Originally Posted by terrymorse

I found the paper!

While this study is not precisely "alternating hard and easy weeks", this 4-week program preloaded the first week with 5 days of high intensity (block periodization), followed by 3 weeks with just one high intensity day. And they report power increases over the traditional "two intense days per week" training program:

Block periodization of high-intensity aerobic intervals provides superior training effects in trained cyclists

...The present study suggests that block periodization of training provides superior adaptations to traditional organization during a 4-week endurance training period, despite similar training volume and intensity.

Ronnestad et al, 2014