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Summary The exercise intensity of horses competing in 3‐day combined training events at 3 different levels of competition (CCI***, n=7; CCI**, n=11; CCI*, n=23) was investigated. Environmental conditions during all events were cool with 100% cloud cover. Heart rates were continuously recorded at 5 s intervals by a heart rate monitor. Mean ± s.d. heart rate for all horses during each phase were: Phase A=118 ± 11 beats/min, Phase B=179 ± 22.7 beats/min, Phase C=129 ± 13.9 beats/min and Phase D=174 ± 19.6 beats/min. Mean ± s.d. heart rates on Phases A and C were significantly different from mean heart rates on Phases B and D. Plasma lactate concentrations were determined at rest, within 60 s and 10 min after the end of Phase D or the cross country test. Mean ± s.d. lactate concentrations were highest immediately post exercise (mean=18.4 ± 5 mmol/1 for all horses) and had declined significantly in 10 min (mean=15 ± 6.8 mmol/1 for all horses). Mean ± s.d. heart rates and lactate concentrations were not significantly different among levels of competition at each time period. The intensity of work of fit horses successfully competing in 3‐day combined training events consists of both low intensity aerobic exercise and more intense submaximal work with significant anaerobiosis. The work intensity is remarkably constant throughout different levels of competition, despite the increasing distance, number and difficulty of jumping efforts and faster optimum speeds.

Summary The exercise intensity of horses competing in the cross country phase of an advanced horse trial (Group 1; n=17) and an advanced 3‐day combined training event (Group 2; n=7) over a similar course on the same day was investigated. Environmental conditions during the trial were cool. Heart rates were continuously recorded at 5 s intervals by a heart rate monitor. Mean ± s.d. heart rates for Group 1 and Group 2 were 167.7 ± 24.0 beats/min and 171.4 ± 19.2 beats/min, respectively, (P>0.05). Plasma lactate concentrations were determined at rest, within 60 s post exercise and 10 min post exercise. Mean lactate concentrations were highest immediately post exercise (Group 1=15.18 ± 5.79 mmol/l; Group 2=19.10 ± 4.22 mmol/l) and had declined significantly in 10 min (Group 1=11.15 ± 6.56 mmol/l; Group 2=16.06 ± 6.11 mmol/l). Lactate concentrations were not significantly different between groups at each time period. We concluded that the work effort for the cross country phase was not different between advanced horse trial and 3‐day competitions for horses competing under similar conditions during non stressful environmental conditions.

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Summary The exercise intensity of horses (n=175) competing in the cross‐country phase of 4 combined training events at 5 levels of competition [novice (N), training (T), preliminary (P), intermediate (I) and advanced (A)] was investigated. Environmental conditions varied from cool and humid (mean ± s.d. temperature and humidity=12.1°C ± 0.6 and 88.4% ± 8.9 RH) to moderately hot and humid (27.8°C ± 2.1 and 62.5% ± 7.8 RH). Heart rates (beats/min) were recorded continuously at 5 s intervals with a heart monitor. Mean ± s.d. heart rates (beats/min) for each level of competition were: 154.4 ± 19.2 beats/min (n=45) (N), 160.4 ± 28.1 beats/min (n=47) (T), 160.6 ± 33 beats/min (n=53) (P), 181 ± 26.6 beats/min (n=29) (I) and 194.6 ± 4.2 beats/min (n=4) (A). Plasma lactate concentration was determined at rest in a random sampling of horses (n=36) from all competitions and within 60 s of completion of the cross‐country phase in all horses. Mean ± s.d. lactate concentration at rest was 0.98 ± 0.3 mmol/1. Mean ± s.d. lactate concentrations (mmol/1) of horses after exercise were: N=8.1 ± 7, T=11.5 ± 4.7, P=17.6 ± 6.1, I=19 ± 6.7 and A=21.3 ± 7.3. Mean plasma lactate increased significantly (P<0.001) as levels of competition increased, although there were few significant differences in heart rate between levels. Rectal temperatures were taken immediately after completion of the cross‐country phase and 10 min later. Mean ± s.d. rectal temperatures were significantly higher 10 min after completion of the cross‐country than those taken immediately after cross‐country (P<0.001). Rectal temperatures 10 min after completion of exercise were significantly higher as the level of competition increased for N through I (P<0.001). Rectal temperatures 10 min after completion of exercise were correlated with ambient temperatures (r=0.22, P=0.01). There was no significant correlation between either pulse or respiratory rate taken immediately after completion of exercise with heart rate during the course.