Tight hip flexors, especially a deep muscle called the psoas, can silently stress your spine. Here's why this muscle deserves ...

If you’re a slave to sit-ups and crunches but don’t feel like your core strength is improving, that's because you're not ...

The deep core is made up of a few muscles: the transverse abdominis, the deepest layer of your core attached ... If planks often leave your shoulders and back sore, try these three modifications ...