By Kevin Kuhn
In the second article in this nutrition series, I explained that approximately 55-60% of the “traditional” Power Athlete’s total calories will come from carbohydrates. Though this number will vary based on individual differences as well as sport and activity metabolic demands, the role of carbohydrate for fuel as well as its influence on specific metabolic hormones before, during, and after exercise is of vital athletic importance.
Consuming 5-6grams of carbohydrate per kilogram of body weight is an easy way to calculate that 55-60% of total calories, for most athletes.
Once again we have arrived at a number. And once again I will ask the rhetorical question:Â Is this important?
Well, lets say the specific sport/activity you participate in lasts longer than 30 seconds at a time. In this case, carbohydrate serves as high-intensity fuel. So yes…it is of vital importance to have enough fuel to maintain high intensity activity. No fuel = no performance. But what if your sport/activity is one that last less than 30 seconds. Well, carbohydrate is not necessarily the main fuel source; however, it does still play a significant role. What is that role, you ask?
Well, even if your sport/activity does not last more than 30 seconds…your training does. Training for almost every sport is at least somewhat intermittent, and high intensity intermittent exercise/training depends heavily on carbohydrate for fuel. And that’s just the training for your specific event. What about your supplemental training? By that, I am referring to resistance training. It has been very well documented that resistance training and other forms of conditioning depend very highly on adequate carbohydrate ingestion.
Lets just say, for arguments sake, that the sport/activity you train for requires no carbohydrate for fuel…and that your training is not very dependent on carbohydrate for fuel. Even in this case…to maximize the adaptations to training as well as to promote recovery between training sessions, carbohydrates are still needed.
Before I discuss how the specific timing of carbohydrates can play a role in training adaptation, we must first understand the glycemic index. The glycemic index is just a simple way of ranking carbohydrate food according to the blood-glucose (blood sugar) response after they have been ingested. Carbs with a high glycemic index (like white bread, sports drinks, and candy) elicit a high blood-glucose response while carbs with a low glycemic index (like oatmeal and legumes) cause less of a dramatic spike in blood-glucose.
It is here…that things can get a little tricky. Carbohydrates in general, but “simple” carbs (high glycemic index) specifically have a very bad reputation. There is nothing inherently wrong with carbohydrates. The issue really comes down to when they are ingested…how much are ingested…and whether or not you sit on the couch all day. This next part may be a bit of an aside…but I feel it is necessary to say.
If you are not participating in high intensity training of some sort…you do not need very many carbohydrates…especially simple carbohydrates. This article is not to discuss insulin sensitivity, so I won’t go any further into that. Just know that the body stores carbohydrate in the form of fat very easily in the absence of exercise. Exhibit A: America.
So what should you eat? High glycemic index or low glycemic index carbs? The answer is yes. You should eat both. The specific time you eat either is very important.
The specific issue of nutrient timing with regard to carbohydrate has much to do with insulin. If you’ve spent any time in a gym, you have probably overheard someone (probably a meathead doing bicep curls in the squat rack, no doubt) say “insulin is the most anabolic hormone.” And that is actually true.
Carbohydrate ingestion plays a very big role in muscle/tissue growth and repair.
This is because when you eat/drink carbohydrates, the pancreas releases insulin. The specific role of insulin is to: “…lower blood glucose level by enhancing cellular uptake, enhance the storage of glycogen, enhance fat storage, enhance cellular uptake of amino acids, increase the synthesis of proteins, and suppress the catabolism of proteins.” In practical terms, insulin is needed to escort the carbohydrate (which has been broken down to glucose) into working cells to “fill up the fuel tank.” Since the stored form of glucose (glycogen) can be reduced by as much as 40% after resistance training, insulin due to carbohydrate ingestion post exercise plays a big role in replacing that which was used up. But it does more than just refill the gas tank.
Ingestion of high glycemic index carbohydrates has been shown to elicit an insulin spike that can increase the availability of growth hormone, which is vital to tissue and muscle growth and repair. Dr. Greg Haff, et al., explains in their review of carbohydrate supplementation and resistance training that: “The elevations in growth hormone stimulated by carbohydrate supplementation may ultimately lead to increases in muscle hypertrophy and enhanced resistance training performance.”
