Lower body strength/ stretch
"Meaningful growth requires challenge and stress."
Here is a quick 4 minutes video, explaining what makes muscles grow.
- by Sharon Horesh Bergquist
Here is another fantastic video from TED-Ed.
It explains how this "Hard wired physical response which travels throughtout your entire body" affects you. The impact on your body and your health. I knew it was powerfull but this demonstrates the full extent of its range.