Muscle Glycogen Studies 9-10-07

The Graphs are now up!

3 Energy Systems Summary


Phosphagen

* Explosive movements- i.e. a 1 time throw, dive, jump, 8 RM heavy bench press (giving an all out effort for under 30 seconds).
It is the breakdown of CP to Creatine+Phosphate+Energy. This E is used to re-synthesis ATP from ADP. This E cannot be used directly for muscle contraction. We lack an enzyme to do this.


ENZYME: Protein catalyst (predominantly made of protein).
CATALYST: Causes a reaction to occur much faster than it would normally occur.
W/o enzymes it would take hours to get from one end of the class to another.




Glycolysis: breakdown of CHO to pyruvate.
Anaerobic/fast: w/o oxygen giving 100% for about 1-3 minutes. The ultimate example of using this system is the 800m sprint.
Pyruvate is further broken down to lactate. See Pg. 40 of packet to read article about the difference between lactic acid and lactate plus the hydrogen ions.

Aerobic/slow: w/oxygen. Pyruvate breaks down to acetyl CoA to go into the Kreb’s Cycle.


Oxidative Phosphorylation/Oxidative System:
Produces the greatest amount of ATP. Long Steady Distance (LSD)- i.e. spin class, aerobics class
98% of energy for a marathon comes from the oxidative system but the sprint at the end could make or break your time and the energy primarily comes from the Phosphagen System.
Vast Majority of energy during x activity comes from x system, however all three play a role in everything we do. This is called the energy continuum.




The Energy Continuum:


The y axis (vertical)= VO2 max (VO2 max: maximal oxygen consumption. It is the single best indicator of aerobic condition-heart, lungs, circulatory system).
X axis (horizontal)= (from left to right) High I/Low D to Low I/High D athletes, where D=duration of exercise and I=intensity of exercise.


Graph 1.



As you can see, this is a linear relationship showing the ability to use the aerobic energy system.
As intensity goes down and duration goes up VO2 max (maximal oxygen consumption) goes up.
Examples of High I/Low D athletes would be: Olympic lifters
Examples of Moderate I/Moderate D athletes would be: mostly team sports
Examples of Low I/High D athletes would be: Marathon runners


The higher your VO2 max, the better the shape you are in. It is the maximum O2 a person can breathe in AND utilize per min. The low for humans is about 10 which would be someone with chronic obstructive pulmonary disease. The highest ever recorded in a human was 90 which was a male cross country skier who uses both upper and lower body. Units are ml/kg/min. Altitude negatively affects VO2 max testing and corrections to the equation need to be made. (Fatigue sets in faster at higher altitudes)



The best way to test VO2 max is with a tread mill and a Douglas bag (to collect exhalation). Run to near exhaustion on a treadmill and breathe in room air and out through a one way valve into a Douglas bag. It is known that there is 20.9% oxygen and 2% CO2 in “room air“. The VO2 max measurement comes from analyzing the difference between the percentages in air inhaled and the percentages in the bag that you have exhaled. Percentage oxygen in the bag should get lower and lower with increased aerobic shape. CO2 should be higher in exhalation than in the “room air“.




How would you test the anaerobic glycolysis system? 800 m dash. Must measure time and H+ ions in blood. Must draw blood. If you are in good shape you would be able to tolerate high levels of H+ ions.


Y axis: H+ tolerance
X: Same as above


Graph 2.



The athletes who’s primary sport involves either VERY short D (high I) activity or VERY long (low I) activity struggle while the moderate athletes thrive.




What about the Phosphagen System? Really explosive activity for 30 sec. Must measure creatine levels. The best test for this is running up a flight of stairs. About 12 stairs. If you are in good shape, your blood will contain a LOT less creatine after your sprint than before it.
Y axis: Creatine usage
X: Same as above


Graph 3.





Olympic Lifters perform this test the best because they have trained this system well even though they don’t run. Quickness, Explosiveness.
However, as I decreases and D increases in athletes, so does tolerance in this system.


The energy continuum concept: energy system utilized during give activity depends on characteristics of that activity.
High intensity low duration = anaerobic
Low intensity high duration= aerobic system
Very simplified.




