What is the definition of a 'practice in pads'?

What can players be made to wear during practices _without_ pads?

• helmets and shoulder pads, no pants
• helmets only, no shoulder pads or pants
• no helmets, shoulder pads or pants

I keep seeing the term 'helmets and shells' - e.g. 'practiced this afternoon in just helmets and shells'. Is that helmets and shoulder pads?

Despite the tragic events, the Eagles went through with their normal routine Sunday. They participated in a morning walkthrough and returned in the afternoon for a practice with shorts, helmets and shells (small shoulder pads).

RENTON, Wash. -- The Seattle Seahawks may have violated the NFL's collective bargaining agreement by allowing Terrell Owens to practice in shoulder pads during his first on-field practice.

League spokesman Greg Aiello said in an email Thursday that the league is gathering facts about Owens' debut practice on Wednesday. The Fort Worth Star-Telegram first reported the possible violation.

The CBA states that players have a three-day acclimation period during the preseason after signing: "Day 1 is for the physical and meetings. Day 2 and 3 the player may participate, but only in helmet and shells or a padded shirt. Day 4 and for the rest of camp is in full pads."

Owens was in shoulder pads for his first practice with the Seahawks. It's unclear if the team may face any discipline.