Another complaint about folks in the gym classes...
A lot of people move very jerkily, even when it comes to simple moves such as knee raises. Now please understand, I'm not trying to cast blame here, nor am I saying that these people are crude louts or any such thing. I'll be honest, though... it's distracting and even painful to watch.
A couple of guys keep crunching their upper bodies during simple knee raises, for example. I don't know what to make of that. It does throw off their rhythm, and it's almost an eyesore. It could be that they just need a little bit of coaching, or it could be that they're led such sedentary lives that they don't know how to move anymore. I just don't know.
Several people look like they're about to tip over when they do moderate tempo knee raises. This is usually because they're standing upright instead of leaning over and bending the supporting leg, as should be done during proper non-alternating knee raises. I don't know... is this because they've never been taught the fine points of this move? Or is it because they're trying to do the moves with as little effort as possible, so they stand vertically instead of supporting one's self with a single bent leg? I honestly don't know.