H_max amplitude was lesser in old than young adults (age; p = 0.029; pooled data: young: 30.9% M_max; old: 16.6% M_max) and changed with pulse duration in both groups (p = 0.045; Figure 3B). H_max amplitude was lesser for RC_0.05than RC₁ (p = 0.032). A significant age × pulse duration interaction for I_H50 (p = 0.004) and post-hoc analysis indicated a greater I_H50 for RC_0.05 compared with RC_0.2 and RC₁ in both age groups (p < 0.001), and a greater I_H50 for old than young adults for RC_0.05 (p < 0.001) (Table 1). The I_H50/I_M50 ratio was greater for old than young adults (p = 0.025) and decreased with the increase in pulse duration (pulse duration: p < 0.001). The H_max latency was greater for old [0.34 (0.03) ms.cm-1] than young adults [0.32 (0.02) ms.cm-1; p = 0.008].

The H_M5% was lesser for RC_0.05 than RC₁ in both age groups (p values ≤ 0.028), while RC_0.05 differed from RC_0.2 (p = 0.006) and RC_0.2 (p = 0.016) in young adults only (Table 1; Figure 3D). Moreover, H_M5% was lesser in old compared with young adults for RC_0.2 (p < 0.001) and RC₁ (p < 0.001) but not for RC_0.05 (p = 0.36). M_Hmax was greater in old than young adults and varied with pulse duration (p < 0.001), with a decrease in M_Hmax from RC_0.05 (p < 0.001) and RC_0.2(p = 0.021) to RC₁ in both groups (Figure 3C; Table 1).

[INSERT FIGURE 3 HERE]