title: Effects of intensified training and subsequent reduced training on glucose metabolism rate and peripheral insulin sensitivity in Standardbreds.
abstract: OBJECTIVE
  To determine the influence of intensified training and subsequent reduced training on glucose metabolism rate and peripheral insulin sensitivity in horses and identify potential markers indicative of early overtraining.
  
  
  METHODS
  12 Standardbred geldings.
  
  
  METHODS
  Horses underwent 4 phases of treadmill-based training. In phase 1, horses were habituated to the treadmill. In phase 2, endurance training was alternated with high-intensity exercise training. In phase 3, horses were divided into control and intensified training groups. In the intensified training group, training intensity, duration, and frequency were further increased via a protocol to induce overtraining; in the control group, these factors remained unaltered. In phase 4, training intensity was reduced. Standardized exercise tests were performed after each phase and hyperinsulinemic euglycemic clamp (HEC) tests were performed after phases 2, 3, and 4.
  
  
  RESULTS
  10 of 12 horses completed the study. Dissociation between mean glucose metabolism rate and mean glucose metabolism rate-to-plasma insulin concentration ratio (M:I) was evident in the intensified training group during steady state of HEC testing after phases 3 and 4. After phase 4, mean glucose metabolism rate was significantly decreased (from 31.1 ± 6.8 μmol/kg/min to 18.1 ± 3.4 μmol/kg/min), as was M:I (from 1.05 ± 0.31 to 0.62 ± 0.17) during steady state in the intensified training group, compared with phase 3 values for the same horses.
  
  
  CONCLUSIONS
  Dissociation between the glucose metabolism rate and M:I in horses that underwent intensified training may reflect non-insulin-dependent increases in glucose metabolism.
authors.affiliation: Department of Equine Sciences, Medicine Section, Faculty of Veterinary Medicine, Utrecht University, Utrecht, 3584 CM Utrecht, The Netherlands. e.roelfsema@uu.nl
authors.forename: Ellen
authors.initials: E
authors.lastname: de Graaf-Roelfsema
authors.forename: Hans A
authors.initials: HA
authors.lastname: Keizer
authors.forename: Eric
authors.initials: E
authors.lastname: van Breda
authors.forename: Inge D
authors.initials: ID
authors.lastname: Wijnberg
authors.forename: Johannes H
authors.initials: JH
authors.lastname: van der Kolk
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D012090:Cumulative Trauma Disorders / Q000175:diagnosis / Q000378:metabolism / Q000662:veterinary; D015309:Glucose Clamp Technique / Q000662:veterinary; D006339:Heart Rate / Q000502:physiology; D006736:Horses / Q000097:blood / Q000378:metabolism*; D007333:Insulin Resistance / Q000502:physiology*; D016014:Linear Models; D008297:Male; D010805:Physical Conditioning, Animal / Q000502:physiology*
chemical_list: D001786:Blood Glucose