PET3361

Post-absorptive state for Carbohydrates

Once in the body, glucose is stored either in the liver or the muscle of glycogen. The process of glucose to glycogen is called glycogenesis. Then when the body need glucose, it undergoes glycogenolysis or gluceoneogenesis to replenish the blood glucose.

Post-absorptive state for lipids

Once you ingest lipids, they are mostly stored as adipose cells

Absorption of lipids

Lipids are hydrophobic (not soluble in water) so they have to form a micelle to be absorbed into the body. We didn't really go over the absorption in detail.

Post-Prandial state for lipids

After feeding, most lipids are stored as adipose, and the intramuscular stores vary between 5-35%. They can also become lipoproteins (chylomicrons, LDL, HDL, VLDL)

Absorption of Carbohydrates

Basically the end product is glucose, fructose, and galactose once the carbohydrates reach the small intestine. Then they are absorbed into the capillaries, with glucose and galactose undergoing active transport with Na, and fructose undergoing facilated diffusion

How does fasting affect performance and metabolism?

Fasting had no affect when low intensity exercise (45% Vo2), but decreased performance with any higher intensity. And this is not reversible if you feed during exercise. The metabolism part is that the liver glycogen stores decrease (no glucose) so you fatigue easily (body needs for energy). Think hypoglycemia to help understand what no glucose does.

How does carbohydrate feeding during recovery influence muscle glycogen?

Feeding after exercise helps replenish the depleted glycogen stores. When you exercise, your body undergoes glycogenolysis to breakdown its glycogen stores and supply glucose, depleting its stores. Ingesting carbohydrates will then increase the blood glucose level, stimulate insulin and glycogenesis and build up its stores again

When is it most beneficial to feed carbohydrates during exercise? What are the guidelines?

Feeding during exercise is only effective when the effort is longer than 90 min. Ingesting an outside source of carbohydrates will spare the muscle glycogen and maintain the blood glucose. Now this only works if you have a modest amount (2-6%) carbohydrate, otherwise you have GI problems. Feeding doesn't have any effect when the subject is hyperthermic, or if the limiting factor is a H+ buildup (lactic acid, burning sensation) or if the duration is under 60 min (thus people "carbo loading" for a 5k is stupid)

What factors influence mobilization of fatty acids?

First I will explain how Fatty acids are metabolized, since this is one of the factors. In order for it to be oxidized, they have to enter the mitochondria, and if this to happen Carnitine has to be present. The enzyme Carnitine palmitoyl transferase completes this job. CPT is the rate limiting enzyme obviously, and it is inhibited when glucose is high. Now on to the factors: Exercise training: This increases the utilization of fat and spares glycogen. It increases the intramuscular triglyceride stores. This is done at 60-75% Vo2 (so moderate) for extended durations. Caffeine: Maybe a fat burner. It is banned in performance if you take a ton amount, but some doses (3-9mg) have proven to be beneficial. There are side effects of course. Carnitine: This was explained already. CPT is the rate limiting enzyme for the oxidation, but the body can make plenty on its own, so no need to supplement. Also a high amount in meats. High fat diets: The theory is that since there is so much fat available, glycogen will be spared, and performance would improve. Maybe? There have been mixed findings.

What are the general guidelines for a pre-competition meal?

Going along with the ideal time for feeding, which is 3-4 hours, one should consume about 100-300g of carbohydrates. These should be either solid or liquid form, and the meal should contain little fat, fiber, and protein. Also, foods with a low GI work best

How does aerobic training increase fat utilization? Which factors affect fat oxidation and how?

I pretty much answered this on question 18. But I will go into more detail. Aerobic training works by increasing the oxygen uptake, increases the number of mitochondria, and increasing the intramuscular triglycerides. All of these will increase fat utilization. Note that this is during aerobic training, so moderate intensity.

How do men and women differ when comparing the use of fat as fuel during exercise?

It seems that males use carbohydrates for energy more, and women have greater fat oxidation, and a higher blood glucose (since rely on fat more). Women also have more type 1 fibers, and a lager capillary density, so this might explain why they have a greater fat oxidation.

What affect does a low-fat diet have on IMTG and performance?

Medium chain triglycerides have been studied with subject on a low fat diet post exercise, and this was not as effective as a normal fat diet at increasing fat oxidation. Some insight on MCTG (medium chain) is that it is easily emptied from the stomach (unlike long chain), and there is it a lot in most foods. Now to see if MCTG actually improve performance. If fed one hour before, there is no real improvement, nor if fed during. If combined with glucose, maybe

How do the muscles obtain and utilize the fatty acids for energy production?

