As a personal trainer, one of the most common goals I hear from female clients is " I don't want to get bulky, I want to tone". In reality, there is no such thing as "toning". I believe what women are actually referring to comes down to two main things, gaining muscle while losing excess body fat. The notion that using light weights for high reps to achieve a "toned" look is unfortunately not a reality. Using a high rep scheme of 15-20 does not make muscles appear long and lean while a low rep scheme of 3-6 does not automatically create a bulging/bulky look. Muscles grow in response to exercise. While a high amount of repetitions will build muscle, lower reps with an increased amount of weight will stimulate much more muscle growth. The myth that lifting heavy will not achieve a "toned" look probably came from the fact that it is hard work and requires a lot of motivation and determination.
Now let's take a look at the second half of achieving the toned look, losing excess body fat. If you're lifting heavy enough, you're already on your way to building muscle, but now you may have to lose some excess fat. Generally, a lower carbohydrate, minimally processed diet works very well for most people. Depending on the intensity and duration of your physical activity, you may need more carbohydrates, but for most people staying on the lower end works well. Using a well balanced approach and high quality foods will help fuel workouts and maintain a lower body fat percentage.
So although the thought behind how to achieve the toned look is a myth, it is attainable, it just takes hard work and dedication. Don't be afraid to lift heavy and keep a well balanced, high quality approach to your nutrition!