I've been using a heart rate monitor (Nike triax c6) for about 5 months. I programmed it for the fourth time today using the watch's zone finder (ride 5 min easy, 5 min medium, 3 min hard). It seems like the zones for the last two are all across the board and I am trying to determine if they are accurate or if something is wrong with the HRM. Below are the results from the 4 times I've done it.
Z1: 132-142
Z2: 142-176
Z3: 176-180
Z1: 129-147
Z2: 147-172
Z3: 172-180
Z1: 155-167
Z2: 167-173
Z3: 173-180
Z1: 144-149
Z2: 149-163
Z3: 163-169
The last two were done within about 30 days of each other. On today's ride I had about an hour between church & watching my kids while my wife went to a meeting so I was hustling to get on the road and might have started from a higher rate than usual. Also I'd already had 4 cups of coffee in the previous 3 hours. I ride ~300-350 miles per month in 20 to 50 mile individual rides (avg speed 18-20) with intervals once a week.
Not that I expect someone to have the answer based on this info. I guess I am just curious to see if this has happened to anyone else and if there is any reason for it. I don't really use the HRM for anything other than as another set of numbers to look at after a ride, so it doesn't much matter to me what the zones are. It just seems odd to me.