Best workout/exercise to tone yam-like legs.

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http://www.myfitnesspal.com/post/search?page=1&phrase=legs

http://www.myfitnesspal.com/post/search?page=1&phrase=thighs

http://www.myfitnesspal.com/post/search?page=1&phrase=lower+body

Bulgarian split squats with increasing weights. Works the whole leg w/o impact problems.
http://gregcorso.com/blog/how-to-do-a-bulgarian-split-squat-bss/

Running, squats (with heavy weights), and lunges (also with heavy weights) have greatly improved my legs and my butt!

My legs are yams. Chubby yams. Very unsightly when I wear dresses but I wear them anyway.

Does anyone have any experience with toning their legs? I could ride my stationary bike for 20 minutes a day - do you think that would make a significant difference?

That would depend on how hard you ride the bike.

My workout is cardio-based and works the largest muscles of the body (legs) and I typically burn between 800 to 1000 calories per session - as per my HRM.
Walking to and from the gym (1.5h), walking on an incline treadmill (20m), eliptical trainer (increase intensity to reach 75% VO2Max for 25 minutes, stationary rowing for 30-45 min. Stationary bike interval training for 30-45min (VO2Max 75% to 90%). It will improve your cardio fitness, burn fat and also tone your legs. Your calorie-controlled diet should also help you to reduce your fat stores.
kind regards,

Ben