Cardio Confusion - Long and Slow or Short and Fast
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on 5/6/2008
by
albert | filed in:
Endurance
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Exercising aerobically within the lower limits of the Target Heart Rate Zone (i.e. 50-70% of the Maximum Heart Rate) for longer durations was once considered to be the most beneficial for fat-burning. Current research findings now indicate that greater fat-burning is accomplished with exercise in the upper limits of the Target Heart Rate Zone (i.e. 70-90% MHR). The following four points reveal the myth of the fat-burning workout and provide support for exercising at relatively higher intensities:
Fat vs. Carbs for Fuel: During low-intensity activities you primarily burn fat; when the intensity of the activity increases so does the percentage of carbohydrates that you burn. While the percentage of energy from fat decreases proportionately as you progress to higher exercise intensities, the total caloric expenditure and total amount of fat used increases significantly.
The Post-Workout Metabolic Boost: Vigorous exercise elevates the resting metabolic rate (RMR) to a greater degree than low intensity exercise. Studies have demonstrated a return to the resting metabolic level within minutes after exercise of low to moderate intensity, while higher intensity exercise has shown a sustained elevation in RMR for many hours. Some experts estimate that exercise must be sustained for 20-30 minutes at 70% or more of aerobic capacity in order to derive any benefit from this elevated caloric expenditure after the workout. This post-excess calorie burn, from a shorter, but more intense session accounts for far greater results than just the calories burned during a longer exercise session itself at low to moderate intensities.
The Dose Response Relationship: The lower cardiovascular stimulus acting on the body at lower exercise intensities causes a smaller increase in aerobic fitness than working at higher intensities of exercise. The person who only exercises at lower intensities is still burning fat, but is not conditioning their body to the same degree to become an even better fat-burning machine!
Hormonal Influences: Intensities above 70% of aerobic capacity are required to stimulate the release of growth hormone. This hormone is involved in the processes of fat release, fat transport and fat metabolism.
The bottom line: When beginning to exercise, do so at an intensity and duration that is appropriate for your fitness level. Also, keep the three C’s of cardio in mind – Make it the most CONVENIENT part of your day, a CONSISTENT part of your lifestyle, and keep it CHALLENGING and FUN.
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