While you probably know whether a bad cold or that new barre class spurred your aching joints or muscles, you might be wondering how totally different things can provoke similar types of pain.

The answer, usually, is through inflammation.

“There’s a process of inflammation that occurs when the body has an infection, and some of the inflammatory mediators that we use to fight the infection cause fever and body aches,” says Erich Voigt, MD, an otolaryngologist at NYU Langone Health.

But a slew of other behaviors and conditions can amp up your body’s inflammatory responses—like repetitive motion and stress—triggering body aches in the process, he notes. So, why exactly do different parts of your body throb and twinge? Beyond getting older, here is a closer look at the most common reasons for your body aches, why your body responds with pain in the first place, and how to find relief.

Cold and flu season is in full swing

cold and flu body aches
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“The body aches related to an infection such as pharyngitis (sore throat

) or flu are related to the immune system’s response to the infection,” says Stephen Parodi, MD, infectious disease expert at Kaiser Permanente. “Our body releases certain chemicals, including ones called interferons, which help fight off the infection, but also cause body aches.” What’s more, your immune system is channeling most of your body’s energy into fighting off the infection, causing you to feel super tired.