Faculty Opinions recommendation of Exogenous ketosis impacts neither performance nor muscle glycogen breakdown in prolonged endurance exercise.

Exogenous ketosis produced by oral ketone ester ingestion during the early phase of prolonged endurance exercise and against the background of adequate carbohydrate intake neither causes muscle glycogen sparing nor improves performance in the final stage of the event. However, such exogenous ketosis may decrease buffering capacity in the approach of the final episode of the event. Furthermore, ketone ester intake during exercise may reduce appetite immediately after exercise.

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Effect of endurance exercise training on muscle glycogen supercompensation in rats

Journal of Applied Physiology ◽

10.1152/jappl.1997.82.2.711 ◽

1997 ◽

Vol 82 (2) ◽

pp. 711-715 ◽

Cited By ~ 61

Author(s):

Akira Nakatani ◽

Dong-Ho Han ◽

Polly A. Hansen ◽

Lorraine A. Nolte ◽

Helen H. Host ◽

...

Keyword(s):

Exercise Training ◽

Endurance Exercise ◽

Muscle Glycogen ◽

Glucose Transporter ◽

Glycogen Synthase ◽

Recovery Period ◽

Chow Diet ◽

Glycogen Accumulation ◽

Transporter Protein ◽

Endurance Exercise Training

Nakatani, Akira, Dong-Ho Han, Polly A. Hansen, Lorraine A. Nolte, Helen H. Host, Robert C. Hickner, and John O. Holloszy.Effect of endurance exercise training on muscle glycogen supercompensation in rats. J. Appl. Physiol. 82(2): 711–715, 1997.—The purpose of this study was to test the hypothesis that the rate and extent of glycogen supercompensation in skeletal muscle are increased by endurance exercise training. Rats were trained by using a 5-wk-long swimming program in which the duration of swimming was gradually increased to 6 h/day over 3 wk and then maintained at 6 h/day for an additional 2 wk. Glycogen repletion was measured in trained and untrained rats after a glycogen-depleting bout of exercise. The rats were given a rodent chow diet plus 5% sucrose in their drinking water ad libitum during the recovery period. There were remarkable differences in both the rates of glycogen accumulation and the glycogen concentrations attained in the two groups. The concentration of glycogen in epitrochlearis muscle averaged 13.1 ± 0.9 mg/g wet wt in the untrained group and 31.7 ± 2.7 mg/g in the trained group ( P < 0.001) 24 h after the exercise. This difference could not be explained by a training effect on glycogen synthase. The training induced ∼50% increases in muscle GLUT-4 glucose transporter protein and in hexokinase activity in epitrochlearis muscles. We conclude that endurance exercise training results in increases in both the rate and magnitude of muscle glycogen supercompensation in rats.

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Mechanism linking glycogen concentration and glycogenolytic rate in perfused contracting rat skeletal muscle

Biochemical Journal ◽

10.1042/bj2840777 ◽

1992 ◽

Vol 284 (3) ◽

pp. 777-780 ◽

Cited By ~ 46

Author(s):

P Hespel ◽

E A Richter

Keyword(s):

Skeletal Muscle ◽

Muscle Glycogen ◽

Rat Skeletal Muscle ◽

Phosphorylase Activity ◽

Tension Development ◽

Glycogen Concentration ◽

The Difference ◽

Resting Muscle ◽

Muscle Glycogen Concentration ◽

Glycogen Breakdown

The influence of differences in glycogen concentration on glycogen breakdown and on phosphorylase activity was investigated in perfused contracting rat skeletal muscle. The rats were preconditioned by a combination of swimming exercise and diet (carbohydrate-free or carbohydrate-rich) in order to obtain four sub-groups of rats with varying resting muscle glycogen concentrations (range 10-60 mumol/g wet wt.). Pre-contraction muscle glycogen concentration was closely positively correlated with glycogen breakdown over 15 min of intermittent short tetanic contractions (r = 0.75; P less than 0.001; n = 56) at the same tension development and oxygen uptake. Additional studies in supercompensated and glycogen-depleted hindquarters during electrical stimulation for 20 s or 2 min revealed that the difference in glycogenolytic rate was found at the beginning rather than at the end of the contraction period. Phosphorylase alpha activity was approximately twice as high (P less than 0.001) in supercompensated muscles as in glycogen-depleted muscles after 20 s as well as after 2 min of contractions. It is concluded that glycogen concentration is an important determinant of phosphorylase activity in contracting skeletal muscle, and probably via this mechanism a regulator of glycogenolytic rate during muscle contraction.

