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JustWendy
New Member
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Posted: 23 Dec 2006 08:43 pm |
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I've been developing my exercise program (was always big on weights, not so big on cardio) and I need clarification.
I understand that as long as I am within the 65 80 percent rage of my maximum heart rate, I am in the aerobic zone and the calories I am burning are coming from my fat stores. Glycogen stores fizzle out in fifteen to twenty minutes and then I am targeting fat.
Having stated this, my question is when I am below 65 percent of my MHR and I am burning calories (breathing, driving, showering, etc.), what am I targeting? It doesn't make sense that I am eating into my lean muscle mass, and it doesn't make sense that I am targeting only glycogen stores.
If I must hit the 65 mark to burn fat, what are people who do not exercise AND consume less calories than they require burning? 
Curious minds want to know.
Thanks!
Last edited on 23 Dec 2006 08:44 pm by JustWendy
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fruitloop
Distinguished Member
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Posted: 24 Dec 2006 05:37 am |
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You don't really go below the aerobic zone. All the normal day-to-day type activity (well, most of it) is aerobic. It's just not very intense  .
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JustWendy
New Member
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Posted: 24 Dec 2006 09:37 am |
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We don't go below the aerobic zone?
I know for a fact that I don't go through the day at 65% of my MHR. Not even close. For it to be aerobic, it needs to be intense enough to get that heart rate up there.
Last edited on 24 Dec 2006 09:38 am by JustWendy
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Nir
Senior Administrator
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Posted: 24 Dec 2006 11:39 am |
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ok, I am going to try to help clarify this. [I'm using my YMCA Fitness Knowledge textbook for some of this - this is what we have to learn to become qualified aerobics instructors]
Our body uses three systems to produce energy. the first two (creatine-phosphate and lactic) are anerobic and the third is the aerobic system. The anerobic systems are only used for high intensity short burst work. So if you are jumping to avoid being run-over by a bus, or sprinting to catch that bus, or doing a set of 10 repetitions of a weight-training exercise (and it is so tough that you fail on the 10th repetition) then you are using the anerobic system.
The aerobic system is used for most of your energy needs. You breath oxygen which facilitates the breakdown of glycogen and fat to produce energy, the by-products being water and carbon dioxyde. So when you are sleeping, when you're sitting and watching TV, walking around etc - most of that energy comes from the aerobic system. You don't burn a lot of energy, but potentially a high percentage of that energy could be from fat. (it depends on when you have last eaten and what you ate etc.).
Now, the ACSM (American College of Sports Medicine) defines the following training zones:
50-60% of MHR = Moderate Aerobic Zone (easy unless you're unfit)
60-70% of MHR = Aerobic Weight Management Zone
70-80% of MHR = Aerobic Fitness Zone (vigorous)
80-90% of MHR = Peak Aerobic Performance Zone (high intensity - potentially unaerobic)
So, 65-80% is a good target to work at, because it is vigorous enough to burn a significant number of calories, but not too intense so you can have an extended aerobic session.
Two points:
1) the longer you work out, the higher the % of the energy coming from fat (starts of being mostly from glycogen). [You have already made that point above]
2) the higher the intensity of the exercise, the higher the proportion of energy being suplied by glycogen
This does not mean that you need to tone down your workout if you are capable of working out near the 80% end - because ultimately if you burn more calories (even if they come from glycogen) this helps you lose fat in the long ran. You will not be burning any less fat at 80% - you'll just be burning a bit more glycogen so the proportion of fat burnt seems less.
One thing that will probably turn things around for you is the use of the kravonen formula to figure out what 65% and 80% mean for you:
65% target = (MHR - RHR) * 0.65 + RHR
MHR is your maximum heart rate (normally estimated as 220-age)
RHR is your resting heart rate, ideally measured when you wake up in the morning. Typical person averaging 70, well-trained individual could be 35-50.
The Kravonen formula tends to set a higher target heart rate, so you'll find yourself pushing yourself harder just to get to that 65% target.
Any questions / clarifications, let me know.
