title: Reduced high intensity training distance had no effect on VLa4 but attenuated heart rate response in 2-3-year-old Standardbred horses.
abstract: BACKGROUND
  Training of Standardbred race horses aims to improve cardiovascular and metabolic functions but studies on the effects of different training strategies from breaking till racing are lacking. Sixteen horses with the goal to race as 3-year-olds were studied from breaking (1-year-olds) to December as 3-year-olds. Horses were allocated to either a control (C) or reduced (R) training program from 2 years of age. The aim was to evaluate the effect of reducing the distance of high intensity exercise by 30% with respect to velocity at lactate concentration 4 mmol/l (VLa4), blood lactate and cardiovascular response. All training sessions were documented and heart rate (HR) was recorded. A standardized exercise test of 1,600 m was performed 10 times and a VLa4 test was performed five times.
  
  
  RESULTS
  C horses initially exercised for a longer time with a HR >180 beats per minute compared to R horses (P < 0.05) but after 6-9 months, time with HR >180 bpm decreased in C and were similar in the two groups (P > 0.05). Over the 2-year period, recovery HR after the 1,600 m-test decreased in both groups but was within 2 months lower in C than in R (P < 0.05). C horses also had lower resting HR as 3-year-olds (P < 0.01) than R horses. In C, post exercise hematocrit was higher than in R (P < 0.05). There was a tendency (P < 0.1) towards a larger aortic diameter in C as 3-year-olds (C: 1.75 ± 0.05, R: 1.70 ± 0.05 cm/100 kg BW). Left ventricle diameter and blood volume (in December as 2-year-olds) did not differ between groups. There were no differences between groups in post exercise blood lactate concentration or in VLa4. Both groups were equally successful in reaching the goal of participation in races.
  
  
  CONCLUSIONS
  Horses subjected to a reduced distance of high intensity training from the age of 2 showed an attenuated heart rate response, but were able to maintain the same VLa4 and race participation as horses subjected to longer training distances.
authors.affiliation: Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, SE-75007, Uppsala, Sweden. Sara.Ringmark@slu.se.
authors.forename: Sara
authors.initials: S
authors.lastname: Ringmark
authors.affiliation: Vetteam AB, SE-81591, Tierp, Sweden. Anna.Jansson@slu.se.
authors.forename: Arne
authors.initials: A
authors.lastname: Lindholm
authors.affiliation: Swedish Centre for Trotting Education, Wången, SE-83040, Alsen, Sweden. ulf.hedenstrom@wangen.se.
authors.forename: Ulf
authors.initials: U
authors.lastname: Hedenström
authors.affiliation: Lindenfarne Horse Park, Campbellville, Toronto, ON, L0P 1B0, Canada. mi.lindinger@gmail.com.
authors.forename: Michael
authors.initials: M
authors.lastname: Lindinger
authors.affiliation: Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, SE-75007, Uppsala, Sweden. Kristina.Dahlborn@slu.se.
authors.forename: Kristina
authors.initials: K
authors.lastname: Dahlborn
authors.affiliation: Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, SE-75007, Uppsala, Sweden. Clarence.Kvart@slu.se.
authors.forename: Clarence
authors.initials: C
authors.lastname: Kvart
authors.affiliation: Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, SE-75007, Uppsala, Sweden. Anna.Jansson@slu.se.
authors.forename: Anna
authors.initials: A
authors.lastname: Jansson
mesh_terms: D000818:Animals; D002320:Cardiovascular Physiological Phenomena; D006339:Heart Rate; D006736:Horses / Q000502:physiology*; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D010805:Physical Conditioning, Animal
chemical_list: D019344:Lactic Acid