Join Date: May 2007
This study relates to what I've been rambling on about....
J Appl Physiol. 2005 Jan;98(1):93-9. Epub 2004 Sep 10. Related Articles, Links
Skeletal muscle adaptation: training twice every second day vs. training once daily.
Hansen AK, Fischer CP, Plomgaard P, Andersen JL, Saltin B, Pedersen BK.
Dept. of Infectious Diseases M7641, and The Copenhagen Muscle Research Centre, Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen, Denmark.
Low muscle glycogen content has been demonstrated to enhance transcription of a number of genes involved in training adaptation. These results made us speculate that training at a low muscle glycogen content would enhance training adaptation. We therefore performed a study in which seven healthy untrained men performed knee extensor exercise with one leg trained in a low-glycogen (Low) protocol and the other leg trained at a high-glycogen (High) protocol. Both legs were trained equally regarding workload and training amount. On day 1, both legs (Low and High) were trained for 1 h followed by 2 h of rest at a fasting state, after which one leg (Low) was trained for an additional 1 h. On day 2, only one leg (High) trained for 1 h. Days 1 and 2 were repeated for 10 wk. As an effect of training, the increase in maximal workload was identical for the two legs. However, time until exhaustion at 90% was markedly more increased in the Low leg compared with the High leg. Resting muscle glycogen and the activity of the mitochondrial enzyme 3-hydroxyacyl-CoA dehydrogenase increased with training, but only significantly so in Low, whereas citrate synthase activity increased in both Low and High. There was a more pronounced increase in citrate synthase activity when Low was compared with High. In conclusion, the present study suggests that training twice every second day may be superior to daily training.
I also believe that the following study helps to demonstrate that endurance athletes' dont need to be quite so obsessive about rushing to refill muscle glycogen with high starch diets... the body's ability to conserve and efficiently partition glucose is under-estimated, especially in response to glycogen sapping exercise.
J Physiol. 2003 May 1;548(Pt 3):919-27. Epub 2003 Mar 21. Links
Skeletal muscle fat and carbohydrate metabolism during recovery from glycogen-depleting exercise in humans.
* Kimber NE,
* Heigenhauser GJ,
* Spriet LL,
* Dyck DJ.
Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
The primary aim of the present study was to determine whether intramuscular triacylglycerol (IMTG) utilization contributed significantly to the increase in lipid oxidation during recovery from exercise, as determined from the muscle biopsy technique. In addition, we also examined the regulation of pyruvate dehydrogenase (PDHa) and changes in muscle acetyl units during an 18 h recovery period after glycogen-depleting exercise. Eight endurance-trained males completed an exhaustive bout of exercise (approximately 90 min) on a cycle ergometer followed by ingestion of carbohydrate (CHO)-rich meals (64-70 % of energy from carbohydrate) at 1, 4 and 7 h of recovery. Duplicate muscle biopsies were obtained at exhaustion, and 3, 6 and 18 h of recovery. Despite the large intake of CHO during recovery (491 +/- 28 g or 6.8 +/- 0.3 g kg-1), respiratory exchange ratio values of 0.77 to 0.84 indicated a greater reliance on lipid as an oxidative fuel. However, there was no net IMTG utilization during recovery. IMTG content at exhaustion was 23.5 +/- 3.5 mmol (kg dry wt)-1, and remained constant at 24.6 +/- 2.6, 25.7 +/- 2.8 and 28.4 +/- 3.0 mmol (kg dry wt)-1 after 3, 6 and 18 h of recovery. Muscle glycogen increased significantly from 37 +/- 11 mmol (kg dry wt)-1 at exhaustion, to 165 +/- 13, 250 +/- 18, and 424 +/- 22 mmol (kg dry wt)-1 at 3, 6 and 18 h of recovery, respectively. PDHa was reduced at 6 and 18 h when compared to exhaustion, but did not change during the recovery period. Acetyl-CoA, acetylcarnitine and pyruvate contents declined significantly after 3 h of recovery compared to exhaustion, and thereafter remained unchanged. We conclude that IMTG has a negligible role in contributing to the enhanced fat oxidation during recovery from exhaustive exercise. Despite the elevation of glucose and insulin following high-CHO meals during recovery, CHO oxidation and PDH activation were decreased, supporting the hypothesis that glycogen resynthesis is of high metabolic priority. Plasma fatty acids, very low density lipoprotein triacylglycerols, as well as intramuscular acetylcarnitine stores are likely to be important fuel sources for aerobic energy, particularly during the first few hours of recovery.
This serves to demonstrate just how precious glucose stores are to the athlete's body. Fat burning even in the presence of insulin until depleted MG is restored! However, there is another side to this. It has been demonstrated that following carbo-loading, to supra-normal MG levels, that CHO is burned at an increased rate until CHO levels level out. It appears that the body likes a nice balance, not too much, nor too little. Personally, I find that my muscles dont operate so well when CHO-loaded, they feel all jammed up and sore. Following a few days rest I'll get this feeling if I've over-filled my legs... it then takes a couple of hours of training before my legs feel loose and able to fire effectively with all cyclinders!
Happiness is success.
Contentment is wealth.