title: Exercise intensity during off-road cycling competitions.
abstract: OBJECTIVE
  This study was designed to quantify and describe the intensity profile of cross-country mountain-biking races using heart rate (HR) recorded during competitions.
  
  
  METHODS
  Nine mountain bikers participated in four cross-country circuit races of international and national levels. Each cyclist was tested before the competitions to determine lactate threshold (LT), the onset of blood lactate accumulation (OBLA4), and the relationship between percentage of maximum HR and percentage of VO(2max).
  
  
  RESULTS
  To control for intersubject variability, only the five off-road cyclists who completed all four competitions were included in the statistical analysis. The four races' mean absolute and relative time expressed in percentage of race duration (147 +/- 15 min) spent in the EASY(ZONE) (HR below LT) were 27 +/- 16 min and 18 +/- 10%, in the MODERATE(ZONE) (HR between LT and OBLA4) were 75 +/- 19 min and 51 +/- 9%, and in the HARD(ZONE) (HR above OBLA4) were 44 +/- 21 min and 31 +/- 16%. The average HR was 171 +/- 6 beats x min(-1), corresponding to 90 +/- 3% of maximum (84 +/- 3% of VO(2max).
  
  
  CONCLUSIONS
  This study shows that cross-country events are conducted at very high intensity, especially at the start of the race. Coaches must take into account the distribution of the effort and the high exercise intensity characteristic of mountain-biking cross-country events when prescribing specific training programs.
authors.affiliation: Laboratorio di Fisologia, Sport Service MAPEI, Castellanza, Varese, Italy. mapeisport@tin.it
authors.forename: Franco
authors.initials: F
authors.lastname: Impellizzeri
authors.forename: Aldo
authors.initials: A
authors.lastname: Sassi
authors.forename: Manuel
authors.initials: M
authors.lastname: Rodriguez-Alonso
authors.forename: Piero
authors.initials: P
authors.lastname: Mognoni
authors.forename: Samuele
authors.initials: S
authors.lastname: Marcora
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D015308:Anaerobic Threshold / Q000502:physiology*; D001642:Bicycling / Q000502:physiology*; D004734:Energy Metabolism; D015444:Exercise; D006339:Heart Rate; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance; D005082:Physical Exertion / Q000502:physiology; D011336:Probability; D012016:Reference Values; D012494:Sampling Studies; D012680:Sensitivity and Specificity
chemical_list: D019344:Lactic Acid