PHOENIX - Do you know what's on the gym equipment you may use every day? 

Microbiologists at the University of Arizona have been running tests on gym equipment for years and found germ hotspots that could make you sick if you're not careful. The U of A study showed 28% of all gym surfaces were contaminated, some at extremely high levels.

Gym bag

The inside of your gym bag could be teeming with bacteria from those sweaty gym clothes and shoes. Gym bags are also rarely cleaned, leading to a hotspot for germs. U of A researchers found Staph, salmonella and a kind of bacteria that can cause eye infections in the gym bags they tested. 

Yoga mats

The mats researchers tested were the communal ones at the gym. Some of those hadn't been cleaned very well, if at all. 

Tests found cold and flu bugs on those mats, along with athlete's foot.

Gym shower

The thing you use to clean yourself could be the dirtiest thing in the gym.

Tests found warts, ringworm, athlete's foot and more in gym showers. They're hot and humid, leading to a perfect environment for germs to grow.

“You never know who’s been in the shower before you at the gym," Jessica Rigler with the Arizona Department of Health Services said. "So if you want to make sure you’re not picking up someone’s foot fungus or any other germs they’ve left behind, it’s really important to wear your shower shoes."

What can you do?

Experts say the most obvious things to do are also the best. Wash your hands often and wipe down the equipment before and after you use it. Keep your hands away from your face and mouth to avoid transmitting whatever may be on them. And when it comes to the shower, always wear shower shoes or flip flops to avoid contact with the shower floor. 

Wash your clothes in hot water, not cold, to make sure and kill any germs on them. And take time to wipe out your gym bag.

But experts say not to be fooled by the sanitizing spray gyms usually keep on hand. Even alcohol-based sanitizers don't kill everything.

"There are things like Norovirus that those sprays are not effective against," Rigler said. "There are some germs that are just a little bit more hearty and they can't be killed with something with an alcohol base."