Research Paper Volume 1, Issue 9 pp 818—830

Figure 1. Chronic contractile activity-evoked increases in skeletal muscle endurance performance and mitochondrial content are reduced in old, compared to young animals. (A). Fatigue resistance during 5 min of 1 Hz in situ stimulation of the control (CON, open squares) and chronically stimulated (STIM, closed circles) tibialis anterior muscles from young (solid lines) and old (dashed lines) animals (n = 7-8). (B) Electron micrographs depicting skeletal muscle morphology and SS and IMF mitochondrial volumes in young and old, control (CON, open bars) and chronically stimulated (STIM, closed bars) extensor digitorum longus (EDL) muscle sections. All images were taken at the same magnification. Scale bar located at the lower right of each picture represents 1 μm. (C) COX enzyme activity in EDL muscle homogenates (n = 9-13). Data represent the mean ± SEM. * P < 0.05 vs. Young; ¶ P < 0.05 vs. CON.