Biological variation of venous acid-base status measurands in athletes

Analysis of acid-base status (ABS) is requested in a wide range of clinical scenarios, including in the assessment of athletes' performance and follow up, but there is a lack of high-quality biological variation (BV) data. The aims of this study were to estimate the BV of ABS related parameters in athletes and to evaluate if variables related to exercise may influence the estimates.

Eleven samples from 30 triathletes were drawn, on a monthly basis. The samples were measured for pH, pCO₂, bicarbonate, base excess, TCO₂, Ca²⁺ and lactate. A CV-ANOVA was performed to calculate within-subject (CV_I) estimates and a linear mixed model was applied to analyze the effect of the folowing variables on the BV; health status, sampling interval, intensity and duration of the exercise.

For all ABS parameters except for lactate, higher CV_I estimates were found in athletes than what have been reported for the general population. No significant effect of the exercise and sampling related variables were observed, except for Ca²⁺.

This difference founds in ABS parameters between athletes and the general population could be explained by the physiological stress during exercise. Laboratories attending this population could use these BV estimates to establish quality goals.