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Plasma ammonia and lactate responses using incremental and constant speed exercise tests
Author(s) -
HARRIS R. C.,
HARRIS D. B.,
DUNNETT M.,
HARRIS PAT A.,
FALLOWFIELD J.,
NAYLOR J. R. J.
Publication year - 1999
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/j.2042-3306.1999.tb05281.x
Subject(s) - ammonia , incremental exercise , constant (computer programming) , blood lactate , lactate threshold , chemistry , medicine , computer science , biochemistry , heart rate , blood pressure , programming language
Summary Plasma NH 3 , formed during intense exercise, results principally from the deamination of AMP in muscle. Its formation during exercise may be influenced both by the pool of fibres recruited and by changes in the intracellular environment affecting ADP homeostasis. This study compared incremental and constant speed exercise as possible protocols for the investigation of plasma NH 3 accumulation with intense exercise. Six trained Thoroughbred horses, one of which had recently been operated on for recurrent laryngeal neuropathy, undertook a step‐wise treadmill test with 1 min incremental steps of 6, 8, 10, 11 and 12 m/s (7.5% incline). Two and 4 weeks later horses performed a constant‐speed, maximum‐exercise tolerance test at 115% V̇O 2max (7.5% incline). Blood samples from the jugular vein were drawn at 20 s intervals in all 3 tests, for plasma NH 3 and lactate. There were marked differences between and within horses in their time dependant lactate and NH 3 responses to exercise. Three of the 6 horses studied showed a distinct threshold for onset of plasma NH 3 accumulation with incremental exercise. Distinct thresholds for the onset of NH 3 accumulation were apparent also in 5 of the 6 horses during exercise at constant rate. The present study demonstrates clearly the practicality of measuring NH 3 concentration curves, even during a short incremental step test which has the advantage that other measures relating to cardiovascular and respiratory functions can be measured simultaneously.