Fédération mondiale de curling
Hummelt first joined the World Curling Federation as president of the Austrian Curling Association in 1982, which was known as the International Curling Federation (ICF) at the time. In 1988, he was elected the vice-president of the ICF, and was later elected the president of the ICF in 1990. The ICF was renamed as the World Curling Federation in 1991, and Hummelt served as president of the World Curling Federation for a ten-year tenure, which ended in 2000 when he retired. Following his retirement, Hummelt was named as the first Honorary President of the World Curling Federation in recognition of his contributions. Hummelt continued to serve as Austria's representative to the World Curling Federation until his death.