Muscles obtain the energy by undergoing B-oxidation. Exercise increases the necessary enzymes for this, and also increases the number of capillaries (so more surface area for exchange) and also increases oxygen transport (need oxygen for B-oxidation.

Post-Prandial state for Carbohydrates

Post-prandial means after feeding, so you ingest the carbohydrate and it is stored as glycogen. Remember that glucose is the main fuel for almost all the muscles, so the cells are continuously removing glucose from the body stores. Also fructose and galactose are mostly converted to glucose before storage, but some fructose is preferred to storage as glycogen, and with fructose the glycogen synthesis rate is faster.

Absorption State of Proteins

Protein can also be metabolized to glucose in gluconeogenesis.

How is performance improved with carbohydrate intake?

Really most of the previous questions go over this. Performance usually improves with more carbohydrates. Various studies show that more carbs repair muscle better, increase performance in runners, Increases performance at high intensity with a high intake. More carbs=better performance!

Post-Prandial state of protein

Stored in Muscle

Post-absorptive state of protein

Stored in skeletal muscles mostly

How does muscle damage influence glycogen resynthesis?

The eccentric phase (muscle lengthening) causes the soreness and the damage is accompanied by the decrease in muscle glycogen resynthesis. The reason for this might be due to damage on the sarcolemma and this could potentially affect glucose muscle uptake. Another guess is it might be due to the inflammatory response which increases glucose oxidation because of neutrophils.

What is the effect of exercise on amino acid oxidation?

The glucose-alanine cycle (simply the cycle of the muscle glutamate being transaminated to for alanine, and this going to the liver to form glucose) increases with intensity

What are the guidelines for carbohydrate intake?

The guidelines are essentially the same as the guidelines to enhance storage; but in this case it is asking for the general daily guideline. So 5-7 g/kg a day for moderate duration, 7-12 g/Kg if heavy or completion, 10-12 g/Kg if doing some crazy ass training (ultra marathons) Dependent on activity level

What are the guidelines for enhancing glycogen storage on recovery?

The guidelines for feeding after exercise are to consume 1-1.5 g/Kg each hour for the first 4 hours, high GI foods work best to maximize the glucose. If food doesn't work with the athlete, they can also take a drink with 70-90g carbohydrate immediately after. TIMING IS THE KEY WITH ALL RECOVERY. • Now for feeding over a day, feeing amount should coincide with the training. So heavy training, eat more carbs. Usually more carbs yields better performance.

Which hormones control blood glucose and how? How does exercise influence these responses?

The hormones the control the blood glucose are insulin, glucagon, epinephrine, and norepinephrine. Insulin and glucagon are antagonist hormones where one controls the uptake and the other controls the release. So once the body has just ingested glucose, the pancreas releases insulin from its beta cells and this helps the cells uptake the glucose. Then once the body needs energy, glucagon is released for the pancreas by its alpha cells and this releases the glucose to increase the blood glucose level. Now for the sympathetic hormones, when blood glucose is low, receptors in the hypothalamus are activated and epinephrine and norepinephrine are released by the adrenal glands. These increase glycogenolysis and increase blood glucose. Exercise influence: With insulin, less seems to be released as the duration increases. It is opposite with glucagon. And norepinephrine and epinephrine increase with duration.

What factors enhance glycogen synthesis and how?

The main enzyme that drives synthesis is Glycogen Synthase, or GS. There are two forms of this enzyme, called D-form and I-form, with the I-form being the more active form. This I-form is activated be exercise, insulin, or just general glycogen depletion. • Now the factors that affect the synthesis: the timing of the ingestion (sooner is better), the type of carbohydrate, the amount, dependent on other nutrients, what type of exercise was done

What is the most important factor determining fuel selection during exercise and how does it influence the total contribution from each fuel source?

The most important factor is the intensity of the exercise, followed by the duration. Carbohydrates are mostly used all the time, with fat use depending on the duration (since B-oxidation takes so long to activate). Protein is rarely used as a fuel source, unless empty on all other sources.

Identify the adaptations that occur when switching to a high fat diet?

These are just the potential benefits of a high fat diet, these of course being a shift from glycogen to fats for oxidation. The body will adapt to rely on B-oxidation more, and glycogen storage will deplete since not replenishing it

What are the different ways that we measure substrate utilization?

These are the indirect calorimetry, the biopsies, blood tests, and with mass spectrometry. The calorimetry works by collecting expired gas and looking at the RER (remember this decrease with more fat utilization), the biopsies and basically parts of the muscles removed, the blood tests can be used to check the free fatty acid amount, and the mass spectrometry is with the isotopes being analyzed

What effect does hydrogenation have on fatty acids?

