[2] Hummelt first came out onto the world stage in the 1967 Scotch Cup as the third for the German team skipped by David Lampl.

Hummelt then participated in the 1984 Air Canada Silver Broom as the alternate for the Austrian team, which finished the round robin without a win.

He became the president of the Austrian Curling Association at the time of its formation in 1980,[4] and held this post until his death.

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.