“High-intensity interval training (HIT) describes physical exercise that is characterized by brief, intermittent bursts of vigorous activity, interspersed by periods of rest or low-intensity exercise.”
There are probably more research studies currently in progress, involving various forms of high-intensity interval training (HIIT), than any other exercise-related topic being looked at today. A great deal of the HIIT research (also known as SIT, HIT, and HIIE) that has been published over the past decade by researchers like Martin Gibala, PhD, from McMaster University in Ontario, Canada, continue to show amazing results when compared to traditional exercise. Gibala and colleagues offer their definition of HIIT above.
In a study by Matsuo and colleagues (2014), a group of sedentary men performed 13 minutes of high intensity interval training five times a week for 8-weeks. The (HIIT) group burned more calories per minutes on average than men who performed 40 minutes of traditional steady state cardio. During the study the HIIT group saw a 12.5% gain in maximal oxygen consumption (VO2 max) using 27 less minutes of exercise. Tomoaki Matsuo, Ph.D, co-author of the study published in Medicine and Science in Sports and Exercise, suggest doing three-minute HIIT stages with two-minute active recovery stages repeated for three rounds.
Research presented in the Journal of Medicine and Science in Sports and Exercise shows that when test subjects exercised using high-intensity intervals, the total amount of calories their body expended during one-hour post workout was elevated up to 107 percent more than with low-intensity, short duration exercise, and 143 percent more than with low intensity, long duration exercise! That’s because interval exercise peaking at levels above a 70 percent maximum-intensity effort, speeds up metabolism for up to three hours after exercise – a benefit not found with low-intensity exercise.
A study published in the Journal of Applied Physiology (1990) by Makrides et al., showed that 12-weeks of high-intensity training produced greater increases in total work accomplished in 30 seconds in old (60-70 year old, 12.5%) than young (20-30 year old, 8%) test subjects.
One study in the journal Metabolism compared 20-weeks of aerobic training with only 15-weeks of high intensity interval training (HIIT) in which participants did 15 sprints for 30-seconds and lost nine times more body fat than the aerobic and control groups. They also lost 12 percent more visceral belly fat than the aerobic group.
A study in the International Journal of Obesity compared the effect of 15-weeks of HIIT with aerobic exercise. The HIIT group resulted in significant decreases in overall fat mass (3.3 pounds) while the aerobic exercise group had a fat gain of 1 pound on average. The HIIT group also had a significant 9.5 percent decrease in belly fat, while the aerobic group increased their belly fat by 10.5 percent by the end of the study. A 2012 study at Colorado State University found that test subjects who worked out on a stationary bike for less than 25 minutes, with just a few sprints mixed in, expended an additional 200 calories a day, due to excess-post oxygen consumption (EPOC) or commonly known as the after-burn effect.
A 2015 study published in the Journal of Strength and Conditioning Research by Falcone and colleagues, compared the energy expenditure of single exercise sessions using resistance, aerobic, and combined exercise involving the same duration. The test subjects were young, active men. All sessions were 30-minutes. The resistance training session used 75 percent of their 1-RM, the aerobic session, on a treadmill, used 70 percent maximum heart rate while a high-intensity interval session (HIIT) session was done on a hydraulic resistance system (HRS). The HRS workout used intervals of 20-seconds of maximum effort followed by 40-seconds of rest. The HIIT session using the HRS had the highest caloric expenditure of the three workouts. The data suggest that individuals can burn more calories performing HIIT with HRS than spending the same amount of time performing steady-state exercise.
A 2007 study published in the Journal of Applied Physiology looked at moderately active women who in their early twenties. The subjects were tested for power output on a stationary bike to determine what their VO2max was and then made to ride for 60-minutes at 60% of VO2max intensity. These tests were then repeated again at the end of the study to gauge the effectiveness of HIIT for this particular subject group. This particular training protocol showed some of the following results: a lower heart rate in the last 30 minutes of the 60-minute session, whole body fat oxidation increased significantly by 36 percent in only two-weeks using just 7 workout sessions.
A final study, published in the journal Cell Metabolism (2012), observed healthy but inactive people who exercised intensely. The research concluded even if the exercise was brief, it produced an immediate change in their DNA. “While the underlying genetic code in the muscle remains unchanged, exercise causes important structural and chemical changes to the DNA molecules within the muscles.”
As the HIIT research continues to demonstrate, it would be advantageous to supplement your current exercise routine with at least one HIIT session each week to maximize your training results. HIIT continues to show significant results when looking at total caloric expenditure, gains in VO2max, and elevated post oxygen consumption (EPOC).
Matsuo T, Saotome K, Seino S, Shimojo N, Matsushita A, Iemitsu M, Ohshima H, Tanaka K, Mukai C. (2014). Effects of a low-volume aerobic-type interval exercise on VO2max and cardiac mass. Sports Exerc. 46(1):42-50. doi:10.1249/MSS.0b013e3182a38da8
Falcone PH, Tai CY, Carson LR, Joy JM, Mosman MM, McCann TR, Crona KP, Kim MP, Moon JR (2015). Caloric expenditure of aerobic, resistance, or combined high-intensity interval training using a hydraulic resistance system in healthy men. Strength Cond Res. 29(3):779-85. doi: 10.1519/JSC.000000000000066
Makrides L. Heigenhauser GJ. Jones NL (1990). High-intensity endurance training in 20- to 30- and 60- to 70-yr-old healthy men. Journal of Applied Physiology. 69(5):1792-8.