Thanks for the advice from all, but a few points of clarification are needed here. I weight train everyday during lunch at work, which leaves little to no time for my cardio. Therefore, I decided to bike in the evening so as not to compromise my weight training. The back pain is not a result of any weak muscles (far from it), but a degenerative disc in the lumbar area which pressess against the sciatic nerve every now and then. It requires surgery which I have been putting off.
Performance is my interest and desire because of my competitive nature. I've been an athlete all my life, and I always push myself, regardless of what it is that I do. Although I have no desire to compete in races, I have challenged myself to be able to roll with some of the faster riders that race in the park, regardless of my age. Just my way of setting persoanl goals, challenging myself and having fun while getting my cardio in. So, while I appreciate the advice, I do't believe the xootr, or whatever its called, is for me.