Fiber type-specific muscle glycogen sparing due to carbohydrate intake before and during exercise

Abstract

The effect of carbohydrate intake before and during exercise on muscle glycogen content was investigated. According to a randomized crossover study design, eight young healthy volunteers (n = 8) participated in two experimental sessions with an interval of 3 wk. In each session subjects performed 2 h of constant-load bicycle exercise ( approximately 75% maximal oxygen uptake). On one occasion (CHO), they received carbohydrates before ( approximately 150 g) and during (1 g.kg body weight(-1).h(-1)) exercise. On the other occasion they exercised after an overnight fast (F). Fiber type-specific relative glycogen content was determined by periodic acid Schiff staining combined with immunofluorescence in needle biopsies from the vastus lateralis muscle before and immediately after exercise. Preexercise glycogen content was higher in type IIa fibers [9.1 +/- 1 x 10(-2) optical density (OD)/microm(2)] than in type I fibers (8.0 +/- 1 x 10(-2) OD/microm(2); P < 0.0001). Type IIa fiber glycogen content decreased during F from 9.6 +/- 1 x 10(-2) OD/microm(2) to 4.5 +/- 1 x 10(-2) OD/microm(2) (P = 0.001), but it did not significantly change during CHO (P = 0.29). Conversely, in type I fibers during CHO and F the exercise bout decreased glycogen content to the same degree. We conclude that the combination of carbohydrate intake both before and during moderate- to high-intensity endurance exercise results in glycogen sparing in type IIa muscle fibers.

Effects of excess body mass on strength and fatigability of quadriceps in postmenopausal women

“…12,27,28,31,32 We also found a correlation between fatigue and carbohydrate intake, which may be linked to the fact that high intensity exercises mainly use anaerobic metabolism (glycolysis), recruiting type II muscle fibers (glycolytic fibers). 33 This finding has important implications for nutritional counseling as a strategy for optimizing functional performance, particularly as it relates to muscular endurance.…”

High-fat diet overrules the effects of training on fiber-specific intramyocellular lipid utilization during exercise

“…Such adaptation is detrimental to endurance exercise performance. We have previously demonstrated that net muscle glycogen breakdown during exercise in F is enhanced compared with exercise with exogenous CHO supply before and during exercise (17). Hence, it is tempting to speculate that fasting exercise may be an effective strategy for stimulating energy provision via fat oxidation, while maintaining the intact potential for glycogenolytic ATP production.…”

Periodic acid–Schiff’s reagent assay for carbohydrates in a microtiter plate format

“…Schiff's reagent, it is a useful method for qualitative or quantitative assay of carbohydrates. The periodic acid-Schiff's reagent (PAS) 1 stain is widely used in histology for visualising mucins [9; 10; 11], glycoproteins [12], glycogen [13] and other polysaccharides [14] in tissue and cells. PAS staining is also used for identifying the presence of polysaccharides, glycoproteins [15; 16] and mucins [17] in polyacrylamide or agarose gels and after transfer to membranes (blots).…”