title: Gait models and mechanical energy in three cross-country skiing techniques.
abstract: Fluctuations in mechanical energy of the body center of mass (COM) have been widely analyzed when investigating different gaits in human and animal locomotion. We applied this approach to estimate the mechanical work in cross-country skiing and to identify the fundamental mechanisms of this particular form of locomotion. We acquired movements of body segments, skis, poles and plantar pressures for eight skiers while they roller skied on a treadmill at 14 km h(-1) and a 2 deg slope using three different techniques (diagonal stride, DS; double poling, DP; double poling with kick, DK). The work associated with kinetic energy (KE) changes of COM was not different between techniques; the work against gravity associated with potential energy (PE) changes was higher for DP than for DK and was lowest for DS. Mechanical work against the external environment was 0.87 J m(-1) kg(-1) for DS, 0.70 J m(-1) kg(-1) for DP and 0.79 J m(-1) kg(-1) for DK. The work done to overcome frictional forces, which is negligible in walking and running, was 17.8%, 32.3% and 24.8% of external mechanical work for DS, DP and DK, respectively. The pendulum-like recovery (R%) between PE and KE was ~45%, ~26% and ~9% for DP, DK and DS, respectively, but energy losses by friction are not accounted for in this computation. The pattern of fluctuations of PE and KE indicates that DS can be described as a 'grounded running', where aerial phases are substituted by ski gliding phases, DP can be described as a pendular gait, whereas DK is a combination of both.
authors.affiliation: CeRiSM, Center of Research in Mountain Sport and Health, University of Verona, 38068 Rovereto, Italy Department of Neurological and Movement Sciences, University of Verona, Verona 37129, Italy barbara.pellegrini@univr.it.
authors.forename: Barbara
authors.initials: B
authors.lastname: Pellegrini
authors.affiliation: CeRiSM, Center of Research in Mountain Sport and Health, University of Verona, 38068 Rovereto, Italy Department of Neurological and Movement Sciences, University of Verona, Verona 37129, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Zoppirolli
authors.affiliation: CeRiSM, Center of Research in Mountain Sport and Health, University of Verona, 38068 Rovereto, Italy Department of Neurological and Movement Sciences, University of Verona, Verona 37129, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Bortolan
authors.affiliation: Department of Neurological and Movement Sciences, University of Verona, Verona 37129, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Zamparo
authors.affiliation: CeRiSM, Center of Research in Mountain Sport and Health, University of Verona, 38068 Rovereto, Italy Department of Neurological and Movement Sciences, University of Verona, Verona 37129, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Schena
mesh_terms: D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D008954:Models, Biological; D012865:Skiing / Q000502:physiology*; D055815:Young Adult
keywords: Locomotion; Mechanical work; Roller skiing