Influence of sampling time in the assessment of anaerobic threshold in horses

Abstract

Validity and reproducibility of anaerobic threshold (VLA4) is still matter for debate. Factors influencing blood lactate concentration, including blood collection procedure, are critical. This study aimed to evaluate influence of blood sampling times on VLA4 computing in two different horse breeds. Five Standardbreds and six Haflingers were included in this study. All the horses performed a standardised exercise test on treadmill (SET). An automatic collection device was employed to obtain blood samples every 60 seconds, in order to standardise sampling time. VLA4 was computed using the lactate data at the end of each step of the SET, and the corresponding velocity (VLA40min). The detection was then repeated for the concentrations at 1 (VLA41min), 2 (VLA42min) and 3 min (VLA43min) after the end of the 3rd step maintaining constant plasma lactate concentration of the first and the second step. VLA4 resulted increased with the VLA40min, while with the VLA41min, VLA42min and VLA43min the value of the VLA4 decreased progressively. Difference, expressed as a percentage, between VLA40min and VLA43min mean values was 16.8 and 16.6%, for Standardbred and Haflinger horses, respectively. Hence, blood samples drawn within a time frame of 3 min after the end of the SET seem to induce changes when computing of VLA4. The results suggest to carefully pay attention in standardise sampling time, collecting blood in a time frame of two minutes, one minute after the end of exercise.