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This study examined the effect of increasing BW ratio (BWR) between rider and horse, in the BWR range common for Icelandic horses (20% to 35%), on heart rate (HR), plasma lactate concentration (Lac), BWR at Lac 4 mmol/l (W4), breathing frequency (BF), rectal temperature (RT) and hematocrit (Hct) in Icelandic horses. In total, eight experienced school-horses were used in an incremental exercise test performed outdoors on an oval riding track and one rider rode all horses. The exercise test consisted of five phases (each 642 m) in tölt, a four-beat symmetrical gait, at a speed of 5.4±0.1 m/s (mean±SD), where BWR between rider (including saddle) and horse started at 20% (BWR20), was increased to 25% (BWR25), 30% (BWR30), and 35% (BWR35) and finally decreased to 20% (BWR20b). Between phases, the horses were stopped (~5.5 min) to add lead weights to specially adjusted saddle bags and a vest on the rider. Heart rate was measured during warm-up, the exercise test and after 5, 15 and 30 min of recovery and blood samples were taken and BF recorded at rest, and at end of each of these aforementioned occasions. Rectal temperature was measured at rest, at end of the exercise test and after a 30-min recovery period. Body size and body condition score (BCS) were registered and a clinical examination performed on the day before the test and for 2 days after. Heart rate and BF increased linearly (P0.05), but negative correlations (P<0.05) existed between body size measurements and Hct. While HR, Hct and BF recovered to values at rest within 30 min, Lac and RT did not. All horses had no clinical remarks on palpation and at walk 1 and 2 days after the test. In conclusion, increasing BWR from 20% to 35% resulted in increased HR, Lac, RT and BF responses in the test group of experienced adult Icelandic riding horses. The horses mainly worked aerobically until BWR reached 22.7%, but considerable individual differences (17.0% to 27.5%) existed that were not linked to horse size, but to back BCS.

This study compared the effect of ridden tölt and trot at 3 speeds on physiological responses in trained adult (15.3 ± 1.6 yr) Icelandic horses. The experiment had a crossover design with 8 horses, 2 treatments (incremental exercise test in tölt and trot), and 2 riders. Each horse performed 2 tests per day (1 gait with 2 riders, minimum 4.5 h between) on 2 separate days, with 1 d of rest in between. The exercise test consisted of three 642-m phases at 3.0 m/s (Speed3), 4.0 m/s (Speed4), and 5.0 m/s (Speed5) and was performed outdoors on a 300- m oval gravel riding track in northern Iceland in May 2012. Heart rate (HR) was measured during warm-up, the exercise test, and after 5, 15, and 30 min of recovery. Blood samples were taken at rest, after warm-up, after each phase of the exercise test, and after 5, 15, and 30 min of recovery. Respiratory rate was counted for at least 15 s at rest, at the end of the exercise test, and at the end of the 30-min recovery, and rectal temperature was measured on these occasions. There were no differences in HR between tölt and trot at any time point (P > 0.05). At Speed3, hematocrit and plasma lactate concentration were greater (P < 0.05) in tölt (40% ± 1%, 1.1 ± 0.06 mmol/L) than in trot (39% ± 1%; 0.9 ± 0.06 mmol/L). There was a prolonged recovery of hematocrit and respiratory rate, a slower decrease in rectal temperature, and a tendency of a prolonged recovery of plasma lactate concentration (P = 0.0675) after tölt. In conclusion, there were only minor differences in physiological responses to tölt and trot in this selected group of experienced adult Icelandic horses and the biological and practical significance of the slightly elevated physiological responses to tölt and the slower recovery remains to be determined. [ABSTRACT FROM AUTHOR]

This study examined the response in terms of heart rate (HR), respiratory rate (RR), haematocrit (Htc), rectal temperature (RT), and some plasma variables in Icelandic horses of different sexes and ages performing the riding assessment in a breed evaluation field test (BEFT). The study was conducted in Iceland on 266 horses (180 mares and 86 stallions, divided into four age groups; 4, 5, 6 and ⩾7 years old). RT and RR were recorded and blood samples were taken before the warm-up and after the riding assessment. Horse HR, velocity and distance were recorded during the warm-up, the riding assessment and a 5-min recovery period. The distance covered in the BEFT was 2.9±0.4 km (range: 1.8 to 3.8 km, n=248), the duration was 9:37±1:22 min:s (range: 5:07 to 15:32 min:s, n=260) and the average speed was 17.8±1.4 km/h (range: 13.2 to 21.3 km/h, n=248). Average HR was 184±13 b.p.m. (range: 138 to 210 b.p.m., n=102) and peak HR 224±9 b.p.m. (range: 195 to 238 b.p.m., n=102), and 36% of the BEFT was performed at HR ⩾200 b.p.m. Post-exercise plasma lactate concentration (Lac) was 18.0±6.5 mmol/l (range: 2.1 to 34.4 mmol/l, n=266), and there was an increase in total plasma protein, plasma creatine kinase and aspartate amino transferase concentration, as well as RR, RT and Htc. Stallions covered a longer total distance (in the warm-up and BEFT) (P<0.05), at a faster speed during BEFT (P<0.001) than mares and had higher Htc and lower HR and post-exercise Lac values. There were few effects of age, but the 4- and 5-year-old horses had lower Htc than older horses and 4-year-old horses had higher post-exercise RR than older horses, although they were ridden for a shorter distance, shorter duration and at lower peak velocity (P<0.1). The results showed that the riding assessment in the BEFT is a high-intensity exercise. The results also showed that aerobic fitness was higher in stallions and that age had a limited effect on the physiological response. It is suggested that these results should be used as a guide for the development of training programmes and fitness tests in Icelandic horses that would improve both performance and welfare of the horse. [ABSTRACT FROM PUBLISHER]

This study evaluated the physiological response to an experimental 100 m flying pace race (EPR) in Icelandic horses with pace-competition experience, and whether there was an effect of rider. A cross-over design with nine horses and two riders was used. The EPR was performed twice (once with each rider) with four days of rest in-between. The EPR consisted of two runs (I and II), of which at least 100 m was in pace at full speed according to international competition rules. Plasma lactate concentration increased and was greater after pace run II than I (18.5±1.3 vs 11.9±0.7 mmol/l; P<0.001). Heart rate was higher during pace run I than II (207±3 vs 205±3; P=0.02). Heart rate and Lact had not recovered 30 min post exercise but Hct was back to resting level after 30 min recovery. Speed did not differ between riders and pace runs (pooled mean ± standard deviation of pace runs: 10.4±0.7 m/s, range 9.2-12.1 m/s) but HR and Lact were higher from warm-up and until 30 min recovery with rider 1 than 2 (P<0.001). There was a negative correlation between post EPR Lact with rider 1 and previous best record (r2=0.72, P=0.032). To conclude, a 100 m flying pace race in the Icelandic horse is a high-intensity exercise and anaerobic metabolism is crucial for performance. The rider had an effect on the physiological response but it is unclear if it was due to body weight, riding style or both. The practical relevance of the differences observed between riders remains to be proven but our results indicate that they may have limited impact on single day competitions since the speed was the same with the two riders. [ABSTRACT FROM AUTHOR]