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Paul Kayley 05-27-2007 05:04 AM

Muscle glycogen - train low, race high!
Muscle glycogen depletion in the recruited muscle fibers used during a specific endurance activity is a powerful trigger for endurance adaptations. The latest recommendation on the endurance grape vine relates to muscle glycogen - "Train low and race high!"

This makes a lot of sense to me. Although getting the balance right is critical to avoiding over-training and stalled adaptation.

Mike ODonnell 05-27-2007 08:04 AM

Makes sense as you carb load before a you are not going to train in hyperglycemic state....always good to train harder and then make the race easier...train single speed, run with resistance/up hill, etc....

Greg Everett 05-27-2007 10:49 AM

paul - how depleted are we talking here?

Paul Kayley 05-28-2007 02:46 PM

Hey Greg, thats a very good question. IMO&E, total depletion at the end of a training session would be counter productive, as it would be a taking the stimulus a couple of steps too far, resulting in cell damage and the need for prolonged recovery.

The volume and intensity of the training used would of course depend upon the fiber range being targeted. It is quite easy, with experience, to feel the point where you start to near the 'bottom of the tank' in terms of muscle glycogen(MG). This is the point in a training session where I start to back off. Going home feeling tired but not completely wiped out. The term 'train low, race high' isn't suggesting training in a depleted state, it is discouraging continuously and repeatedly carboloading the cells.... this just gives the athlete more work to do in order to stimulate change. Its training with a constant tail wind!

It might be worthwhile mentioning that the MG stored in a single muscle cell is locked in that cell, exclusively for that cell's use. It cannot be accessed for use by other muscle cells or to bolster ebbing blood glucose levels. This also means that the stimulus of MG depletion is also cell specific.

I've probably missed loads out, so ask away if I have... thats a rushed answer as I'm rushing about!

Greg Everett 05-28-2007 03:32 PM

Interesting... Looking forward to reading more on this.

Derek Simonds 05-29-2007 02:59 PM

I have been thinking about your post for most of the day. If you are an endurance athlete that eats a mostly paleo / low carb diet are you already on the low side pre-exercise?

I did a 2 hour ride with my sister on Saturday that turned into a little more of a hammer than originally planned as we rode out with a 20 knot tailwind. Oops! I definitely was at the "bottom of the tank" when we got back. I ate my normal meat, salad and small amount of carb meals for the remainder of the day. Sunday morning we did a 45 minute high intensity ride with a 20 minute tempo transition run. It ended up being a pretty tough brick. Afterwards I couldn't eat right away but when I could I was ravenous.

What made me think about this is how I was eating in the past when constantly training for triathlons. It was definitely more carb focused. Today I train 3 days a week endurance and I don't feel like I need the extra carbs except Sunday when I was so hungry I could have ate the paper plate my food was served on.

This also played into a question that I was going to ask Paul. On my heart rate monitor during the Saturday ride it showed that I burned 1734 Kcal's. Is the only factor in determining calories burned average heart rate over time? I am sure there is some algorithm that the watch uses to calculate the calories burned, but does muscle glycogen depletion come into play for calories burned?

Meaning if I worked out for 1 hour and felt near the bottom of the tank at an average heart rate of 140 and the monitor showed 900 Kcal's versus working out for 1 hour at an average heart rate of 140 but not feeling depleted did the first example actually burn more calories?

I hope this made some sort of sense, as is appears I am rambling again.

Paul Kayley 06-01-2007 08:51 AM

Hi Derek,

I had to read this a fews times, but I think I know what you are asking...


Meaning if I worked out for 1 hour and felt near the bottom of the tank at an average heart rate of 140 and the monitor showed 900 Kcal's versus working out for 1 hour at an average heart rate of 140 but not feeling depleted did the first example actually burn more calories?
Both burn the same calorific total, the latter will burn less fat calories. The relative contribution of fats to total energy output is inversely proportional to exercise intensity, and a low to moderate exercise intensities its also proportional to muscle glycogen depletion.

When talking about 'the tank' I am refering to muscle glycogen stores, not liver glycogen. Exercising with low liver glycogen, unless you are ketone adapted or fueling on the go, will lead to an early knock and curtail workout capacity. I suspect that following your second workout, because you delayed eating, your liver glycogen stores will have been low following the workout, and then continued to deplete into the used muscles. When the liver empties too much, IME, a ravenous hunger ensues which seems to dominate all powers of self control... its linked with other hormonal triggers like ghrelin etc.

The key - train low, but dont entertain extremes. I will post more later on usual I'm pushed for time...

Derek Simonds 06-01-2007 09:43 AM

Thanks that is actually what I thought. Not all the stuff about the liver but the burning fat part :D.

I can't wait to read more.

Paul Kayley 06-02-2007 03:48 PM

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!

Derek Simonds 06-02-2007 06:25 PM

Thanks for posting the info Paul. I like what I am reading. I also really like the 2 a days with 1 day recovery. On the F, S and S I can train that way so it looks like I will adapt my schedule and work 2 on Friday and 2 on Sunday with some active recovery on Saturday.

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