"Sometimes players don't like to be lambasted and I don't like doing it," he said. "I'm sure there are lots of managers up and down the country who have had their teams in earlier than my team so it's no boot camp, that's a load of nonsense.
"It's a fantastic training facility and they've worked a little bit harder than usual, that's all they've done.
The Rams boss denied suggestions any extra toil was responsible for the knee injury picked up by Giles Barnes in training this week.
The club are awaiting scan results on the problem but the midfielder is certain to be missing against Roy Keane's side.
Jewell explained: "He was playing football when he did it and believe it or not you have to run around to play football.
"Does a boot camp style meaning getting in at 10 o'clock and leaving again at 3 o'clock? That's boot camp is it?
"There's been hard work on the training ground but nothing I didn't do as a player so that being the cause of the injury just isn't true."
He added: "It was an unfortunate one in training. There was no-one near Giles and unfortunately he twisted his knee.
"We are waiting on the results of the scan when the swelling goes down so fingers crossed it is nothing too serious."