For weight loss, 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.
Fitness Weight Gain
Exercise can create seemingly paradoxical effects. Those who attain greater fitness shed fat but gain lean, dense muscle. They also develop 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 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 high compared to steady-state aerobics.
EPOC Fat Burn
Sprinting raises your metabolic rate so that you continue to burn calories at a higher rate following your workout. This afterburn, measured as excess post-exercise oxygen consumption, or EPOC, is greater after interval sprinting than after lower-intensity cardio. The intensity of the exercise determines the duration and magnitude of the EPOC. Intense sprint-interval training can increase your metabolic rate so that you burn 140 calories more than what is burned following low-intensity aerobic exercise.
How fast you lose weight from sprinting depends on how much you weigh and how often, how long and how intensely you exercise -- and also on how much you eat. A 155-pound person burns 298 calories in an hour of walking at 3.5 mph; the same person burns 307 calories running at 10 mph for 15 minutes and benefits from significantly greater afterburn following the run. Steady-state cardio increases your appetite, but intense sprinting might decrease your appetite, says fitness expert Tom Venuto at BurntheFat.com. A 30 minute sprint can add 600 or more calories to your daily calorie expenditure and lead to greater weight loss.
There are limits to sprinting. You should not sprint more than three or four times per week, to allow for recovery from the muscular stress. Take off one full day from exercise but do low- or moderate-intensity cardio on nonsprint days. Sprinting is not for everyone. Consult your physician before making significant changes to your exercise program.