Getting stronger is actually a much more complex process that people give it credit for. On the surface, I think the majority of exercise goers would make the assumption that getting stronger is about building bigger muscles (I know, not everyone thinks this). Though this isn’t necessarily incorrect, it doesn't represent the full story. Getting stronger is also a “skill” because getting stronger at one exercise doesn’t always mean you get stronger in another exercise. Why is that? Well, strength is driven by neurological components as well. The brain is the master and commander of the human body. When you do a movement for the first time, it is typically quite inefficient at it. However, over time the body learns how to become more and more efficient, meaning it gets better at knowing how to use the right muscles at the right time in the right sequence. By doing such, the body actually expresses more force through skill, allowing you to lift more weight. So, to think strength is purely a structural outcome of having bigger muscles is only partially true. There is a skill to strength, which is why over time you become a more skilled lifter at certain exercises and for the most part, strength follows suit.