So, I'm just getting into racing and hitting the power meter hard this winter in preparation for next year's season. Due to my northern latitude and work schedule I don't always have time to get out on the real roads before night falls so I'm on my trainer a lot. The thing that I have noticed is that with each pedal stroke my head sways side to side approx 2 cm. This is when I'm riding at higher efforts, e.g. L3 and above. I'm guessing that when I am riding roads with similar effort my bike is doing the swaying. I'm wondering if I should be trying to restrain the sway so that my head is staying still.
The interesting thing that I have noticed is that when I do try to restrain it my efficiency drops and I experience more fatigue at the same wattage - which I'm guessing is because with the sway I am supplementing my leg muscles with my core muscles and when I restrain the sway I am isolating the leg muscles. Restraining the sway seems like a bad idea since, hey, if I have core muscles why not use them (with my FTP I'll take what I can get).
As far as optimum form goes, do those with it maintain an entirely sway-free head and bike while riding on the road? Or are they actually using a little side to side sway to their advantage?