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[RC] Field trials - part four - Ridecamp GuestPlease Reply to: Bill Proctor oasisarab@xxxxxxxxxxx or ridecamp@xxxxxxxxxxxxx ========================================== And the last email exchange that I will put up here This one from Tom?s consulting Vet <<Re: Papers showing changes in fat vs carb utilization for energy depending on diet. Key findings in the first paper are summarized in the statement that: "Metabolism was studied during 1 h of exercise at 67% (V) over dotO(2max) performed in the fasted state. 2% FAT resulted in a 27% reduction (P< 0.05) in total fat oxidation vs. 22% FAT without altering the stable isotopically determined rates of plasma free fatty acid or glucose disappearance." This was a three week trial, diet first week providing 32% of calories from fat (don't know why they did that???), then a 2 week adaptation period on either 2 or 22% of calories from fat. Numbers clearly show that when the fat was available, the muscle used it and vice versa. Particularly interesting was that the rate of utilization of substrate from the blood did not change for either glucose or FFAs, indicating, as I suspected, the muscle is largely self-regulating when it comes to energy supply. The low fat diet was documented to result in low triglyceride stores in the muscle. If rate of disapperance of FFAs from the blood was the same but overall fat oxidation decreased on the low fat diet, this must be where the difference lies. The muscle easily substituted carbs for fat (glycogen for intramuscular TG stores) to get the job done. However, you can look at the this from the flip side and say that when the fats are available, the muscle will use them instead of carbs. Relevance to Smokey: Not entirely sure. The natural equine diet (no added fat in grain mix or supplemental oils) is low in fat to begin with, no more than the 2% figure, so Smokey, and all horses not being fat supplemented, would be starting out primed to use intramuscular carbs over fats in the first place. If there is a linear relationship between HR and VO2 max when working below the anaerobic threshold, he would be estimated to have been working at somewhere between 55+% to low 60's% of VO2max, a little lower than what was used in this experiment, on his heaviest training day. I can't access the numbers for the two easier days but I'm assuming average working heart rate was lower on those days, working at 50% or so of VO2max, maybe lower. (Jump in here any time Tom! Not sure those figures are correct.) At least a partial explanation for what we saw with Smokey's numbers lies in the observation that the rate of disappearance from the blood of either glucose or FFAs was stable on both the high and the low fat diets and was independent of the intramuscular levels of fat or glycogen. To explain a rise in blood glucose with a stable rate of extraction from the blood, we need to have either a higher blood glucose to begin with or a change in the extraction rates that is directly linked to the intensity of the exercise. Kandi's poster was hypothesizing that at the heavier work load (but still well within the aerobic capacity) there would be an increase in release of FFAs into the blood and in extraction of FFAs from the blood. To make Smokey's observed blood glucose pattern fit, the extraction rate for FFAs would have to increase with the intensity of the aerobic work load, while the extraction rate for glucose drops. In other words, with the higher intensities he was releasing more FFAs and extracting more FFAs as an energy source and extracting less of the available glucose. If this is true, it explains the numbers. Another possible explanation is that the rate of extraction of glucose is linked to the glycogen status of the muscle. This is where loading would come in. If Smokey's glycogen status actually improved between the first and third work days, which I think is certainly possible given the generous level of supplementation and relatively low work levels, and if glycogen status is linked to extraction rate from the blood, he would be extracting progressively less glucose with each day as long as the intensity of exercise remained at a relatively low level (which it did). Don't know if I have ever seen studies that looked specifically at utilization of blood glucose in relationship to glycogen status though. Tom? ====================== Second paper. Like many, many others, this one confirms an ergogenic benefit for supplemental carbohydrate during exercise. However, the intensity of exercise in this one was much too high to draw any parallels with Smokey's situation. I don't know where the cutoff point is (Kandi: Can your guy help here?) but at 95% of VO2max there is no way that fats could provide energy quickly enough to sustain peak performance. Smokey, however, was well below that level. ========================== Third paper This is the one I think is most pertinent to Smokey. VO2 max of 55% is probably right on the nose. Notice here that while the level of fat oxidation dropped with the glucose supplementation, that drop was relatively small. With no supplementation at all, rate of fat oxidation was 0.28 +/- 0.023 g/min while in the most effective supplementation protocol it was still 0.24 +/- 0.023 g/min. Important to note that **glucose oxidation decreased during exercise compared to the resting state in all trials - carb supplemented or not**. This reflects the superior ability of fat to provide calories for low level aerobic work. The muscle will preserve its glycogen stores by preferentially burning fats as much as possible to meet energy demands. CHO oxidation will kick in when the rate of energy generation needed exceeds what can be obtained from the slow burning fats. Supplementing carbs was unable to completely reverse this, but did result in higher CHO oxidation and higher exogenous glucose oxidation when carbs were supplemented during the work. This suggests to me that even at only 55% VO2max fats are unable to provide energy quickly enough to meet demand and exogenous carbohydrates can and will be used, as will glycogen - to a point. The most important observation these researchers made in reference to Smokey was: "Plasma glucose levels decreased transiently after the onset of exercise in all trials and then returned to preexercise values in the W and FG (<similar to>4.5 mmol/l) trials but were elevated by similar to1.0 mmoYI in the G trial (P < 0.001). " **In other words, the boys supplemented with the 6% glucose drink had higher blood glucose levels than the unsupplemented or the glucose and fructose supplemented groups, and higher than their normal resting glucose, showing there is definitely a ceiling on how much exogenous glucose can be used. This group not only hit the ceiling, they hit at a point where oxidation of fat was only modestly reduced.** Giving more glucose beyond this point would only have driven blood sugars higher. Smokey hit the ceiling too, partially for the same reasons as in this study - using only what he needed to make up for the difference from what fats could not provide quickly enough. His higher blood glucoses as the days went on may be related either to better/higher mobilization of FFAs at the higher intensities (guess this is possible with these low work levels, Kandi?), and/or (and I suspect more likely) because of a loading effect over the previous days that allowed him to draw down intramuscular stores of glycogen to meet glucose needs more efficiently, lowering his reliance on exogenous glucose. The final part of this study, which showed increased times to fatigue at 90% peak power, suggests a glycogen sparing effect of the supplementation. Smokey thus started each subsequent day's ride with more glycogen on board than he would have had if he had not been supplemented the day before. Furthermore, he was fed and given more AGL immediately after work, packing in yet more glycogen for a loading effect. As you can see the field trials generated a long list of discussions regarding blood glucose utilization. This discussion between members of Tom?s list contained well over 100 posts to the list. It included not only Tom and his Vet but several members of the list, including Vets, riders and trainers. The results from these field trials where also duplicated by several other testers and others that where interested in learning the proper fueling of the endurance horse. Not all of the result where all exactly the same due to different horses, weather conditions, terrain, etc. but where all very similar. As I said at the beginning I will not respond to the flame throwers. I am retired and just wish to live out the rest of my life (what little of it there is) in privacy. In closing, the field trials were real, they took place and were carefully documented. They are there for any who wish to study and/or deny ever took place. This is all I have to say in the matter. Bill Proctor =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Ridecamp is a service of Endurance Net, http://www.endurance.net. Information, Policy, Disclaimer: http://www.endurance.net/Ridecamp Subscribe/Unsubscribe http://www.endurance.net/ridecamp/logon.asp Ride Long and Ride Safe!! =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
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