While my fastball velocity isn't exactly where it was in the first 7 appearances, it's still improving. Dead arm might not be a clinical term,but it's one of the easiest conditions for a pitcher to identify. Some easy ways to describe it is that you may throw once every 5 days, but your arm feels like it thrown 12 days in a row, or when you throw there is a change of pace, without throwing a changeup. Which is exactly how I felt during that period. In my experience, the best way to get rid of dead arm, is to just throw through it.
Even if a pitcher can't recognise he has dead arm, chances are his coaches and even team mates will. The main sign being the fastball velocity being down, but also how that pitcher can act on the field. You can tell from guys' mannerisms and just their body language. You can tell when a guy's not feeling real good or he's not happy with the way he's feeling or the way he's throwing.
For Australian Ryan Rowland-Smith, he believes dead arm is mostly a Spring Training thing. Which may be true since you're coming off an offseason where you have your own throwing program, and then all of a sudden you're throwing everyday and doing extra work. You're on your legs all day, also you're in the heat, playing games in the middle of day and you're up early in the morning. So all those things factor into it.
When you're suffering from dead arm, all your 'stuff' may not be there. You lose some zest on your fastball, your changeup isn't moving, and your curveball isn't as tight, so it's your mental capacity and your mental toughness that has to be there, plus your ability to locate and to think with and against the hitter. However, dead arm goes away, and like the first rainy day after a two-week heat wave, it's a refreshing relief.