The Generality of Strength: Relationship between Different Measures of Muscular Strength in Older Women

The aims of this study were: (i) to analyze the relationship between the performance of different measures of muscular strength, and (ii) to identify which measurements present a greater relationship with an overall strength score. Sixty older women (aged 69 ± 6 years) were submitted to muscular strength measurements from isotonic, isokinetic, and isometric tests. An overall-strength score was generated with z-scores of the values obtained in all tests. Interquartile intervals were created for each measure and the overall-strength score. Pearson's r (0.463-0.951, p < 0.05) and Cronbach's α (0.500-0.966) suggested that subjects had relatively similar strength performance compared to their peers in the different tests. Greater associations were observed between tests for similar tasks. In addition, strong-magnitude associations were revealed between all the tests and the overall-strength score (r = 0.710-0.806; α = 0.760-0.846). Factor analysis identified that only two principal components may be sufficient to explain the strength of the sample. All strength measures had high loadings (0.716-0.916) on a common factor with 1 component. The associated eigenvalue with 2 components was 6.8 (84% of the variance). The present results support the phenomenon of the generality of strength in older women. Although greater correlations were observed for tests performed at the same joint, movement, or type of muscular action, the eight tests satisfactorily represented a measure of general muscular strength cross-sectionally.