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Adaptations of skeletal muscle to endurance exercise and their metabolic consequences

Journal of Applied Physiology ◽

10.1152/jappl.1984.56.4.831 ◽

1984 ◽

Vol 56 (4) ◽

pp. 831-838 ◽

Cited By ~ 1018

Author(s):

J. O. Holloszy ◽

E. F. Coyle

Keyword(s):

Skeletal Muscle ◽

Blood Glucose ◽

Exercise Training ◽

Endurance Exercise ◽

Muscle Glycogen ◽

Lactate Production ◽

Strenuous Exercise ◽

Mitochondrial Content ◽

Respiratory Capacity ◽

Endurance Exercise Training

Regularly performed endurance exercise induces major adaptations in skeletal muscle. These include increases in the mitochondrial content and respiratory capacity of the muscle fibers. As a consequence of the increase in mitochondria, exercise of the same intensity results in a disturbance in homeostasis that is smaller in trained than in untrained muscles. The major metabolic consequences of the adaptations of muscle to endurance exercise are a slower utilization of muscle glycogen and blood glucose, a greater reliance on fat oxidation, and less lactate production during exercise of a given intensity. These adaptations play an important role in the large increase in the ability to perform prolonged strenuous exercise that occurs in response to endurance exercise training.

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Influence Of Branched-chain Aminoacids (BCAA) Supplementation On Free Fatty Acids Oxidation During Endurance Exercise After Muscle Glycogen Depletion

Medicine & Science in Sports & Exercise ◽

10.1097/00005768-200505001-01836 ◽

2005 ◽

Vol 37 (Supplement) ◽

pp. S349

Author(s):

Thomas B. Adolpho ◽

Patr??cia Lopes Campos ◽

Bruno Gualano ◽

Josilene Carla Gomes ◽

Fernanda Baeza Scagliusi ◽

...

Keyword(s):

Fatty Acids ◽

Free Fatty Acids ◽

Endurance Exercise ◽

Muscle Glycogen ◽

Glycogen Depletion ◽

Branched Chain

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Influence Of Branched-chain Aminoacids (BCAA) Supplementation On Free Fatty Acids Oxidation During Endurance Exercise After Muscle Glycogen Depletion

Medicine & Science in Sports & Exercise ◽

10.1249/00005768-200505001-01836 ◽

2005 ◽

Vol 37 (Supplement) ◽

pp. S349

Author(s):

Thomas B. Adolpho ◽

Patrícia Lopes Campos ◽

Bruno Gualano ◽

Josilene Carla Gomes ◽

Fernanda Baeza Scagliusi ◽

...

Keyword(s):

Fatty Acids ◽

Free Fatty Acids ◽

Endurance Exercise ◽

Muscle Glycogen ◽

Glycogen Depletion ◽

Branched Chain

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Menstrual cycle phase and sex influence muscle glycogen utilization and glucose turnover during moderate-intensity endurance exercise

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00700.2005 ◽

2006 ◽

Vol 291 (4) ◽

pp. R1120-R1128 ◽

Cited By ~ 65

Author(s):

Michaela C. Devries ◽

Mazen J. Hamadeh ◽

Stuart M. Phillips ◽

Mark A. Tarnopolsky

Keyword(s):

