Cycling legs vs Running legs

Today my cycling legs were feeling pretty sluggish on my commute to work. Made it out and back ok (and even remembered to bring my shoes ;^) but definately feeling the wear of all these workouts. Immediately switched into my running stuff and headed out for a 4 miler after my ride home and interestingly ran it faster than any other training run thus far, and with an average hr of only 152, right in the heart of my zone2. It could be that I'm sacrificing my cycling legs for stronger running legs. Well, nonetheless - it's an improvement, so I'm happy about that.