text: Yo, listen up, I got a tale to tell,
  'Bout head-down tilted bedrest, it's a microgravity cell.
  We simulate the conditions, reduced external force,
  To peep at circadian blood pressure, let's explore the source.
  
  For 42 days straight, we tilted six degrees,
  Analyzing profiles of blood pressure with ease.
  Heart rate, stroke volume, cardiac output, and resistance,
  All under scrutiny, we won't miss a single instance.
  
  Seven volunteers, healthy and strong,
  From 25 to 31, they came along.
  We strapped Portapres for 22 hours a day,
  Baseline, tilt, and recovery, that was the way.
  
  Using 'Modelflow,' we estimated stroke volume,
  From finger blood pressure, yo, it was the move.
  Head-down tilt swiftly reduced BP's sway,
  Especially diastolic, we saw it fade away.
  
  But long-term tilt didn't mess with BP's height,
  The level stayed steady, it didn't take flight.
  Heart rate's day-night difference, it remained untouched,
  While cardiac output fought, it truly clutched.
  
  Heart rate climbed up, stroke volume went down,
  Maintaining the balance, no need to frown.
  Physical activity and posture got the upper hand,
  They ruled the diurnal BP, it's a command.
  
  Yo, stroke volume and heart rate changes were seen,
  During head-down tilt, it wasn't just routine.
  Other factors played a role, beyond blood's flow,
  Affecting cardiovascular performance, we now know.