Relationship between Slope of the Plasma Lactate Accumulation Curve and Working Capacity in Andalusian Horses

Abstract

The main objective of this study was to analyse the relationship between the slope of the plasma lactate accumulation in response to exercise and working capacity in two groups of Andalusian horses of different age.The horses were subjected to increasing intensity tests, comprising both submaximal and maximal velocities. Heart rate was monitored throughout the exercise and jugular venous blood samples were withdrawn at rest, after each workload and during the first 30 min. of recuperation. Working capacity was assessed by means of these functional indices: HRmax (maximum mean heart rate during exercise), Vmax (maximum velocity), STEPmax (maximum number of workload completed), VLA2 (aerobic threshold), VLA4 (anaerobic threshold), PLA (lactate peak), pHmin (minimum pH) and PCVmax (maximum packed cell volume).HRmax, pHmin, VLA2, VLA4, STEPmax and Vmax were positively correlated with working capacity, whereas PLA and PCVmax were negatively correlated with working capacity. The slope of the plasma lactate accumulation curve were inversely related to VLA2, VLA4, Vmax, STEPmax and pHmin and positively related to HRmax and PCVmax. Besides, the plasma lactate slope was higher in the youngest Andalusian horses.These results indicated that the slope of the plasma lactate concentrations after several exercise intensities might be considered as a marker of aerobic potential, providing useful information about fitness and training degrees in the Andalusian horse. Exercise, fitness, heart rate, packed cell volumePhysical exercise requires a balance between production and consumption of energy within working muscles. It has been postulated that there is a critical intensity or threshold above which the cardiovascular, respiratory and/or muscular responses are of insufficient magnitude to supply energy through aerobic pathways. As a consequence, anaerobic pathways become predominant, and large amounts of lactate (LA) are produced. LA is considered to be a small and easily diffusable anion, and it may be translocated rapidly between the water compartments of the body. Muscle LA produced during exercise can be utilised by the active muscles, exported via the blood to other organs, principally liver and heart, or taken up by other muscles with adequate oxygen supply and utilised as a source of fuel (Brooks 1986;Marlin et al. 1987).Three different models of plasma LA accumulation have been proposed. The single breakaway point is the classical model of aerobic-anaerobic transition. M a r g a r i a et al. (1933) established that lactic acid was formed and plasma LA accumulated during times of local muscle hypoxia, such as the onset of exercise and during times of oxygen deficit.

Heart rate of Mangalarga Marchador mares under marcha test and supplemented with chrome

“…These observations were also described by Muñoz et al (1999), who found lower HR response to the exercise in trained and adapted horses to the exercise in relation to untrained animals.…”

Metabolic responses to submaximal field exercise tests and relationships with racing performance in pacing Standardbreds

“…Field exercise tests, however, have an advantage over laboratory tests, in that the athlete is tested whilst performing the activity for which they have trained under conditions more reflective of competition (MacDougall and Wenger 1991). Field tests have also been used to describe the relationship between heart rate, blood lactate concentrations and speed (Anderson 1975;Bayly et al 1987;Evans et al 1993;Harkins et al 1993;Von Wittke et al 1994;Guhl et al 1996;Davie and Evans 2000) and the effects of training (Anderson 1975;Wilson et al 1983;Linder et al 1992;Valette et al 1996) in Thoroughbred horses and Andalusian horses (Munoz et al 1999). The difficulty with field tests, however, is in the control over the different variables during the testing conditions.…”