Muscle Glycogen during Prolonged Severe Exercise

Hermansen, Lars; Hultman, E.; Saltin, Bengt

doi:10.1111/j.1748-1716.1967.tb03719.x

Cited by 657 publications

(324 citation statements)

References 17 publications

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“…Under these conditions, the rate of muscle glycogen utilization is high, although a certain amount still remains in muscle after exhaustion (14). However, in exercise performed below AT there is no lactate accumulation and exercise duration can be limited by glycogen depletion, which limits energy production, since carbohydrates are essential to Krebs cycle function (15). Since many studies (5,16), but not all of them (9), have demonstrated that caffeine can increase intramuscular triacylglycerol and/or extramuscular FFA, there may be a glycogen economy (Randle effect) retarding the beginning of exhaustion only during exercise performed below AT.…”

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Effects of caffeine on time to exhaustion in exercise performed below and above the anaerobic threshold

Denadai

1998

Braz J Med Biol Res

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Controversy still exists concerning the potential ergogenic benefit of caffeine (CAF) for exercise performance. The purpose of this study was to compare the effects of CAF ingestion on endurance performance during exercise on a bicycle ergometer at two different intensities, i.e., approximately 10% below and 10% above the anaerobic threshold (AT). Eight untrained males, non-regular consumers of CAF, participated in this study. AT, defined as the intensity (watts) corresponding to a lactate concentration of 4 mM, was determined during an incremental exercise test from rest to exhaustion on an electrically braked cycle ergometer. On the basis of these measurements, the subjects were asked to cycle until exhaustion at two different intensities, i.e., approximately 10% below and 10% above AT. Each intensity was performed twice in a double-blind randomized order by ingesting either CAF (5 mg/kg) or a placebo (PLA) 60 min prior to the test. Venous blood was analyzed for free fatty acid, glucose, and lactate, before, during, and immediately after exercise. Rating of perceived exertion and time to exhaustion were also measured during each trial. There were no differences in free fatty acids or lactate levels between CAF and PLA during and immediately after exercise for either intensity. Immediately after exercise glucose increased in the CAF trial at both intensities. Rating of perceived exertion was significantly lower (CAF = 14.1 ± 2.5 vs PLA = 16.6 ± 2.4) and time to exhaustion was significantly higher (CAF = 46.54 ± 8.05 min vs PLA = 32.42 ± 14.81 min) during exercise below AT with CAF. However, there was no effect of CAF treatment on rating of perceived exertion (CAF = 18.0 ± 2.7 vs PLA = 17.6 ± 2.3) and time to exhaustion (CAF = 18.45 ± 7.28 min vs PLA = 19.17 ± 4.37 min) during exercise above AT. We conclude that in untrained subjects caffeine can improve endurance performance during prolonged exercise performed below AT and that the decrease of perceived exertion can be involved in this process.

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“…Moreover, exhaustion does not seem to occur due to the depletion of glycogen sources. Some studies have found muscular glycogen economy during endurance exercise after caffeine ingestion (15,18).…”

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Effects of caffeine on time to exhaustion in exercise performed below and above the anaerobic threshold

Denadai

1998

Braz J Med Biol Res

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“…In humans, muscle glycogen stores represent an essential energy source during submaximal exercise, and depletion of muscle glycogen stores promotes muscle fatigue (15)(16)(17)(18). Due to the close homology between the liver and skeletal muscle glycogen phosphorylase isoenzymes, the available GPi do not demonstrate tissue specificity (1,3,19) and thus may impair glycogen mobilization in skeletal muscle.…”

