Complex enzyme activities were measured spectrophotometrically as described in Methods. All activity results are averages of 4 assays from the pooled sample ± SEM for each age group. Citrate synthase activities were used to normalize mitochondrial proteins. Activities for young (4-5 months), middle-aged (10-12 months), and old (20-26 months) WT and dwarf pectoralis CI-CV are plotted as follows: (A) CI activity. Coefficients of variance for WT and dwarf were 8.4 % and 19.3% (young), 14.5% and 19.6% (middle-age), and 4.1% and 16.2% (old), respectively. (B) CII activity. Coefficients of variance for WT and dwarf were 6.7% and 3.7% (young), 3.5% and 7.7% (middle-age), and 11.8% and 5.1% (old), respectively. (C) CIII activity. Coefficients of variance for WT and dwarf were 6% and 7.3% (young), 9.6% and 11.3% (middle-age), and 2.8% and 5.7% (old), respectively. (D) CIV activity. Coefficients of variance for WT and dwarf were 3.2% and 5% (young), 4.9% and 5.7% (middle-age), and 3.3% and 8.7% (old), respectively. (E) CV activity. Coefficients of variance for WT and dwarf were 9.9% and 4.5% (young), 18.2% and 14.1% (middle-age), and 2.2% and 7.4% (old), respectively. * - p<0.05 compared to young, ** - p<0.001 compared to young, † - p<0.05 compared to middle-aged, †† -p<0.001 compared to middle-aged, ‡ - p<0.05 compared to WT, and ‡‡ - p<0.001 compared to WT.