<p>In this study, we have developed and evaluated AMPI electrodes with remarkable attributes, including ultra-low on-skin impedance, good ionic conductivity, adhesion, and stretchability. Through the incorporation of plasticizer PEG into the protonic PAA/PAMPS hydrogel, we achieved a high ionic conductivity (~0.028 S · cm⁻¹) alongside exceptional mechanical properties (toughness of ~42 kJ · m⁻³ and elongation at break of ~390%). Furthermore, the addition of ionic conductive components, such as salts (NaCl, LiCl, and LiBr) or the ionic liquid ChCl, significantly reduced impedance. Specifically, our AMPI hydrogel with 4 wt% LiCl, exhibits an ultra-low impedance of ~24 kΩ · cm² in the low-frequency range (only ~5% of that of commercial Ag/AgCl electrodes) and good adhesion properties and stability. These characteristics facilitated excellent and stable sensing capabilities, enabling the recording of human electrophysiological signals with a high SNR of ~25 dB and no significant degradation after 5 h of monitoring. Additionally, leveraging the swelling ability of AMPI gels, the prepared ECG sensing module enabled continuous and stable monitoring of ECG signals during exercise, maintaining a dynamic equilibrium between water loss and hydration. Overall, our AMPI hydrogels amalgamate a straightforward fabrication process with exceptional properties, offering promising prospects for the field of epidermal electronics and long-term health monitoring devices.</p>