I enjoyed a short (6.33 km) but steep (600 m D+ and 600 m D-) trail run yesterday. It was a gorgeous day, but I focused more on running than filming. However I believe something essential of that trail experience has been preserved in the video.
A technical note: D refers to the French word dénivelé, which means altitude. With European trail running races you will often see a number followed by D+, which is short for denivélé positif, ie. elevation gain. D- would be denivélé negatif, ie. elevation loss. The measurements are usually in meters. For example, 600 m D+ would be equivalent of 1,969 ft. elevation gain.