In January 2019, Paul ran his fourth HURT 100 miler. We learn all about his wet and muddy adventure out in Hawaii, the difference between a "business mode" and "party mode" mindset in ultra endurance running, and the effects a low-carb diet has had on his running performance.

During the Q&A with Dr. Mark, we cover questions about staying in running shape when life gets too busy to rack up the miles, and how to know if you're burning fat when you run.