Hardcore runners aren't letting this weather stop them from exercising.

Most runners have heard that you should do core exercises. However, new research finds that having a six-pack won't make you a better runner.

Before she became a physical therapist, Kayla Borders was a competitive runner and even though she worked her core, she had consistent lower back pain.

Kayla Borchers says, "It felt like just muscle tension and just a dull ache."

It's a common complaint among runners, but the true cause has been unclear. So, in a new study led by Ajit Chaudhari and his team at the Ohio State University Wexner Medical Center, researchers examined runners' muscle use during activity.

Using motion detection technology and force measuring floor plates, experts built simulations that show how every bone in the body moves, and show the pressure on every joint while running.

This allowed them to virtually manipulate the strength of each muscle.

Dr. Ajit Chaudhari says, "What if you turned off certain muscles, so they were weak, fatigued, not well conditioned, what does that change?”

Dr. Chaudhari adds, “What other muscles would have to take up the slack and what are the effects of that?”

What they found is that back pain is commonly caused by weak deep core muscles that are used to stabilize the body and are not to be confused with surface muscles like the abs that many runners typically focus on.

Dr. Chaudhari says, "If those deep core muscles are not contributing, then that's increasing, or likely to increase, the loads on your spine in a way that may lead to low back pain."

So, Dr. Chaudhari says skip the sit-ups and opt for exercises that force you to hold your body in place.

Dr. Chaudhari says, "Exercises that are really focused on stabilizing your core, especially on unstable surfaces, that's what's really going to make you a better runner."

READ MORE | Keep exercising, even when it's cold

Kayla now recommends these exercising tips to her patients and incorporates them into her own fitness routine. 

Now, she's not only pain free, but faster than ever.

Kayla says, "I am able to go out and run farther and stronger and faster than what I used to and I'm not running as much as I used to."

Experts say there is a lot of misinformation out there on the best way to strengthen your core, but that anything with a large range of motion is usually just working those beach muscles and won't strengthen the deep core.