Contraction and relaxation during force-length relationship in human right atrial cardiac muscles. Preserved force-length relationship from 80 to 100% Lmax in isolated isometric contracting right atrial cardiac muscles from non-diabetic (non-DM, closed circles, n = 8) and type 2 diabetic (DM, open circles, n = 6) patients. The contractile parameters, developed force (Fdev, A) and maximum rate of contraction (+dF/dtmax, B) were not different between both groups. However, both relaxation parameters, minimum rate of relaxation (-dF/dtmin, C) and time constant of relaxation (Tau, D) were impaired in muscles from type 2 diabetic patients. Overall this indicates preserved contraction but impaired early and late relaxation in human diabetic right atrial myocardium with preserved LV ejection fraction. Two-way ANOVA: length effect: * = p < 0.05 vs. 80% Lmax for both non-DM and DM group; Group effect: # = p < 0.05 vs. non-DM. Data are mean ± SEM.