This is the process of removing a double bond; adding more carbons; making it saturated. This is done because a saturated fat has a higher melting temperature, and makes it less rancid. So it can be stored longer. But of course this usually makes the fat unhealthy...

What factors influence carbohydrate use during exercise and how?

Use during exercise is dependent on the intensity, duration, your initial levels of glycogen, and your training status. It seems with a light intensity exercise, the body doesn't use too much of its glycogen stores, but it increases with moderate and heavy exercise. This also correlates with duration, with moderate lasting 120 minutes until glycogen is depleted, and high only lasting up to 60 min.

What affect does exercise training have on triglyceride and the various lipoprotein levels?

With anaerobic exercise there really is no affect on any of the lipoproteins. With aerobic training total cholesterol might decrease, and LDL and TG decrease, and HDL increases. So if you want to help lower your CAD risks, you have to have a form of aerobic exercise. On the side, anabolic steroids decrease HDL.

What is the recommended timing for carbohydrate feeding before exercise?

With feeding before exercise, the ideal time seems to be 3-4 hours before. There is some evidence that feeding 30 min before just spiked their blood glucose, then fell within 10 min of exercise. Now when they looked at the intensity affect of the feeding time, they found that high intensity had a decrease in performance and moderate intensity actually had no difference

Over long duration exercise bouts, what advantages does a high CHO diet have over a high fat diet?

With long duration exercise there is no significant difference between a high fat and a high carbohydrate diet. With high intensity, there is a noticeable drop in the high fat diet though

What is the typical composition of a high-fat diet and why might they be considered potentially beneficial?

• A high fat diet is considered anything thing above 35% of your total calories, usually up to 70%. They have some potential benefits beings that they increase the availability of lipids for fuel, at the trade of lower glycogen storage. Eventually your body gets better at fat oxidation and you increase B-oxidation. But is it really worth it? Sure you burn more fat, but because you have more fat.

What are the multiple variations in defining a fatty acid?

• Fatty acids can be broken down to trigylcerides (the main storage form of fat in the body) phosolipids (the walls of cells) and sterols (which are fat like substances, like cholesterol). Fatty acids can also can defined based on their length, essentiality, the saturation, or cis/trans. For length we have short, medium, and long chain There are only two essential Fatty acids, because the body lacks the enzyme to add the necessary double bond past the 9th carbon. These are linolenic (omega 3) and linoleic acid (omega 6) Saturation means whether there are double bonds present Cis puts a bend in the molecule, or both carbons are on the same side of the double bond. Trans is opposite sides.

What is protein turnover and how is it related to synthesis and degradation?

• For protein turnover, we assume that if the rate of synthesis and breakdown are increases, then the rate of amino acids leaving the "pool" increase and more dietary protein are used. For turnover you have to imagine that there in just a huge pool of amino acids, and the body uses these for synthesis and discards the amino acids when done. • Now that we defined turnover, we look at muscle protein synthesis (MPS). These terms are somewhat related, because if synthesis is greater than degradation, then you have hypertrophy.

What is the deal with Leucine?

• Leucine is the amino acid that maximizes MPS the greatest. Whey gives is most leucine for the lowest amount (12% leucine) but other sources have it. It affects body composition also for the better. Eating a majority of your protein in one meal maximizes synthesis the best (enough protein to maximize). Leucine is the best source because it activates the mTOR pathway, this is the major anabolic pathway for MPS. So eat Leucine frequently to maximize hypertrophy!!!

What are the differences between whey and casein protein?

• Now that we know that the timing of the feeding is an important factor, let's look at the type of protein. The two proteins were are looking at is whey and casein Whey is a more water soluble and is easily digested. It is 20% of the protein in milk (showing that you don't need a powder) and is 1% of the by-product from cheese making. Casein is digested slower and is the other 80% of milk protein, and 4% of the by-product in cheese making • The final line is whey is better (faster digested protein is better, reaches muscles faster)

Why would medium chain fatty acids be considered as an alternative fuel source for exercise?

• Since MC fatty acids are emptied form the stomach slower, they are available faster. So because of this, they increase fat oxidation, which in turn decreases glucose reliance. Long chains form chylomicrons and slow gastric emptying, so bad during exercise

How do single high fat meals, short-term, moderate-term and long-term high fat diets affect performance?

• Single high fat meals If fed a high fat meal 1 hr before exercise, this did not increase any performance. Also during had no effect on performance. Maybe if combined with glucose • Short-term high fat If put against a high carbohydrate diet, the high carbohydrate is substantially better than the high fat in exercise to exhaustion. • Moderate-term high fat With this diet, the result varied with moderate intensity, and like you would probably guess, the high carbohydrate group performed better during high intensity. • Long-term high fat Now with the long-term studies, there was no real difference among groups. Of course during high intensity, fatigue is achieved faster. So no real difference in moderate intensity, but substantial with high intensity. Now if you continue this diet for 7 weeks, then there will be dramatic differences in performance endurance.

