Sprinting Is Easier

"Get Fit in One Fifth of The Time" - peer-reviewed science
"Sweat for Hours" - layperson anecdote; bros; inexperienced trainers

There are defined mechanisms in physiology and exercise science which don't rely on endlessly adding time; AND they do a better job at improving cardiac output, excess post-workout oxygen consumption, leanness and overall fitness metrics.

http://journals.plos.org/plosone/article…