The levels of testosterone, oddly, decrease. This runs counter to the idea that this would be a task that would be done by persons seeking a thrill. This may be due to the position that the soldiers hold: having excess testosterone in the body could lead to poor mechanics and performing the jump incorrectly. Also, post-jump epinephrine (or adrenaline) levels increase. This is due to the body needing this substance to stay alert during the jump.