We all resistance train and lift weights for different reasons. Some may train for general health, others to get strong, change our body composition or to improve athletic performance. However, I would guess that we all like to look in the mirror to check if our muscles have gotten bigger. One of the common questions around resistance training is “are bigger muscles stronger?”. Luckily, a whole host of researchers have looked into this and can provide a consensus answer.
Are Bigger Muscles Stronger Muscles? TL;DR Answer
Scientific studies have consistently shown that bigger muscles are stronger than smaller muscles. Muscles increase their number of contractile elements as they get bigger. As a result, there are more components that can be producing force at a given time in a given contraction. More force production leads to greater displays of strength. Therefore, as muscles get bigger, they also get stronger.
Muscle Structure and Physiological Cross-Sectional Area
A working knowledge of the way muscles are organized is necessary before we dive into the relationship between muscle size and strength. The next two sections have a brief outline of muscle structure and what muscle physiological cross-sectional area is. This knowledge will assist in the understanding of why bigger muscles are usually stronger than smaller muscles.
Muscle Structure
Muscles are broken down into a hierarchical structure.
Muscle is made up of contractile proteins called actin and myosin at the microscopic level. These two proteins interact during muscle contractions. This interaction is called a cross-bridge cycle. Actin and myosin molecules are housed within a sarcomere (E in the above figure). Thousands of actin and myosin molecules within a sarcomere go through their contraction cycle during a muscle contraction. A collection of sarcomeres makes up a muscle fiber, and thousands of muscle fibers make up a muscle.
The contraction-relaxation cycling of actin and myosin at the microscopic level leads to muscle contractions seen at a macroscopic scale. Our bones move because these microscopic contractions pull on our tendons which are attached to bone. All of our movements start with very small proteins sliding back and forth and interacting with each other.
Our muscle fibers run on angles relative to the origin and insertion of the muscle fibers (see above). Pinnation angle is the angle of the muscle fibers run relative to connective tissue within the muscle (Aagaard et al., 2001). An increase in pinnation angle increases the number of sarcomeres that can contribute to a given contraction. Therefore, a muscle with a greater pinnation angle will be stronger than a muscle with a smaller pinnation angle, with everything else being equal.
By Uwe Gille – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3181778
What is Muscle Physiological Cross-Sectional Area?
Muscle physiological cross-sectional area (PCSA) is calculated using a line perpendicular to the angle that individual muscle fibers run in the muscle. This line is shown in green in the above figure. The muscle PCSA provides a more accurate measure of the functional ability of the muscle because it takes into account the number muscle fibers that can be active in a given contraction. As a result, muscle PCSA is often considered the effective cross-sectional area (Vigotsky et al., 2018).
Read More: how many sets and reps should you perform to get stronger and build muscle?
The Relationship Between Muscle Size and Strength
One of the most interesting aspects of resistance training is the role of muscle size (and growth) on strength. Muscle size is particularly interesting and well researched because it is relatively easy to train muscle hypertrophy and see significant changes, and there is a clear positive relationship between muscle size and strength, with greater muscle size associated with greater strength capacity. This is because the body activates and utilizes more muscle fibers to produce more force. Therefore, if you have more muscle fibers there are more fibers to activate, and a greater number of active fibers means more force is produced. However, the relationship between muscle size and strength isn’t perfectly linear because other factors also influence strength (which we will touch on later) (Vigotsky et al., 2018).
Muscle volume is impacted by the number of sarcomeres (contractile part of the muscle) in parallel and in series. An increase in sarcomeres in parallel results in a wider muscle with greater PCSA. This allows for a greater number of contractile elements to contract at a given time, which increases the force that the muscle can produce (Aagaard et al., 2001; Vigotsky et al., 2018). Increasing the number of sarcomeres in series increases the length of the muscle and affects two muscle properties called the force-length and force-velocity relationships.
Muscle Size and Strength Research
One of the key research studies looking at the relationship between muscle size and strength was published in 2001. They had 11 participants train their lower body for 14 weeks and measured the changes in their muscle and strength levels from pre to post-training (Aagaard et al., 2001).
The study found that individual muscle fibers increased their area by an average of 18.4% and overall quadriceps size increase by 10%. In addition, maximum quadriceps strength increased by 16% following the training. (Aagaard et al., 2001). This study showed that changes in muscle strength is nearly linearly related to changes in muscle fiber size.
Scientific research consistently shows that greater muscle mass leads to greater expression of strength (Jones et al., 2008). Therefore, a limiting factor of maximal strength is maximum amount of muscle mass we can pack onto our body.
Read More: do you need to train to failure to build muscle?
Other Factors That Influence Strength
Central Nervous System
The central nervous system is directly responsible for the amount of force we produce in muscle contractions. The nervous system starts contractions by activating weaker and less explosive muscle fibers. The contraction ramps up to activating larger, stronger and more explosive muscle fibers as the need for force increases. During maximal effort contractions, like we see in max strength training, all motor units will be recruited.
The nervous system will then increase the frequency of electrical signals sent to the muscle fibers to further increase the force produced. The combined maximal recruitment of muscle fibers and maximal frequency of electrical signals will impact the max strength potential of a muscle.
The Skill of Producing Max Force
Research also suggests that there is a skill to producing maximum force. Research shows that it takes practice to be able to maximally contract muscles (Vigotsky et al., 2018). Therefore, you need to practice lifting weights at low repetitions and high intensity to be able to truly show how strong you are.
Muscle Fiber Type Composition
Muscle fiber type composition influences your strength level (Jones et al., 2008). Fast-twitch muscle fibers are called Type 2 fibers. These fibers contract strongly and explosively but fatigue quickly. Fast twitch fibers are also more susceptible to hypertrophy training and growing in size. A higher proportion of Type 2 muscle fibers will typically lead to a stronger individual, or muscle group.
On the other hand, type 1 muscle fibers are commonly considered ‘endurance fibers’. These muscle fibers are resistant to fatigue but aren’t as explosive or strong as fast twitch fibers.
Resources to Build Muscle Size and Increase Strength
- Why Exercise Order is the Key to Strength and Hypertrophy Gains
- 9 Scientifically Backed Ways to Increase Strength
- How to Incorporate Progressive Overload into Your Training
- Why Thick Handle Training Increases Your Strength Quickly
References
Aagaard, P., Andersen, J. L., Dyhre-Poulsen, P., Leffers, A.-M., Wagner, A., Magnusson, S. P., Halkjaer-Kristensen, J., & Simonsen, E. B. (2001). A mechanism for increased contractile strength of human pennate muscle in response to strength training: Changes in muscle architecture. The Journal of Physiology, 534(2), 613–623. https://doi.org/10.1111/j.1469-7793.2001.t01-1-00613.x
Jones, E. J., Bishop, P. A., Woods, A. K., & Green, J. M. (2008). Cross-Sectional Area and Muscular Strength: A Brief Review. Sports Medicine, 38(12), 987–994. https://doi.org/10.2165/00007256-200838120-00003
Vigotsky, A. D., Schoenfeld, B. J., Than, C., & Brown, J. M. (2018). Methods matter: The relationship between strength and hypertrophy depends on methods of measurement and analysis. PeerJ, 6, e5071. https://doi.org/10.7717/peerj.5071