Physiological, metabolic and biochemical responses of horses competing in the speed and endurance phase of a CCI**** 3‐day‐event

Abstract

Summary The present study was undertaken to investigate physiological, metabolic, haematological and biochemical changes in horses competing in the Speed and Endurance test of a Concours Complet International (CCI) **** 3‐day‐event held under FEI rules. A total of 28 horses competing in the Burghley Horse Trials Speed and Endurance test were selected to be monitored: 11 horses in 1993 and 17 horses in 1994. Of the 28 horses selected, 17 completed the Speed and Endurance test and went on to complete the showjumping test. Mean ± s.d. shade temperature and relative humidity, black globe temperature and wind speed were 13 ± 1 and 20 ± 2°C, 54 ± 3 and 55 ± 10%, 17 ± 2 and 29 ± 4°C and 2.7 ± 0.7 and 1.2 ± 0.3 m/s, for 1993 and 1994, respectively. Mean heart rate during Phases A, B and D was not significantly different between years, but mean heart rate during Phases C and X was significantly higher in 1994. Mean (± s.d.) heart rate on Phases B and D for all horses in both 1993 and 1994 was 198 ± 8 and 188 ± 11 beats/min, respectively. Mean heart rate during Phase D showed a poor correlation with mean speed (r=0.412). Total mean (± s.d.) weight loss from the start of Phase A to the end of Phase D was 15.5 ± 6.1 kg in 1993 and 16.5 ± 5 kg in 1994 and did not differ significantly between years. Following 14–18 h completion of Phase D, mean bodyweight was not significantly different from that at the start of Phase A in either year. Mean rectal temperature at the end of Phase D was 41 ± 0.6°C and 41.1 ± 0.6°C in 1993 and 1994, respectively (P>0.05). Both the lowest (39.7°C) and highest (41.8°C) rectal temperatures were recorded at the end of Phase D in 1994. Plasma lactate concentrations at the end of Phase D were 8.5–38.5 mmol/1. The highest lactate concentration also coincided with the highest plasma glucose concentration (11.4 mmol/1) as well as the joint fastest time in either year, although overall lactate showed only weak correlations with mean speed on Phase D (r=0.12, 1993; r=0.58, 1994). While the Speed and Endurance test at CCI**** level run in a temperate climate presents a considerable challenge to the fitness and ability of the horses competing, the metabolic and physiological changes are not extreme. The majority of horses that finish the test appear to undergo a rapid and considerable degree of recovery and are able to present sound at the final inspection, take part in the showjumping test and complete the competition.

Comparative Exercise Physiology

“…an even greater reliance on aerobic energy sources during exercise and during endurance riding will work about 96% aerobically (Eaton 1994). Similarly, an eventing horse relies primarily on aerobic energy sources, with anaerobic energy during jumping efforts (Marlin et al 1995).…”

Airway cooling and mucosal injury during cold weather exercise

“…Horses in Experiment 1 were probably not generating a maximal amount of minute ventilation (V), and the conditions in which they were exercising were milder than those conditions routinely found in some equine training or competitive environs. Furthermore, a horse's basal temperature (~38°C) is somewhat higher than in man (37°C) and increases during strenuous exercise (Marlin et al 1995), resulting in a greater thermal gradient across the airway wall compared to a human airway with the same intraluminal temperature. All of these factors suggest that considerable heat and water loss is possible in the distal airways of exercising horses.…”

The Influential Games: How the Barcelona Olympics Changed the Sport of Eventing

“…These results can be explained by the international research programme that was set up in response to the Barcelona Games in preparation for Atlanta 1996. Groups based at research facilities around the world launched several studies shortly after the Barcelona Olympics to determine the best ways to develop heat tolerance in equine athletes through training, acclimation and nutrition (for example, Marlin et al, 1995;Lindinger, Geor, Ecker, & McCutcheon, 1995). Prior to this verified methods of managing horses tolerance to hot and humid conditions had not been established.…”