Solid-state ¹³C cross-polarization (CP) magic-angle spinning (MAS) nuclear magnetic resonance (NMR) experiments are carried out for the first time on rapidly frozen muscle biopsies taken in M. longissimus in vivo and at 1 min, 45 min, and 24 h post-mortem from three pigs. Two of the pigs were CO₂-stunned (control animals), and one was pre-slaughter-stressed (treadmill exercise) followed by electrical stunning to induce difference in metabolism post-mortem. ¹³C resonance signals from saturated and unsaturated carbons in fatty acids, carboxylic carbons, and carbons in lactate and glycogen are identified in the solid-state NMR spectra. The ¹³C CP MAS spectra obtained for post-mortem samples of the stressed, electrically stunned pig differ significantly from the post-mortem control samples, as the intensity of a resonance line appearing at 30 ppm, assigned to carbons of the methylene chains, is reduced for the stressed pig. This spectral difference is probably due to changes in lipid mobility and indicates altered membrane properties in the muscle of the stressed/ electrically stunned animal when compared with the control animals already 1 min post-mortem. In addition, the post-mortem period changes in glycogen carbons can be estimated from the ¹³C CP MAS spectra, yielding a correlation of r = 0.74 to subsequent biochemical determination of the glycogen content.