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The Experimental Type 2 Diabetes Therapy Glycogen Phosphorylase Inhibition Can Impair Aerobic Muscle Function During Prolonged Contraction

et al. 2006

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Glycogen phosphorylase inhibition represents a promising strategy to suppress inappropriate hepatic glucose output, while muscle glycogen is a major source of fuel during contraction. Glycogen phosphorylase inhibitors (GPi) currently being investigated for the treatment of type 2 diabetes do not demonstrate hepatic versus muscle glycogen phosphorylase isoform selectivity and may therefore impair patient aerobic exercise capabilities. Skeletal muscle energy metabolism and function are not impaired by GPi during high-intensity contraction in rat skeletal muscle; however, it is unknown whether glycogen phosphorylase inhibitors would impair function during prolonged lowerintensity contraction. Utilizing a novel red cell-perfused rodent gastrocnemius-plantaris-soleus system, muscle was pretreated for 60 min with either 3 mol/l free drug GPi (n ‫؍‬ 8) or vehicle control (n ‫؍‬ 7). During 60 min of aerobic contraction, GPi treatment resulted in ϳ35% greater fatigue. Muscle glycogen phosphorylase a form (P < 0.01) and maximal activity (P < 0.01) were reduced in the GPi group, and postcontraction glycogen (121.8 ؎ 16.1 vs. 168.3 ؎ 8.5 mmol/kg dry muscle, P < 0.05) was greater. Furthermore, lower muscle lactate efflux and glucose uptake (P < 0.01), yet higher muscle VO 2 , support the conclusion that carbohydrate utilization was impaired during contraction. Our data provide new confirmation that muscle glycogen plays an essential role during submaximal contraction. Given the critical role of exercise prescription in the treatment of type 2 diabetes, it will be important to monitor endurance capacity during the clinical evaluation of nonselective GPi. Alternatively, greater effort should be devoted toward the discovery of hepatic-selective GPi, hepatic-specific drug delivery strategies, and/or alternative strategies for controlling excess hepatic glucose production in type 2 diabetes.

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“…Glycogen deposits are important for maintaining physical performance during endurance exercises (25)(26)(27)(28)(29). We previously reported that young (12-wk-old) mice fed a sea snake lipid diet had significantly higher levels of muscle glycogen as well as plasma glucose levels than animals fed a lard diet following a 5 min swimming exercise; and so the improved swimming endurance is likely intimately related with the glycogen and plasma glucose metabolism as energies for swimming exercise in young mice (10).…”

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confidence: 99%

Effect of Erabu Sea Snake (Laticauda semifasciata) Lipids on the Swimming Endurance of Aged Mice

Shirai

Higuchi

Suzuki

et al. 2007

J Nutr Sci Vitaminol

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SummaryThe effect of Erabu sea snake ( Laticauda semifasciata ) lipids on the swimming endurance was investigated in aged mice. Fifty three-week-old male Crlj:CD-1 (ICR) mice were fed one of three experimental diets containing either 6% lard, 6% fish oil, or 6% sea snake lipids for 16 wk. The swimming exercise was carried out in an acrylic plastic tank filled with 25 cm of water maintained at 23˚C. Swimming times to exhaustion were measured with a load of 2% of their body weights attached to the tails of the mice. The swimming times to exhaustion of the group that were fed the sea snake lipid diet tended to be longer than those of the lard diet group, and were significantly improved compared with the fish oil diet group ( p Ͻ 0.05). The plasma and muscle lactate levels were significantly lower in the sea snake lipid diet group than in the lard and fish oil diet groups ( p Ͻ 0.05). The liver glycogen and plasma glucose levels of the sea snake lipid diet group did not differ markedly from those of the lard diet group ( p Ͼ 0.05), and were significantly higher than those of the fish oil diet group ( p Ͻ 0.05). These results suggest that an intake of sea snake lipids but not the fish oil, which is also rich in n -3 polyunsaturated fatty acids ( n -3 PUFAs), is useful for improving the swimming endurance of aged mice by attenuating lactate production and/or enhancing lactate clearance during swimming exercise, and the n -3 PUFAs contained in the sea snake lipids did little or nothing for this improved endurance.

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Muscle Glycogen during Prolonged Severe Exercise

Cited by 657 publications

References 17 publications

Effects of caffeine on time to exhaustion in exercise performed below and above the anaerobic threshold

Effects of caffeine on time to exhaustion in exercise performed below and above the anaerobic threshold

The Experimental Type 2 Diabetes Therapy Glycogen Phosphorylase Inhibition Can Impair Aerobic Muscle Function During Prolonged Contraction

Effect of Erabu Sea Snake (Laticauda semifasciata) Lipids on the Swimming Endurance of Aged Mice

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