Biomechanical and metabolic aspects of backward (and forward) running on uphill gradients: another clue towards an almos
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ORIGINAL ARTICLE
Biomechanical and metabolic aspects of backward (and forward) running on uphill gradients: another clue towards an almost inelastic rebound L. Rasica1 · S. Porcelli1,2 · A. E. Minetti3 · G. Pavei3 Received: 23 June 2020 / Accepted: 10 August 2020 © The Author(s) 2020
Abstract Purpose On level, the metabolic cost (C) of backward running is higher than forward running probably due to a lower elastic energy recoil. On positive gradient, the ability to store and release elastic energy is impaired in forward running. We studied running on level and on gradient to test the hypothesis that the higher metabolic cost and lower efficiency in backward than forward running was due to the impairment in the elastic energy utilisation. Methods Eight subjects ran forward and backward on a treadmill on level and on gradient (from 0 to + 25%, with 5% step). The mechanical work, computed from kinematic data, C and efficiency (the ratio between total mechanical work and C) were calculated in each condition. Results Backward running C was higher than forward running at each condition (on average + 35%) and increased linearly with gradient. Total mechanical work was higher in forward running only at the steepest gradients, thus efficiency was lower in backward running at each gradient. Conclusion Efficiency decreased by increasing gradient in both running modalities highlighting the impairment in the elastic contribution on positive gradient. The lower efficiency values calculated in backward running in all conditions pointed out that backward running was performed with an almost inelastic rebound; thus, muscles performed most of the mechanical work with a high metabolic cost. These new backward running C data permit, by applying the recently introduced ‘equivalent slope’ concept for running acceleration, to obtain the predictive equation of metabolic power during level backward running acceleration. Keywords Backward acceleration · Efficiency · Mechanical work · Metabolic cost · Metabolic power Abbreviations C Metabolic cost CBA Metabolic cost of backward running acceleration BCoM Body centre of mass PE Potential energy of BCoM
KE Kinetic energy of BCoM TE Total energy of BCoM WEXT Positive external work WINT Positive internal work WTOT Total work WEXT− Negative external work
Communicated by Jean-René Lacour. * G. Pavei [email protected] 1
Institute of Biomedical Technologies, National Research Council, Segrate, Italy
2
Department of Molecular Medicine, University of Pavia, Pavia, Italy
3
Laboratory of Physiomechanics of Locomotion, Department of Pathophysiology and Transplantation, Physiology Division, University of Milan, Via Mangiagalli 32, 20133 Milan, Italy
Introduction Backward running is commonly used in rehabilitation and as an injury prevention strategy (e.g. Soligard et al. 2008; Gilchrist et al. 2008; Heiderscheit et al. 2010; Rössler et al. 2016), thanks to the reduced knee joint forces and lower vertical peak of the ground reaction force compared with forward r
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