A few weeks ago someone was asking about using their average HR during a 5k race to establish their zones instead of a time trial. I can't find the thread. Is this an acceptable method?
yup. I went through my TT and figured out my max. Then some time later I did a 5k and noted my rate at the end when I was ready to puke my guts out - and you know what... it was actually 1 beat higher.