Have really focused on my eating and exercise since early December. M weight has gone from 171 to 158.
I am 5 foot 8, 46 years old. My winter Canadian exercise program is as follows:

1) Every other day a 1 hour weight session/exercise ball session. This is the exact same inner core strength workout that I was put through a couple years back when I hired a personal trainer. I am getting cut and have really noticed my inner core strength increasing dramatically. This seems to be working for me.

2) Daily 1 to 1.5 hour ride on my Spincycle. I warm up for 5-10 minutes with light pedalling and than follow a program where I pedal sitting down for 5 minutes with my hear rate in the 130-135 BPM zone and than every 5 minutes I stand up on the pedals and pump a little harder for 1 minute which puts my heart in the 150-155 BPM zone. Than I sit down and pedal for another 5 and keep repeating this for 60-90 minutes.

I am wondering if there is something I can do in this 60-90 minutes that would be better for me conditioning wise. I am only interested in staying fit and lean, my speed on the bike or my ability to race is not something I am interested in at this point. I love to cycle but as you all know, 90 minutes on a spinner is like 4 hours of outside riding. I want to make sure that this time is spent in the most beneficial manner. Should I be varying my hear rate more? Should I be staying closer to the 130 BPM and forget the 150-155 spikes etc.