What part of your body do you bump into things most often?

Doubtful. My mom is 160cm tall, and she had shelves and cabinets installed throughout the apartment at her height, which is about waist-level for me. Considering how often she leaves doors open and my habit of looking down rather than forward, you can't compare yourself to me. Understand that besides height, the circumstances matter; even someone who is "a meter tall when jumping" might bump their head more often under the right conditions.