I have 2 training rackets. One (150g) for shadow work (dry swings in the office). The other (130g) for drills and casual play. I don't tire out as quickly as I used too and I am a bit quicker in my swing and reaction speeds.
It depends how you use it. If you stood for an hour 3 times a week smashing with it, your arm would get stronger no doubt. But, if you stood for an hour playing fast drives with it, your speed at that would improve. Likewise, defending smashes for a period of time. The best way to get the most out of this racket is to pick the area of your game you want to improve and work on it. Then, when you pick up your normal racket, you'll feel the difference
Is it something mainly to improve strength? As an ex national champ weightlifter, I dont lack in that area.
it's different in a sense that what you used to do is to shoot for the highest weight possible? with the racket, it also build your stamina since you're going thru the same motion over and over again. also, it will start to help you build muscle memory which i don't think weightlifters do, but i can be wrong, please give insight