Menstrual Cycle ◽

Endurance Exercise ◽

Muscle Glycogen ◽

Constant Infusion ◽

Moderate Intensity ◽

Glucose Turnover ◽

Cycle Phase ◽

Metabolic Clearance ◽

Menstrual Cycle Phase ◽

Glycogen Utilization

Numerous studies from our and other laboratories have shown that women have a lower respiratory exchange ratio (RER) during exercise than equally trained men, indicating a greater reliance on fat oxidation. Differences in estrogen concentration between men and women likely play a role in this sex difference. Differing estrogen and progesterone concentrations during the follicular (FP) and luteal (LP) phases of the female menstrual cycle suggest that fuel use may also vary between phases. The purpose of the current study was to determine the effect of menstrual cycle phase and sex upon glucose turnover and muscle glycogen utilization during endurance exercise. Healthy, recreationally active young women ( n = 13) and men ( n = 11) underwent a primed constant infusion of [6,6-2H]glucose with muscle biopsies taken before and after a 90-min cycling bout at 65% peak O2 consumption. LP women had lower glucose rate of appearance (Ra, P = 0.03), rate of disappearance (Rd, P = 0.03), and metabolic clearance rate (MCR, P = 0.04) at 90 min of exercise and lower proglycogen ( P = 0.04), macroglycogen ( P = 0.04), and total glycogen ( P = 0.02) utilization during exercise compared with FP women. Men had a higher RER ( P = 0.02), glucose Ra ( P = 0.03), Rd ( P = 0.03), and MCR ( P = 0.01) during exercise compared with FP women, and men had a higher RER at 75 and 90 min of exercise ( P = 0.04), glucose Ra ( P = 0.01), Rd ( P = 0.01), and MCR ( P = 0.001) and a greater PG utilization ( P = 0.05) compared with LP women. We conclude that sex, and to a lesser extent menstrual cycle, influence glucose turnover and glycogen utilization during moderate-intensity endurance exercise.

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Carbohydrate loading and metabolism during exercise in men and women

Journal of Applied Physiology ◽

10.1152/jappl.1995.78.4.1360 ◽

1995 ◽

Vol 78 (4) ◽

pp. 1360-1368 ◽

Cited By ~ 140

Author(s):

M. A. Tarnopolsky ◽

S. A. Atkinson ◽

S. M. Phillips ◽

J. D. MacDougall

Keyword(s):

Endurance Exercise ◽

Muscle Glycogen ◽

Protein Oxidation ◽

Endurance Athletes ◽

O2 Consumption ◽

Glycogen Concentration ◽

Performance Time ◽

Carbohydrate Loading ◽

Endurance Cycling ◽

Muscle Glycogen Concentration

During endurance exercise at approximately 65% maximal O2 consumption, women oxidize more lipids, and therefore decrease carbohydrate and protein oxidation, compared with men (L.J. Tarnopolsky, M.A. Tarnopolsky, S.A. Atkinson, and J.D. MacDougall. J. Appl. Physiol. 68: 302–308, 1990; S.M. Phillips, S.A. Atkinson, M.A. Tarnopolsky, and J.D. MacDougall. J. Appl. Physiol. 75: 2134–2141, 1993). The main purpose of this study was to examine the ability of similarly trained male (n = 7) and female (n = 8) endurance athletes to increase muscle glycogen concentrations in response to an increase in dietary carbohydrate from 55–60 to 75% of energy intake for a period of 4 days (carbohydrate loading). In addition, we sought to examine whether gender differences existed in metabolism during submaximal endurance cycling at 75% peak O2 consumption (VO2 peak) for 60 min. The men increased muscle glycogen concentration by 41% in response to the dietary manipulation and had a corresponding increase in performance time during an 85% VO2 peak trial (45%), whereas the women did not increase glycogen concentration (0%) or performance time (5%). The women oxidized significantly more lipid and less carbohydrate and protein compared with the men during exercise at 75% VO2-peak. We conclude that women did not increase muscle glycogen in response to the 4-day regimen of carbohydrate loading described. In addition, these data support previous observations of greater lipid and lower carbohydrate and protein oxidation by women vs. men during submaximal endurance exercise.

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