Strength training Strength training

typically produces a combination of the two different types of hypertrophy; contraction against 80–90%^{[citation needed]} hypertrophy to dominate (as in hypertrophy (professional of the one repetition maximum for 2–8 repetitions causes myofibrillatedpowerlifters, olympic lifters and strength athletes), while several repetitions (generally 12 or more) against a sub-maximal load facilitates mainly sarcoplasmicbodybuilders and endurance athletes). The first measurable effect is an increase in the neural drive stimulating muscle contraction. Within just a few days, an untrained individual can achieve measurable strength gains resulting from "learning" to use the muscle. As the muscle continues to receive increased demands, the synthetic machinery is upregulated. Although all the steps are not yet clear, this upregulation appears to begin with the ubiquitous second messenger system (including phospholipases, protein kinase C, tyrosine kinase, and others). These, in turn, activate the family of immediate-early genes, including c-fos, c-jun and myc. These genes appear to dictate the contractile protein gene response.

Muscle hypertrophy due to strength training does not occur for everyone, and is not necessarily well correlated with gains in actual muscle strength: it is possible for muscles to grow larger without becoming much stronger.^[5]