title: Quantifying training intensity distribution in a group of Norwegian professional soccer players.
abstract: OBJECTIVE
  This study was designed to quantify the daily distribution of training intensity in a group of professional soccer players in Norway based on three different methods of training intensity quantification.
  
  
  METHODS
  Fifteen male athletes (age, 24 ± 5 y) performed treadmill test to exhaustion to determine heart rate and VO2 corresponding to ventilatory thresholds (VT1, VT2), maximal oxygen consumption (VO2max) and maximal heart rate. VT1 and VT2 were used to delineate three intensity zones based on heart rate. During a 4 wk period in the preseason (N = 15), and two separate weeks late in the season (N = 11), all endurance and on-ball training sessions (preseason: N = 378, season: N= 78) were quantified using continuous heart rate registration and session rating of perceived exertion (sRPE). Three different methods were used to quantify the intensity distribution: time in zone, session goal and sRPE.
  
  
  RESULTS
  Intensity distributions across all sessions were similar when based on session goal or by sRPE. However, intensity distribution based on heart rate cut-offs from standardized testing was significantly different (time in zone).
  
  
  CONCLUSIONS
  Our findings suggest that quantifying training intensity by using heart rate based total time in zone is not valid for describing the effective training intensity in soccer. The results also suggest that the daily training intensity distribution in this representative group of high level Norwegian soccer players is organized after a pattern where about the same numbers of training sessions are performed in low lactate, lactate threshold, and high intensity training zones.
authors.affiliation: Institute of Public Health, Sport, and Nutrition, University of Agder, Kristiansand, Norway.
authors.forename: Erling A
authors.initials: EA
authors.lastname: Algrøy
authors.forename: Ken J
authors.initials: KJ
authors.lastname: Hetlelid
authors.forename: Stephen
authors.initials: S
authors.lastname: Seiler
authors.forename: Jørg I
authors.initials: JI
authors.lastname: Stray Pedersen
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D005080:Exercise Test; D006339:Heart Rate; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000502:physiology*; D009664:Norway; D010101:Oxygen Consumption; D010807:Physical Endurance; D012123:Pulmonary Ventilation; D012916:Soccer; D013647:Task Performance and Analysis; D013997:Time Factors; D055815:Young Adult
chemical_list: D015415:Biomarkers; D019344:Lactic Acid