What are the proposed benefits to supplementing with specific AAs following exercise?

• So now we know that you need to feed ASAP after exercise, and that whey is better. Now let's look at the quality of the proteins (the 20 amino acids and what works best). It seems the only the nine essential amino acids and involved in MPS. Now looking further at this nine, the three BCAA seem to affect MPS the most. These are Leucine, Iso-Leucine, and Valine. Again going further shows that Leucine affects it to the greatest extent. The optimal amount of Leucine is 2-3g to maximize synthesis, and this is every 2-3 hours. Glutamine might also prevent some overtraining side effects by increasing immune function.

Identify the sources and contribution of fat used by the muscles for energy production.

• Sources of lipids are usually a mixed source (2 or more Fatty acids present) and some obvious "visible" sources are oils, butter, salad dressing, and some more "invisible" sources are milk, cheese, meats, and nuts. Once in the body, most in stored in adipose tissue, some is as muscle triglycerides, and some is as blood triglycerides. • Now for the contribution to energy, adipose is the major fuel. About 5-35% production is intramuscular (this depends on your fitness level and intensity) and the lipoproteins (VLDL,LDL etc) are very minimal.

How does exercise influence protein synthesis?

• Studies show that if given 1.4 g/kg or 2.4 g/kg, compared to .8 g/kg, then the first two groups had a higher turnover. This shows that more protein is better, up to a point (since the 2.4 g/kg group was too much higher)

What are the differences in the classic and the taper for carbohydrate loading?

• The classic way is was just a normal diet for say 3 days, then a high carb diet for 3 days and have them exercise to exhaustion to deplete their stores, then continue the high carb diet. The taper is say deplete the stores on day one, replenish with a 50% carb diet on day 2 (with a taper in exercise) then high carb on day 3 (still tapering exercise), and continue that high carb till completion. • Comparing the classic to the taper, the taper had significantly higher muscle glycogen, but the post run stores seemed the same, and performance seemed the same. Also when you store glycogen, realize you store 3g of water with every 1g glycogen, so that could of factored into the performance.

Identify factors that affect N balance

• The intake in determined based on the diet of protein, and the output is in the urine, fecal, and sweat (sweat is a minimal output, but it increases when the muscles are glycogen depleted)

What are the current recommendations for daily protein intake for different individuals?

• The normal recommendations vary with age. 0-1 years old is 1.5 g/kg/d 1-3 years is 1.1 g/kg/d 4-13 years is .95 g/kg/d 14-18 years in .85 g/kg/d 18 and up is .80 g/kg/d. • Now this is for sedentary, increases with active individuals. 1.2-1.4 g/kg/d for endurance. 1.6-1.7 g/kg/d for strength training

What is the relationship between Coronary artery disease and the lipoproteins?

• The saturated fats raise total cholesterol the most, which is why these fats should be limited. Monosaturated fats do not raise cholesterol, and linolenic (omega 3) can lower total triglyceride and VLDL amounts. So basically higher cholesterol is associated with higher mortality (correlation with atherosclerosis if you want to know). • The lipoproteins that present risk factor are LDL, TG, total CHL, and chylomicrons. HDL is the "good cholesterol," so more is better

Why is it important to eat as soon as possible following exercise?

• The sooner one ingests protein, the greater the muscle recovers. The reason is because blood flow is what delivers the protein and is obviously greater immediately after exercise. So you want to fed ASAP while that blood flow is increased

When determining N balance, what do we measure?

• This is nitrogen balance, which is one of the main factors that is looked at with protein (since it's not a big fuel source in exercise). It is the difference between the intake and output of nitrogen, so you can have positive and negative balance. To find out the nitrogen amount form the protein amount, multiply the amount by .16 (because protein in 16% nitrogen). And if given the nitrogen amount, multiply be 6.25

How are amino acids used to maintain exercise intensity and duration?

• This is that glucose-alanine cycle that we talked about. The cycle uses the alanine in the muscles that is formed from the transanimation at glutamate, and this is shuttled to the liver to undergo gluconeogenesis. This helps maintain the blood glucose.

How does carbohydrate loading affect glycogen and performance?

• This was kinda answered in the previous question. The muscle glycogen storage was significantly greater with the taper loading, BUT the post storage was no different in the either type. Surprisingly performance was the same in the taper and in the classic. Theories could be from the fact that glycogen also stores water.