Exercise Intensity - Mike Help?

Mike or anyone out there that knows, I've been logging my exercise for a while now. Lately though I have questioning the intensity of my workouts especially because I've been wearing a HRM. Most weeks I alternate classes in spinning, circuit training with 5 - 8 pound weights and run/walk.

In the past, I've always done (for an hour class) 60 minutes vigorous workout, but then it's not vigorous the whole 60 minutes. Today, for example, my heart stayed around 130 BPM for about 10 minutes of the ride while we warmed up. When we really got going, it stayed over 150 for about 45 minutes of the class. A few times it peaked at 175, but just when we sprinted hills or something really pushing. When I was done, my average BPM was 153. My range for fat burn is 145 - 165.

So my questions is what should I be using for intensity and total time for something like today? Should it be vigorous for the whole 60 minutes? And actually I want to know for the curcuit training too.

I guess I'm just really getting more into the exercising and want to be more accurate with it.

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