a camcorder that can record in high speed.
But you have not provided enough information.
Coaching and training what?
Indoor activities would likely dictate good low-light video capture behavior so the camcorder needs lenses and imaging chip(s) generally larger than those found in most consumer cams under about $1,300. Unless you can control the lighting by adding lighting. Worklights - like those found in hardware stores would work well - but could be distracting to whomever is being trained/coached. And they get hot.
Some Sony camcorders have "SmoothSlowRecord" (in the $900 range and up) that allows a 3-second burst of 120 FPS resulting in 12 second slow motion playback. It is not "great resolution" though...
Something in the Casio Exilim line might do what you need. Photron, Vision Research, For-A (among others) make good high-speed cameras to provide "great resolution in slow motion".
I'm looking for a camcorder that has great resolution in slow motion. I use the camera for coaching and training.