Magic Number Mix-up

I met with my rheumatologist the other day.  We had a decent discussion about my level of physical activity.  We've come to an understanding/agreement.  I can run.  With some limitations. Depending on the impact the activity has on my knees, I can either go for a distance limitation (a 5K or 3.1 miles) or a longevity limitation (1 hour).  If I'm running, I can do a 5K.  If I'm biking, then I can go for 1 hour.  See how that works?  So when I go work out on the elliptical now, I go for 3.1 miles.  I went for a bike ride today and did 4 miles..not a long ride and it only took me 20 minutes.  I'm not fond of bike riding.  You don't burn as many calories biking...or if you do, it's because you went twice as long.  However, the other thing my doctor and I discussed is the need to vary my cardio activities.  Muscles can grow accustomed to a specific movement or exercise.  When this happens the muscles become less efficient.  The best way to avoid this is to mix things up.  This week I went running, did the elliptical, and biked.  I also tossed in some weights for good measure.   Running is good.  It's great!  But it shouldn't be the only thing I'm doing and when I am doing it, my doctor recommends that my runs aren't the same....walk parts, run parts, go up hill, etc.  DO NOT do the same loop at the same pace every time you run.  This seems logical.  It means that "interval" training (when you do a short hard burst....1 minute....at the highest pace you can handle, and then crank it down to a comfortable pace you can maintain and "recover" for 2 minutes, then repeat) is REALLY good for you.  It is also why the C25K program is so great.  Each week they change your routine making your running segments longer and your walking segments shorter and building up your endurance all at the same time.  Genius!  So, whatever your fitness routine is, mix it up.  Have some fun.  Try new things.  I'm still tossing around the idea of yoga.  I haven't tried it yet, but I have this "sense" that it would be good for me.  My rheumatologist agrees.