How carb depleting is a 1hr weight training session?

[Luffers]

As per title.....

Anyone got links to studies etc?

[NU_nutrition_TS]

Do you mean a 1 hour resistance training session, cardio session or a mixture of both? If you read through the last few pages of the Against Glycogen Repletion thread you will see I quoted from a study on experienced heavy resistance trainers who only depleted about 25% of their muscle glycogen in one 30 minute session (IIRC).

EDIT: In fact it is the last post in the thread:
http://forum.myprotein.co.uk/326499-post551.html

Bearing in mind this was looking at the muscle glycogen concentrations in the vastus lateralis after a 30 minute leg-only workout of five sets each of three compound and one isolation exercise(s) performed for 6-12 reps, each set taken to failure.

Here's an interesting one:

Quote

Muscle glycogenolysis during differing intensities of weight-resistance exercise

R. A. Robergs, D. R. Pearson, D. L. Costill, W. J. Fink, D. D. Pascoe, M. A. Benedict, C. P. Lambert and J. J. Zachweija
Human Performance Laboratory, Ball State University, Muncie, Indiana 47306.

Skeletal muscle glycogen metabolism was investigated in eight male subjects during and after six sets of 70% one repetition maximum (1 RM, I-70) and 35% 1 RM (I-35) intensity weight-resistance leg extension exercise. Total force application to the machine lever arm was determined via a strain gauge and computer interfaced system and was equated between trials. Compared with the I-70 trial, the I-35 trial was characterized by almost double the repetitions (13 +/- 1 vs. 6 +/- 0) and half the peak concentric torque for each repetition (12.4 +/- 0.5 vs. 24.2 +/- 1.0 Nm). After the sixth set, muscle glycogen degradation was similar between I-70 and I-35 trials (47.0 +/- 6.6 and 46.6 +/- 6.0 mmol/kg wet wt, respectively), as was muscle lactate accumulation (13.8 +/- 0.7 and 16.7 +/- 4.2 mmol/kg wet wt, respectively). After 2 h of passive recovery without caloric intake, muscle glycogen increased by 22.2 +/- 6.8 and 14.2 +/- 2.5 mmol/kg wet wt in the I-70 and I-35 trials, respectively. Optical absorbance measurement of periodic acid-Schiff-stained muscle sections after the 2 h of recovery revealed larger absorbance increases in fast-twitch than in slow-twitch fibers (0.119 +/- 0.024 and 0.055 +/- 0.024, P = 0.02). Data indicated that when external work was constant, the absolute amount of muscle glycogenolysis was the same regardless of the intensity of resistance exercise. Nevertheless the rate of glycogenolysis during the I-70 trial was approximately double that of the I-35 trial.

http://jap.physiology.org/cgi/conten...ract/70/4/1700

Notice how muscle glycogen increased during 2 hours of passive recovery without caloric intake!

[Check1]

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Notice how muscle glycogen increased during 2 hours of passive recovery without caloric intake!

Would that come from breakdown of stored fatty acids? Interesting.

Still, don't think i'll abolish my pwo shake just yet

[Luffers]

1hr of free weight resistance training.

[NU_nutrition_TS]

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Would that come from breakdown of stored fatty acids? Interesting.

Still, don't think i'll abolish my pwo shake just yet

Fatty acids (endogenous) would only have an indirect input into PWO glycogen repletion without caloric intake because fatty acids cannot be synthesised into glucose/glycogen (the reverse is true, however; glucose can be synthesised into fatty acids).

Usually the glucose/glycogen comes from gluconeogenesis using the PWO elevations of lactate, glycerol (from the breakdown of triglycerides, which is where the fatty acids come in) and amino acids (the excess not needed for muscle protein synthesis) as substrates.

The body is remarkably non-wasteful of its resources with re-synthesis of breakdown by-products of cellular respiration back into usable energy substrates.

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1hr of free weight resistance training.

I think you can deduce from the above that it would be between 25-50% of glycogen depleted with a degree of rebound near enough 50% of what was depleted during the 2-hour PWO period (even without dietary intake).

Don't forget that it is ATP/PC that is primarily used with glycogen and fatty acids providing the substrates for ATP regeneration via both aerobic and anaerobic pathways. Since someone doing a 5x5 type workout would only be maximally exerting themselves for a few seconds at a time during each rep with monentary pauses between and longer rests between sets, there is time for the anaerobic and aerobic pathways to do their job. Longer rests between exercises would also allow a degree of aerobic ATP regeneration using fatty acids.

[Luffers]

Thanks Nu

I just wondered because a lot of people ask me whether they should do weights before cardio or vice versa. I always tell them to do weights first using up glycogen so that when they go to do cardio there is more chance of burning fat. Having said that i've known lots of guys to do it the other way around and they are still big and muscly.

I guess it depends on how many carbs they've eaten and how stocked glycogen levels are?

[NU_nutrition_TS]

^Yes! Both as someone who trained and instructed others, I tended to favour resistance work first, followed by cardio-type stuff. But it obviously can work the other way around.