Energy Nutrients: can break these down to get E for physical activity. Aka “Food stuffs”
1. Protein
2. CHO (Carbohydrates)
3. Lipids/Fats


Protein does not play an important role in giving us energy for exercise. It is not a good idea to break down muscle for energy. Usually don’t get more than five percent or less energy from protein for any exercise. For long distance activities you can get 5-10% from protein. Ironman: 10-15% from protein. Other athletes that may start using more significant %s of protein are low cal dieters. They must increase their protein intake so as not to let their bodies us their own muscles as an energy source. For the athlete, carbs are by far the most important form of energy.


For every 1 mile you run you burn about 100 kcals. If CHO=X and Lipids=y and protein is not a factor as an energy source, then: x+y=100 kcals.




Factors affecting CHO vs. Fat utilization
1. Intensity/duration
2. Diet prior to activity


The left Y axis: % CHO used as fuel
The right Y axis: % Fat used as fuel (with 0 at top and 100 at bottom-inversely related to CHO)
X axis: Low to high intensity (left-right) and long to short duration(left-right)


Graph 4.



As you increase intensity and shorten duration from walking (left) to sprinting (right), the energy use of 50/50% CHO/Fat goes to almost 100 CHO and no Fat usage.
At rest you are getting 1/3 of energy from CHO, and 2/3 from fat. As intensity increases and duration decreases, your body prefers to use more and more CHO. To lose weight, you must be decreased intensity and increased duration.

Y axis: % of fuel supply
X axis: min of work

Graph 5.

During long duration exercise, CHO are the predominant energy source at first, over fat; However, fat usage slowly becomes predominant as the activity continues. It takes a while for the fat burning to kick in. For fat burning to kick in, fat has to go through beta oxidation, then the kreb’s cycle, and then the electron transport chain. That takes time. Must rely on CHO even at low intensities. Takes about 20 min for fat burning to kick in. If you are in great aerobic shape, it can take only minutes for fat burning to kick in. It could take 30 min. for the average out of shape American to get into fat burning (non-aerobically trained athlete).


Intensity is relative to your aerobic level, thus duration is also. Tom can run at 70% of his VO2 max for 2 hours and be burning mostly fat. However, if someone who doesn’t run, tries to run at 70% of their VO2, they would only be able to do this for 15 min and be burning mostly CHO.

3 major places we store CHO (forms)
1. Liver glycogen
2. Muscle glycogen
3. Blood glucose


All CHO need to be broken down or be converted to glucose to be used by the human body. The body is very strict about the levels of glucose it keeps in the blood. So it stores it as glycogen-a polymer or glucose molecules linked together-in the muscles or liver. Of the three stores, the most important by far for physical activity is muscle glycogen. Regardless of if you are an aerobically trained athlete or a resistance trainer.


Factors affecting muscle glycogen utilization:
1. Intensity of exercise
2. Duration of exercise
3. Mode of exercise- type of activity e.g. bike, run, swim, etc.
4. Fitness level- muscle glycogen use becomes more efficient for better trained athletes. Better trained athletes will use much less muscle glycogen.
5. Muscle fiber type-slow/fast twitch. How much slow/fast twitch you have is determined by genetics and cannot be changed.


Left Y axis: % CHO used as fuel 100-0 Right Y axis: % of fat used as fuel (inversely related to CHO-0 on top, 100 on bottom) X axis: Hours of running from 0-4 hours









Graph 6. The type of food, fats or carbohydrates, affect how we perform during exercise and what type of energy source is available to our body during that exercise. CHO is by far the most important food stuffs for active ppl. In this study, athletes performed at 70% of their VO2 max for as long as they could. Fatigue onset corresponded with muscle glycogen depletion. During long duration activity of constant intensity (LSD) fatigue sets in when muscle glycogen was depleted. Using predominantly fat during this test. Glycogen usage decreases quickly. Even though most of your energy comes from fat, muscle glycogen is the limiting factor and creates fatigue. Fat utilization is highly determined by CHO levels.




Graph 7.
Y axis: Muscle glycogen content (decreasing in downward direction)
X axis: Minutes on bike machine


This study was done with the athletes performing at 70% of their VO2 max as long as they could. Measured by biopsy (cutting) of muscle. Fatigue onset corresponded to muscle glycogen depletion. During long duration activity of constant intensity (LSD), fatigue onset occurs when muscle glycogen was depleted.


