New Delhi, June 19 -- Olympic 1,500-meter bronze medalist and world champion Jenny Simpson remains under medical care Thursday but shows "encouraging improvement" after collapsing while pacing a mile group at an event in Raleigh earlier this week.

In a post on Instagram, Fleet Feet, the company where Simpson serves as its chief running officer, wrote she "continues to exhibit the strength and resilience that have long defined her. True to form, she has already asked about her mile time and whether she won."

The 39-year-old Simpson underwent CPR at the track Tuesday night and an automated external defibrillator was also used before being transported to the hospital. She was taking part in a community track event hosted by Sir Walter Runn...