The aim of this thesis was to use allometric models to analyze the relationship that running economy(ECO) and mechanical efficiency (Ef) have on the performance of middle- and long-distance runners.Based on the results of three original studies, we concluded that allometric scaling can improve therelationship between ECO and performance in recreational middle- and long-distance runners, mainlydue to morphofunctional aspects. Similarly, the mechanical works, especially the external mechanicalwork, may be considered to be predictive of running performance and a specific allometric exponentcan improve these predictions. The results also showed that Ef is an important predictor of theperformance of long-distance runners. However, when the specific allometric exponents were applied,there was no improvement in the prediction of this performance. The results also showed that it isimportant to consider the contribution of anaerobic energy expenditure when calculating Ef, becauseotherwise the results may be overestimated, as already reported in other studies. In general, when theobjective is to predict the performance of middle- or long-distance runners through metabolic ormechanical powers, it is useful to adopt a specific allometric exponent of the group investigated.However, when this prediction is performed considering the Ef, particularly in high-performance longdistancerunners, the allometric application is not necessary.
