heart rate training

yes average HR seems low, most of your training should be done between 70% and 80% of maximum heart rate,
a quick formula to calculate your maximum HR is to substract your age from 220: 220 - 18 = 202
so you should aim for 140 to 150 average HR readings for aerobic training intensity,

it is possible that you did a lot of coasting so that brings the average HR down, did you enter your age and weight parameters correctly on your HR monitor ?

It is real hard to say anything without knowing how the ride went. You could have done the entire ride @ 18.7, or you could have done it @ 16 with efforts of 25+. Obviously something happened to raise your HR to 173.......

With HR I would focus more on what you can hold for a given duration (what can you hold for 5min, 20min, 1hr, etc.)

Your heart rate should be low. That is the goal. It indicates that your heart is not holding you back.

The question is: Can you ride faster (higher power output) or is something else holding you back? You can get an answer to that by trying to ride faster (higher power output) on the same route.

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Just to see how foolish heart rate calculations are: A different formula starting with 202bmp gives 70-80% as 160-175bpm. Just depends on whose advice you take and how they think you should train.

Also, the wind at your tail or in your face could skew any sort of interpretation. Were there parts with a minor down/up gradients?

Speed against effort, especially with the missing blanks is almost a meaningless association. Your HR is supposed to be where it belongs relative to the amount of training you put in, the amount of rest you give yourself, and it's relationships to your age. Welcome to the wonderful world of metrics.

The beauty of these numbers is to compare against itself over time. Start your log and see if things change as time progresses.

If you can figure out what your HR is at your LT, it can be a useful tool for determining your effort. A decent way to figure out your LT HR is to do some 20 min intervals with a good warm up and take a look at your average HR. If you do a couple you should start to see a trend. Also a good indication is the HR you start your deep breathing. I have developed such a feel for my HR @ LT that I can pretty much tell when I have reached my LT HR without even looking at my HR monitor.

so i did a harder ride and got 145 an average of 145 which seemed good for the effort i put it
as for max heart rate im going with 193.47

And thank you guys for your input. ill be trying to figure out what my heart rate at my LT is suggested by bgoetz.
As for right now ill be using the heart rate to determine how many calories im burning