• force;
  • inter-individual variation;
  • muscle size;
  • muscle strength;
  • vastus lateralis


Introduction: Inter-individual variability in measurements of muscle strength and its determinants was identified to: (1) produce a normative data set describing the normal range and (2) determine whether some measurements are more informative than others when evaluating inter-individual differences. Methods: Functional and morphological characteristics of the vastus lateralis were measured in 73 healthy, untrained adult men. Results: Inter-individual variability (coefficient of variation) was greater for isometric maximal voluntary contraction (MVC) torque (18.9%) compared with fascicle force (14.6%; P = 0.025) and physiological cross-sectional area (PCSA; 17.2%) compared with anatomical cross-sectional area (ACSA, 13.0%; P < 0.0005). The relationship between ACSA and isometric MVC torque (r2 = 0.56) was weaker than that between PCSA and fascicle force (r2 = 0.68). Conclusions: These results provide a normative data set on inter-individual variability in a variety of muscle strength-related measurements and illustrate the benefit of using more stringent measures of muscle properties. Muscle Nerve 49: 879–886, 2014