Figure 8. Frailty grades the age‐dependent reduction in peak Ca²⁺ current, Ca²⁺ flux and the gain of SR Ca²⁺ release in voltage‐clamped myocytes.

A, representative Ca²⁺ currents recorded from cells from mice with different FI scores. B and C, peak Ca²⁺ current and the integral of the Ca²⁺ current (Ca²⁺ flux) declined with age. D, the gain of SR Ca²⁺ release decreased with age. E and F, the age‐related declines in peak Ca²⁺ current and Ca²⁺ flux were graded by FI score. G, the gain of SR Ca²⁺ release was negatively correlated with frailty score. Differences between age groups were assessed using a Mann–Whitney Rank Sum test and correlations were evaluated with linear regression analysis (n = 11 adult and 32 aged myocytes). Filled symbols indicate adult mice and open symbols indicate aged mice.