What exercises allow you to produce as much output as possible? What exercises and will allow you to target the muscles you want to hit and push things to failure while minimizing the risk of injury?
Machines will allow you to do all of those things. Machines allow you to maintain a fixed position and doesn’t require stability so you can purely focus on output. Some of my favorites are hack squats, leg presses, leg extensions, smith machine, seated leg curls, and lying leg curls. Don’t get me wrong; there are barbell exercises that can push a ton of growth, but I prefer to do them first while the body is still fresh, and fatigue has not yet hit. The great thing about machines is they allow you to position your body in the perfect position to hit the targeted muscle, and they allow you to safely push things to failure. Let’s say you are doing leg press, and the first rep you don’t feel it in your quads, which are the muscles you want to target. You can simply rack the weight, move your feet down a bit so your knees can travel forward more so you feel it hit your quads perfectly. Those reps where you feel your target muscles working are the reps that will yield the most growth. In comparison, if you are doing squats and you leave the set feeling wrecked without targeting the muscle intended, it’s not going to create maximal tension in the muscle you want to grow. You have to feel the muscles working, plain and simple.