Exercise Advice — Cardiac Exercise Research Group (CERG), NTNU
by Cardiac Exercise Research Group · Norwegian University of Science and Technology (NTNU)
Exercise guidance from the Norwegian university lab that generated most of the 4x4 interval research. Includes a demonstration video, seven-week progressions, and a researcher-answered FAQ, so readers can run the 4x4 protocol at the correct heart-rate intensity. The 4x4 is the most-cited single HIIT session in the literature and is endlessly rewritten by longevity blogs and app funnels. This is the primary institutional page: the actual intensity anchor (90-95% HRmax), the recovery structure, and a researcher-written FAQ addressing safety and progression. Free, and it gives the learner a protocol they can execute correctly today.
More resources on HIIT Workouts
The One-Minute Workout: Science Shows a Way to Get Fit That's Smarter, Faster, Shorter
McMaster physiologist Martin Gibala explains the interval research his own lab produced, then gives graded protocols from ten-second sprints upward. Readers finish able to judge which interval format suits their time budget and why brief intense efforts work.
From Polarized to Individually Optimized Endurance Training... in 5 Steps
Recorded lecture for the ACSM Northland regional chapter in which exercise physiologist Stephen Seiler walks through five steps of endurance training design, covering intensity distribution, session duration, and how hard intervals should be dosed against a large low-intensity base.
Science and Application of High-Intensity Interval Training: Solutions to the Programming Puzzle
672-page reference from the researchers who defined HIIT programming. Part one breaks sessions into nine manipulable variables and physiological targets; part two applies them across twenty sports. Readers gain a systematic method for designing intervals rather than copying workouts.
Physiological adaptations to interval training and the role of exercise intensity
Peer-reviewed Journal of Physiology review comparing HIIT, sprint interval training and moderate continuous training. Readers come away able to explain how exercise intensity drives mitochondrial biogenesis and VO2max gains, and why low-volume protocols match far larger training volumes. This is the Source Truth behind nearly every popular HIIT claim. It separates HIIT from SIT from MICT with actual definitions, then explains the intensity-dependent signalling that causes adaptation. It also corrects the common overclaim by showing where work-matched comparisons do and do not favour intervals.