Recovery from training exists on a continuum. By this, I mean that recovery is directly influenced by anabolic (tissue growth/repair) as well as catabolic (tissue breakdown/degradation) hormones. High intensity exercise has been shown to increase levels of cortisol, which is a catabolic hormone. Cortisol acts to stimulate the breakdown of muscle protein and simultaneously prevent synthesis of new muscle protein. The unfortunate icing on this cake is that cortisol acts more catabolic on type II muscle fibers, which are the primary muscle fibers used in strength and power movements. If cortisol levels remain elevated for an extended period of time, muscle atrophy and reductions in muscle power and strength can occur. Cortisol has also been shown to impair the function of the immune system. Reductions in immune function may open up the doors to illness or slow and limit the recovery process. But…carbohydrate supplementation post exercise has been shown to elicit insulin-mediated reductions in cortisol. So supplementing with carbohydrates post exercise may not only refuel the tanks, but also increase the availability of growth hormone while simultaneously clearing the catabolic and immune suppressing effects of cortisol. How can something that does all that have such a bad reputation?
Dr. Haff, et al., in the conclusion of their review of carbohydrates and resistance training, state that carbohydrate supplementation before, during, and after training:
“may serve to promote a faster recovery, which may enhance subsequent exercise and training sessions”
“offer some ergogenic benefit, through increasing work output when the athlete is performing high-volume training with moderate loads”
“effect the overall net protein synthesis rate postexercise, which could magnify the hypertrophic response to training.”
He also explains that all these effects of carbohydrate supplementation may add up to better quality training sessions which could ultimately improve performance for Power Athletes.
Generally speaking, before exercise, as well as just about any other time except immediately post exercise, carbohydrates should be “complex” or low glycemic index. During as well as immediately post exercise; however, carbohydrates should be simple/high glycemic index in nature to provide quick fuel and promote refueling.
I’ve explained that high glycemic index carbs post exercise increase refueling as well as promote recovery by increasing anabolic hormones and decreasing catabolic hormones, but these effects can be even greater when the carbohydrate is combined with protein.
The combined effect of these two macronutrients post exercise does a few things such as: Increase the amount of “refueling” that can occur, limit the amount of muscle protein that is degraded, and increase the amount of muscle protein that is synthesized.
SO combine those carbs and protein post training! And keep the carbs low to moderate on the glycemic index unless you are working out or you just finished.
-Kevin Kuhn
SourcesÂ
Haff, G.G. (2008). Carbohydrates. In J. Antonio, Kalman, J.R. Stout, M. Greenwood, D.S. Willoughby, and G.G. Haff (Eds.), Essentials of Sports Nutrition and Supplements (pp. 349-370). Totowa, New Jersey: Humana Press
Haff, G.G., Lehmkuhl, M.J., McCoy, L.B., & Stone, M. H. (2003). Carbohydrate Supplementation and Resistance Training. Journal of Strength and Conditioning Research. 17(1). 187-196.
Stoppani, J., Scheett, T.P., & McGuigan M.R. (2008). Nutritional Needs of the Strength/Power Athletes. In J. Antonio, D. Kalman, J.R. Stout, M. Greenwood, D.S. Willoughby, and G.G. Haff (Eds.), Essentials of Sports Nutrition and Supplements (pp. 349-370). Totowa, New Jersey: Humana Press
Bio:Â
Kevin Kuhn, M.S.Ed., is the head strength and conditioning coach for the Indiana Invaders professional running club in Indianapolis, Indiana. He is also the sole proprietor of Kuhnesiology by Kevin Kuhn LLC, where he contracts out of Fitness Garage, located in Zionsville, Indiana. He specializes in athletic performance with great interest and experience in running-specific strength and conditioning, corrective exercise, exercise and sport nutrition, as well as general fitness and weight-loss. In 2009 he earned his B.S. in Exercise Science from Cedarville University and in 2011 he earned his Master’s degree in Exercise Physiology with an emphasis in Strength and Conditioning from Baylor University. He plans to begin his Ph.D. in Sport Physiology at East Tennessee State University in the Fall of 2012. Kevin has been certified by the National Strength and Conditioning Association as a Certified Strength and Conditioning Specialist (CSCS) and by the International Society of Sports Nutrition as a Certified Sports Nutritionist (CISSN). While in college, he competed in both Cross Country and Track and Field, specializing in 800 meters, 1500 meters, and 3k Steeplechase.
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