There is various science around from multiple sources that suggest that HIIT High Intensity Interval Training or SHIT Super High Intensity Training puts the bod

There is various science around from multiple sources that suggest that HIIT High Intensity Interval Training or SHIT Super High Intensity Training puts the body in a different mode for some time afterwards. When the heart is stimulated to between 80 and 95% capacity (depending on source of information) this then prompts physiological changes that last long past the exercise event. CSIRO in Australia has been researching this for many years and is the premium (though still slightly woeful) scientific body in Australia. Not many real hills where I live, but there is one nearby and you often see people sprinting up it (sometimes backwards) and walking down, multiple times. One good plain language summary (not from CSIRO) is: "The “LifeSprints” study by Boucher in 2011 suggests that in the lower intensity steady state cardio trials, not enough levels of epinephrine (adrenaline) were present to stimulate fat breakdown in the muscle cells. During and after higher intensity exercise epinephrine and norepinephrine floats around in the system which stimulates “hormone sensitive lipase” to start breaking down fat in the fat cells. Therefore, the presence of epinephrine could be considered a major lipoliptic factor in fat breakdown (Trapp, Chisholm & Boutcher, 2007). During higher intensity exercise reaching maximal levels, not only does the body switch to carbohydrate as a main source of energy, a by-product of the anaerobic system (as seen in maximal intensities) is lactic acid. Lactic acid is said to be a blocker of epinephrine."