High intensity interval training (HIIT) involves brief bouts of high intensity exercise combined with lower intensity rest/recovery periods. For example, if an individual performed eight, 20 second “all out” sprints with 3-4 minutes of rest between sets in order to fully recover; this individual would be HIIT training. According to Powers and Howley (2015) when HIIT training is prescribed a number of variables must be considered which includes the type of exercise, the intensity and duration of both the high and low parts of an interval, the number of intervals done, and the intensity and duration of recovery between sets.
Compared to aerobic training which is done continuously (compared to intervals) at a low to moderate intensity; HIIT training is performed at near maximal heart rate (90% or greater) and can lead to large physiological changes in a relatively short period of time (Powers & Howley, 2015). For example, subjects who performed six separate HIIT sessions using a Wingate protocol were able to increase oxidative capacity, fat oxidation, glycogen levels, and exercise performance.
These findings were confirmed by Menz et al. (2015) who discovered that three weeks of HIIT training increased VO2 max by 3.5% compared to a control group. Additional research done Babraj (2009) found that two weeks of HIIT improved insulin sensitivity by 23% in young men.
The research is somewhat conflicted in determining if HIIT is more beneficial than steady state cardio for improving VO2 max and other physiological variables. A study conducted by Foster et al. (2015) found that 8 weeks of either HIIT or steady state aerobic exercise in sedentary college aged subjects led to increases in both VO2 max and mean power output. However; there were no significant differences between groups. The authors concluded that although HIIT is more time efficient and “enjoyable”, that it is not superior to conventional aerobic exercise training.
In conclusion, HIIT training may be a preferred method of increasing aerobic and anaerobic capabilities compared to traditional aerobic training when time is limited or when an individual perceives aerobic training as monotonous or unenjoyable.
Powers, S. K., & Howley, E. T. (2015). Exercise physiology: Theory and application to fitness and performance. McGraw-Hill.
Menz, V., Strobl, J., Faulhaber, M., Gatterer, H., & Burtscher, M. (2015). Effect of 3-week high-intensity interval training on VO2max, total haemoglobin mass, plasma and blood volume in well-trained athletes.European journal of applied physiology, 115(11), 2349-2356.
Babraj, J. A., Vollaard, N. B., Keast, C., Guppy, F. M., Cottrell, G., & Timmons, J. A. (2009). Extremely short duration high intensity interval training substantially improves insulin action in young healthy males. BMC endocrine disorders, 9(1), 3.
Foster, C., Farland, C. V., Guidotti, F., Harbin, M., Roberts, B., Schuette, J., ... & Porcari, J. P. (2015). The Effects of High Intensity Interval Training vs Steady State Training on Aerobic and Anaerobic Capacity. Journal of sports science & medicine, 14(4), 747.
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