As you quotes some journals you might like to research these questions yourself (you'll find more reliable and rounded answers than I can generate off the top of my head)....
Originally posted by lysworld
Thanks for the reply.
The topic of high fat diets and performance are definitely not well researched, due to the dogma of high carbohydrate and performance. I am not questioning this has been shown to increase performance as you most probably can confirm. However in regards to endurance events and as you quite rightly pointed out, as glycogen depletion is the direct cause of fatigue, the body needs to tap in to both energy systems. With lactate production as a marker of anaerobic metabolism and the LT (or whatever people decide to call it) is the rate at which BL is at a rapidly increasing level, to enhance performance in endurance events wouldn$B!G(Bt it be best to not deplete carbohydrate stores until the end, relying on an increased contribution from the body$B!G(Bs fat stores? By training in a state of glycogen depletion, perhaps the body would learn to utilise the oxidative system optimally?
If high fat diets do not increase performance why do 'performance research' in high fat diets? There are far bigger questions to be answered in scienece (i.e. a cure for cancer) and sport (i.e. what is the optimal carbohydrate loading regime).
As lactate begins life as glucose/glycogen via glycolysis, glycogen depletion results in lower lactate production and lower exercise performance; therefore WORSE PERFORMANCE. You suggest that the rider should race in a depleted state and then supplement at the end; this is not a good option as the rider would 1. be last and/or fatigued by the time it was time to eat carbohydrate and 2. carbohydrate won't be absorb effectivly to increase performance.
Using energy from fat stores (and no energy from glucose due to glycogen depletion) is not a good idea because 1. its bad for your health and 2. energy from fat is supplied at a lower rate (i.e. WORSE PERFORMANCE).
Training in a glycogen depleted state to increase aerobic metabolism is a bad idea because 1. its not specific (you shouldn't be racing in a glycogen depleted state), 2. there may be no transfer of adaptations from a glycogen depleted state to a non glycogen depleted state and 3. increases in aeroboic metabolism (i.e. increased VO2 max) are induced by high intensity efforts that are difficult in a glycogen depleted state.
Originally posted by lysworld
As BL is a response to anaerobic metabolism, if there are very little carbohydrates to burn, the body has to look elsewhere. Therefore the use of lactate as an energy source increases and is utilised on production (lactate shuttle theory) as an energy source therefore lowering the BL levels. These are two that show this can happen
Int J Sport Nutr Exerc Metab 2001 Jun;11(2):248-57
The effect of low-carbohydrate diet on the pattern of hormonal changes during incremental, graded exercise in young men. (Not in performance athletes though )
Maughan RJ, Greenhaff PL, Leiper JB, Ball D, Lambert CP, Gleeson M..Diet composition and the performance of high-intensity exercise. J Sports Sci. 1997 Jun;15(3):265-75
From what you have written I think you have miss understood the lactate shuttle theory. Also BL is measured because it closely represents what is happening in the muscles (i.e. muscle lactate). It is the concentrations of lactate in the muscle that limit contractions rather than blood lactate. Therefore reducing BL independantly of ML won't inprove performance.
Originally posted by lysworld
Therefore if this is the case, would my question of increasing the mitochondial density of non-anaerobic working muscle (RT or CV) to consume lactate as an energy source decrease BL level?
Possibly (but I haven't done any reading on this topic), but given that it won't effect muscle lactate concentrations significantly its unlikely to improve performance. Most cyclists are in a possition where more 'on the bike' training will improve perforance; training spent aerobicaly training the 'non cycling' muscles is therefore wasted time. BL is removed in large part by the liver; perhaps you should be training that
!
Originally posted by lysworld
*Glycogen depletion will lead to a decrease in/limited 'exercise capacity' and therefore decrease potential for performance.
(A) Very good point, therefore $B!F(Bif carbohydrates are completely depleted, how can the athlete perform?$B!G(B I am sure there are elite athletes who are diabetic, so carbohydrate loading is most probably (I am assuming form what I know) dangerous to them. Therefore what do they consume to produce their best performances?
(B) What are your ideas for the comparison of animals energy system to humans? They are considered $B!F(Bsimilar$B!G(B in order to test them or it would not be valid. Here is my questioning of this area. A Cheetah is one of the fastest land animals and can sprint for a long time when hunting (an assumption). But, what carbohydrates do Cheetahs consume, I would guess they ate mainly proteins and fats from its prey. Why could this not be true in humans?
(A) Athletes can perform in a glycogen depleted state but at a reduced level (i.e. the 'knock' or 'bonk'). Diabetics have carbohydrate and can eat carbohydrate; carbohydrate loading is not dangerous for diabetics (although some will have to monitor their insulin, blood glucose levels and actual intake to remain safe). Diabetics have carbohydrate to produce their best performances; there are no secrets or magic pills!!!!
