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Medical Forum / General / Nutrition / April 2008different definitions of 'intensity' with respect to exercise?
Most sites that I've looked at seem to define exercise "intensity" as the percentage of maximum heart rate, e.g. http://exercise.about.com/cs/cardioworkouts/l/aa022601a.htm However there are at least some sites that seem to use it differently: http://www.living-a-healthy-lifestyle.com/burn-fat.html "Generally speaking however, aerobics is a low intensity exercise which will burn fat over a period of time. Weight lifting is high intensity carried over a short time period." That can't be using "intensity" the same way, since aerobics makes your heart beat faster than weight lifting. Is there a standard definition for exercise "intensity"? What I'm really trying to find out is what kind of exercise burns fat vs. what kind uses glycogen and glucose. Most sources say that: (1) "low intensity" exercise burns a higher percentage of fat, and "high intensity" exercise uses a higher percentage of glycogen; (2) "high intensity" exercise means exercise with a higher heart rate; and (3) weight lifting burns a high percentage of glycogen. But the three statements taken together are contradictory since weight lifting, with its lower heart rate, would be a low intensity exercise by that definition. Would it be a correct statement to say that as far as **aerobic** exercise is concerned, low intensity (lower heart rate) means more energy from fat and less from glycogen, and high intensity (higher heart rate) means more energy from glycogen? But that rule doesn't apply to anaerobic exercise like weight lifting? -Bennett >Most sites that I've looked at seem to define exercise "intensity" as >the percentage of maximum heart rate, e.g. [quoted text clipped - 12 lines] >What I'm really trying to find out is what kind of exercise burns fat >vs. what kind uses glycogen and glucose. Aerobic exercise that uses both upper and lower body(very large muscle groups) is best since you are not pushing small muscles to exhaustion. Most sources say that: (1) >"low intensity" exercise burns a higher percentage of fat, and "high >intensity" exercise uses a higher percentage of glycogen; (2) "high >intensity" exercise means exercise with a higher heart rate; and (3) >weight lifting burns a high percentage of glycogen The bottom line is higher intensity burns more fat than lower intensity. It maybe a smaller percentage of fat but its a smaller percentage of a much larger number. . But the three >statements taken together are contradictory since weight lifting, with >its lower heart rate, would be a low intensity exercise by that >definition. More aerobic activities involve more muscles. Running, cross-country skiing, etc are very aerobic since all the major muscles are used so the limiting factor is aerobic capacity. You can work a hand grip all day and it will burn etc but it is not going o tax your aerobic system one bit because of the tiny muscles involved. Same goes for anything that solely focuses on the upper body. >Would it be a correct statement to say that as far as **aerobic** >exercise is concerned, low intensity (lower heart rate) means more >energy from fat and less from glycogen, and high intensity (higher >heart rate) means more energy from glycogen? But that rule doesn't >apply to anaerobic exercise like weight lifting? Depends on the muscles involved. If you compare running at one heart rate to a higher heart rate than less energy will come from fat. > Most sources say that: (1) > >"low intensity" exercise burns a higher percentage of fat, and "high [quoted text clipped - 5 lines] > intensity. It maybe a smaller percentage of fat but its a smaller > percentage of a much larger number. I know, but what's the answer to the original question about the meaning of "intensity"? Is weight lifting considered a "high intensity" exercise or not? By what you just said, it would be high intensity because it's using a higher percentage of calories from glycogen. But by the "percentage of MHR" definition used on pages such as http://exercise.about.com/cs/cardioworkouts/l/aa022601a.htm , it would be low intensity. > I know, but what's the answer to the original question about the > meaning of "intensity"? It means exercising to the point where the duration in time is limited by the body. > Is weight lifting considered a "high > intensity" exercise or not? Yes, although the heart may not be the limiting factor as in sprinting. -- Ron >> Most sources say that: (1) >> >"low intensity" exercise burns a higher percentage of fat, and "high [quoted text clipped - 9 lines] >meaning of "intensity"? Is weight lifting considered a "high >intensity" exercise or not? Yes, It works specific muscles very intensely for a very short time and burns much fewer calories but a higher percentage of fat compared to a 30 min run at very low intensity. It burns few calories because the duration is short since the muscle are too exhausted to continue other than a very short period of time. Weight lifting is for strength building etc. > By what you just said, it would be high >intensity because it's using a higher percentage of calories from >glycogen. True >But by the "percentage of MHR" definition used on pages >such as http://exercise.about.com/cs/cardioworkouts/l/aa022601a.htm , >it would be low intensity. Burns fewer calories but not low intensity. |
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