Threshold workout in the heat

Tom and I met a half hour early and warmed up together. No afib day for Tom so we went and ran 5 sets of 400-500's at 85-90%. It was hot out. It's the last day of the most recent heat wave. I let the HRM do the talking. I did the 500's down end 400's up. I ran faster than expected and my recovery was good despite the weather conditions. 2:22-23's on the 500's and around 1:50 on the 400's. One of my fastest yet.