Graph 8.
Y axis: Muscle glycogen content of muscle (decreasing downward)
X axis: Day A, B, C, D with intensity increasing to the right


These athletes performed day A at 50% of VO2 max- low intensity for 2 hours-didn’t use much muscle glycogen.
Day B was at 60% for 2 hrs. and intensity was raised on each of the four test days (with rest days between). At 90% the athletes could not complete the 2 hrs. and muscle glycogen depletion was great. Muscle glycogen is still the limiting factor. The athletes still had enough fat to use but fatigue set in when muscle glycogen was depleted.

In conclusion to these studies: As intensity increases,; greater use of muscle glycogen to depletion/exhaustion occurs. As duration increases, greater use of muscle glycogen to exhaustion occurs.
DISPITE FAT BEING UNLIMITED.

Y axis: Muscle glycogen content (decreasing downward)
X axis: # of sprint bouts from 0-6

Graph 9.

As intensity of exercise increases, the amount of muscle glycogen utilized also increases. Although glycogen is a primary fuel during sprint bouts, plenty of glycogen remains at exhaustion. (gollnick and et all 1973)

These athletes had their VO2 max tested before this study. The athletes would sprint for 1 minute at 10% above their VO2 max with 10 min. breaks. (Supramax-above VO2 max)
Group averaged about 6 sprint bouts. At the end of the test, they had at least 40% of their muscle glycogen left at exhaustion. This study was testing the fast/anaerobic glycolysis system. Fatigue set in because of the accumulation of H+ ions, NOT because of depletion of muscle glycogen.
During VERY high intensity, short duration activity where anaerobic glycolysis is predominant, muscle glycogen levels are not depleted despite fatigue. High levels of H+ are the culprit of fatigue in this case.


In conclusion to these studies: Limiting factor for low to moderate intensity and long duration activity is muscle glycogen despite fat availability.


Limiting factor for very high intensity very low duration activities is the accumulation of H+ ions despite muscle glycogen and fat availability.


Fat storage can be high but muscle glycogen stores are limited. While you can store almost unlimited fat, you can only store enough muscle glycogen to jog 3 miles. You need muscle glycogen to kick start fat burning. Think of fat as a log and muscle glycogen as kindling. If you have used up all the kindling on the first log of fat and try to put another on the fire, the log will not be able to burn. It needs the kindling, I.e. more muscle glycogen. As you get into better shape your body will need less kindling to get into the fat burning.

Mode of Exercise:
In this study, the athletes were required to run on a treadmill at two resistances, level and uphill. Muscle biopsies were taken from three leg muscles, the gastrocnemius, the soleus, and the vastus lateralus and tested for muscle glycogen content for both the level and uphill sessions. The vastus lateralus used very little muscle glycogen on the level surface and significantly more on the uphill. The gastrocnemius used a lot of muscle glycogen on the level surface and somewhat more on the uphill. The Soleus used a moderate amount of muscle glycogen on the level surface and a bit more on the uphill. This shows the specificity of training certain muscles for certain activities. If you want to get ready for a marathon up Pike’s peak you will need to do a lot of uphill training. If you are training for the Boston Marathon you need to train on very flat surfaces.




There are two types of Skeletal Muscle fiber: ST(slow twitch) and FT (fast twitch).


SLOW TWITCH:
1.generate force or tension slowly, consistently, and for long distances
2. Aka red fiber, type I, slow oxidative
3. Doesn’t fatigue quickly, can last for long duration


FAST TWITCH:
1. Explosive movements
2. Aka type II, white fibers
3. Fatigue very quickly


All muscles are a combination of both. Genetics determines the percentage of both in each muscle.


Different muscles are mostly one or another e.g. posture muscles need to contain mostly slow twitch fibers as they are in use for very long durations.


Utilization of Fats
The major stores of fat are:
1.Viceral/internal fat around organs (apple/android/male type-belly & back, and pear-shaped/gynoid/female type-hips thighs & butt)
2. Subcutaneous- under the skin.
3. Blood-FFA (free fatty acids)
If you estimate someone’s subcutaneous fat you can estimate their overall internal fat storage. That is because 1/3 of our fat is subcutaneous and 2/3 is internal (this varies for different ages, ethnicities, etc.).
4. Muscle triglycerides
At Low/rest intensity- 2/3 fat burned is from blood then when that is used, the visceral fat supplies the blood with more.
At moderate I- we burn mostly visceral fat
And at High I- we burn mostly muscle triglycerides (75% of VO2 max)