Abstract
The aim of this study was to compare the performance (1RM) of resistance-trained subjects, using different methods of adjusting for body mass (BM): ratio standard, theoretical allometric exponent (0.67), and specific allometric exponents. The study included 11 male and 11 female healthy non-athletes (mean age = 22 years) engaged in regular resistance training for at least 6 months. Bench press (BP), 45° leg press (LP) and arm curl (AC) exercises were performed, and the participants were ranked (in descending order) according to each method. The specific allometric exponents for each exercise were: for men – BP (0.73), LP (0.35), and AC (0.71); and for women – BP (1.22), LP (1.02), and AC (0.85). The Kruskal-Wallis test revealed no differences between the rankings. However, visual inspection indicated that the participants were often classified differently in relation to performance by the methods used. Furthermore, no adjusted strength score was equal to the absolute strength values (1RM). The results suggest that there is a range of values in which the differences between exponents do not reflect different rankings (below 0.07 points) and a range in which rankings can be fundamentally different (above 0.14 points). This may be important in long-term selection of universally accepted allometric exponents, considering the range of values found in different studies. The standardization of exponents may allow the use of allometry as an additional tool in the prescription of resistance training.
Highlights
The measurement of muscle strength is fundamental in sports, as well as in prevention and rehabilitation
Other variables, such as the cross-sectional area (CSA) of muscles, may be biologically more closely correlated with MS11-14, but reliable measurements of CSA are expensive and made using computed tomography[12] or magnetic resonance[14], which makes the use of body mass (BM) more attractive
According to Box 1, exceptional circumstance (EC) was not found in any of the tests, which confirmed the linearity of the relation between muscle strength (MS) and BM and made it possible to use allometry as the scaling method
Summary
The measurement of muscle strength is fundamental in sports, as well as in prevention and rehabilitation. If any kind of scaling is adopted8,9,it is often limited to the use of the ratio standard (MS/BM)[10] Other variables, such as the cross-sectional area (CSA) of muscles, may be biologically more closely correlated with MS11-14, but reliable measurements of CSA are expensive and made using computed tomography[12] or magnetic resonance[14], which makes the use of BM more attractive. Several natural phenomena, such as the ratio between MS and BM, follow the power law ((y=axb), and a growing number of studies have been conducted to evaluate whether allometry may be satisfactorily used to compare the MS of individuals or groups. Allometric scaling is achieved by linearizing a power function using the least squares method (equation 2) and the natural logarithm (ln) of the dependent and independent variables, which are, in this case, MS and BM
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