PHILADELPHIA (WPVI) -- Shoshana shows us how to use some light weights and your legs to engage your core strength.

Core training has always been part of military PT and fitness testing. From crunches to sit-ups, flutter kicks, leg tucks and plank poses, the U.S. military uses many exercises to test core strength.

The core never gets enough credit for the work it does on the run. But without a stable center, you’d not only run with hunched-over posture, low back aches, or knee pain, but you’d also waste a ton ...

You’ll warm up with dynamic stretches meant to wake up your spinal mobility and activate your core. Then, you have three strength sets, with two exercises each, which you’ll perform back to back.