Previously Christiansen was the Tactical Strength and Conditioning (TSAC) Program Manager at the National Strength and Conditioning Association (NSCA). Christiansen has worked with tactical athletes in the Special Operations Forces (SOF) community, including the 7th Special Forces Group, a Special Missions Unit in the greater D.C. area, as the TSAC Coordinator at the NSCA, as an Exercise Physiologist at the Army Physical Fitness Research Institute, and as a contractor in Baghdad, Iraq. Additionally, Christiansen has worked with sport athletes at Iowa State University, Illinois State University, and the Colorado Rockies Major League Baseball (MLB) organization. He is also a Certified Strength and Conditioning Specialist with Distinction (CSCS,*D), a Tactical Strength and Conditioning Facilitator with Distinction (TSAC-F,*D) and a Registered Strength and Conditioning Coach with Distinctions (RSCC*D).