Lots of people ask how can i tone my body? or how can I convert fat into muscle? The truth is that fat can not be converted into muscle, it can only be utilized as energy to feed the needs of the body. So, first thing you need to understand is that if you are looking for more muscle definition you first have to burn the fat that surrounds the muscle. but the second step would be to tone and toning can happen simultaneously while burning fat. Toning is directly correlated to the density of the muscle. Remember the last time you felt someones arms and even though they were pretty relaxed they seemed to be flexed. The only way you can account for such an effect is to maximize the resistance training of that muscle. In other words there are no shortcuts, the more toned you want a certain muscle group to be the more you have to stimulate that muscle group. Over time you will start developing these things between your muscle fibers that are called cross bridges or cross links and these are the connections that allow your muscles to contract. So, you have one layer of your muscle fibers called myosin which binds onto another layer called actin as you see on the later slides. Myosin pulls actin towards the center, causing the muscle to contract. The interesting part is that over time of repetitive resistance training, you will develop more cross links and hence create more dense muscles. Some of the cross-bridges will be constantly contracted, thus it will feel like you are flexing, which will account for the hardness of your muscles. A good example is your neck muscles, if you notice you don't have to put much effort to keep your neck up, because the muscle fibers of your neck are constantly flexed.