XPost: rec.running, rec.answers 
 From: gontang@electriciti.com 
  
 Archive-name: running-faq/part2 
 Last-modified: 10 Mar 2003 
 Posting-Frequency: 14 days 
  
          SOURCES: Fats are stored as adipose, body fat, and muscle fat 
 (triglycerides). CHOs are stored as muscle and liver glycogen (long  chains 
 of glucose) and blood glucose. 
          During a workout the early phases are characterized by a  reliance 
 on CHOs, both muscle glycogen and blood glucose. The blood  glucose comes 
 from the breakdown of liver glycogen. Again this is  dependent upon 
 intensity (see above). However, the muscle can also use  fat as a fuel, The 
 sources of this are from the inside of the muscle or  from the outside - 
 i.e. from adipose tissue. The problem is that levels  of fats from adipose 
 take a while to reach high enough levels for their  use to become 
 significant. Their concentration in the blood only reaches  very high 
 levels when the intensity of the exercise is low (i.e. 50% of  max or less) 
 and if the duration is sufficient (1 hour or more).  However, when the 
 concentration of fats from outside of the muscle is  high enough the muscle 
 can use these instead of glycogen and delay the  use of glycogen, this is 
 critical at times since muscle glycogen is a  "rate-limiting" fuel for 
 muscle. That is when muscle glycogen runs out,  or gets very low, then you 
 feel terrible - you've BONKED or HIT THE WALL  (see below). 
  
          BONKING/HITTING THE WALL: Lots of people talk about the  phenomenon 
 of bonking. It hits some people harder than others, I don't  know why and 
 have never seen any good information why? However, bonking  is a 
 combination of two processes. The first is a lack of muscle  glycogen (see 
 above). The second is low blood glucose. When muscle  glycogen is low the 
 muscle runs into a fuel crisis. It cannot burn fats  at a rate high enough 
 to sustain the muscle's maximal output. The  consequence is that your 
 muscle switches to burning more fats and so you  have to slow down. The 
 crappy feeling that you experience at the same  time, often characterized 
 by nausea and disorientation, is likely a  consequence of low blood 
 sugar/glucose (hypoglycemia). 
  
 The trick then is  to alleviate/delay the onset of these symptoms by 
 consuming sugar  solutions, or simply by becoming so well trained that you 
 don't have to  worry (see TRAINING below). Why is low blood sugar bad? 
 Because your  brain, eye tissue, and others are able to burn only glucose. 
 That is  when the levels of glucose are low your brain runs out of fuel, so 
 you  feel awful. Your vision might become impaired also. 
  
           FATS vs. CHOs: However, as I've said above your muscle can burn 
 fats  and if given the chance your muscle will burn whatever fuel it has in 
 the greatest abundance, even lactate! So, if supplied with enough fat 
 muscle can burn fat and hence, "spare" muscle glycogen. This is the idea 
 behind many runners drinking caffeine/coffee before a race. The caffeine 
 has effects that cause release of fats from adipose tissue and the level 
 of fats in the blood increases. The end result is that for the early 
 phases of the race the runner's muscle's can use fat and delay the use  of 
 muscle glycogen, hence, sparing that glycogen for later use. 
  
 One  should be cautioned, however, that this mechanism for increasing fat 
 usage has only been shown with some very high doses of caffeine that are 
 not achievable without taking caffeine pills. It also critically  dependent 
 upon the person's habitual caffeine intake ("big" coffee  drinker appear 
 not to derive as great of a benefit as non-habitual  users). There are 
 other ways to maximize the use of muscle glycogen,  however. 
  
          CHO LOADING: CHO loading is a practice that many athletes use 
 before a longer duration event to "supercompensate" their muscles with 
 glycogen, delay it's running out (see above). The practice is of little 
 use when the duration of the event is less than 60 minutes, since muscle 
 glycogen will usually be able to meet the demands of such a duration. 
 However, it should be noted that repeated bouts of high intensity  exercise 
 will also deplete one's muscles of glycogen (for example  wrestling 3-4 
 bouts in one day). 
  
 There are two basic protocols for CHO  loading, one is just as good as the 
 other. However, they involve an  initial bout of exercise to deplete the 
 muscle's glycogen (under normal  dietary conditions), followed by a period 
 of high CHO diet (i.e. 70% or  more of one's total calories from CHO). This 
 period should be the 4-5  days prior to the event and should be a time when 
 the athlete tapers  their training, so as not to deplete muscle glycogen 
 too much. The  result is an overload of glycogen in one's muscles. 
  
 Two notes:  1) This procedure will result, if done correctly, in most 
 people gaining 2-5  pounds. Why? Because muscle and liver glycogen is 
 stored with water and  increasing glycogen will increase water content - 
 i.e. increased weight  is water.  2) Preliminary evidence indicates that 
 this procedure is less  effective in women. That is to say that if a female 
 runner were to  increase her CHOs to 70% (or >) of her caloric intake she 
 may not have  an increase in muscle glycogen. Why? It may relate to a 
 gender  difference in the ability to store muscle glycogen or in the amount 
 of  CHOs that 70% of the female athlete's diet represents (i.e. 70% of a 
 2000 calorie diet would be 1400 Cal from CHO, eating this may not be 
 enough to increase muscle glycogen content). Stay tuned for more info here! 
  
          TRAINING: When one trains or conditions by completing endurance 
 exercise changes occur at many levels, including the muscle. The changes 
 that occur at the level of the muscle include an increased ability to 
 utilize fats. Not surprisingly then one's endurance is increased. How?  An 
 increased utilization of fats means less reliance on glycogen, less 
 reliance on glycogen means you don't run out of the fuel that allows you 
 to maintain a high rate of muscle contraction, and hence a high rate of 
 running/exercising. Another adaptation that occurs is that your muscle 
 uses less glucose, this is important for tissues such as brain (see 
 above). 
  
  
 --------------------------------------------------------------------------- 
 Conversion chart (Jack Berkery BERKERY@CRDGW2.crd.ge.com) 
  
 1 yard =        .9144 meter 
 100 yards = 91.4400 meters 
 220 yards = 201.1680 meters 
 440 yards = 402.3360 meters 
 880 yards = 804.6720 meters 
  
 1 meter = 1.094 yards 
 100 meters = 109.400 yards 
 200 meters = 218.800 yards 
 400 meters = 437.600 yards 
 800 meters = 875.200 yards 
  
 1 mile = 1.609 Kilometers 
 1 mile = 1760 yards = 5280 feet 
 1 Kilometer = .6214 miles = 1094 yards = 3281 feet 
  
 Kilmoeters to miles     Miles to Kilometers 
 ------------------------------------------------------ 1 km = .6214 miles 
 1 mile = 1.609 km 
  
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