High-intensity interval training (HIIT), also called high-intensity intermittent exercise (HIIE) or sprint interval training (SIT), is a form of interval training, a cardiovascular exercise strategy alternating short periods of intense anaerobic exercise with less-intense recovery periods, until too exhausted to continue.
Though there is no universal HIIT session duration, these intense workouts typically last under 30 minutes, with times varying based on a participant's current fitness level. The intensity of HIIT also depends on the duration of the session.
HIIT regimens produced significant reductions in the fat mass of the whole body. Some researchers also note that HIIT requires "An extremely high level of subject motivation" and question whether the general population could safely or practically tolerate the extreme nature of the exercise regimen.
Effects of HIIT:
Cardiovascular Effects
A 2015 study found that HIIT training and traditional endurance training both lead to significantly improved cardiovascular fitness in healthy adults ages 18–45 but greater improvements in VO2 max were seen in those participating in the HIIT exercise regimen.
HIIT regimens of one month or longer effectively improve cardiovascular fitness in adolescents and lead to moderate improvements in body composition.
In people with coronary artery disease found that HIIT leads to greater improvements in VO2 max.
HIIT (defined as four intervals of four minutes at 85–95% of max heart rate with three-minute intervals at 60–70% of max heart rate) is more effective than moderate-intensity continuous training at improving blood vessel function and markers of blood vessel health.
Metabolic Effects
HIIT significantly lowers insulin resistance compared to continuous training or control conditions and leads to modestly decreased fasting blood glucose levels and increased weight loss compared to those who do not undergo a physical activity intervention.
HIIT is also more effective than moderate-intensity continuous training at fasting insulin levels.
Body Fat
A 2007 study examined HIIT's physiological effects on fat oxidation in moderately active women. The participants in the study performed HIIT (defined as ten sets of 4-minute cycling bursts at an intensity of 90% VO2max separated by 2 minutes of rest) every other day over a 2-week period. The study found that seven sessions of HIIT over a 2-week period improved whole-body fat oxidation and the capacity for skeletal muscle to oxidize fat in moderately active women.
- A 2010 systematic review of HIIT summarized the results of HIIT on fat loss and stated that HIIT can result in modest reductions of subcutaneous fat in young and healthy individuals, but greater reductions for overweight individuals.
- A 2018 meta-analysis examining 39 studies found HIIT, particularly running, to be a time-efficient strategy in decreasing abdominal and visceral fat-mass deposits.
Brain-Power
HIIT is beneficial to cognitive control and working memory capacity when compared against "A blend of board games, computer games, and trivia quizzes" and that this effect is mediated by the BDNF polymorphism.
A 2017 study examining the effect of HIIT on cognitive performance among a group of children concluded that the study "Suggests a promising alternative to enhance cognition, via short and potent exercise regimens". A meta-analysis by the same group showed that HIIT can elicit short term brain improvements similar to those usually observed with aerobic exercise.
The Basis of HIIT:
HIIT exercise sessions generally consist of a warm-up period followed by repetitions of high-intensity exercises separated by medium intensity exercises for active recovery, then a cool-down period.
The high-intensity exercise should be done at near maximum intensity. The medium exercise should be around 50% intensity (Though this can vary depending on the workout).
The specific exercises performed during the high-intensity portions vary.
Most of the research on HIIT has been done using a cycling ergometer, but other exercises like a rowing ergometer, running, stair climbing and uphill walking can also be effective.
But the best part about HIIT is that there is no special formula to HIIT.
Depending on one's level of cardiovascular development, the moderate-level intensity can be as slow as walking.
A common formula involves a 2:1 ratio of work to recovery periods, for example, 30–40 seconds of hard sprinting alternated with 15–20 seconds of jogging or walking, repeated to failure. The entire HIIT session may last between four and thirty minutes, meaning that it is considered to be an excellent way to maximize a workout that is limited by time constraints.
HIIT is a highly modifiable and personalizable workout format. To get started on some HIIT workout checkout: Torch Calories at Home With Any of These 30-Minute HIIT Workouts on YouTube or 13 Best HIIT Workouts to Burn Fat and Build Muscle Fast
Written By - Joshua
Edited By - Dana Asnan
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