This year, Terrence Ogden, founder of Project Grit, completed a 75-mile ruck with 20 other participants, including several CrossFitters and was struck by how natural a fit rucking is for CrossFit athletes. Rucking builds endurance, strength, and mental toughness. CrossFit is a great way to prepare for rucking and rucking is a great addition to a CrossFit program.