Post Workout Carbohydrate Intake

Post Workout Carbohydrate Sources

By Kyle Hunt

Hunt Fitness

Research in discussion

Effects of ingesting protein with various forms of carbohydrate following resistance-exercise on substrate availability and markers of anabolism, catabolism, and immunity

                Richard B Kreider, Conrad P Earnest, Jennifer Lundberg, Christopher Rasmussen, Michael Greenwood,       Patricia Cowan and Anthony L Almada

http://www.jissn.com/content/4/1/18

 

Overview        

            The ingestion of carbohydrate and protein following resistance training is a general protocol for most athletes interested in optimizing their gains from training. The combination of carbohydrate and protein has been shown to increase insulin levels, optimize glycogen re-synthesis, enhance protein synthesis, and lesson the immunosuppressive effects of intense exercise. There has been a lot of research conducted on the varying recovery properties of different protein and amino acid sources but much less research done on different forms of carbohydrate sources. Theoretically, ingesting a carbohydrate source that has a high glycimic index would offer the greatest increase in insulin levels, glycogen re-synthesis, and protein synthesis. The big question is whether or not the glycimic index (speed of delivery) makes a difference when combined with protein and taken post workout.

 

 

 

Analysis

            The purpose of the study was to determine whether the type of carbohydrate ingested along with protein (whey) following a resistance exercise affects blood glucose availability and insulin levels, markers of anabolism and catabolism, and/or general immune markers.

            The research group used forty subjects (19 males 21 females) who had all participated in at least one year of resistance training prior to the experiment. Before the start of the program, one repetition maxes were found for the given exercises in the program along with starting body weight. Before the start of the training sessions the subjects gave “pre-exercise” blood and after completing the given resistance training workout the subjects gave “post-exercise” blood.

            Following the post exercise blood sample, the subjects received in a double blind and randomized manner a carbohydrate and protein supplement consisting of 40g whey protein with 120g sucrose, powdered honey or maltodextrin. The remaining group was served as a non supplement control group.

            The research group had three major findings after concluding the study. One, ingesting a carbohydrate and protein supplement following resistance training promoted significant increases in insulin level. This was not a major finding as many studies have showed the same thing. Two, there were no significant differences observed among the forms of carbohydrate served on the insulin levels. This suggests that all three carbohydrate sources tested when combined with protein are effective for post workout recovery. Lastly, the group found that glucose was maintained to a greater degree in the subjects ingesting honey as the carbohydrate source. This was an interesting point because honey has the lowest glycimic value of the three carbohydrates tested and symbolized a “mix” carbohydrate source. The honey used in the study was made up of a mixture of fructose, glucose, wheat starch, and maltose. The study also concluded that the differences in post workout supplementation did not significantly affect time course of testosterone, cortisol or general markers of immunity. Like previously mentioned the findings support the growing literature that ingesting post workout carbohydrates combined with protein stimulates insulin levels and anabolic processes. However, the study brings up an interesting point in regards to post workout carbohydrate intake; faster absorption might not be as beneficial as originally imagined.

            It has generally been thought that insulin levels increase the greatest amount in conjunction with higher glycimic index carbohydrates. Thus it would provide the greatest benefit to combine protein with the highest possible glycimic index carbohydrate post workout such as dextrose, maltodextrin or like substance to benefit from all of the anabolic processes of insulin. However, the research showed there was little to no difference between carbohydrate sources tested in the study. A possible explanation for this could be the effect of the whey protein supplement on the carbohydrate source. Glycimic Index values are determined fasted and as an isolated food item. When the carbohydrate is combined with the whey protein a whole new cascade physiological response occurs compared to the carbohydrate isolated.

            Post workout supplementation protocol is one of the most debated aspects in sports nutrition. In addition, over the last few years a lot of post workout supplements have came onto the scene marketed as recovery formulas with dextrose, waximaize, or maltodextrin as their carbohydrate source. The reasoning behind having those carbohydrate sources is their extremely high glycimic index values. Dextrose, waximaize and maltodextrin all have glycimic values at or above 100.

            It is important to consume protein and amino acids post workout because of the powerful stimulation effects on protein synthesis. Insulin is therefore included because insulin has been found to be a potent stimulator of protein synthesis. The research study showed no significant differences on insulin response of the three forms of carbohydrate tested. Also, honey was found to maintain elevated blood glucose levels to a greater degree than either sucrose or maltodextrin. These findings suggest that it might be more beneficial to ingest a mix of high and moderate glycimic carbohydrate sources post workout to promote a sustained elevation in blood glucose. Also, by combining varying carbohydrate sources consisting of a range of GI values it could prevent rebound hypoglycemia that some individuals may encounter when ingesting extremely high GI carbohydrate sources in large amounts.

