Primarily means for the most part, so it means This type of physical fitness is mostly influenced by an individual's exercise habits.
Placebos are fake medications or treatments that can trick your brain into thinking it's better. Often someone will think they are very sick when they actually aren't, and that's dangerous for the mind so people will give them fake medications. Its of cures and things atet will help seasickness and motion sickness are placebos. You could have a moral dilemma about wether it's actually helping you or if it just feels like it does.
Withdrawal!
hope this helps!