While on a run with Quinn, i started to think of all the ways physics related to our current actions. We traveled all around town, up and down hills, on different surfaces like grass and pavement, and leaves, and lucky for us friction was a factor. Because of friction on our shoes and on the ground, we didn't slip and fall while running. While we kept pushing our legs into the ground with a force to keep us going, the ground was pushing that same force back onto our legs so we didn't fall through the ground. All those surfaces were pushing back on our legs, even if the force we pushed with changed by increasing or decreasing.
When the daylight slowly came to fall to night, i used my flashlight to alert cars coming behind us that we were in the road. This light energy was traveling from my phone to the driver's eyes, so they luckily didn't hit us.
Also, as the hour slowly came to a close and fatigue was setting in, our muscles kept working hard to keep us running. For the last couple hundred yards, we both increased our velocity by accelerating and moving our legs faster and faster. We were using stored energy in our bodies to continue to run and get even faster.