Muscle Growth Is Very Strongly Correlated with Strength Gains after Lower Body Resistance Training: New Insight from Within-Participant Associations

In healthy young men who had not previously trained, 15 weeks of leg resistance training was associated with a strong relationship between increases in quadriceps muscle size and increases in knee extension strength.

When guys who’ve never lifted weights before train their legs for 15 weeks, the more their muscles grow, the stronger they get—so muscle growth is mostly why they get stronger.

In healthy young men who have not previously trained, greater electrical activity in the quadriceps muscle during maximum effort is linked to larger increases in knee extension strength after 15 weeks of resistance training.

When guys who’ve never lifted weights before start training, the more their thigh muscles ‘fire up’ during max efforts, the stronger they tend to get—both in holding a heavy position and in lifting one heavy weight.

When guys who’ve never lifted weights start training, most of their strength gains come from their muscles getting bigger—not from their brain and nerves getting better at telling muscles to work harder.

When scientists look at how one person changes over time—like how their muscles grow and get stronger together—they find a super strong link. But when they compare different people to each other, that link looks much weaker.