There are multiple definitions:

1. R-R interval(English)

   • ECG, HRV, LFP
   • Cardiology, Electrophysiology

2. running-related injury(English)

   • FSP, FST, RTS
   • Sports medicine, Injury
   • https://doi.org…259671211020283
   • https://doi.org…47.2021.2016355

3. renal resistive index(English)

   • reflects the complex interplay between systemic circulation and renal microcirculation and should be considered a marker of systemic cardiovascular risk beyond its prognostic relevance for kidney disease
   • AKD, CKD, CVD, RAS
   • Kidney and adrenals, Hemodynamics
   • https://doi.org…nostics13101687