Strength vs. Movement
One of the most common problems with strength training in the US today is an incomplete understanding of what strength actually is. It is a skill: the neurological ability to fire motor units simultaneously (and rotate them as they fatigue, in the case of strength endurance). In order for strength to be useful, the body must be able to channel that tension efficiently to where force is required (a further skill). Hypertrophy (muscle mass) is secondary; it supports increased strength but is not required, and can limit other dimensions of performance.
The body will maximize whatever you concentrate on most. If you focus on tension, you will get tension. If you focus on movement, you will get movement. There are very few cases where increasing tension all by itself is useful. In basic physiological terms, athletic performance, or in day to day life, tension needs to be developed in focussed concert with relaxation, co-ordination, and spatial awareness to create lasting benefit for the whole person.
I promise, I'll get to the details soon!