There are multiple definitions:

1. long-distance runner(English)

   • SS
   • Exercise & Training
   • https://pubmed.…ih.gov/3982265/

2. low-dose radiation [therapy](English)

   • applied in treating acute respiratory distress syndrome in COVID-19 patients
   • ACE2, cACE2, COVID-19, COX, sACE2
   • Pulmonology
   • https://doi.org…55/2022/8698825

3. lumbar disc replacement(English)

   • DDD, IBF
   • Spine (or spinal cord), Surgery, Orthopedics
   • https://doi.org…965/001c.116900