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. 2024 Nov 15;603(1):187–209. doi: 10.1113/JP286938

Table A2.

Force–velocity parameters and peak power of fast MyHC IIa fibres at 15°C

Men Women Combined P value
Young (39) Old (38) Young (36) Old (37) Young (75) Old (75) Age Sex Age × Sex
Po (mN)
pH 7.0 + 4 mm Pi 1.25 ± 0.37 0.75 ± 0.30 0.69 ± 0.17 0.53 ± 0.20 0.98 ± 0.41 0.64 ± 0.28 0.004 0.001 0.155
pH 6.8 + 12 mm Pi 1.09 ± 0.37 0.66 ± 0.26 0.59 ± 0.14 0.45 ± 0.18 0.85 ± 0.36 0.56 ± 0.25 0.004 0.001 0.160
pH 6.6 + 20 mm Pi 0.95 ± 0.27 0.57 ± 0.22 0.51 ± 0.13 0.40 ± 0.17 0.74 ± 0.31 0.49 ± 0.21 0.003 0.001 0.106
pH 6.2 + 30 mm Pi 0.75 ± 0.23 0.44 ± 0.16 0.40 ± 0.11 0.33 ± 0.13 0.58 ± 0.26 0.38 ± 0.16 0.003 0.001 0.175
Po (kN m−2)
pH 7.0 + 4 mm Pi 156 ± 28 180 ± 33 162 ± 20 185 ± 32 161 ± 24 182 ± 33 0.003 0.383 0.939
pH 6.8 + 12 mm Pi 136 ± 25 158 ± 29 141 ± 18 158 ± 33 139 ± 22 158 ± 31 0.010 0.757 0.702
pH 6.6 + 20 mm Pi 120 ± 22 138 ± 29 122 ± 17 141 ± 31 121 ± 20 139 ± 30 0.011 0.708 0.884
pH 6.2 + 30 mm Pi 94 ± 17 107 ± 23 94 ± 15 114 ± 26 94 ± 16 111 ± 25 0.006 0.553 0.537
V max (fl s−1)
pH 7.0 + 4 mm Pi 3.98 ± 0.51 3.91 ± 0.58 3.75 ± 0.51 3.25 ± 0.67 3.87 ± 0.52 3.58 ± 0.71 0.070 0.009 0.175
pH 6.8 + 12 mm Pi 3.72 ± 0.50 3.58 ± 0.45 3.48 ± 0.45 2.99 ± 0.58 3.60 ± 0.55 3.29 ± 0.59 0.025 0.005 0.199
pH 6.6 + 20 mm Pi 3.46 ± 0.49 3.37 ± 0.38 3.25 ± 0.41 2.83 ± 0.62 3.36 ± 0.47 3.10 ± 0.58 0.042 0.003 0.227
pH 6.2 + 30 mm Pi 3.05 ± 0.50 2.86 ± 0.42 2.86 ± 0.35 2.46 ± 0.60 2.96 ± 0.44 2.66 ± 0.55 0.008 0.009 0.476
Peak power (µN fl s−1)
pH 7.0 + 4 mm Pi 153.0 ± 46.1 99.1 ± 37.1 87.5 ± 23.6 64.1 ± 23.5 121.6 ± 49.4 81.8 ± 35.6 0.003 0.000 0.255
pH 6.8 + 12 mm Pi 134.1 ± 42.9 87.8 ± 33.4 77.3 ± 21.8 55.9 ± 22.2 106.9 ± 44.6 72.1 ± 32.5 0.005 0.000 0.288
pH 6.6 + 20 mm Pi 110.8 ± 34.7 70.4 ± 24.9 62.0 ± 18.3 45.6 ± 18.6 87.3 ± 37.2 58.2 ± 25.2 0.004 0.000 0.170
pH 6.2 + 30 mm Pi 69.4 ± 21.0 45.3 ± 16.2 37.5 ± 11.3 28.6 ± 12.5 54.1 ± 23.3 37.1 ± 16.7 0.006 0.000 0.170
Peak power (W L−1)
pH 7.0 + 4 mm Pi 19.4 ± 4.6 24.5 ± 6.2 20.8 ± 3.2 23.3 ± 6.9 20.0 ± 4.0 23.9 ± 6.5 0.005 0.673 0.782
pH 6.8 + 12 mm Pi 17.0 ± 4.2 21.7 ± 5.7 18.3 ± 2.9 20.2 ± 6.1 17.6 ± 3.7 21.0 ± 5.9 0.007 0.779 0.874
pH 6.6 + 20 mm Pi 14.1 ± 3.7 17.7 ± 5.0 14.7 ± 2.6 16.5 ± 5.6 14.4 ± 3.2 17.1 ± 5.3 0.012 0.902 0.793
pH 6.2 + 30 mm Pi 8.8 ± 2.3 11.3 ± 3.1 8.9 ± 1.6 10.4 ± 4.1 8.9 ± 2.0 10.9 ± 3.6 0.007 0.967 0.762
a/Po
pH 7.0 + 4 mm Pi 0.048 ± 0.010 0.057 ± 0.014 0.055 ± 0.009 0.065 ± 0.020 0.051 ± 0.010 0.061 ± 0.018 0.014 0.059 0.659
pH 6.8 + 12 mm Pi 0.053 ± 0.011 0.064 ± 0.018 0.062 ± 0.012 0.076 ± 0.057 0.057 ± 0.012 0.070 ± 0.028 0.009 0.072 0.703
pH 6.6 + 20 mm Pi 0.054 ± 0.013 0.063 ± 0.017 0.061 ± 0.012 0.073 ± 0.034 0.057 ± 0.013 0.068 ± 0.027 0.046 0.097 0.806
pH 6.2 + 30 mm Pi 0.048 ± 0.012 0.061 ± 0.018 0.052 ± 0.011 0.062 ± 0.031 0.050 ± 0.012 0.061 ± 0.025 0.021 0.414 0.773

Absolute (µN fl s−1) and size‐specific (W l−1) peak power were calculated with the fitted‐parameters from the force–velocity curves. The absolute (mN) and size‐specific (kN m−2) Po for each fibre was the average from all the contractions within each condition. The maximal shortening velocity (V max) was calculated using the Hill equation (1938), and the a/Po ratio is a unitless parameter describing the curvature of the force–velocity relationship. The number of fibres (n) for each cohort is reported in parentheses. Values are the mean ± SD.