What is HIIT?
High intensity interval training (HIIT) is a cardio protocol that involves alternating bouts of extreme effort and oxygen demand with low intensity recover periods. It is considered one of the most effective methods of improving exercise performance and metabolic function.
What are the benefits?
HIIT helps to target fat loss instead of muscle loss (which is a downfall to regular endurance training). Unlike typical endurance training which has been shown to increase amino acid catabolism (6), research suggests HIIT induces an anabolic hormone response (5). This means typical endurance training increases the breakdown of proteins in the body. Thus, HIIT may be a useful tool in preserving lean muscle mass. It can increase aerobic exercise capacity, improve blood pressure, and improve insulin sensitivity (1,2). HIIT has also been shown to increase metabolic function (4), but not alter perceptions of hunger (3).
How do I do it?
There are different methods of completing the training including: sprinting, rowing, cycling, swimming, sled pushing, weight pulling, and battle ropes.
HIIT typically consists of repeated 10-30 second sprint interval sessions at maximal exertion, interspersed with recovery periods corresponding to the sprint duration. For example, 10 seconds all out should yield about 30-60 sec. rest while 30 seconds all out should yield about 2 to 4 min. rest. You should limit HIIT to 2-3 sessions a week, 20 minutes maximum (including rest). It would be most optimal to do HIIT training after any resistance training due to it’s fatiguing nature.
1) Weston, M., Taylor, K. L., Batterham, A. M., & Hopkins, W. G. (2014, April 18). Effects of Low-Volume High-Intensity Interval Training (HIT) on Fitness in Adults: A Meta-Analysis of Controlled and Non-Controlled Trials. Sports Medicine. Springer Nature. https://doi.org/10.1007/s40279-014-0180-z
2) Shepherd, S. O., Wilson, O. J., Taylor, A. S., Thøgersen-Ntoumani, C., Adlan, A. M., Wagenmakers, A. J. M., & Shaw, C. S. (2015, September 24). Low-Volume High-Intensity Interval Training in a Gym Setting Improves Cardio-Metabolic and Psychological Health. (S. E. Alway, Ed.), PLOS ONE. Public Library of Science (PLoS). https://doi.org/10.1371/journal.pone.0139056
3) Todd A. ASTORINO, Brendyn HEATH, Jason BANDONG, Gina M. ORDILLE, Ramon CONTRERAS, Matthew MONTELL, & Matthew M. SCHUBERT. (2017). Effect of periodized high intensity interval training (HIIT) on body composition and attitudes towards hunger in active men and women. The Journal of Sports Medicine and Physical Fitness. https://doi.org/10.23736/S0022-4707.17.07297-8
4) Grace, F., Herbert, P., Elliott, A. D., Richards, J., Beaumont, A., & Sculthorpe, N. F. (2017, May). High intensity interval training (HIIT) improves resting blood pressure, metabolic (MET) capacity and heart rate reserve without compromising cardiac function in sedentary aging men. Experimental Gerontology. Elsevier BV. https://doi.org/10.1016/j.exger.2017.05.010
5) Lee CL, Hsu MC, Astorino TA, Liu TW, Chang WD. Effectiveness of two weeks of high-intensity interval training on performance and hormone status in adolescent triathletes. J Sports Med Phys Fitness 2017;57:319-29. DOI: 10.23736/S0022-4707.16.06149-X
6) Lynis Dohm, G., Puente, F. R., Smith, C. P., & Edge, A. (1978, August). Changes in tissue protein levels as a result of endurance exercise. Life Sciences. Elsevier BV. https://doi.org/10.1016/0024-3205(78)90519-2