A couple of days ago, I switched to running early in the morning, after having always run in the late evening or (every now and then) in the afternoon.
I have eaten a light breakfast 45-60 minutes beforehand. But both training sessions have been awful compared to my evening ones. One was a running treadmill session, what would usually have been easy was quite tough, and my average heart rate was about 20 bpm higher than it would ordinarily be.
The other was on the elliptical, and I was literally not able to train more than at about 60 - 70% of what I normally would do; this was not laziness, it was just already too tough for my body at that intensity.
a) Is this normal after such a switch? Will I be able to train normally after a period of adjustment?
b) Is it 'equivalent' training in some sense to what I would do normally, or worse?
c) What are the likely reasons for this? It seems unlikely that low glycogen would have such a dramatic effect?