Fig. 5.

Actb-msKO skeletal muscle shows increased susceptibility to stressful stimuli. (A) Repeated maximal treadmill tests show a significant reduction in running time on the second trial in Actb-msKO mice. (B) Quantification of serum CK activity following treadmill test. Actb-msKO did not exhibit elevated sarcolemmal permeability. (C) Percentage force drop following five eccentric contractions on isolated extensor digitorum longus muscles. At 3 and 12 months of age, Actb-msKO muscle was significantly more susceptible to eccentric-contraction-induced force loss. (D) Quantification of force production from an in vivo eccentric contraction protocol testing the anterior leg compartment of control and Actb-msKO mice indicates a statistically significant column factor exists as determined by Two-way ANOVA. (E) Contraction number when force drop percentage was within 2% of final force drop percentage. Actb-msKO mice reached their final force drop percentage significantly faster than control mice. *P≤0.05 compared with control values, as determined by t-test.