If you truly want strong legs without lifting, listen to me. Not trying to sound cocky, but I know what im talking about. Plyometrics will give you EXTREMELY strong legs. I have been jumping in track and field for the past 3 years, and plyos have helped me become a MUCH stronger and more explosive jumper, wiht almost all of the power coming out of my quads, hamstrings and calves. Bound 100 meters on a local track, and if you don't know what bounding is it is basically taking huge strides while running, many people call it "prancing." Also, One legged hops are clutch. Hop 50 meters down a track on your right leg, focusing on bringing your right knee out in front of you each time. The next 50 use your left leg. There are so many more things i could go into detail about without using weights. I have never lifted in my 3 years, and through tons of plyos, speed workouts (repeat 200s, 300s, 400s) and luckily good genes my legs have become very strong, and have helped me suceed in track. If you want more detailed stuff pm me