Role of muscle mass on sprint performance: gender differences? by Jorge Perez-Gomez, German Vicente Rodriguez, Ignacio Ara, Hugo Olmedillas, Javier Chavarren, Juan Jose González-Henriquez, Cecilia Dorado and José A. L. Calbet

Excerpt

The authors state in the title, as well as in the methods, that the investigation measured muscle mass. However, muscle mass was never measured, only lean mass. Using the equipment cited in the methods (DXA, Hologic QDR-1500), it is impossible to directly measure muscle mass without a prediction equation; only bone, fat, and lean mass can be measured. The authors state, “Lower limb lean mass (kg) was calculated from the regional analysis of the whole body scan and it has been considered equivalent to the lower limb muscle mass”; however, lean mass and muscle mass are not equivalent and should not be used synonymously. There is a distinct difference between lean mass and muscle mass. Muscle mass is a measurement of only muscle tissue, while lean mass includes muscle and all other tissues except bone and fat. Therefore, lean mass includes skin, tendons, and connective tissue. This alone suggests that muscle mass cannot be equivalent to lean mass and should not be referred to in the manuscript or, more importantly, in the title. The use of the term “muscle mass” in the title is misleading and inaccurate since muscle mass was not measured. There are several published studies that demonstrate accurate methods to estimate whole body and segmental muscle mass (Kim et al. 2002; Fuller et al. 1992; Shih et al. 2000; Visser et al. 1999; Levine et al. 2000; Heymsfield et al. 1990; Wang et al. 1996). The fact that these methods were not utilized in the current investigation is a concern; however, changing the “lower limb muscle mass” values to “lower limb lean mass” values would be sufficient to correct the error. Furthermore, the authors fail to reference their statement regarding the equivalence between muscle mass and lean mass, yet, if the authors can provide a reference that justifies this statement, then it will be less of a concern. Additionally, the studies mentioned under the References section (Kim et al. 2002; Fuller et al. 1992; Shih et al. 2000; Visser et al. 1999; Levine et al. 2000; Heymsfield et al. 1990; Wang et al. 1996) provide further detailed information regarding muscle mass and measurement methods. I hope this information can be of some assistance, and I appreciate your attention to detail. …