What is the predominant factor causing an increase in strength during the initial weeks of training?

Whole muscle cross-sectional area changes reflect hypertrophy, which requires sustained training over several weeks to months and is not the primary driver of early strength gains.

Overall limb circumference increases only after sustained hypertrophy and connective tissue changes, making it a lagging outcome rather than a mechanism of early strength improvement.

Neuromuscular adaptations - including improved motor unit recruitment, increased firing rate, and enhanced synchronization - are the dominant mechanisms behind strength gains in the first several weeks of resistance training. These neural changes allow the nervous system to more effectively activate existing muscle fibers without requiring significant hypertrophy. This neural phase precedes meaningful structural changes in muscle tissue.

Muscle-fiber cross-sectional area increases are a hypertrophic adaptation that requires a prolonged training stimulus and does not account for the rapid strength gains seen in the first weeks.