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Keywords:

  • horse;
  • equine;
  • exercise;
  • cardiovascular

Summary

The purpose of this study was to test the hypotheses that ageing would result in a decline in maximal heart rate (HRmax) and maximal aerobic capacity (V̇O2max) and, secondarily, that those effects would be reversible with training. Eighteen, healthy, unfit Standardbred mares representing 3 age groups: young (Y = mean ± s.e. 6.8 ± 0.4 years, n = 6); middle-aged (MA = 15.2 ± 0.4 years, n = 6); and old (O = 27.0 ± 0.2 years, n = 6) were used. HRmax, V̇O2max and oxygen pulse at V̇O2max (OPmax) and the velocities producing HRmax (V̇HRmax) and V̇O2max (VV̇O2max) were measured during pretraining and post-training incremental exercise tests (GXT). During training, mares exercised 3 days/week (Weeks 1–8) and 4 days/week (Weeks 9–12) at a submaximal intensity (∼60% HRmax) for ∼30 min/day. There were no differences (P>0.05) between Y and MA, before (218 ± 2 vs. 213 ± 3 beats/min; 116 ± 3 vs. 109 ± 3 ml/kg bwt/min; 0.55 ± 0.01 vs. 0.52 ± 0.02 ml/kg/beat; 9.0 ± 0.3 vs. 9.3 ± 0.2 m/s; 8.8 ± 0.2 vs. 8.8 ± 0.2 m/s) or after training (224 ± 2 vs. 218 ± 2 beats/min; 131 ± 3 vs. 120 ± 2 ml/kg bwt/min; 0.58 ± 0.01 vs. 0.55 ± 0.01 ml/kg/beat; 10.5 ± 0.2 vs. 9.5 ± 0.1 m/s; 10.6 ± 0.2 vs. 9.5 ± 0.1 m/s) for HRmax, V̇O2max, OPmax, V̇HRmax or VV̇O2max, respectively. Old horses had lower HRmax, V̇O2max and OPmax and reached them at lower velocities compared to Y and MA (P<0.05), both before (193 ± 3 beats/min; 83.2 ± 2.0 ml/kg bwt/min; 0.43 ± 0.01 ml/kg/beat; 7.8 ± 0.1 m/s; 7.2 ± 0.1 m/s) and after training (198 ± 2 beats/min; 95 ± 2 ml/kg bwt/min; 0.48 ± 0.01 ml/kg/beat; 8.2 ± 0.2 m/s; 8.0 ± 0.2 m/s). Training did not alter HRmax in any age group (P>0.05) but did cause increases in V̇O2max, OPmax and VV̇O2max for all groups (P<0.05). Interestingly, training increased VHRmax only in Y (P<0.05). These data demonstrate that there is a reduction in HRmax, V̇O2max, OPmax, VHRmax and VV̇O2max in old horses, and that training can partially reverse some effects of ageing.