June 16, 2010
LOW GI Post Workout
If anybody reads enough bodybuilding boards, or other fitness forums we know what I am speaking on. It’s standard for people to say that high-GI is needed PWO. Dextrose, Maltodextrin, grape juice, the list goes on and on as people have a belief that it will help the recovery of glycogen. Mind you almost all of these people don’t intake metcon training, or endurance training. Glycogen stores just don’t deplete as quickly as some would like to believe. Not to mention when it comes into immediately restoring these glycogen amounts, I always have to ask. “What are you eating the rest of the day?” Meaning a steady influx of proper carbs, throughout the day is as much as 95% of the population needs for proper replenishment. Now let us dive into that a little further.
First off lets get a couple things clear that some may not understand unless they have done quite a bit of nutritional reading, or academics in the realm of it at a University etc.. First off, glycogen replenishment is biphasic and is insulin independent during the first phase (30-60 minutes). Excess amounts are not needed at all and can contribute to excess glucose circulating. Meaning in the first 30-60 minutes PWO there is a rapid synthesis of of muscle glycogen, that requires no insulin what so ever. Following this rapid phase, it slows considerably for the next few hours. However, When carbohydrate ingestion is delayed by several hours, this may lead to ~50% lower rates of muscle glycogen synthesis. Simply stated for us, there is absolutely no reason for High GI Post workout. Oatmeal is commonly what we use.
Now lets dabble in Glut4 receptors, how they are triggered, and why it further initiates our thoughts on what we do. In a study performed by Ivy, it was simply stated as this.
Regulation of GLUT4 protein and glycogen synthase during muscle glycogen synthesis after exercise.
Ivy JL, Kuo CH.
Department of Kinesiology, The University of Texas at Austin, 78712, USA.
The pattern of muscle glycogen synthesis following its depletion by exercise is biphasic. Initially, there is a rapid, insulin independent increase in the muscle glycogen stores. This is then followed by a slower insulin dependent rate of synthesis. Contributing to the rapid phase of glycogen synthesis is an increase in muscle cell membrane permeability to glucose, which serves to increase the intracellular concentration of glucose-6-phosphate (G6P) and activate glycogen synthase. Stimulation of glucose transport by muscle contraction as well as insulin is largely mediated by translocation of the glucose transporter isoform GLUT4 from intracellular sites to the plasma membrane. Thus, the increase in membrane permeability to glucose following exercise most likely reflects an increase in GLUT4 protein associated with the plasma membrane. This insulin-like effect on muscle glucose transport induced by muscle contraction, however, reverses rapidly after exercise is stopped. As this direct effect on transport is lost, it is replaced by a marked increase in the sensitivity of muscle glucose transport and glycogen synthesis to insulin. Thus, the second phase of glycogen synthesis appears to be related to an increased muscle insulin sensitivity. Although the cellular modifications responsible for the increase in insulin sensitivity are unknown, it apparently helps maintain an increased number of GLUT4 transporters associated with the plasma membrane once the contraction-stimulated effect on translocation has reversed. It is also possible that an increase in GLUT4 protein expression plays a role during the insulin dependent phase.
Simply stated muscle contraction, and the exercise itself performed by anyone at a high enough level, enables glut4 to work it’s magic in a biphasic series of events. IN another study performed by Costill a few other things were found in regards to carbs, before during, and after exercise. The mechanisms responsible for optimal glycogen storage are linked to the activation of glycogen synthetase by depletion of glycogen and the subsequent intake of carbs. Although diets rich in carbs may increase the muscle glycogen stores and enhance endurance exercise performance when consumed in the days before the activity, they also increase the rate of carb oxidation and the use of muscle glycogen. When consumed in the last hour before exercise, the insulin stimulated-uptake of glucose from blood often results in hypoglycemia, greater dependence on muscle glycogen, and an earlier onset of exhaustion than when no carb is fed. Ingesting carbs during exercise appears to be of minimal value to performance except in events lasting 2 h or longer. The form of CHO (i.e., glucose, fructose, sucrose) ingested may produce different blood glucose and insulin responses, but the rate of muscle glycogen resynthesis is about the same regardless of the structure.
IN essence, through studies and other conversations with trainers, and what we have seen work in our arena, the entire “replenish glycogen quickly” theory went out the window for us long ago. Now I know some of you are saying, well what about marathon endurance events since that is what we do. There was a study done at the University of Western Ontario which stated as follows. “The effects of simple-carbohydrate (CHO)- and complex-CHO-rich diets on skeletal muscle glycogen content were compared. Twenty male marathon runners were divided into four equal groups with reference to dietary consumption: depletion/simple, depletion/complex, nondepletion/simple, and nondepletion/complex. Subjects consumed either a low-CHO (15% energy [E] intake), or a mixed diet (50% CHO) for 3 days, immediately followed by a high-CHO diet (70% E intake) predominant in either simple-CHO or in complex-CHO (85% of total CHO intake) for another 3 days. Skeletal muscle biopsies and venous blood samples were obtained one day prior to the start of the low-CHO diet or mixed diet (PRE), and then again one day after the completion of the high-CHO diet (POST). The samples were analysed for skeletal muscle glycogen, serum free fatty acids (FFA), insulin, and lactate and blood glucose. Skeletal muscle glycogen content increased significantly (p less than 0.05) only in the nondepletion/simple group. When groups were combined, according to the type of CHO ingested and/or utilization of a depletion diet, significant increases were observed in glycogen content. Serum FFA decreased significantly (p less than 0.05) for the nondepletion/complex group only, while serum insulin, blood glucose, and serum lactate were not altered. It is concluded that significant increases in skeletal muscle glycogen content can be achieved with a diet high in simple-CHO or complex-CHO, with or without initial consumption of a low-CHO diet”.
