Found this great bit of info from mercola.com. Apparently the best way to really pick up a cardio workout is to have short high intensity peaks in your workout to really push yourself.
New findings suggest that it pays to alternate short bursts of high-intensity exercise with gentle recovery during workout regimens at least once a week.
Using Interval Training
Although this alternating technique, called interval training, has existed for decades, a new study has confirmed that it can dramatically improve cardiovascular fitness and the body’s fat-burning capabilities.
Researchers asked eight college-age men and women to sprint for 30 seconds, and then either stop or pedal gently for four minutes. After only two weeks of this interval training, 75 percent of them doubled their endurance.
A control group, which did not do any interval training, showed no improvement in endurance. The marked improvement in the interval training group was even more startling because the volunteers were already fairly fit.
Another study also showed that interval training enhances the body’s ability to burn fat. Eight women in their early 20s were told to cycle for 10 sets of four minutes of hard riding, followed by two minutes of rest. After two weeks, the amount of fat burned in an hour of continuous moderate cycling increased by 36 percent, and their cardiovascular fitness improved by 13 percent.