title: Muscle variables of importance for physiological performance in competitive football.
abstract: OBJECTIVE
  To examine how match performance parameters in trained footballers relate to skeletal muscle parameters, sprint ability and intermittent exercise performance.
  
  
  METHODS
  19 male elite football players completed an experimental game with physical performance determined by video analysis and exercise capacity assessed by intermittent Yo-Yo IR1 and IR2 tests, and a repeated sprint test (RST). Muscle tissue was obtained for analysis of metabolic enzyme maximal activity and key muscle protein expression.
  
  
  RESULTS
  Total game distance, distance deficit from first to second half and high-intensity running in the final 15 min of the game were all correlated to the players' Yo-Yo IR1 performance (r = 0.55-0.87) and beta-hydroxyacyl-CoA-dehydrogenase (HAD) maximal activity (r = 0.55-0.65). Furthermore, platelet/endothelial cell adhesion molecule-1 (PECAM1) protein expression was weakly (r = 0.46) correlated to total game distance. Peak 5-min game distance faster than 21 km h(-1) was related to the Na(+)-K(+) ATPase subunit (α1, α2, β1 and FXYD1) protein levels (r = 0.54-0.70), while Yo-Yo IR2 performance explained 40 % of the variance in high-intensity game distance. Total and 1-min peak sprint distance correlated to myosin heavy chain II/I ratio (MHCII/I ratio) and sarcoendoplasmic reticulum Ca(2+) ATPase isoform-1 (SERCA1) protein (r = 0.56-0.86), while phosphofructokinase (PFK) maximal activity also correlated to total sprint distance (r = 0.46).
  
  
  CONCLUSIONS
  The findings emphasize the complexity of parameters predicting physical football performance with Yo-Yo IR1 and HAD as the best predictors of total distance, while high expression of Na(+)-K(+) ATPase proteins and the Yo-Yo IR2 test are better predictors of high-intensity performance. Finally, sprint performance relates to skeletal muscle fiber-type composition.
authors.affiliation: Faculty of Natural and Health Sciences, University of the Faroe Islands, Jónas Broncksgøta 25, 3rd floor, Tórshavn, Faroe Islands. magnim@setur.fo.|Center for Health and Human Performance, Food and Nutrition, and Sport Science, University of Gothenburg, Gothenburg, Sweden. magnim@setur.fo.
authors.forename: Magni
authors.initials: M
authors.lastname: Mohr
authors.affiliation: Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Martin
authors.initials: M
authors.lastname: Thomassen
authors.affiliation: Athlete Health and Performance Research Center, Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar.|Department of Physiology, Faculty of Biology and Medicine, Institute of Sport Science, University of Lausanne, Lausanne, Switzerland.
authors.forename: Olivier
authors.initials: O
authors.lastname: Girard
authors.affiliation: Athlete Health and Performance Research Center, Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar.
authors.forename: Sebastien
authors.initials: S
authors.lastname: Racinais
authors.affiliation: Department of Nutrition, Exercise and Sports, Section of Integrated Physiology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Lars
authors.initials: L
authors.lastname: Nybo
mesh_terms: D000328:Adult; D005538:Football / Q000502:physiology*; D006801:Humans; D008297:Male; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D010807:Physical Endurance; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism
chemical_list: D000254:Sodium-Potassium-Exchanging ATPase
keywords: Fatigue; Metabolic enzymes; Muscle ion transporters; Sprint ability; Work rate