Solutions of 0.6 M NaCl and 0.3 M CaCl2 having similar conductivities were used to evaluate the ionic strength effects on spent fowl meat tenderness. Breast fillets were deboned immediately after bleeding (hot-boned) and NaCl or CaCl2 was injected into them at two different times (< 30 min post-mortem and after 24 h storage) followed by tumbling and solution replenishment to evaluate the effects of delayed application. Hot-boned and cold-boned (24 h) were used as controls. All tumbling was conducted at -635 mm Hg, 20 C, 20 rpm for 1 h. All fillets were baked and then sheared with an Allo-Kramer cell. The results indicated that CaCl2 and NaCl reduced the shear values similarly, suggesting that elevated ionic strength at a similar conductivity to NaCl may play a major role in spent fowl meat tenderization with CaCl2. Replenishing muscle at 24 h post-mortem with 0.3 M calcium solution to 10% (wt/wt) after tumbling did not exert further tenderization, indicating that injecting a 10% level of 0.3 M calcium solution into spent hen fillets was sufficient to cause maximum tenderization. The delayed application of both CaCl2 and NaCl solutions resulted in a tenderizing effect, perhaps by eliminating the toughening effect of the prerigor physical stimulation effect of the earlier injection process. The additional tenderizing effects of calcium or sodium solutions injected at 24 h post-mortem may allow poultry processors to tenderize their spent fowl meat without the time constraints present in the prerigor state.