Gender differences on neuromuscular strategy during drop jump: a comment on Helm et al. (2019)
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LETTER TO THE EDITOR
Gender differences on neuromuscular strategy during drop jump: a comment on Helm et al. (2019) Riccardo Di Giminiani1 · Tihanyi Jozsef2 · Masedu Francesco1 Received: 25 February 2020 / Accepted: 4 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Dear Editor, We recently read an interesting article by Helm and colleagues titled “The relationship between leg stiffness, forces and neural control of the leg musculature during the stretch–shortening cycle is dependent on the anticipation of drop height” (Helm et al. 2019). The authors in their conclusions asserted that the preactivation of lower leg muscles during the aerial phase of drop heights affects leg stiffness. The level of this muscle anticipation depends on certain conditions of drop heights (low, medium and high drop height; known condition: the subject knows the drop height; unknown condition: the subject is not aware of the drop height; cheat condition: the subject jumps from a low drop height instead of a high drop height) to optimize the damping process at the impact with the ground and to protect the musculoskeletal system from excessive loading. We would like to underline two important issues that may vitiate the potency of these conclusions, specifically, the group of subjects recruited and the selection of the statistical model to analyze the data. Communicated by Westerterp/Westerblad. Comment on: Helm M, Freyler K, Waldvogel J, Gollhofer A, Ritzmann R (2019) The relationship between leg stiffness, forces and neural control of the leg musculature during the stretch– shortening cycle is dependent on the anticipation of drop height. Eur J Appl Physiol 119:1981–1999. https://doi.org/10.1007/s0042 1-019-04186-7. * Riccardo Di Giminiani [email protected] 1
Laboratory of Biomechanics of the Musculoskeletal System and Motion Analysis, Department of Biotechnological and Applied Clinical Sciences, University of L’Aquila, Via Vetoio (Coppito 2), 67100 L’Aquila, Italy
Department of Biomechanics, University of Physical Education, Budapest, Hungary
2
The authors recruited twenty-two participants of both sexes (10 females and 12 males), but the dependent variables were quantified by pooling the data of both, without considering sex-specific effects on kinetic, kinematic and motor control strategies reported in the literature (Lyle et al. 2014; Prieske et al. 2015; Stearns-Reider and Powers 2018). Specifically, sex differences in leg stiffness have been reported by Lyle et al. (2014) in drop jumps. These differences have been attributed largely to a different feedforward control strategy in which females activate the knee extensor earlier than males to counteract the rate tension development deficit in the hip extensors (Stearns-Reider and Powers 2018). Additionally, smaller knee flexion angles recorded in females in comparison to males at ground contact (Prieske et al. 2015) could influence the ratio between ground reaction force and center of mass displacement (i.e., leg stiffness). Sex di
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