Carbohydrate-Loading and Exercise Performance

  title={Carbohydrate-Loading and Exercise Performance},
  author={John A. Hawley and Elske Jeanne Schabort and Timothy David Noakes and Steven C. Dennis},
  journal={Sports Medicine},
SummaryThis review suggests that there is little or no effect of elevating pre-exercise muscle glycogen contents above normal resting values on a single exhaustive bout of high-intensity exercise lasting less than 5 minutes. Nor is there any benefit of increasing starting muscle glycogen content on moderate-intensity running or cycling lasting 60 to 90 minutes. In such exercise substantial quantities of glycogen remain in the working muscles at the end of exercise. However, elevated starting… 

Rapid carbohydrate loading after a short bout of near maximal-intensity exercise.

This study shows that a combination of a short-term bout of high-intensity exercise followed by a high-carbohydrate intake enables athletes to attain supranormal muscle glycogen levels within only 24 h.

Carbohydrate loading in human muscle: an improved 1 day protocol

Findings showed that combining physical inactivity with a high intake of carbohydrate enables trained athletes to attain maximal muscle glycogen contents within only 24 h.

The Use of Carbohydrates During Exercise as an Ergogenic Aid

Surprisingly, small amounts of carbohydrate ingestion during exercise may also enhance the performance of shorter (45–60 min), more intense (>75 % peak oxygen uptake; VO2peak) exercise bouts, despite the fact that endogenous carbohydrate stores are unlikely to be limiting.

High-carbohydrate versus high-fat diets in endurance sports

There is currently very little or no evidence to support the use of high-fat diets and long term health effects of such diets in athletes are unknown.

Carbohydrate metabolism in exercising horses

The aim of this review is to describe the present understanding of carbohydrate metabolism in the exercising horse, its implications on nutrition and athletic performance, and to contrast it with that in other species.

Effects of carbohydrate restriction on exercise performance

The effects of exercise with carbohydrate restriction and/or low-muscle glycogen state on metabolic adaptation and exercise performance is reviewed and the molecular mechanisms and availability are described.

Graded reductions in preexercise muscle glycogen impair exercise capacity but do not augment skeletal muscle cell signaling: implications for CHO periodization.

Novel data is provided demonstrating that when exercise is commenced with muscle glycogen below 300 mmol/kg dry wt (as achieved with the sleep-low, train-low model) further graded reductions in preexercise muscle glycogens reduce exercise capacity at 80% peak power output by 20-50% but do not augment skeletal muscle cell signaling.

Carbohydrate and exercise.

  • L. BurkeJ. Hawley
  • Education
    Current opinion in clinical nutrition and metabolic care
  • 1999
Strategies to maintain or enhance carbohydrate availability, such as the ingestion of carbohydrate before, during and after exercise, are critical to the performance of a variety of sports events, and are a key recommendation in current sports nutrition guidelines.

Regulation of Muscle Glycogen Metabolism during Exercise: Implications for Endurance Performance and Training Adaptations

An overview of the regulatory control of CHO metabolism during exercise is presented (with a specific emphasis on muscle glycogen utilization) in order to discuss the effects of both high and low CHO availability on modulating exercise performance and training adaptations, respectively.



No effect of glycogen level on glycogen metabolism during high intensity exercise.

It is concluded that during short-term intense exercise during which muscle glycogen availability exceeds glycogen demand, rate of glycogen breakdown, lactate accumulation, and performance are regulated irrespective of the preexercise Muscle glycogen level.

The effects of carbohydrate loading on muscle glycogen content and cycling performance.

Muscle glycogen contents were similar at the end of the 3-hr trial, indicating a greater utilization of glycogen when subjects were CHO loaded, which may have been responsible for their improved cycling performance.

Influence of carbohydrate ingestion on fuel substrate turnover and oxidation during prolonged exercise.

This study examined effects of ingesting a 10% carbohydrate (CHO) drink (CI) or placebo (PI) at 500 ml/h on total glucose appearance, blood glucose oxidation, and muscle glycogen utilization in 14 male endurance-trained cyclists.

The role of dietary carbohydrates in muscle glycogen resynthesis after strenuous running.

It appears that muscle glycogen can be normalized between daily strenuous running activity, and frequent feedings of a high carbohydrate diet did not enhance Muscle glycogen synthesis when compared to equal amounts of carbohydrates in two meals.

Muscle glycogen loading with a liquid carbohydrate supplement.

Glycogen loading can be accomplished at least as effectively and more comfortably by substituting a maltodextrin drink for some of the pasta and rice in a glycogen loading diet.

Effect of glycogen depletion on the ventilatory response to exercise.

Changes in exercise VE accompanying glycogen depletion were not explained by changes in CO2 flux to the lungs suggesting that other factors served to modulate VE in these experimental conditions.

Muscle glycogen during prolonged severe exercise.

A close relationship between utilized glycogen and combusted carbohydrate was found, and it seems highly probable that at high relative workloads primarily the glycogen stores in the exercising muscles will limit the capacity for prolonged strenuous work.

Muscle Glycogen Utilization During Work of Different Intensities

It is suggested that the main determinant for the metabolic response observed during exercise in man is related to the recruitment pattern for motor units in the muscles.

Effect of exercise-diet manipulation on muscle glycogen and its subsequent utilization during performance.

It is demonstrated that muscle glycogen can be elevated to high levels with a moderate exercise-diet regimen and carbohydrate loading is of no benefit to performance for trained runners during a 20.9-km run.

Diet, muscle glycogen and physical performance.

It has been shown that the glycogen content and, consequently, the long-term work capacity can be appreciably varied by instituting different diets after glycogen depletion.