SAEVA Congress 2018 Proceedings | 12-15 February 2018 | ATKV Goudini Spa
Anaerobic energy capacity is related principally to the glycolytic combustion of glucose that is stored in large amounts in the working skeletal muscles as glycogen . The end product of glycolysis is lactate and plasma or whole blood concentrations of lactate can be readily measured in field settings with a variety of handheld commercial devices that now cost <$ 300 .
An alternative anaerobic pathway that is important in thoroughbred and standardbred racehorses is the myokinase reaction : ADP + ADP ↔ ATP + AMP ; AMP → IMP + NH 3 . Although a lot of work has been done regarding lactate in equine athletes , studies into the NH 3 response to strenuous exercise are limited . This is likely due to the difficulty and expense in having tests run . However , recent advents in analytical chemistry have resulted in the development of NH 3 analyzers that might lead to a new dimension in anaerobic energy assessment of racehorses .
Assessing aerobic energy capacity The measurement of VO 2 max is regarded as the single best assessment of aerobic capacity as it reflects all the integrated physiologic and metabolic events associated with the transfer of oxygen from ambient air to mitochondria and its use in the production of ATP in those organelles . VO 2 max has been significantly correlated with the athletic performance of people engaged in events lasting more than 90 sec and similar findings have been reported for racing standardbreds . It appears to be particularly important in thoroughbred racehorses because , even in races of comparatively short duration , aerobic metabolism is still responsible for the great majority of energy production . The VO 2 max of the very best horses has been variously estimated to be > 180 ml /( kg . min ), with some researchers putting the figure above 200 ml /( kg . min ). By comparison , only the very best human endurance trained athletes have a VO 2 max greater than 100 ml /( kg . min ).
Because the indirect measurement of oxygen consumption ( VO 2 ) is technically very difficult or impossible in exercising horses , determining VO 2 under these conditions has typically been performed ergospirometrically using an open-flow system on a treadmill rather than in the field . The associated cost of these facilities and their reliance on the availability of electricity has largely limited their existence to major academic and research institutions . This in turn has restricted the ability of investigators to measure VO 2 max when attempting to assess the athletic potential of horses under field conditions .
Of critical importance in the determination of an individual horse ’ s VO 2 max , whether on a treadmill or in the field , is the design of the facemask that it must wear for this purpose . Resistance to airflow through the mask must be minimal and wearing the mask should not compromise pulmonary gas exchange , if the objective is to measure the true VO 2 max of the horse . It is for these reasons that the majority of systems used for determination of VO 2 max on treadmills favour the use of open- or biased-flow through gas collection systems . Of the masks that have been previously designed for field measurement of VO 2 in horses , none have been demonstrated to not interfere with gas exchange , based on direct measurement of arterial blood gases or inference from other data recorded during a field test . The exercise intensity at which compromise occurs varies from mask to mask but , until recently , none have been demonstrated to measure what appears to be the subject ’ s true VO 2 max .
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