The purpose of this study was to estimate the work intensity of a reining pattern and to determine hematological responses of trained Quarter Horses during a reining competition. Twelve Quarter Horses between four and eight years of age were equipped with a heart rate monitor at a National Reining Horse Association approved Horse Show. Heart rates were continuously recorded from approximately the last 30 minutes of the warm-up until two minutes after leaving the arena. The performance of each participant was video recorded and heart rates subsequently assigned to the different maneuvers. Blood samples were taken at rest and one minute after completion of the pattern. Average time needed to complete the pattern was 2:53 +/- 0:09 minutes over a distance of about 680 meters (3.9 m/s mean average velocity). The heart rate increased continuously from the beginning of the performance until a plateau was reached during canter. Highest heart rates were induced by roll-backs and stopping with 181 +/- 13 bpm. One minute after completion of the pattern heart rate dropped to 86 +/- 12 bpm. During the pattern mean plasma lactate increased significantly (P<0.001) to 5.1 +/- 1.9 mmol/l. PCV increased (p<0.05) to 48.6 +/- 2.8% with concomitant significant changes in the number of red blood cells (10.6 +/- 0.8 x 10(12)/l), hemoglobin concentration (17.5 +/- 1.2 g/dl) and related parameters. The number of white blood cells increased significantly to 10.01 +/- 1.50 x10(9)/l with a shift in the numbers of neutrophils from 4.38 +/-0.51 x 10(9)/l to 5.53 +/- 0.87 x 10(9)/l and in lymphocytes from 2.89 +/- 0.56 x 10(9)/l to 3.96 +/- 0.86 x 10(9)/l.
The reining pattern and its preceding warm-up period induced increased anaerobic glycolysis and subsequent mild accumulation of lactate. Performing a reining pattern represents only a submaximal workload with no signs of fatigue in adult Quarter Horses, Aerobic conditioning in combination with fast power training seems to be indicated in the training of reining Quarter Horses in addition to practicing motor skills