            Personally I feel like the study was very well put together. However, in the future I would be interested to look into the differences between mixed carbohydrate sources and see if there is any benefit to the combination of high GI sources with low GI sources or if a single moderate GI source provided the most benefit. I tend to suggest a mix of a moderate to high GI source combined with a moderate to low GI source post workout. The idea is to create an initial insulin response but one that is able to be sustained over an extended period of time. An exception to that is during extreme fat loss phases where I feel it is more beneficial to control insulin levels throughout the day and just have a moderate to low GI carbohydrate source post workout.

Conclusion

            It is a general consensus that combining protein and carbohydrates together post workout significantly increase glucose and insulin responses thus anabolic processes. The findings suggest that each of the three types of carbohydrates tested can be used as an effective carbohydrate source to combine with protein and consume post workout. However, it was found that blood glucose levels could remain elevated if a “mix” carbohydrate source was consumed such as honey.

In a post resistance workout setting there seems to be no added benefit to consume an extremely high GI carb source such as dextrose, waximaize or maltodextrin. In fact, like mentioned I would recommend a mix of a high and moderate glycimic index carbohydrate source to generate an insulin response and maintain it over a greater period of time. The study does not say that having a high GI carbohydrate source such as dextrose, maltodextrin, or waximaize post workout is not effective. It is effective it’s just not any MORE effective than having a moderate carbohydrate source or a mix. I would try a few different protocols and determine what your body responds to best.

 

Post Workout CHO Intake Q & A

Here are some of the more common questions I get regarding post workout intake.

Q- If you are following a low carbohydrate diet do you still need carbohydrates post workout?

  1. There this definitely a great deal of benefit to consuming carbohydrates post workout. Like mentioned the ingestion of carbohydrates and protein create a cascade of events including increased protein synthesis, increased glucose and nutrient uptake within the muscle cell and it stems from the insulin response. Typically in a low carbohydrate setting I would recommend partitioning the majority of your carbohydrates to be consumed pre and post workout, post workout being the last place to take carbohydrates from so you can still benefit from the muscle building properties of carbs plus protein post workout. However, if you are following a ketogenic diet where the idea is to keep the body producing ketone bodies the only way to do that is to limit all insulin response therefore no significant carbohydrate can be ingested at one time or at all. In those cases its best to follow the plan and avoid carbohydrates.

 

Q- Do you have to have a supplement post workout or is whole food alright?

  1. Whole food is definitely alright. For me personally I am about 50/50 when it comes to supplements vs. whole food post workout. Some days I might have a shake along with some carbs and some days I might just have a meal. It really comes down to personal preference and convenience. There are some benefits from having whey protein post workout but most of the benefits stem from maximizing protein synthesis. Since whey protein is about 10-11% leucine it only takes about 30g to hit the leucine threshold to maximize protein synthesis. To make up for that with a whole food source such as chicken, you just need to slightly increased the serving size in comparison to the whey. A great whole food post workout meal could be 6oz chicken, 8oz sweet potato, a little bit of brown sugar and stevia on the sweet potato and there you go! Solid whole food post workout meal.

 

Q- How important is it to restore glycogen levels post resistance training workout?

  1. Well this is a good question. Yes, stored glycogen levels are typically on the low side following a resistance training workout, especially if it was an intense workout. But the benefits of restoring glycogen post workout are a much different need to resistance training than it is to endurance training. Your body has about 400g of glycogen stored in muscle cells and about 100g stored in the liver. It only takes about 60 minutes of moderate (65-70% vo2) exercise to completely burn through stored glycogen. To an endurance athlete it is extremely important to restore the glycogen levels so they can train again. A resistance trainer is looking to restore glycogen for another reason. There is only two ways glucose gets into the muscle cell. One is through muscle contraction and another is through the action of insulin. For this discussion we are going to focus on insulin. Insulin acts on GLUT-4 which transports glucose into the muscle cell from the blood. A resistance trainer is looking to benefit from the increased uptake of nutrients, amino acids and the increased muscle protein synthesis response this creates. This really hits on the overall meaning of this article. Yes, insulin is important for muscle growth and recovery but restoring glycogen is not really the main principle of concern. For muscle growth it is more about taking advantage of the physiological cascade of events insulin creates.

I hope this article helps clear the light on some of the more pressing issues of post workout nutrition intake.

Until next time “One Dream, One Reality”

Kyle Hunt

Hunt Fitness

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About huntfitness

My name is Kyle Hunt, I have a Bachelor's Degree in Exercise Science and I am a Certified Fitness Trainer and Specialist in Fitness Nutrition. I own the fitness website Hunt Fitness. www.KyleHuntFitness.com

Posted on December 18, 2011, in Nutrition and tagged , , , , , , , , . Bookmark the permalink. Leave a comment.

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