That’s an important question about the mysterious process all strength athletes are interested in. Physical strength is the ability to exert strength against an external resistance, but that’s not what you are interested in: you’re not a bodybuilder. For us, strength is a complex cognitive, mental, neural, endocrine, muscular-joint-skeleton system of producing the most efficient movement that will result in a successful lift. So you may have gotten stronger because:

  1. You improved your technique (the movement has become mechanically more efficient + you have cognitive mastery over the process that makes it mentally more “economical”)
  2. Your nervous system developed the ability to recruit more motor units
  3. You have more muscle to contract and produce strength (which doesn’t mean much if this muscle is not optimally recruited)
  4. Your emotional state is optimal for sub-maximal/maximal strength efforts. You are more focused, less anxious, etc.
  5. You have more fuel inside your cells (your nutrition is better)
  6. There’s less inflammation in your body, less cytokines to “inform” the brain not to over-reach

The first three have to do with your physical training at the weight room. Both periodization and routine composition play a major role. The other three items are unrelated to training. So, “getting stronger” should be rephrased as “getting better at strength sports tasks”. And that is very complex. Don’t think muscle: think body and mind.