145 to 160 would be about right for zone 2, for a 41 year old. Go to your local college or athletic center and have your Threshold power and max HR tested. It isn't that expensive. The internet formulas are not accurate. And people rarely go hard enough to determine it themselves. You need to suddenly feel like you are going to vomit while at the same time near passing out. It often takes a competitive situation or lab to properly determine max HR.