Last edited on 24 Dec 2006 11:41 am by Nir
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JustWendy
New Member
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Posted: 24 Dec 2006 11:57 am |
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Nir,
Thanks for responding. I just came off a 12-hour shift so I need to read this, digest it, and I'll get back to you.
I know I'll have to dialogue further with you.
In the meantime, have a wonderful holiday...
Wendy
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fruitloop
Distinguished Member
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Posted: 24 Dec 2006 08:13 pm |
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Nir explained it better, as he does. I mean that aerobic isn't necessarily cardio.
Happy Christmas, everyone!
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JustWendy
New Member
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Posted: 24 Dec 2006 08:42 pm |
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Cardio means anything that benefits the heart. Housework can benefit the heart.
Aerobic means that you are at least at 65% of your MHR. There is no way you are at an aerobic state while cleaning your house or going through your day-to-day activities.
So the question remains: what ARE you burning when not in the aerobic state. People who don't exercise vigorously (at 65% or more) for at LEAST 20 minutes do not enter into the aerobic zone. They may be in the cardio zone, but not the aerobic zone.
So WHAT are we burning? Glucose? Or lean muscle mass?
Aerobic is ALWAYS cardio. But cardio isn't always AEROBIC.
Last edited on 24 Dec 2006 08:42 pm by JustWendy
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Nir
Senior Administrator
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Posted: 24 Dec 2006 09:52 pm |
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So WHAT are we burning?
[again] a low level of activity, below 65% MHR, primarily uses the aerobic (it means 'with oxygen') energy system, which burns a combination of glycogen (=carbs) and fat. This happens all the time. It happens when you are doing your housework. It happens when you are sitting down and reading thelegacywebsite. It happens when you are asleep. You are burning a combination of glycogen and fat all the time. However, clearly you are not burning much of either (because your energy requirements are not particularly significant). In fact, the lower your level of activity (e.g. sleep) the higher the % of calories coming from fat but (obviously) the lower the absolute number of calories being burnt.
65%-80% is just a target that indicates sufficiently vigorous activity to burn a significant amount of calories (again: from a combination of glycogen and fat).
What does ACSM recommend as a workout schedule?
For those maintaining or increasing their fitness, at least 3 sessions per week, of length 20-60 minutes, at intensity 55-90% (depending on your ability. it should feel vigorous).
For those who are unfit, who want a health benefit, it has been shown that doing some moderate activity (e.g. walking, housework etc, target heart rate is a modest 50-69% of MHR), 5-7 times a week for 30 minutes (and this is commulative i.e. can do it in 3 x 10 minute sessions throughout the day) has a significant benefit compared to those who are completely inactive. This is why you have been hearing so much about walking - it is to encourage unfit people do some activity, which whilst not give them the full benefits enjoyed by those developing their fitness, gives almost all of the health (reduced risk of disease) benefits.
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fruitloop
Distinguished Member
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Posted: 25 Dec 2006 09:24 am |
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JustWendy wrote: Cardio means anything that benefits the heart. Housework can benefit the heart.
Aerobic means that you are at least at 65% of your MHR. There is no way you are at an aerobic state while cleaning your house or going through your day-to-day activities.
So the question remains: what ARE you burning when not in the aerobic state. People who don't exercise vigorously (at 65% or more) for at LEAST 20 minutes do not enter into the aerobic zone. They may be in the cardio zone, but not the aerobic zone.
So WHAT are we burning? Glucose? Or lean muscle mass?
Aerobic is ALWAYS cardio. But cardio isn't always AEROBIC.
Aerobic means 'with air' or 'with oxygen'. As long as you are breathing OK, your body is working aerobically. If you are working hard enough to get totally out of breath, that will be anaerobic. Your heart rate will be high, as well. Sitting on the couch (like I am now), you have plenty of oxygen, so that is aerobic. You don't need to be at 65% of your MHR, thats is just a target to make sure you are getting a good workout.
I think I just said exactly the same thing Nir did.
I'm not sure exactly how your body decides whether to burn muscle or fat for energy. I think it has to do with how much you have cut calories (or that is one factor). It can definitely sacrifice muscle, even if you are just sitting around.
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