That being said, it is completely why we keep a steady stream of carbs throughout the day, while at the same time, adjusting the amount of carbs PWO. While we may up the amount of carbs PWO, the structure or GI level of the carb does not change. We just haven’t found a reason to yet, and it’s been about ten years now. I like to refer to it as eating the rainbow of carbs. I know most people reading this are zone or paleo eaters, so it’s not far fetched from what you do. I myself eat a large amount of veggies each day. Peppers, squash, zuchinni, bok choy, collard greens, the list goes on and on. However I will try to eat differing colors throughout the day. Is it backed by science? Of course not, however I have found it to be helpful in keeping my kid interested in cooking and picking things out, while staying completely healthy. Enough about carbs, lets get to fats, how they are mobilized, why we keep a steady stream of them in our diet, and how.
The fat of the matter
Lets dive right into the numbers game, and why it is so important in the way my team and I train and eat. When performing mild exercise at about 25% of VO2 max, 20% or less of the energy comes from carbs. At the same time the other 80% of energy comes from fat. In some studies performed it indicates that exercise induced lipolysis usually provides FFA at a rate higher than what is needed for exercise. What this means is that the plasma FFA coming from the adipose tissue is the main source of energy while engaging in mild exercise. However the use decreases while the use of muscle triglycerides increase when you step up the intensity to about 65% of VO2 max.
When this happens fats and carbs appear to be used about equally for energy. FFA and triglycerides contribute almost equally for the energy that comes from fat. When exercise exceeds 85% of VO2 max, carbs increasingly become the dominant fuel that is used. At this point the fat amount used diminishes as muscle glycogen becomes the preferred source of energy. One key note however, is these numbers will be quite a bit lower in untrained individuals.
In studies performed by Wolfe and Lange some interesting theories have come into play. Lange found that humans are not designed to use fat during exercise. Also stating at the same time that fat oxidation can be used to keep a metabolic rate up to 60% of VO2 max. Other theories abound such as inadequate FFA being mobilized from adipose, may in fact limit FFA being delivered to the muscle. However Wolfe states that fat oxidation is largely increased when effort increases to 85% of VO2 max. However carbs are still the dominant energy source. Also, sub optimal muscular procedures can limit fat oxidation. Meaning the high amount of carbs being utilized at high intensity exercise may limit the amount of fats being oxidized.
The intaking of carbs in before or during exercise delaying fat oxidation is a common mistake amongst trainers. From the physiology side of things although fat oxidation may actually be reduced , the available carbs would provide a more valuable energy source. When it comes to bonking, or hitting the wall, carb intake before or during prolonged exercise could help. But once you cross the 90-120 minutes or more of high intensity exercise (climbing mountains etc), glycogen stores become very low and the body shifts to a increased amount of FFA used. Which in turn can lead to a decrease in the effort put towards the exercise. In extreme endurance events such as Primal Quest, FFA may provide nearly 90% of the energy that is used in the latter stages of such a event.
The effect of training on fat metabolism
What we are looking at now, is how fat utilization changes somewhat for endurance athletes, over others. However it also depends on if you do hours of MMA, BJJ, hiking etc… Some of us may not be endurance athletes so to speak, but enjoy getting out for hours on a bike, or hike, and don’t realize that some things may need to be adjusted around that time period. Such as up the amount of carb PWO, or on and on and on. The theories that abound are still being researched and tried. Coggan and others have found some interesting things on energy used, in endurance athletes, and how the numbers can change. They have suggested that endurance athletes may actually use fats more efficiently at levels near 75-80% VO2 max. Pendergrast and crew also found that fat, especially intramuscular fat, plays a huge role as exercise gets bumped up to 80% or more in endurance trained athletes. Dr Costill stated that highly trained athletes could use as much as 75% of their energy from fat, even when performing at above or about 70% of their VO2 max. The ability to use this in this manner is huge, saving glycogen for the later stages of the race, when the push is needed. At the same time, it becomes needed to consume carbs during the race etc, to help prevent complete glycogen depletion. Relying solely on fatty acids, would ensure a slowing down at the end of the race.
In conclusion, I hope that cleared up the way that we sometimes do things around here. Carbs and fats both play a extremely important role in our training. The teeter-totter of how to plan it out is a whole other ball game. Next month we will dive into protein, and supplements that we use to improve our times. The month following that, will be how we tie it all together. I encourage discussion on this, whether you are from the PM boards, sherdog, or wherever. I can be reached by email, or PM on a site. I would also like to thank Robb Wolf, Alan Aragon, Greg, Everett, Kim, and a few others over the years for teaching me what they know off merely posting in forums and having conversations. Good luck in training everyone!