How Muscle Size Affects Power

Bigger muscles are usually stronger muscles, but are they more powerful? A new study examines the relationship between muscular size and power.

Muscle size has a lot to do with strength, as is obvious to anyone with eyes. However, if you look at the lower weight classes in powerlifting, Olympic lifting, and strongman competitions, it’s also clear that size isn’t the only determinant when it comes to strength. Some people make strength gains without any significant change in muscle size at all. A recent study in the Journal of Strength and Conditioning Research sought to better our knowledge on the topic.

Measuring muscle size accurately isn’t as simple as it may sound. After all, we can’t just take the muscle out of our bodies and put it on a scale. Without a lab setting, some people might sling a tape measure around themselves to figure it out. Generally, when measuring muscles from the outside, we take the widest part of a muscle (the cross-section, as though slicing it clean in half), and measure around it. The problem is, there’s other stuff in there too. All manner of fluids, connective tissues, bones, and other muscles get in the way and confuse the results when using this method.

Because of this measurement problem, the researchers in this study measured the volume of the pectoralis major as well as the cross-section. Volume isn’t a perfect indicator of muscle size either, since there is intra-muscular fluid and other tissues in the mix, but in this study the researchers wanted multiple measurements to support the resulting data.

The researchers asked whether the pec size would influence strength and power during the bench press and bench throw. Most previous studies have compared muscle size to strength during single joint movements, not to power output during multi-joint movements as were used in this study, so we have new information to glean from this research.

Not surprisingly, the relationship between muscle cross-section and strength was strong. Interestingly, power had a stronger relationship to muscle volume than it did to muscle cross-section. Also, muscle size as measured by the various methods seemed to have a stronger correlation with strength than it did with power.

This information can help coaches and athletes make prescriptions for developing muscle size and strength. For power sports, a focus on practice may be more beneficial, with a secondary focus on size. However, with any weight-classed sport, the weight of the extra muscle has to be considered along with the advantages of added strength or power.


1. Ryota Akagi, et. al., “Relationship of pectoralis major muscle size with bench press and bench throw performances, Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.0000000000000306.

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