Cross-sectional area (CSA), peak Ca²⁺-activated force (P_o), P_o/CSA, and unloaded shortening velocity (V_o) were measured in slow (containing type I myosin heavy chain, MHC) and fast (containing type II MHC) chemically skinned soleus muscle fiber segments obtained from three strains of weight bearing and 7 day hindlimb suspended (HS) mice. HS reduced soleus slow MHC content (from ~50% to ~33%) in CBA and ICR strains without effecting slow MHC content in C57BL/6 mice (~20% of total MHC). Two-way ANOVA revealed HS-induced reductions in CSA, P_o, and P_o/CSA of slow and fast fibers from all strains. Fiber V_o was elevated post-HS, but not consistently across strains. No MHC x HS treatment interactions were observed for any variable for C57BL/6 and CBA mice and the two significant interactions found for the ICR strain (CSA, P_o) appeared related to inherent differences in slow vs. fast fiber CSA. In the mouse HS models studied here, fiber atrophy and contractile dysfunction were partially dependent on animal strain and generally independent of fiber MHC isoform content.