From an evolutionary standpoint (and as my sig pic says: 'Nothing in biology makes sense except in the light of evolution'!) hunters would be doing a degree of fasted 'cardio' first - stalking/hunting down their prey before the heavier resistance work, carrying the kill back to camp, and only after that would they be refilling the fuel tank!

[Luffers]

So if someone is on a low carb diet then it would make sense to do weights first then cardio?

I think what I'm actually asking is, will glycogen get restocked fully i.e 300g in the muscle's and 100g in the liver, through other mechanisms (gluconeogenesis) if dietary cho is low? I'm guessing not?

[Tauren]

So realistically a person shouldn't ever be running close to running out of glycogen during a 1 hour workout, even if they are eating low carb? (Which makes sense as I heard marathon runners only run out of stored glycogen right near the end of a run).

I had an incredibly weird couple of workouts recently where after a high-carb, high-calorie binge weekend, my performance went through the roof, but has now fallen back partially once I resumed my diet. I'm trying to work out for myself what the exact causes were.

[NU_nutrition_TS]

If you ever review studies looking at training in a glycogen depleted state the glycogen depletion is almost always accomplished by fasting followed by endurance-type training (usually on a treadmill or cycle ergometer). Obviously endurance exercise is considered more glycogen depleting than resistance training.

In a carb-loaded state there is more input from blood glucose than fatty acids during exercise and glycogen is similarly spared:

Quote

Muscle glycogen utilization during prolonged strenuous exercise when fed carbohydrate

E. F. Coyle, A. R. Coggan, M. K. Hemmert and J. L. Ivy

The purpose of this study was to determine whether the postponement of fatigue in subjects fed carbohydrate during prolonged strenuous exercise is associated with a slowing of muscle glycogen depletion. Seven endurance-trained cyclists exercised at 71 +/- 1% of maximal O2 consumption (VO2max), to fatigue, while ingesting a flavored water solution (i.e., placebo) during one trial and while ingesting a glucose polymer solution (i.e., 2.0 g/kg at 20 min and 0.4 g/kg every 20 min thereafter) during another trial. Fatigue during the placebo trial occurred after 3.02 +/- 0.19 h of exercise and was preceded by a decline (P less than 0.01) in plasma glucose to 2.5 +/- 0.5 mM and by a decline in the respiratory exchange ratio (i.e., R; from 0.85 to 0.80; P less than 0.05). Glycogen within the vastus lateralis muscle declined at an average rate of 51.5 +/- 5.4 mmol glucosyl units (GU) X kg-1 X h-1 during the first 2 h of exercise and at a slower rate (P less than 0.01) of 23.0 +/- 14.3 mmol GU X kg-1 X h-1 during the third and final hour. When fed carbohydrate, which maintained plasma glucose concentration (4.2-5.2 mM), the subjects exercised for an additional hour before fatiguing (4.02 +/- 0.33 h; P less than 0.01) and maintained their initial R (i.e., 0.86) and rate of carbohydrate oxidation throughout exercise. The pattern of muscle glycogen utilization, however, was not different during the first 3 h of exercise with the placebo or the carbohydrate feedings. The additional hour of exercise performed when fed carbohydrate was accomplished with little reliance on muscle glycogen (i.e., 5 mmol GU X kg-1 X h-1; NS) and without compromising carbohydrate oxidation. We conclude that when they are fed carbohydrate, highly trained endurance athletes are capable of oxidizing carbohydrate at relatively high rates from sources other than muscle glycogen during the latter stages of prolonged strenuous exercise and that this postpones fatigue.

Muscle glycogen utilization during prolonged strenuous exercise when fed carbohydrate -- Coyle et al. 61 (1): 165 -- Journal of Applied Physiology

Contrast the above with this study looking at free fatty acid availability and glycogen utilisation during exercise:

Quote

Effects of elevated plasma FFA and insulin on muscle glycogen usage during exercise

D. L. Costill, E. Coyle, G. Dalsky, W. Evans, W. Fink and D. Hoopes

Seven men were studied during 30 min of treadmill exercise (approximately 70% VO2 max) to determine the effects of increased availability of plasma free fatty acids (FFA) and elevated plasma insulin on the utilization of muscle glycogen. This elevation of plasma FFA (1.01 mmol/1) with heparin (2,000 units) decreased the rate of muscle glycogen depletion by 40% as compared to the control experiment (FFA = 0.21 mmol/1). The ingestion of 75 g of glucose 45 min before exercise produced a 3.3-fold increase in plasma insulin and a 38% rise in plasma glucose at 0 min of exercise. Subsequent exercise increased muscle glycogen utilization and total carbohydrate (CHO) oxidation 17 and 13%, respectively, when compared to the control trial. This elevation of plasma insulin produced hypoglycemia (less than 3.5 mmol/1) in most subjects throughout the exercise. These data illustrate the regulatory influence of both plasma insulin and FFA on the rate of CHO usage during prolonged severe muscular activity.

http://jap.physiology.org/cgi/content/abstract/43/4/695