Invited Session at ECSS Vienna 2016 "HIIT training - Mechanisms and applicability" HIIT Training - Mechanisms of Adaptation. Professor Martin Gibala. McMaster University.
Interval exercise refers to alternating periods of more intense effort with a period of less intense action, or complete rest, within a single training session. Owing to the wide variety of terms used to describe this basic type of exercise, a classification scheme delineates "high-intensity interval training" (HIIT) from "sprint interval training" (SIT).
HIIT generally refers to submaximal exercise protocols in which the workload elicits a relative intensity corresponding to about 80% of peak heart rate. SIT describes protocols where the intensity corresponds to 100% of the workload that produces maximal oxygen uptake.
Numerous studies have examined physiological adaptations to HIIT and traditional Moderate-Intensity Continuous Training (MICT), matched for total work or energy expenditure. Several recent systematic reviews and meta-analyses have concluded that HIIT elicits superior physiological adaptations in average healthy individuals and people with lifestyle-induced cardiometabolic diseases.
Over the last decade, research has shed new light on the potency of low-volume interval training, which involves a relatively small amount of exercise, to elicit physiological adaptations comparable to MICT in a time-efficient manner. Studies that have directly compared MICT to low-volume HIIT or SIT protocols have reported similar improvements in markers of aerobic energy metabolism and clinical indices of health status, despite large differences in total exercise and training time commitment.
Recent evidence supports the general contention that exercise intensity is more important than duration for exercise training-induced increases in cardiorespiratory fitness.
