VLA2 and VLA4 and they are used to predict the horse's fitness ( Trilk et al 2002) and degree of training (Agüera et al. 1995). The aim of this study was evaluate the training degree using aerobic/aerobic indexes and check improvement of aerobic capacity in Lusitanian breed. Two groups of 10 young mares (trained PSL-Pure Lusitanian from different farms- and untrained AR Alter Real from Coudelária of Alter do Chao- all of them from Portugal) were used. Training test consisted levels of increasing intensity of 4, 5, 6, 7 and 8 m/s each one followed by 2 minutes rest, when the blood samples were taken, covering 1,000 meters in each level. PSL group were trained during two months. The same test were underwent to two groups. Plasma lactate concentration were obtained. VLA2/VLA4 were considered functional indexes.

The relation between lactate and speed fitted an exponential model. A one–way analysis of variance between the two tests, obtaining significant differences between them, made a comparison of VLA2 and VLA4. The Tukey-test exhibited significant differences when comparing the first and the second test in PSL, but they were no significant in AR. Differences were found between mares PSL before and after training which show that training improves aerobic capacity coinciding with Agüera et al, 1995 in Andalusian horses. However, it was surprising that untrained animals (AR-group) had better aerobic capacity may because of their genetic selection and way of life in a State Centre as Coudelaria of Alter do Chao.