(B) Comparing animals to humans provides very little value at all!!!!! Cheetah is one of the quickest animals; however has four legs, different muscle fibre composition, only sprints for 10's of sconds (not ride for hours), etc. etc. Why isn't this the case for human's; because many many research studies over decades have shown that during exercise without glucose performance is limited (i.e. protein or fat are not as important).
Originally posted by lysworld
*Insulin response is supressed during exercise and remains at low levels at rest and exercise unless food is eaten.
Extraction from Glucose Ingestion and Performance, Izumi Nishibata
Ingestion of large amount of glucose (simple sugar) before the initiation of endurance exercise may impair performance (Foster, C., D. L. Costill, and W. J. Fink. Effects of preexercise feedings on endurance performance. Med. Sci. Sports 11: 1-5, 1979) Blood glucose concentration increases when glucose is ingested. Then, blood insulin concentration increases to decrease or stabilize blood glucose concentration by increasing uptake and consumption of blood glucose by various organs. Insulin also depresses the mobilization of fat from adipose tissue. If you begin high intensity endurance exercise with high insulin concentration, blood glucose concentration may soon abruptly decrease because the exercising musculature consumes large amount of blood glucose with the stimulation of high insulin concentration. When blood glucose is decreased and fat cannot be used as an energy source because of the prevention by insulin, the exercising musculature can only depend on its muscle glycogen as its energy source. This hastens the muscle glycogen depletion and decreases performance. When you ingest glucose after the initiation of exercise, blood glucose does not increase as rapidly as you ingest it before the initiation of exercise, because exercise decreases gastric emptying and absorption of ingested glucose. Also catecholamine secreted by the stimulation of the stress of exercise prevent insulin secretion. The higher the exercise intensity is, the larger amount of catecholamine is secreted.
This is the most basic advice ever, not to eat too soon before a ride. Generaly people recomend that you shouldn't eat high GI in the 2 hours prior to exercise. Your orignial post you implied not eating during exercise for insulin control; this would be bad advice given that insulin is suppressed during exercise and carbohydrate consumption during exercise can imporve performance.
Originally posted by lysworld
Would you not consider doing a trial on performance after a low-carb, high fat diet as there is a need for such research especially from those who are competing for real and not just testing in the lab?
There is nothing to suggest that a high fat diet would improve performance and lots of lab & anecdotal evidence that suggests it would result in WORSE PERFORMANCE. Repeating the test would be a waste of time.
Originally posted by lysworld
Also, why are high fat diets damaging to health? Obesity is interchangeable with type II diabetes that is treated with low/no sugar (possibly GI, depending on the severity) and high fats, which reduce serum cholesterol and triglycerides improving their health status. Again it is for this reason that I question the proposal that a high fat diet is so directly linked with health problems. From what I have read, it is now believed that it is a high fat and high carbohydrate (like you stated) that is the main cause.
Obesity is a result of excess energy intake (i.e. to many kcals) and independant to the composition of the diet.
High fat diets can be bad for health, immediatly after a fatty meal plasma triglycerides increase proportionatly to the fat load of meal and remain high for up to 10 hours latter. The triglycerides are carried in LDL and chylomicrons, which both have negative effects on cholesterol transport and are considered atherogenic.
Please read the work on postprandial triglyceride response, by Cohn, Patsch, Austin, etc.
Originally posted by lysworld
Final thing have you guys heard of g-push?
No, but I have heared that water and carbohydrate are good ergogenic aids! Why look elsewhere for performance improvements when the basics are done badly.
Originally posted by lysworld
PS: I have to be $B!F(Bargumentative$B!G(B for my rationale, I am not contesting the use of high CHO for performance, but trying to find a reasoning for the possible advantages of low-carbohydrate training for health and performance.
Thanks
There is no problem with you being arguementative; however its a little frustrating when people quote books and journals yet haven't done some basic reading.
In all of the books and reading (except the ATKINS book!) you will see that carbohydrate is important in IMPROVING AND MAINTAINING PERFORMANCE.
Also, interms of health, the very early research shows that high fat meals and diets are bad for your health and this remains correct today. However more information is becoming available on carbohydrate, fat and protein metabolism which is being miss interpurted by the public. It is likely (and perhaps obvious that) some carbohydrates are bad and some fats are good; but that doesn't mean that all carbs are bad and all fats are good.
Finaly, dehydration and glycogen depletion present the largest limits on performance; therefore carbohydrate and water are the most important parts of an athletes diet.