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. 2018 Jan 18;124(4):980–992. doi: 10.1152/japplphysiol.00864.2017

Table 3.

In vitro contractile properties of soleus and extensor digitorum longus muscles of female skmERαWT and skmERαKO mice at 22 wk of age

skmERαWT skmERαKO P Value
Soleus muscle
    n 15 16
    Mass, mg 9.9 (0.5) 10.9 (0.4) 0.114
    Optimal muscle length, mm 8.9 (0.2) 9.3 (0.2) 0.240
    Physiological CSA, mm2 1.47 (0.066) 1.56 (0.051) 0.275
    Peak twitch force, mN 20.0 (0.9) 21.6 (1.3) 0.310
    Twitch time to peak force, ms 31.2 (0.7) 34.2 (0.8) 0.013
    Twitch one-half relaxation time, ms 39.5 (1.7) 37.9 (1.7) 0.563
    Po, mN 152.9 (5.0) 157.7 (7.3) 0.599
    +dP/dt, N/s 1.7 (0.05) 1.8 (0.09) 0.172
    −dP/dt, N/s 2.1 (0.07) 2.3 (0.2) 0.147
    Active stiffness, N/m 326.6 (10.9) 324.6 (17.7) 0.926
    Peak concentric force, mN 44.1 (2.8) 40.7 (2.9) 0.423
    Peak eccentric force, mN 292.0 (12.2) 310.7 (13.1) 0.309
    Freq50, Hz 21.4 (0.6) 21.6 (1.0) 0.921
Extensor digitorum longus muscle
    n 13 15
    Mass, mg 9.2 (0.2) 9.1 (0.3) 0.743
    Optimal muscle length, mm 10.5 (0.2) 10.7 (0.3) 0.688
    Physiological CSA, mm2 1.87 (0.042) 1.80 (0.058) 0.582
    Peak twitch force, mN 87.2 (5.1) 89.5 (5.0) 0.766
    Twitch time to peak force, ms 20.4 (1.0) 22.3 (0.4) 0.182
    Twitch one-half relaxation time, ms 20.1 (1.2) 24.6 (1.3) 0.034
    Po, mN 319.7 (8.9) 296.6 (11.9) 0.091
    +dP/dt, N/s 9.0 (0.3) 8.8 (0.4) 0.675
    −dP/dt, N/s 15.2 (1.2) 11.2 (1.04) 0.024
    Active stiffness, N/m 614.0 (29.7) 610.9 (34.1) 0.947
    Peak concentric force, mN 130.7 (8.4) 114.7 (11.1) 0.057
    Peak eccentric force, mN 558.2 (19.5) 478.9 (27.8) 0.031
    Freq50, Hz 31.7 (2.0) 26.1 (1.3) 0.034

Values are means (SE). CSA, cross-sectional area; Po, maximal isometric tetanic force; +dP/dt, maximum rate of tetanic force development, −dP/dt, maximum rate of tetanic relaxation, Freq50, frequency at which 50% isometric tetanic force is generated.