Strength Is About Much More Than Muscle Size
When people think about strength, they often picture someone with large muscles lifting impressive amounts of weight. While muscle size certainly contributes to strength, it is only one piece of the puzzle. Two people with identical amounts of muscle can display remarkably different levels of strength, illustrating that strength is influenced by a combination of muscular, neural, and biomechanical factors.
Understanding these mechanisms helps explain why some individuals become stronger without gaining much muscle, why experienced lifters can outperform larger novices, and why body proportions often influence performance in certain exercises.
Bigger Muscles Usually Produce More Force
The most obvious determinant of strength is muscle size.
As muscle fibers grow through resistance training, their physiological cross-sectional area increases. Larger muscles contain more contractile proteins—primarily actin and myosin—which allows them to produce greater force during contraction (Schoenfeld, 2010).
Hypertrophy can also improve strength through biomechanics. As muscles become thicker, the muscle belly may sit farther from the joint's axis of rotation. This can modestly increase the muscle's moment arm, improving its mechanical advantage and allowing the muscle to generate greater joint torque for the same amount of contractile force. While this effect is generally smaller than the direct increase in force production from hypertrophy, it likely contributes to why increasing muscle size consistently improves strength over time.
For this reason, individuals interested in maximizing long-term strength should not dismiss hypertrophy training. Building muscle effectively builds a larger engine capable of producing more force.
Your Nervous System Determines How Much of That Muscle You Can Use
Muscle size determines your potential for force production, but your nervous system determines how much of that potential you can actually express.
When you attempt to lift a weight, your brain sends signals through the spinal cord to activate motor units—groups of muscle fibers controlled by a single motor neuron. According to the size principle, motor units are recruited from low-threshold to high-threshold as force demands increase (Gordon et al., 2004).
Near-maximal efforts recruit a very high proportion of available motor units, particularly the larger, high-threshold motor units responsible for producing the greatest amounts of force. Resistance training improves your ability to recruit these motor units efficiently and synchronize their activity, allowing more muscle fibers to contribute simultaneously to force production (Duchateau & Enoka, 2002).
This is one reason beginners often experience rapid increases in strength during the first several weeks of training despite gaining relatively little muscle. Their nervous system becomes more efficient at using the muscle they already have.
Heavy Lifting Improves Skill, Not Just Strength
Strength is highly specific.
Although lifting moderate loads close to failure can build muscle extremely effectively, regularly exposing yourself to heavy loads teaches your nervous system how to coordinate those muscles under maximal conditions.
Repeated practice with heavy weights improves intermuscular coordination, allowing different muscles to work together more efficiently. It also improves intramuscular coordination, enhancing the timing and firing frequency of motor units within individual muscles. As technique improves, unnecessary muscle activity decreases while the muscles responsible for the movement become increasingly efficient.
Heavy lifting also improves familiarity with handling maximal loads. Anyone who has unracked 90–95% of their one-repetition maximum knows that heavy weights simply feel different. Learning to stabilize, brace, control the bar path, and confidently produce force under these conditions is itself a trainable skill.
This helps explain why experienced powerlifters often continue improving their one-repetition maximum even when muscle growth has slowed considerably.
Biomechanics Matter More Than Most People Realize
Not everyone is built to perform every lift equally well.
Individual differences in limb length, tendon insertions, joint structure, and overall body proportions substantially influence mechanical advantage.
A lifter with relatively short femurs may naturally squat more upright, reducing the moment arm at the hip and making the lift more mechanically efficient. Conversely, someone with long arms often has an advantage during the deadlift because the bar travels a shorter distance, while shorter arms may benefit the bench press by reducing range of motion.
These biomechanical differences help explain why two equally strong individuals can perform very differently on specific exercises despite possessing similar amounts of muscle.
Importantly, these differences are not limitations—they simply influence which movements are mechanically advantageous for each individual.
Tendons Also Contribute to Force Production
Strength is not determined solely by muscle.
Tendons transmit force from muscle to bone, and resistance training can alter tendon stiffness over time. Stiffer tendons may improve the efficiency of force transmission by reducing energy loss between muscle contraction and movement, potentially contributing to improved maximal force production (Kubo et al., 2003).
Although changes in tendon properties occur more slowly than neural adaptations, they represent another way long-term resistance training improves strength.
Strength Is the Product of Multiple Systems
Perhaps the biggest misconception is that strength is determined by only one factor.
In reality, maximal strength reflects the interaction of several systems working together. Muscle size provides the capacity to produce force. The nervous system determines how effectively that force can be expressed. Technique and motor learning improve movement efficiency. Biomechanics influence leverage and joint torque. Tendons efficiently transmit muscular force to the skeleton.
Improving any one of these factors can increase strength, but the greatest long-term progress typically occurs when they develop together.
This is why effective strength training rarely focuses on only one quality. Building muscle, practicing heavy lifts, refining technique, and accumulating years of consistent training all contribute to becoming stronger.
Key Takeaways
- Muscle size is one of the largest contributors to strength, increasing both force-producing capacity and, in some cases, improving joint mechanics through changes in muscle thickness.
- Neural adaptations play a major role, particularly early in training, by improving motor unit recruitment, coordination, and the ability to express existing strength.
- Strength is ultimately a combination of physiology and biomechanics. Muscle size, nervous system adaptations, technique, tendon properties, and individual leverages all work together to determine how much force you can produce.
References:
1. Schoenfeld, B. J. (2010). The Mechanisms of Muscle Hypertrophy and Their Application to Resistance Training. Journal of Strength and Conditioning Research, 24(10), 2857-2872. https://doi.org/10.1519/JSC.0b013e3181e840f3
2. Gordon, T., Thomas, C. K., Munson, J. B., & Stein, R. B. (2004). The resilience of the size principle in the organization of motor unit properties in normal and reinnervated adult skeletal muscles. Canadian Journal of Physiology and Pharmacology, 82(8-9), 645-661. https://doi.org/10.1139/y04-081
3. Duchateau, J., & Enoka, R. M. (2002). Neural Adaptations with Chronic Activity Patterns in Able-Bodied Humans. American Journal of Physical Medicine & Rehabilitation, 81(Suppl), S17-S27. https://doi.org/10.1097/00002060-200211001-00004
4. Kubo, K., Kanehisa, H., Miyatani, M., Tachi, M., & Fukunaga, T. (2003). Effect of low-load resistance training on the tendon properties in middle-aged and elderly women. Acta Physiologica Scandinavica, 178(1), 25-32. https://doi.org/10.1046/j.1365-201X.2003.01097.x