Respiratory System
The endocrine system would be affected which, in turn, affects just about every other body system.
The respiratory system would be most affected by a lower than normal atmospheric pressure. Decreased atmospheric pressure can lead to reduced oxygen levels in the blood, which can impact lung function and overall respiratory health.
Humans are affected by the ozone layer. If there was no ozone, there would be no human life.
urinary system
thyroid
They wouldn't be people if they didn't have their "human system".
Two come to mind: the nervous system and the muscular system.
Immune system
The musculoskeletal system would be most affected by an acute ankle sprain, with potential impact on the ligaments, tendons, and muscles around the ankle joint. There may also be secondary effects on the nervous system due to pain and swelling in the region.
the circulatory system
boobs
if cellular respiration does not take place, even a normal human would die... athletes are human too... no?