Originally Posted by gregf83

There are a number of studies that suggest beneficial effects to training in a glycogen depleted state:

From Caffeine Ingestion and Cycling Power Output in a Low or Normal Muscle Glycogen State.:


Refs

(8): Skeletal muscle adaptation: training twice every second day vs. training once daily.
(16): Training with low muscle glycogen enhances fat metabolism in well-trained cyclists.
(29): Acute signalling responses to intense endurance training commenced with low or normal muscle glycogen.
(30): Skeletal muscle adaptation and performance responses to once a day versus twice every second day endurance training regimens.