first, sorry for my bad english (now using google translate)
i think that there's nothing to substitue for machine leg extention
is there any exercise for quadricep ? (barbell free weight or gymnastic)
Try a squat. Any kind of squat.
yes of curse squat is great but i mean that do quadricep intensively like machine leg extention
I think you're confusing isolation with intensity. A lot of guys get plenty of quad stimulation w/o extensions. Front squats emphasize the quads a bit more, at least for me.
Sissy squats are excellent for isolating the quad in a manner analogous to the extension machine, and requires no equipment except something to hold onto for balance purposes. Should work perfectly for you.
agreed, or front squats if you want to load on some weight.
Front squat and lunges
Hack squats, leg presses, bulgarian split squats
Also, squatting with a 1-2 second pause at the bottom seems to hit the quads harder than usual, at least for me.
Sled work. Reverse drags especially, but any pushes/pulls with heavy weight. Front squats are great too though, as mentioned, they just seem more of a main lift than an isolation/accessory one to me.Some people seem to love hack squats, although I haven't used them a lot myself.