health and fitness experts extol the benefits of long-duration, low- or moderate-intensity cardio exercise
. Thirty to 90 minutes a day of moderate-intensity cardio exercise, such as running, swimming, or biking, can enhance fitness, health, and weight loss. Increasing the intensity of your workout program by including activities, such as sprinting, can contribute significantly to your weight-loss progress.
An oft-cited 1991 study in “Metabolism” found
that short bursts of high-intensity exercise caused a greater loss of fat for a given amount of effort than moderately intense exercise
This study suggested that high-intensity interval training, or HIIT, can burn nine times more fat than conventional, steady-state cardio
. HIIT involves performing four to six bouts of high-intensity running for 1 to 3 minutes, separated by brief recovery periods of low-intensity cardio, such as walking.
The study results were derived through analysis that attempted to statistically control for the fact that those who did the high-intensity training expended less initial energy
. Their actual rate of fat burning was only threefold that of the steady-state cardio exercisers, still an impressive-sounding advantage. However, neither group in this 15-week study actually lost much weight. Members of the HIIT group lost an average of only 0.1 kg in 15 weeks.
Exercise can create seemingly paradoxical effects. Those who attain greater fitness shed fat but gain lean, dense muscle. They also develop a greater capacity to store carbohydrates in the form of glycogen for use during exertion.
Glycogen is bound with water, so a greater store of glycogen means that you may temporarily gain some water weight
. This is a healthy weight. You have less fat, more muscle, and greater temporary energy stores.
A growing body of more recent research suggests that sprint intervals and other forms of HIIT can produce various health and weight-loss benefits
. A 2005 study published in “Journal of Applied Physiology” found
that six sessions — spread over a 2-week period and consisting of four to seven all-out interval sprints with 4-minute recovery periods — produced improvements in cardiovascular fitness equivalent to daily, hour-long, moderate-intensity cardio exercise
. Likewise, sprint interval training produces improvements in cardiovascular fitness, energy storage, fat and carbohydrate metabolism, and endurance that are disproportionately