In my experience, unless you are needing to respond to an attack, or make one, you dont need to be right at the front of the peleton. My local track training sessions finish off with a game of "devil takes the hindmost" (last person accross the line gets eliminated each lap....f**king hard!) ....brilliant for learning where you should and shouldn't be in a group....too far back and you are screwed, boxed in and you are screwed....you want to be within the first 1/4 of riders so you can jump onto the wheel of the rider who decides to pull out for the long sprint.
So yer.....if it isn't a race, just join the back and work your way up....or ask to move in!
So yer.....if it isn't a race, just join the back and work your way up....or ask to move in!