Does more muscle mean more strength? A new study gives a clear-cut answer

A man doing concentration curls at the gym — (Image credit: Getty Images)

You’d be forgiven if you thought someone with massive arms was super strong. After all, when you get stronger it’s because your muscles are getting bigger, right? Not necessarily.

While strength can correlate to muscle size, there are other factors at play, too, like neural adaptations (simply put, your brain and nerves have gotten better at using them).

The study

The pre-print study (meaning it has not yet been reviewed) looked at how changes in muscle size and muscle activation are related to strength after resistance training. Thirty-nine healthy young men who had not trained before took part in lower-body resistance training, which included leg curls, leg press and leg extension – three times a week, over 15 weeks.

The researchers measured three things before and after training:

Leg strength – testing their one rep max and isometric maximum voluntary torque
Muscle size – using an MRI scan to measure the volume of the quads
Muscle activation – using surface EMG (sEMG), which tracks how well the nervous system activates the muscles during exercise

The results

A man with muscular quads using the leg extension machine

The researchers found that all measurements improved significantly after training; participants experienced roughly a 13% increase in quadriceps muscle size. Their strength improved by about 22% in the isometric test and 29% in the one-repetition maximum test. The data showed there was a strong connection between how much the participants' muscles grew and how much stronger they became.

On the other hand, improvements in the nervous system’s capacity to activate muscles showed only a moderate connection to strength increases. When researchers examined both muscle growth and neural activation simultaneously, muscle growth emerged as over five times more influential in predicting strength improvements.

Overall, the study revealed that muscle growth is a key factor driving strength improvements, more so than changes in the nervous system’s ability to activate muscles, highlighting the importance of hypertrophy-focused training for continued progress in strength.

Bryony is a former Staff Writer in T3’s Active vertical. She is a certified personal trainer and part-time fitness instructor. In her spare time, she could usually be found in her natural habitat – the gym – where her training combined bodybuilding and powerlifting. She used to write about accessible workouts, nutrition and innovative fitness products that could help people reach their fitness goals and take their training to the next level.