been a certified ChiRunning and ChiWalking instructor since 2015. After being unable to run for three years due to heel spur he discovered ChiRunning and became completely injury‑free. He organizes technique runs in Nijmegen and is fascinated by breathing techniques. Since 2023 he is a certified breath coach and treats conditions such as asthma, long COVID, sleep and fatigue complaints and improves sports performance with the BM|ND method and Oxygen Advantage exercises.