An Intuitive but Imperfect Assumption
It seems reasonable to assume that a larger muscle should always be proportionally stronger than a smaller one — more contractile tissue should simply mean more force. The real relationship between muscle size and strength is considerably less tidy than this assumption suggests.
The Same Size, Different Strength
Research examining individual variability in response to progressive resistance training found considerable differences between individuals in "specific tension" — the amount of force produced per unit of muscle cross-sectional area — meaning two people (or the same person at two different points in training) with identical muscle size can display meaningfully different maximal strength (Erskine et al., 2010).
What Explains the Gap
Neural factors — how efficiently the nervous system can recruit and synchronise motor units, and how well-coordinated a lift's specific movement pattern has become through practice — contribute substantially to strength output independent of muscle size, alongside tendon stiffness and fibre-type composition. This is a central reason that targeted strength training and pure bodybuilding-style hypertrophy training, while overlapping, are not interchangeable goals, and why visibly larger muscles do not automatically translate into proportionally greater functional strength.
References & Further Reading
- Erskine RM, Jones DA, Williams AG, Stewart CE, Degens H. Inter-individual variability in the adaptation of human muscle specific tension to progressive resistance training. Eur J Appl Physiol. 2010;110(6):1117-1125.