When it comes to your wallet, size matters. Carrying a big, fat wad of cash in your pocket can mean major trouble for your back.
It’s the go-to spot for stowing your stuff, but sitting on a pile of cards, bills, and coins could put stress on your hip joint and lower back, says Stuart McGill, Ph.D., professor of spine biomechanics at the University of Waterloo.
The problem starts when your sciatic nerve, which is right behind your hip joint, gets pinched between the wallet and your hip itself, and can sometimes be diagnosed as sciatica. It causes pain that starts from your hip, but can send aches all the way down your leg.
In fact, when McGill conducts experiments to study back pain, he has people sit with small, wallet-sized objects under one butt cheek.
Stuffing a wallet in your back pocket also tilts your pelvis to one side, which puts more stress on your spine. Instead of sitting upright, you actually round your lower back, says McGill.
And the bigger your wallet, the more lopsided you’re forced to sit—and the achier you’ll end up, he says.
Switching your billfold to your front pocket won’t help much, as it can create a pinch between your thigh and torso—especially when in you’re in a car—that can also lead to discomfort. Your best bet: Take your wallet out of your pants when you sit down or drive, McGill says.
To minimize the stress on your body, McGill recommends a small wallet that holds only the essentials. Men’s Health associate fashion editor Dan Michel suggests Shinola’s leather cardholder.
Follow these tips and you'll be carrying a smart wallet without wrecking your back.
This article originally appeared in Men's Health US.