HIIT

Interval exercise typically involves repeated bouts of relatively intense exercise interspersed by short periods of recovery, with a common scheme subdividing it into high-intensity interval training (near-maximal efforts) and sprint interval training (supramaximal efforts). ^[1] High-intensity interval training, in a variety of forms, is one of the most effective means of improving cardiorespiratory and metabolic function and, in turn, physical performance. ^[2]

Cellular stress and the resultant metabolic signals for mitochondrial biogenesis depend largely on exercise intensity, and both HIIT and continuous training induce increased aerobic capacity and mitochondrial content. ^[1] An optimal stimulus to elicit both maximal cardiovascular and peripheral adaptations is one where athletes reach at least 90% of their maximal oxygen uptake. ^[2]

In healthy young to middle-aged adults, both endurance training and HIIT elicit large improvements in VO2max, with the gains being greater following HIIT. ^[3] In patients with lifestyle-induced chronic diseases including coronary artery disease, heart failure, hypertension, metabolic syndrome and obesity, HIIT increased cardiorespiratory fitness (VO2peak) significantly more than moderate-intensity continuous training, by a mean difference of 3.03 mL/kg/min equivalent to 9.1%. ^[4] In a multi-centre randomized controlled trial in stable coronary artery disease, low-volume HIIT improved cardiorespiratory fitness more than moderate-intensity steady-state exercise and was a safe, well-tolerated intervention with only one serious adverse event possibly related to HIIT. ^[5] For body composition in overweight and obese adults, HIIT and moderate-intensity continuous training show similar effectiveness across body composition measures, but HIIT required about 40% less training time commitment. ^[6] HIIT has been recognized as a safe and effective alternative to moderate-intensity continuous training for older patients with

Exercise training is a clinically proven, cost-effective primary intervention that delays and in many cases prevents the health burdens associated with many chronic diseases, and low-volume HIT can stimulate physiological remodelling comparable to continuous training despite a substantially lower time commitment. ^[8] Because lack of time remains the most commonly cited barrier to regular exercise participation, the reduced time commitment of low-volume HIIT is of particular practical relevance. ^[8] Dynamic high-intensity interval training significantly lowers resting systolic and diastolic blood pressure, contributing to the prevention and treatment of hypertension. ^[9]