This study was undertaken to examine whether carbohydrate loading gives a good effect to improve the endurance performance in Japanese subjects who had habitually eaten carbohydrate-rich diets. The glycogen content of the vastus lateralis muscle was determined in 6 healthy male subjects with the aid of the needle biopsy technique by setting different diets after glycogen store was depleted by exhaustive exercise.
Glycogen content of the vastus lateralis muscle after mix, low and high carbohydrate diets was 22.7±2.0, 11.6±1.6 and 36.6±4.5 g/wet muscle⋅kg (mean±SD), respectively, while exhaustive time was 75′39″±10′02″, 67′58″±14′11″and 92′10″±22′10″ (mean±SD), respectively. Thus, a good correlation was noted between muscle glycogen content and work time.
It was therefore concluded that the glycogen content of the working muscle was a determinant factor for the capacity to perform long-term heavy exercise and that carbohy-drate loading attained with low carbohydrate diet and exhaustive exercise followed by high carbohydrate diet had a good effect to perform heavy exercise even in Japanese who lived on carbohydrate-rich diet.

Muscular endurance and blood flow of the forearm were measured in 65 healthy male and 53 healthy female subjects, all aged 19-75 years. Muscular endurance was measured using a hand-ergometer with a load equal to 1/3 of the maximum grip-strength of the subject. The blood flow in the forearm was determined before and immediately after exercise using mercury-in-rubber strain-gauge venous occlusion plethysmography.
The following results were obtained
1) The muscular endurance of both the male and female subjects was observed to increase with age (p<0.05) .
2) The forearm blood flow before exercise by the male and female participants was did not change with age (p>0.05) . However, the forearm blood flow immediately after exercise showed a tendency to increase with age in both groups (p<0.05) .
3) A close relationship was found between muscular endurance and forearm blood flow immediately after exercise in both the male group (r=0.584, p<0.001) and the female group (r=0.776, p<0.001) .
4) In forearm blood flow (both before and immediately after exercise) and muscular endurance, differences between male and female subjects in the same age group were not significant (p>0.05) .
5) These results agree with some of the changes seen in the morphorogical muscle characteristics with aging.