Yoga is great for flexibility and strength training that we need in our daily lives. But cardio is also necessary for overall health if we are striving for QUALITY OF LIFE.
As I mentioned in Yoga Chuck’s Physical Routine I ride a bike or spinner for the cardio my body needs. I ride three times per week and thirty minutes or more each ride. Of course if weather permitting, I'm outside riding. Basically the heart rate needs to increase above resting to be considered cardiovascular. Cardio exercise can come in many different forms from cycling, running, swimming, aerobics, various machines, walking, ....
I've done Ashtanga Modified Primary Yoga classes in heated rooms and sweating within minutes and increasing the heart rate at different times in the class. Ashtanga, Hot Yoga, and Power Yoga increase your heart rate above your resting rate that are good for your heart. I consider these types, fitness Yoga. A lot of people like myself can't handle a steady diet of this yoga so we choose other forms of Yoga like Hatha that is still good for the heart but we need to add cardiovascular exercise for the heart.
I feel I have control on a bike and the spinning is good for the knees and hips as well. I can get to a comfortable cadence (RPM: revolutions per minute of one pedal) and hold for the duration of the exercise. To be at the optimal cadence 90 - 95 RPM is what works the best. I know this from my training and racing days. I don't recommend anyone to attempt this without months of training and even then it may never be comfortable for you. I know when I get off the bike after riding the high cadence my legs feel great having more feeling and control from what I believe is the brain being able to communicate with the legs, the brains signals are received without interruption (Yoga Chuck's theory).
Check out the website/video of Parkinson's Disease Cycling Therapy. My MS has similar results lasting part of the day after cycling. It also gives me a natural high.
Remember to get cardiovascular exercise even if you go out for a walk it's beneficial. Again, you need a regular diet of exercise to receive the benefits it offers, so just commit the time for yourself to experience the continued quality of life you deserve.
Healthy & Happy,