Cardio is the preferred method of training for fat loss. But should you do low intensity for longer durations (steady-state) or high intensity for shorter durations (HIIT)? See the case below.
Research has shown that as exercise intensity increases, fat oxidation decreases as the body switches to anaerobic energy pathways. Maximum rates of fat burning occur at a relatively low exercise intensity of ~ 70–74% max heart rate.
Adrenalin is the primary lipolytic (fat-mobilizing) messenger in the body. Studies have shown that adrenalin increases as exercise intensity increases. Because high-intensity exercise cannot be maintained for long periods of time, using intervals of high and low intensity should burn more calories and work faster than long and slow.
A University of New South Wales study compared HIIT and lowintensity steady-state cardio. HIIT consisted of an eight-second sprint on a cycle ergometer followed by 12 seconds of low-intensity cycling for 20 minutes, three times per week. The comparison group’s workout consisted of steady-state cycling at 60% VO2 max for 40 minutes three times per week. After 15 weeks the HIIT group lost significantly more subcutaneous fat than the slow and steady group.
HIIT is it. This study and numerous others consistently show that HIIT cardio is more effective at reducing subcutaneous fat and in less time per week than slow and steady cardio sessions.
HIIT can be done on any cardio equipment that allows good control of the intensity. You can self-select the interval lengths, though most studies use no longer than 30 to 60 seconds of high-intensity activity followed by two to three minutes of active rest for a total of 20 to 25 minutes per session, three times per week.