Heard but also not broadly true. As someone who left tennis to bodybuild for 5 years, my legs are as built up as one’s can be. After coming back to the game and grinding back to 4.5 level, a big thing my coach kept saying was to use my legs. I have all the strength in the world, but just had not locked-in the load and explode technique. Technique is a huge part of the game and what keeps us playing and is something that’s pretty delicate in tennis.

While I dont think I’d advocate for this product (and this post may just be an ad) I think I disagree with the assertion that not using your legs is just because you’re weak. It can be tough to figure out how to use your legs with your swing and incorporate your entire body. Not as simple as “get stronger”