Natural abundance 13C nuclear magnetic resonance spectroscopy was used to detect signals from glycogen in the human gastrocnemius muscle. The reproducibility of the measurement was demonstrated, and the ability to detect dynamic changes was confirmed by measuring a decrease in muscle glycogen levels after exercise and its subsequent repletion. Single frequency gated 1H decoupling was used to obtain decoupled natural abundance 13C NMR spectra of the C-1 position of muscle glycogen.