I want to Weight Train to Tone and Strengthen, but not add Bulk

Hi, I really like your videos on YouTube. They help alot!
I'm a long distance runner. I've just recently started weight training. I get different answers from everybody but my question for you is: how can I avoid bulking up? I'm confused about what amount of weight I should lift. Should I avoid heavy squats and lunges? I just want tone and definition.

YouTips4U Answer: long distance runners often don't spend needed time doing resistance training to maintain upper body strength so it's really good that you are considering adding it to your life because it is important for your muscles. Don't worry about bulking up. As a woman that is really hard achieve unless you gain a lot of weight on top of your muscles. That will usually give the appearance of bulk. You being a long distance runner burns a lot of excess calories and keeps your metabolism revved and therefore your less likely to store fat; very hard to bulk up, but you do need the strength training and its very good for your body. Keep the repetitions between 12-15 and do 2-3 sets of each weight exercise. That will tone and strengthen your muscles and not add bulk. Don't lift excessively heavy weight, but just enough to feel muscle fatigue as you approach your last 2-3 reps. Also, I really don't recommend using heavy weights with squats and lunges. Both squats and lunges are very good for toning, but you don't want to use heavy weights as you can damage your knees that way. Adding some weight for resistance is fine with lunges. With squats it can be tricky and should only be done with light weight and only if you have no history of back problems as this tends to place excess strain on the spine.