High-intensity interval training
[1] HIIT involves exercises performed in repeated quick bursts at maximum or near maximal effort with periods of rest or low activity between bouts.
[1] Although there are varying forms of HIIT-style workouts which may involve exercises associated with both cardiovascular activity and also resistance training, HIIT's crucial features of maximal effort, duration, and short rest periods (thereby triggering the anaerobic pathways of energy production) materially differentiate it from being considered a form of cardiovascular exercise.
[5] Compared with longer sessions typical of other regimens, HIIT may not be as effective for treating hyperlipidemia and obesity, or improving muscle and bone mass.
[6] However, research has shown that HIIT regimens produced reductions in the fat mass of the whole-body in young women comparable to prolonged moderate-intensity continuous training (MICT).
The entire HIIT session may last between four and 30 minutes, meaning that it is considered to be an excellent way to maximize a workout limited by time constraints.
[15] The idea is to combine aerobic exercise with intense weight and resistance training to achieve a high level heart rate for an extended period of time, in order to maximize strength and endurance.
[16] A version of HIIT is based on a 1996 study[1] by Ritsumeikan University Professor Izumi Tabata (田畑泉) et al. initially involving Olympic speedskaters.
It included 3 minutes of warm-up, 10 repetitions of 60-second bursts at 60% peak power (80–95% of heart rate reserve) each followed by 60 seconds of recovery, and then a 5-minute cool-down.
[19] In 2011 Jorge Zuniga, assistant professor of exercise science at Creighton University, set out to determine how to fit the highest volume of work and oxygen consumption into the smallest amount of time.
Dr Niels Vollaard at the University of Stirling proposed that when high-intensity intervals are done at "all-out" intensities, associated health benefits plateau after performing 2 or 3 sprint repetitions.
[23] In a BBC Horizon program in February 2012, Jamie Timmons, professor of systems biology at the University of Loughborough, led Michael Mosley through this exercise bike regimen, each time using three sprints instead of two.
Its conclusion was "HIIT is the recommended routine" but "the magnitude of differences in various parameters between regimens was small; therefore, preference for either modality may be up to the individual".
[29] Improvement to cardiorespiratory fitness, as measured by VO2 max, of individuals with lifestyle-induced chronic cardiovascular or metabolic diseases (including high blood pressure, obesity, heart failure, coronary artery disease, or metabolic syndrome) who completed a HIIT exercise program can be nearly double that of individuals who completed a MICT exercise program (19.4% increase and 10.3% increase, respectively).
[34] A 2021 systematic review examined the effects of HIIT combined with resistance training in teens (ages 10–19), without providing a nutritional plan.
The study found that 8 to 12 weeks of HIIT combined with resistance training can substantially reduce waist size and body fat percentage.
[39] The reduction in fat mass and BMI at a young age create effects against obesity that are also tantamount in preventing other health issues such as diabetes, coronary heart disease, and cancer.
[37][38][39] The American College of Sports Medicine suggests consulting one's doctor before starting a HIIT regimen, particularly if there is a history of coronary heart disease.
[41] High-intensity exercise has the potential to elicit rapid increases in systemic blood pressure that may be transmitted to the brain, which could lead to hyper-perfusion injury in at-risk populations such as sedentary adults.
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.
Pulse wave velocity is used to monitor arterial stiffness; which increases with age and high blood pressure, leading to a higher probability of cardiovascular problems including hypertension or a stroke.
[citation needed] A 2020 study examined the impact of HIIT and moderate intensity continuous training (MICT) on overweight individuals by measuring the effect on cardiorespiratory fitness (CRF).
