I was talking about doing intervals and repeats at 6 minute mile pace earlier and then my 75 year old diabetic grandfather told me that when he was in the army as a youth he used to train HIIT at 4 minute mile pace and that 6 minute pace was so slow he could probably pull it off to this day. So I took him on the track and we did some 400 repeats @ 1:30 ... guess how many he got through before we had to call the ambulance to have him defibbed 3 times ???
I’ll cash app the closest guess $420