She stretches Achilles tendons. She did an Achilles tendon surgery two years earlier. The bib is indeed the Boston marathon world record bib: http://citiusmag.com/wp-content/uploads/2017/04/joan-benoit-boston-960x546.jpg And on 4/20/1983 (two days after the Boston marathon that year) it did rain in Portland around 5:25am.
She then had a knee injury and surgery next year. 17 days after the surgery, she won the olympic trial and then won the olympic marathon, which was the first ever women’s marathon in Olympic Games. She ran the olympic trial at the age of 50 in 2008 and barely missed the trial cutoff at age 52 in 2010 Chicago marathon.