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Relative aerobic and anaerobic energy contribution in race fit endurance and Thoroughbred racehorses during strenuous exercise

Comparative Exercise Physiology, ISSN: 1755-2559, Vol: 15, Issue: 5, Page: 299-306
2019
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Metrics Details

  • Citations
    4
    • Citation Indexes
      4
  • Captures
    32

Article Description

The objective was to compare fit Arabian endurance and Thoroughbred racehorses' responses to a maximal intensity standardised incremental treadmill test (MaxSIT) with respect to: (1) their relative aerobic contributions during maximal exercise; and (2) selected physiological parameters related to performance. Six high-level endurance Arabians and six race-ready Thoroughbreds performed a MaxSIT starting at 8 m/s and increasing by 1 m/s increments 60 s until maximum oxygen consumption (VO) was reached. Heart rate (HR), blood lactate concentration (BLac), haematocrit (Hct), minute ventilation (VE) and oxygen consumption (VO) were measured. VO, the speeds at which the HR were 200 and 160 bpm, respectively (V, V), the speed at which the BLac reached 4 mmol/l (V) and lactate at HR (BLa) were calculated. The relative aerobic energy input was determined using ΔBLac increase as previously described. Data were expressed as median with interquartile range and analysed with a Wilcoxon rank sum test (P<0.05). Endurance horses had greater VO (202.5 ml/(kg.min) (190.3- 211) vs 152.7 ml/(kg.min) (140.5-158.3); P<0.001) and had a greater aerobic energy contribution to total exercise effort (89.9% (87.0-96) vs 82.8% (81.1-84.1); P=0.009) than Thoroughbreds. Endurance horses reached HR>200 bpm on the treadmill, but had a lower HR (210 bpm (205-217) vs 226 bpm (219-228); P=0.008), BLa (3.8 mmol/l (2.7-5.5) vs 4.8 mmol/l (3.6-5.2); P<0.001) and Hct (56.4% (54.9-57.5) vs 61.5% (59-64); P=0.002). Endurance horses median VLa was 11.6 m/s (11.0-13.0); V=11.9 m/s (10.9-12.3) and V=8.5 m/s (7.2-8.6). Because of the HR and speed characteristics of modern endurance races, we proposed BLa as a new calculated parameter with which to assess endurance horses. Trained endurance horses accumulate less lactate, have a greater VO and relative aerobic contribution to their energy requirements at maximal intensity exercise despite a lower blood haematocrit.

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