It’s not how much you work out but how hard. Short Bouts Considered Appropriate Activity Goal
Centers for Disease Control & American College of Sports Medicine= 1995
In an attempt to combat the alarming trend in declining fitness levels of the American population, a group of experts was brought together in 1995 by the Centers for Disease Control and Prevention (CDC) and the American College of Sports Medicine (ACSM) to review the pertinent scientific research and to develop a clear, concise “public health message” regarding physical activity. The panel concluded that every US adult should accumulate a daily caloric expenditure due to exercise of between 120 and 210 Calories, and that the activity does not need to be continuous. In fact, it was stated, “…accumulation of physical activity in intermittent, short bouts is considered an appropriate approach to achieving the activity goal.” This recommendation was based on the mounting evidence indicating that the health benefits of physical activity are linked to the total amount of physical activity performed, suggesting that the amount of activity is more important than the specific manner in which the activity is performed (i.e., mode, intensity, or duration of the activity bouts).
Overall Review Scientific Support for Short Burst Training
- A five-minute-per-day fitness program has demonstrated physical and psychological improvements (1).
- High-intensity exercise, either intermittent or continuous, increases recovery oxygen consumption (burns more calories) more than prolonged low-intensity exercise (2-5).
- Sixty seconds is an optimal time to exercise at high intensity in order to maximize post-exercise oxygen consumption (6).
- In comparison to low- to moderate-intensity exercise, high-intensity intermittent-training causes metabolic adaptations in skeletal muscle that favors lipid oxidation (burning fat) (7).
- Muscle triglyceride lipolysis (using intramuscular fat) is stimulated only at higher exercise intensities (8).
- A minimally intense bout of exercise is needed to improve the thermic effect of food (elevates the body’s metabolism with the intake of food) (9).
- Both type I and type II muscle fibers contribute significantly to high-intensity exercise, whereas low- to moderate-intensity exercise utilizes primarily type I fibers (10).
- The loss of muscle mass, and hence muscle strength, associated with aging is in part due to a decrease in the size of the muscle cells, with the Type II fibers showing a preferential atrophy (11).
- Beta-endorphin levels associated with positive changes in mood state are increased in short-term, high-intensity exercise (12).
- Human growth hormone somatotropin, an activator of lipolysis and muscle growth, is stimulated by the exercise intensity threshold. This enhances maintenance of muscle mass and strength with aging (13).
- Plasma glutamine, an essential amino acid for the normal functioning of the immune system, is decreased after long-duration exercise and increased after short-term, high-intensity exercise (14).
- Short bouts of exercise may enhance exercise adherence, increase weight loss and produce similar changes in cardiorespiratory fitness when compared to long bouts of exercise (15).
- Increases in high-density lipoprotein cholesterol levels have been demonstrated with intermittent exercise as compared to continuous exercise (16).
- Compared to exercise duration, exercise intensity had a 13.3 times greater effect on systolic blood pressure, a 2.8 times greater effect on diastolic blood pressure, and a 4.7 times greater effect on waist circumference in men (17).
- Total energy expenditure and energy expenditure from vigorous activities, but not energy expenditure from non-vigorous activities, related inversely to mortality (18).
- Moderate-intensity aerobic training that improves maximal aerobic power does not change anaerobic capacity, whereas high-intensity intermittent training may improve both anaerobic and aerobic energy-supplying systems significantly, probably through imposing intensive stimuli on both systems (19).
