Changes in acid-base status of marathon runners during an incremental field test |
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Authors: | J. A. Zoladz A. J. Sargeant J. Emmerich J. Stoklosa A. Zychowski |
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Affiliation: | (1) Department of Physiology and Biochemistry, Academy of Physical Education, Al. Jana Pawla II 68, 31-571 Cracow, Poland;(2) Department of Muscle and Exercise Physiology, Faculty of Human Movement Sciences, Vrije Universiteit, Meibergdreef 15, NL-1105 AZ Amsterdam, The Netherlands |
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Abstract: | Summary Four top-class runners who regularly performed marathon and long-distance races participated in this study. They performed a graded field test on an artificial running track within a few weeks of a competitive marathon. The test consisted of five separate bouts of running. Each period lasted 6 min with an intervening 2-min rest bout during which arterialized capillary blood samples were taken. Blood was analysed for pH, partial pressure of oxygen and carbon dioxide (P02 and PCO2) and lactate concentration ([la–]b). The values of base excess (BE) and bicarbonate concentration ([HCO3–]) were calculated. The exercise intensity during the test was regulated by the runners themselves. The subjects were asked to perform the first bout of running at a constant heart rate fc which was 50 beats · min–1 below their own maximal fc. Every subsequent bout, each of which lasted 6 min, was performed with an increment of 10 beats · min–1 as the target fc. Thus the last, the fifth run, was planned to be performed with fc amounting to 10 beats · min–1 less than their maximal fc. The results from these runners showed that the blood pH changed very little in the bouts performed at a running speed below 100% of mean marathon velocity ( m). However, once mwas exceeded, there were marked changes in acid-base status. In the bouts performed at a velocity above the mthere was a marked increase in [la–]b and a significant decrease in pH, [HCO3–], BE and PCO2. The average marathon velocity ( m) was 18.46 (SD 0.32) km·h–1. The [la–]b at a mean running velocity of 97.1 (SD 0.8) % of mwas 2.33 (SD 1.33) mmol ·l–1 which, compared with a value at rest of 1.50 (SD 0.60) mmol·l–1, was not significantly higher. However, when running velocity exceeded the vm by only 3.6 (SD 1.9) %, the [la–]b increased to 6.94 (SD 2.48) mmol·l-1 (P<0.05 vs rest). We concluded from our study that the highest running velocity at which the blood pH still remained constant in relation to the value at rest and the speed of the run at which [la–]b began to increase significantly above the value at rest is a sensitive indicator of capacity for marathon running. |
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Keywords: | Acid-base balance Graded field test Heart rate Lactate concentration Marathon running |
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