title: Adaptations to Speed Endurance Training in Highly Trained Soccer Players.
abstract: The present study examined whether a period of additional speed endurance training would improve intense intermittent exercise performance in highly trained soccer players during the season and whether the training changed aerobic metabolism and the level of oxidative enzymes in type I and type II muscle fibers.
  
  
  
  During the last 9 wk of the season, 13 semiprofessional soccer players performed additional speed endurance training sessions consisting of two to three sets of 8-10 repetitions of 30-m sprints with 10 s of passive recovery (SET). Before and after SET, subjects completed a double-step exercise protocol that included transitions from standing to moderate-intensity running (~75% HRmax), followed by transitions from moderate- to high-intensity running (~90% HRmax) in which pulmonary oxygen uptake (V˙O2) was determined. In addition, the yo-yo intermittent recovery test level 1 was performed, and a muscle biopsy was obtained at rest.
  
  
  
  The yo-yo intermittent recovery test level 1 performance was 11.6% ± 6.4% (mean ± SD) better (2803 ± 330 vs 3127 ± 383 m, P < 0.05) after SET compared with before SET. In the transition from standing to moderate-intensity running, phase II pulmonary V˙O2 kinetics was 11.4% ± 16.5% faster (P < 0.05), and the running economy at this intensity was 2.3% ± 3.0% better (P < 0.05). These improvements were apparent despite the content of muscle proteins regulating oxidative metabolism (3-hydroxyacyl CoA dehydrogenase, COX IV, and OXPHOS), and capillarization was reduced (P < 0.05). The content of 3-hydroxyacyl CoA dehydrogenase and citrate synthase in type I and type II fibers did not change.
  
  
  
  In highly trained soccer players, additional speed endurance training is associated with an improved ability to perform repeated high-intensity work. To what extent the training-induced changes in V˙O2 kinetics and mechanical efficiency in type I fibers caused the improvement in performance warrants further investigation.
authors.affiliation: 1Department of Nutrition, Exercise and Sports, University of Copenhagen, DENMARK; 2Team Denmark (Danish Elite Sport Organization), Copenhagen, DENMARK; and 3DTect, Copenhagen, DENMARK.
authors.forename: Michael
authors.initials: M
authors.lastname: Nyberg
authors.forename: Matteo
authors.initials: M
authors.lastname: Fiorenza
authors.forename: Anders
authors.initials: A
authors.lastname: Lund
authors.forename: Magnus
authors.initials: M
authors.lastname: Christensen
authors.forename: Tue
authors.initials: T
authors.lastname: Rømer
authors.forename: Peter
authors.initials: P
authors.lastname: Piil
authors.forename: Morten
authors.initials: M
authors.lastname: Hostrup
authors.forename: Peter M
authors.initials: PM
authors.lastname: Christensen
authors.forename: Simon
authors.initials: S
authors.lastname: Holbek
authors.forename: Thomas
authors.initials: T
authors.lastname: Ravnholt
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Gunnarsson
authors.forename: Jens
authors.initials: J
authors.lastname: Bangsbo
mesh_terms: D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism; D000222:Adaptation, Physiological; D000328:Adult; D056352:Athletes; D054874:Athletic Performance / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000502:physiology; D010101:Oxygen Consumption; D064797:Physical Conditioning, Human / Q000379:methods*; D010807:Physical Endurance; D012420:Running / Q000502:physiology; D012916:Soccer / Q000502:physiology*; D055815:Young Adult
chemical_list: D009124:Muscle Proteins; D015094:3-Hydroxyacyl CoA Dehydrogenases