Turnover of human muscle glycogen with low-intensity exercise.
Med Sci Sports Exerc
; 26(8): 983-91, 1994 Aug.
Article
en En
| MEDLINE
| ID: mdl-7968433
ABSTRACT
To determine whether glycogen turnover occurs during prolonged low-intensity exercise, five subjects performed plantar flexion of the right leg at 15% MVC for 5 h. At rest and during the initial 2.5 h of exercise gastrocnemius glycogen was monitored in both legs with natural abundance 13C NMR. At 2.5 h exercise, a step-up infusion of 99% enriched 1-13C glucose was begun and maintained over the next 1.5 h of continued exercise to monitor 1-13C glucose incorporation into the exercising muscle's glycogen pool. Exercise was continued for an hour following the infusion, and NMR scans were performed throughout the session. During the first 2 h of exercise, glycogen 1-13C signal amplitudes dropped approximately 30% and remained there at 2.5 h, indicating that glycogen concentration had leveled. Following infusion, glycogen signal amplitudes rose to 123% of resting values, remaining there during an hour of subsequent exercise. There was no change of glycogen 1-13C signal in the nonexercising leg. Venous glucose levels remained stable until the infusion was begun and then rose < 7% (5.57-5.96 mmol.l-1) during the infusion. Venous insulin and C-peptide levels did not change during the infusion. We conclude that the human gastrocnemius can degrade and synthesize glycogen simultaneously during prolonged low-intensity exercise.
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Banco de datos:
MEDLINE
Asunto principal:
Músculo Esquelético
/
Esfuerzo Físico
/
Glucógeno
Límite:
Adult
/
Female
/
Humans
/
Male
Idioma:
En
Revista:
Med Sci Sports Exerc
Año:
1994
Tipo del documento:
Article