Validation of a portable equine metabolic measurement system

Abstract

In equine sports medicine, VO2 has been measured exclusively with stationary systems, in laboratories equipped with a treadmill. Measurement during exercise in field conditions has not previously been reported because of the lack of portable equipment designed for horses. A commercially available portable metabolic measurement system, based on breath-to-breath gas analysis and flow spirometry, was adapted to the horse's physiology and morphology (Cosmed K4b2 and Equimask) and its validity tested by (1) repeatability of the measures and (2) comparing metabolic data to those obtained by a reference method (RM). To test the reproducibility of the measurements, 5 healthy saddle horses were subjected twice at 2 day intervals to a similar submaximal standardised incremental exercise test on a treadmill. The same horses performed twice at one week interval an incremental treadmill test to fatigue: the oxygen consumption and ventilation were measured once with the K4b2 system and once with the RM. The metabolic and ventilatory data obtained with both systems were compared. There was a good reproducibility of the metabolic measurements obtained by the K4b2 system at any workload. The VO2 obtained by both systems at any workload was not significantly different. However, the K4b2 expired fraction in CO2 (FETCO2) and carbon dioxide production (VCO2) were significantly lower at high and at maximal workloads. As a consequence, the values of the respiratory exchange ratio were too low and incompatible with normal physiological values. The good reproducibility of the metabolic and ventilatory measurements and the fact that the VO2 measurements at any workload were similar to the data obtained with the reference method suggested that this system may be used for comparison of repeated VO2 measurements in practical field conditions. The K4b2 system could be used to improve knowledge of the energetic cost in different equine sports disciplines and offer the opportunity to undertake performance tests with genuine track conditions, on ridden or harnessed horses, rather than under laboratory conditions.