Report Achilles tendon in Running Tips Posted June 19, 2017 I'm in week 3 of C25K and have begin having issues with my Achilles. They aren't stretching out well and are making running difficult. I took two extra rest days at one point last week, which picked my timetable back a little and seemed to help, but after two more scheduled runs the issue has returned. Do I need to go easier, or run through it? They do seem to loosen up a bunch as I run, but for hours after I finish are as tight as piano strings.