After much work I have a AeT and AnT difference of less than 10%. So Sept I started to do hard interval work. Almost immediately my HRV started to go way up. I am 65 and my previous HRV was what I considered normal for my age 30-40 ish. But I was hitting 70-80 ish. Also the increases didn’t seem to match the training days. I am trying to understand what is happening. I read that sometimes HRV can skyrocket when you are severely overtrained, but I didn’t feel that bad. I feel like my previous zone 1 & 2 work had well prepared me to take on more HIT. Currently I am holding mid-80’s fitness score on Training Peaks so I feel like I had a great base. I know that HRV is only a good for looking backwards, I still use Scott’s “how do I feel today test” and I kept training because I felt good. Any opinions are welcome.