Strength starts with the core. Common misconception is that the core is “just your abs” (read more about functional core vs 6 pack abs ). Though the abdominal muscles and oblique muscles are part of the core, the spinal erectors, rhomdodis, trapexius, and gluteal connect to the axial spine make up a part of your core as well. In simple terms, if you were to remove your head, legs, and arms, the part remaining would be considered your core.
To train properly and develop “real” strength you must train the body as it was intended to be used. Most exercise and weight machines just aren’t geared for that. Ideally, you need to be in a position where you are using your internal system (core) to support yourself instead of relying on external forces such as benches and machines with a backrest.