Ok, I'm ready to get back to our nutrition discussion...but with a caveat or two. Remember, I am not a nutritionist, dietitian, etc. The field of nutrition is so vast, and can be so complicated, that I dare not delve into the majority of it, and how it relates to anything but performance...and only performance for those who lie outside of the special population groups. What do I mean by this? This means that what I write in this blog about nutrition is focused solely (for the most part) on improving athletic/sport performance for healthy individuals...not people with disease processes such as diabetes, thyroid complications, morbid obesity, and the likes. It's not that I don't want to help these people, it's simply that I am not professionally qualified to do so, and it is outside my scope of practice as a Fitness Professional to do so. My area of expertise is sports performance, so it is within the confines of that arena, that I am legally allowed to provide nutritional information.
So...that being said, let's talk a little more about carbohydrates, and their role in performance. I think we have covered, for the most part, the role that CHO play in not only sport performance, but our daily lives. CHO provide fuel for the body...fuel that supports our activities, as well as our brain function. So really, all we have left to discuss (from a performance standpoint) is how much CHO, what kind of CHO, and when.
I know these types of posts can be pretty boring, so I'll do my best to keep your yawning to a minimum.
Let's start with how much. To understand how much CHO is needed to support sport related activities, we need to have an understanding of how much energy CHO really provides us. We'll discuss aerobic activities first. Depending on how long this post gets, I may choose to cover glycogen usage during anaerobic activities on another day. Those of you who participate in endurance (aerobic) activities such as running and cycling, recreational tennis, etc. might like to know that muscle glycogen provides roughly 50% of total energy needs. Yep that's right...not ALL energy comes from CHO stores. There is some degree of 'bleed over' where the use of proteins and fat also contribute to meeting the energy needs of the activity. Realize however, that this is true only during moderate intensity exercise, which the National Academy of Sports Medicine defines as activity that is performed at an intensity of 60% VO2 Max. VO2 Max...what the heck is that? Those of you who have had your VO2 Max identified know what I am talking about. Those of you who haven't...don't worry. There is another way that you can monitor exercise intensity...the RPE scale. RPE stands for Rate of Perceived Exertion...in other words, what is your perception about the level of intensity of your activity? There are a number of RPE scales that can be used, some more detailed than others. I use a simple scale of 1-10. The number 1 represents a level of activity that is not very physically demanding...think of something easy like carrying in groceries, or taking out the trash. BTW...while zero is not represented on the scale, it represents the level of intensity equal to that of sitting on the couch, watching TV. Ten, on the other hand, represents an intensity that you would equate to the hardest work you have ever done. This should be something that requires you to put forth every ounce of energy you have, to perform the task. Got it? Good. So...an activity that you would rate as a 6 out of 10 would (roughly) represent a work capacity of about 60% of your max. This can be loosely (good enough for weekend warriors or fitness enthusiasts) related to 60% of VO2 Max. BTW...VO2 Max is a measure of cardio-respiratory fitness levels.
On the opposite end of the spectrum is high-intensity aerobic exercise. Activities of this sort are often the same as those that I listed above however, these intensities are are usually achieved by those who are competing or training at a higher level than the typical weekend warrior. High intensity exercise is defined as activities performed above 79% VO2 Max...or an 8 out of 10 on the RPE scale. These are the activities, or the performance level of those activities that leave you breathing hard, sweating, and unable to hold a conversation while performing them. During activities performed at this level of intensity, muscle glycogen (stored CHO) provides nearly 100% of the energy.
The next thing you should know, is that CHO contain 4kcal per gram. Fat contains 9kcal per gram, so why wouldn't we want to consume more fat than protein...I mean, come on...fat has nearly twice the amount of energy per gram than CHO! Here's the deal...first of all, remember that glycogen is used more readily therefore, shoveling in more fat would simply result in greater storage of unused calories...fat. Second, increasing fat intake actually results in lower glycogen synthesis...or use. So don't fall into the trap of thinking that fat is actually a better fuel due to its calorie denseness.
Okay, this is getting a little long, so I'm shutting it down! I'll talk about anaerobic exercise and CHO use another day.
Thanks for reading!
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