title: Mechanical work and efficiency of 5 + 5 m shuttle running.
abstract: OBJECTIVE
  Acceleration and deceleration phases characterise shuttle running (SR) compared to constant speed running (CR); mechanical work is thus expected to be larger in the former compared to the latter, at the same average speed (v mean). The aim of this study was to measure total mechanical work (W tot (+) , J kg(-1) m(-1)) during SR as the sum of internal (W int (+) ) and external (W ext (+) ) work and to calculate the efficiency of SR.
  
  
  METHODS
  Twenty males were requested to perform shuttle runs over a distance of 5 + 5 m at different speeds (slow, moderate and fast) to record kinematic data. Metabolic data were also recorded (at fast speed only) to calculate energy cost (C, J kg(-1) m(-1)) and mechanical efficiency (eff(+) = W tot (+) C (-1)) of SR.
  
  
  RESULTS
  Work parameters significantly increased with speed (P < 0.001): W ext (+)  = 1.388 + 0.337 v mean; W int (+)  = -1.002 + 0.853 v mean; W tot (+)  = 1.329 v mean. At the fastest speed C was 27.4 ± 2.6 J kg(-1) m(-1) (i.e. about 7 times larger than in CR) and eff(+) was 16.2 ± 2.0 %.
  
  
  CONCLUSIONS
  W ext (+) is larger in SR than in CR (2.5 vs. 1.4 J kg(-1) m(-1) in the range of investigated speeds: 2-3.5 m s(-1)) and W int (+) , at fast speed, is about half of W tot (+) . eff(+) is lower in SR (16 %) than in CR (50-60 % at comparable speeds) and this can be attributed to a lower elastic energy reutilization due to the acceleration/deceleration phases over this short shuttle distance.
authors.affiliation: Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Via Felice Casorati, 43, 37131, Verona, Italy. paola.zamparo@univr.it.
authors.forename: Paola
authors.identifier: http://orcid.org/0000-0002-6919-6721
authors.initials: P
authors.lastname: Zamparo
authors.affiliation: Department of Pathophysiology and Transplantation, University of Milano, Milan, Italy.
authors.forename: Gaspare
authors.initials: G
authors.lastname: Pavei
authors.affiliation: Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Via Felice Casorati, 43, 37131, Verona, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Nardello
authors.affiliation: Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Via Felice Casorati, 43, 37131, Verona, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Bartolini
authors.affiliation: Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Via Felice Casorati, 43, 37131, Verona, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Monte
authors.affiliation: Department of Pathophysiology and Transplantation, University of Milano, Milan, Italy.
authors.forename: Alberto E
authors.initials: AE
authors.lastname: Minetti
mesh_terms: D003198:Computer Simulation; D004735:Energy Transfer / Q000502:physiology*; D000072696:High-Intensity Interval Training / Q000379:methods*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008954:Models, Biological; D010101:Oxygen Consumption / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D012420:Running / Q000502:physiology*; D055815:Young Adult
keywords: Energy cost; External and internal work; Mechanical efficiency; Shuttle runs