I live in a remote area of the city where there's no affordable gym nearby,in my apartment gym there are only DB upto 12.5kg,leg extn and curl machine.Any suggestions how to plan my leg workout with these light free weights? One idea is doing mad volumes of lunges and curls,is that a good idea?(I can't do pistol squats)
When it comes to powerlifting, nothing really beats out doing squats. You can do a lot of leg work but the technique you gain from doing squats is missed. That said, leg extensions and leg curls will work your quads and hamstrings. Personally, I find the leg extension to be uncomfortable.
One of my favourite quad building exercises is Bulgarian split squat or elevated split squats:
3 sets of 10-12 Bulgarian split squats usually leave me feeling like I can't walk the next day. I squat 165 kg for a 1 RM, but doing split squats at just bodyweight is a good challenge for myself. The unilateral aspect of the workout is also great for improving the weaknesses between the right and left leg muscles. With 12.5 kg dumbbells, I think these could be rather difficult.
Distance from the bench in a Bulgarian split squat is an individual thing, however:
The closer you stand to the bench, the more the Bulgarian split squat will emphasize your quads – though if you’re too close, it might give you some knee pain. Standing further away will tax your hip flexors more heavily, though it could also strain your groin. Experiment to find a distance that works for you.
The key to the exercise, from that same article, is this:
Lower until your front thigh is almost horizontal, keeping your knee in line with your foot. Don't let your front knee travel beyond your toes.