What Brett Klika and Chris Jordan Actually Published in 2013
In May 2013, exercise physiologists Brett Klika and Chris Jordan published a paper in the American College of Sports Medicine Health and Fitness Journal describing a 12-exercise high-intensity circuit completable in seven minutes using only bodyweight and a chair. The paper made specific claims: that the protocol produced cardiovascular and metabolic adaptations comparable to prolonged endurance training when performed at genuine maximum effort. The New York Times covered it the same week and generated a fitness phenomenon that has outlasted most trends precisely because the underlying science is real.
The 12 exercises are sequenced by design: jumping jacks, wall sit, push-ups, abdominal crunch, step-up onto chair, squat, tricep dip, plank, high knees, lunge, push-up with rotation, side plank. The alternation between upper body, lower body, and core allows each muscle group partial recovery while cardiovascular load is maintained. The 30-second bouts at maximum effort followed by 10-second transitions produce the sustained high heart rate that drives adaptation.
The Tabata Research That Preceded It
Izumi Tabata's 1996 study with Japanese speed skaters demonstrated that eight rounds of 20 seconds of maximum effort cycling with 10 seconds of rest produced cardiovascular adaptations comparable to an hour of moderate-intensity cycling across six weeks. The mechanism was maximum oxygen uptake during high-intensity intervals, pushing the cardiovascular system to its ceiling and forcing adaptations to raise that ceiling. The Klika-Jordan protocol applies similar principles to a practical setting without equipment.
Jordan validated the approach across thousands of subjects and found that participants who treated each 30-second bout as genuinely maximal showed measurable VO2 max improvements within four weeks. Those who treated it as moderately hard showed negligible adaptation. The protocol is not a time-saving equivalent to real training for people who have time — it is a time-efficient option for people who genuinely do not, and its efficacy depends entirely on the intensity actually applied. The research supports it as equivalent to longer moderate-intensity work for cardiovascular fitness maintenance and improvement, not as equivalent for building muscle mass or improving body composition substantially.