Try this leg workout tip

Try pausing at the bottom of a rep. This can make it harder as you reduce the stretch reflex or slingshot effect that propels you off the bottom. And making things harder is how you build muscle over time.

https://video.wixstatic.com/video/d84c3c_68ce57c63f254110b55cfe5dda6927e8/1080p/mp4/file.mp4