I think I am ahead

Sill in Zurich and conveniently working in a hotel with a full gym and pool attached. So as soon as I finished work I was straight to the gym before meeting clients for dinner. With flying home tomorrow I was concerned that I wouldn’t get tomorrows swim and bike in and so decided to get ahead of the game and swim today. The pool was almost empty which was great, my performance however wasn’t great. I swam for the full hour but I don’t believe it was my best. I lost count of laps altogether was a little distracted. Following that I hit one of the spinning bikes for 45 minutes, the room was very warm and they didn’t have the air-con on which made it s bit arduous. After 45 minutes I climbed onto one of the running machines to finish off with a 15 minute run. At the back of my min has been my maximum heart rate. I had been assuming that it was: 172 which is (220- my age 48 = 172). This would mean that my working rage should be 78-85% of that or 134 to 146 bpm However, I pushed myself today and only managed to hit 163 bpm which would suggest that I should be operating in the range of 127-138 bpm. This I find a bit strange since in the past I know that I have managed to hit 172!! Very confusing. I will investigate further but in the man time maybe I should be training at the lower rate to ensure staying within the aerobic threshold.