(A) Plasma lactate concentration, (B) heart rate, and (C) hematocrit (least squares means ± SE) before, during, and after an incremental exercise test consisting of three 642 m phases; at 3.0 m/s (Speed3), 4.0 m/s (Speed4) and 5.0 m/s (Speed5) in 8 mature Icelandic riding horses. Blood samples were collected at rest; at end of warm-up; at end of Speed3, Speed4, and Speed5; and at the end of 5-, 15-, and 30-min recovery. Heart rate was recorded during the last minute of warm-up, Speed3, Speed4, and Speed5 and 5-, 15-, and 30-min recovery. The HR at rest was the minimum HR measured before the exercise test. An asterisk (*) indicates significant difference between gaits; bars within a gait with different letters are significantly different (P < 0.05).