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In order to determine the stability of directly measured pH and Pco₂, and calculated [HCO₃] in stored urine, 11 alkali-loaded normal subjects provided 33 spot and sixteen 24-hour mineral oil-covered, thymol-preserved, refrigerated urine samples. For the spot samples, pH and Pco₂ were measured immediately and again at 4 and 24 h. In addition, immediately after voiding, 24 of the spot samples were split into oil-covered and no-oil moieties and analyzed immediately and again at 4 and 24 h. pH and Pco₂ measurements of the 24-hour collections were carried out immediately after completion and again 24 h later. The results demonstrated the importance of using oil to limit the escape of CO₂ from stored urine. Thus, after 24 h the oil-uncovered subgroup of 24 spot urine samples sustained a 82% decline in Pco₂ and a 20% fall in [HCO₃]. In contrast, the corresponding percentage decrements in the oil-covered samples were 16 and 1%, respectively. The results also indicated that even with oil there is loss of CO₂, which increases with time and which shows a statistically significant direct correlation with the baseline level of Pco₂· Nevertheless, modest loss of CO₂ usually produces only slight decrements in [HCO₃] because of the countervailing influence of the resultant increase in pH. We conclude that the use of mineral oil is necessary in order to obtain adequate stability of Pco₂, pH and [HCO₃] in refrigerated urine requiring several hours or more of storage.

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In endurance racing the heart rate (HR) of horses in the veterinary gates has to reach a maximum set to continue racing. There is no literature on the relationship between resting HR (HRresting) and HR after exercise (HRrecovery). This relationship was examined in seven horses and the results were related to their v4 (speed at which the blood lactate concentration is 4 mmol/L). Horses were submitted to an exercise test to determine v4. Thereafter, horses were exercised on a treadmill in randomized order for 10 and 60 min at different speeds. HR was measured before exercise and several times until 30 min of recovery. The relationship between HRresting and HRrecovery was significant in 16 out of 35 comparisons. There were no significant relationships between the v4 of the horses and their HRresting and between v4 and HRrecovery after 10 min of exercise, regardless of the speed of exercise, with one exception. The relationship between the v4 of the horses and their HRrecovery after 60 min of exercise was significant in the fifth minute after exercise at 3.5 m/s only. Conclusion: Because HRresting and HRrecovery are often related, pre-determined arbitrary HRrecovery values may not allow for fair competition during endurance racing.