I did 45 minutes on the treadmill. Maintained my heart rate between 143-154 BPM

My 50 yo friend teased me last night that he I might have a heart attack when I do strenuous exercise because I am so out of shape daw. The nerve. He also said I have no discipline when it comes to my body/health (which is kinda true) But I'll show him! I can turn things around