Related Experiment Video
Updated: Feb 28, 2026

Quantification of Subcellular Glycogen Distribution in Skeletal Muscle Fibers using Transmission Electron Microscopy
Published on: February 7, 2022
Exogenous carbohydrate form during low-muscle glycogen conditions has minimal impact on cycling performance
Ian R Matthews1, Alejandro M Rosales1, Josey K Walker1
1Montana Center for Work Physiology and Exercise Metabolism, School of Integrative Physiology and Athletic Training, The University of Montana, Missoula, MT, USA.
Background:
Skeletal muscle recovery is improved with immediate postexercise carbohydrate feeding. Little is known regarding muscle recovery and performance when feeding is delayed. The purpose of this study was to examine the effects of varying exogenous carbohydrates on cycling performance with delayed feedings and low skeletal muscle glycogen content.
Methods:
Following 60 min of cycling and an overnight fast (12.1 ± 0.4 h), the participants consumed 2.10 ± 0.13 g·kg-1 bodyweight carbohydrate of one of the following: whole potatoes (POT), cooked pasta (PAS), energy gel (GEL) or remained unfed (control, CON), then rested for 120 min. The participants then cycled for 60 min at 65% Wmax and completed a 19.4 km time trial. Muscle and blood samples were collected prefeeding, 120 min postfeeding, and after cycling for glycogen, glucose, and insulin analyses.
Results:
The time trial mean power output was higher in the PAS (213 ± 56W, p = 0.006) and GEL (209 ± 71W, p = 0.011) compared to CON (179 ± 68W), but POT (196 ± 51W, p = 0.199) was not different from CON. Power was similar between POT, PAS, and GEL (p > 0.05). Time trial finish time trended towards significance (p = 0.088) with carbohydrate trials averaging 3 min faster than CON. Muscle glycogen was similar between trials (p = 0.446) and did not change due to feeding (prefeeding: 44 ± 21 mmol·kg-1, postfeeding: 47 ± 23 mmol·kg-1, p = 0.120). Glycogen declined after cycling for 60 min (26 ± 16 mmol·kg-1, p < 0.001) compared to pre-feeding and post-feeding samples. Glucose and insulin were elevated in carbohydrate trials over CON 0-30 min post-feeding (p < 0.05).
Conclusions:
Varied pre-exercise exogenous carbohydrate sources effectively improve cycling time trial performance in a glycogen compromised state.
More Related Videos
Related Concept Videos
Metabolic States of the Body: Fasting and Starvation
Muscle Recovery and Fatigue
Metabolic States of the Body: The Postabsorptive State
Initially, glycogen stored in the liver is broken down to release glucose into the bloodstream, while glycogen in the muscles is broken down to supply glucose for energy directly within the muscle cells. As glycogen stores diminish,...
Energy Supply for Muscle Contraction
Overview of Carbohydrate Metabolism
Glucose transport into cells is facilitated by a family of transport proteins called GLUT (Glucose Transporters). GLUT4 is the primary glucose transporter for insulin-stimulated glucose...
Glucose Homeostasis: Regulation of Blood Glucose
During fasting, when blood glucose levels are low, the pancreas secretes glucagon. it...

