I always see photos of local track racers in that final push on the track, gritting their teeth, as they try to get that win.
But a few years ago when I used to work out with a sprint coach (running) at our local high school track, he used to get all up on my case when I'd grit my teeth while sprinting because it was wasting energy and my energy needed to be utilized solely in my legs. He always emphasized to keep my neck and face relaxed and focus on good, solid breathing.
He's a National Champion sprinter and Arena Football player.
So then I start sprinting at the velodrome and i notice every single guy gritting his teeth, straining at the neck and doing the opposite of what I learned in my other kind of sprinting. I even noticed myself doing it. In fact, just last week at the track I tried to focus on relaxing my face and breathing nice and hard.
I don't know if it really matters in cycling. Just sort of curious if anyone has any thoughts about that.