If you run trails, you may want to carry even more stuff than the basics above. It’s easy to get lost, to stay out later than you intended, or to encounter bad weather or other minor emergencies.

If you’re running for under an hour, you probably don’t need to take a drink with you, as long as you’re hydrated beforehand, says McGregor.

According to Bauer, runners outside should drink six to eight ounces of fluids for every 15-20 minutes during a training run. "If you are running in hot and humid weather for more than six miles ...

You just run up until it’s time to walk down, then repeat. One hill, one workout. How many hill repeats should I do, and how long? Hills are a tool, not a workout.