The effects of endurance exercise in hypoxia on acid-base balance and potassium kinetics: a randomized crossover design in male endurance athletes (original) (raw)
Related papers
European Journal of Applied Physiology and Occupational Physiology, 1989
During resting conditions plasma hydrogen ion concentration ([H +]p) is known to influence ventilation (l/z), whereas the control of plasma potassium concentration ([K+]p) at rest and of both [K+]p and 12E during exercise are controversial issues. To obtain more information about these variables during muscular work, eight trained men performed two successive intense continuous cycle-ergometer tests, the first (test I) during metabolic acidosis, the second (test II) with an alkalotic pH. No correlation was found between [H +]p and [K÷]p or lYE in the direction of change of these variables in test I. Furthermore, no correlation between [H +]p and [K+]e in test I and II was seen. Instead [K+]p and I)'E changed in relation to the exercise intensity. We suggest that the results confirm [K+]p as an indicator of muscular stress. In addition, the similar behaviour of relative values of [K+]p and I/E changes in test I (r = 0.9, m = 1.0, where m is the slope of the regression curve) supports the hypothesis that extracellular potassium controls VE and thereby [H+]p also.
Acid?base balance at exercise in normoxia and in chronic hypoxia. Revisiting the "lactate paradox
European Journal of Applied Physiology, 2003
Transitions between rest and work, in either direction, and heavy exercise loads are characterized by changes of muscle pH depending on the buffer power and capacity of the tissues and on the metabolic processes involved. Among the latter, in chronological sequence: (1) aerobic glycolysis generates sizeable amounts of lactate and H + by way of the recently described, extremely fast (20-100 ms) ''glycogen shunt'' and of the excess of glycolytic pyruvate supply; (2) hydrolysis of phosphocreatine, tightly coupled with that of ATP in the Lohmann reaction, is known to consume protons, a process undergoing reversal during recovery; (3) anaerobic glycolysis sustaining ATP production in supramaximal exercise as well as in conditions of hypoxia and ischemia, is responsible for the accumulation of large amounts of lactic acid (up to 1 mol for the whole body). The handling of metabolic acids, i.e., acid-base regulation, occurs both in blood and in tissues, mainly in muscles which are the main producers and consumers of lactic acid. The role of both blood and muscle bicarbonate and non-bicarbonate buffers as well as that of lactate/H + cotransport mechanisms is analyzed in relation to acid-base homeostasis in the course of exercise. A section of the review deals with the analysis of the acidbase state of humans exposed to chronic hypoxia. Particular emphasis is put on anaerobic glycolysis. In this context, the so-called lactate paradox is revisited and interpreted on the basis of the most recent findings on exercise at altitude.
Acid-base regulation during exercise and recovery in humans
Journal of Applied …, 1992
Arterial pH, Pco~, standard bicarbonate, lactate, and ventilation were measured with a high sampling density during rest, exercise, and recovery in normal subjects performing upright cycle ergometer exercise. Three 6-min constant-work exercise tests (moderate, heavy, and very heavy) were performed by each subject. We found a small respiratory acidosis during the moderate-intensity exercise and an early respiratory acidosis followed by a metabolic acidosis for the heavy-and very-heavy-intensity exercise. During recovery, arterial pH rapidly returned to the preexercise value for the moderate-intensity work. However, arterial pH decreased further during the first 2 min of recovery for the heavy-and very-heavy-intensity work, before a slower return toward the resting values. We conclude that arterial acidosis is the consistent arterial pH reaction for moderate-, heavy-, and very-heavy-intensity cycle ergometer exercise in humans and that this acidosis is blunted but not eliminated by the ventilatory response. During recovery, the return to resting arterial pH and PCO~ and standard bicarbonate appears to be determined by the rate of lactate decline.
Effect of exercise on acid-base status and ventilatory kinetics
Indian journal of physiology and pharmacology, 1998
The normal respiratory responses and changes in acid base status in twenty normal height, weight and age matched subjects were studied; using Auto Spiro AS 300 spirometer for ventilatory parameters and NOVA stat profile 3 analyser for gas analysis. Each subject performed a progressive incremental treadmill exercise by Bruce protocol to their symptom limited maximum. Minute ventilation (VE), tidal volume (VT) and frequency of respiration (f) increased significantly (P<0.001). Acidosis occured following exercise as pH of arterialized venous blood declined significantly (P<0.05). Gas analysis of arterialized venous blood showed a rise in pO2 (P<0.001) and a fall in pCO2 (P<0.001). Recovery of acid base status as well as gaseous pressure in blood did not occur after 10 min. Expired gas pCO2 declined significantly (P<0.05) and pO2 increase significantly (P<0.05). These pressures returned to resting levels 10 min after exercise. Thus in normal young adults heavy exercise...
Potassium kinetics and its relationship with ventilation during repeated bouts of exercise in women
European Journal of Applied Physiology, 2006
The purpose of this study was to determine the electrolyte concentration changes in arterial plasma from high-intensity repeated bouts of cycling exercise in well-trained females and to determine the relationships between arterial plasma lactate, potassium (K+), bicarbonate (HCO3(-)), and pH with minute ventilation. Fourteen female subjects (mean age = 27 +/- 4 years; mean height = 170 +/- 7 cm; mean weight = 62 +/- 7 kg; maximal oxygen uptake = 50 +/- 6 ml/kg/min) were recruited to perform 3 x 5 min bouts of exercise at 236 +/- 27 W with 10 min recovery between each set. Minute ventilation, arterial plasma lactate, potassium, calcium, chloride, and sodium ion concentrations were measured a minute 0, 1, 2, 3, 4, 5 of each set and midway through recovery (21 sampling points total per subject). The results showed that the strongest relationship was between arterial plasma K+ concentration and minute ventilation (r2 = 0.91), and, that arterial plasma lactate mirrored both arterial plasma HCO3(-) and pH. In conclusion, this study demonstrates that women exhibit similar electrolyte responses as reported elsewhere in men, and support the idea that K+ may partly contribute to controlling ventilation during high-intensity exercise and recovery.
Arterial hypoxemia and performance during intense exercise
European Journal of Applied Physiology and Occupational Physiology, 1994
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Re-examination of the incidence of exercise-induced hypoxaemia in highly trained subjects
British Journal of Sports Medicine, 1993
The purpose of this study was to examine the occurrence of exercise-induced hypoxaemia (EIH) during maximal exercise in highly trained athletes. Eleven trained cyclists (mean(s.d.) ape 23(3.5) years; mean(s.d.) VO2maX 66.9(4.8) ml kg-min-) performed a continuous, multistage (270kpmmin-1) cycle ergometer test to exhaustion. Measurements of arterial oxygen-haemoglobin saturation (%HbO2) were obtained simultaneously at rest, every 2min during exercise, and at maximum exercise capacity from arterial blood sampling (%SaO2) and ear oximetry (%SpO2). Exercise induced hypoxaemia (%HbO2 <91%) was present in 64% of the athletes examined when EIH was determined using pulse oximetry, whereas none of the subjects exhibited EIH when %HbO2 was determined using arterial blood. At rest the values for %HbO2 were similar with mean(s.d.) %SaO2 being 97.3(0.6)% and mean(s.d.) %SpO2 being 96.5(1.6)%. During exercise, statistically significant differences were found for %HbO2 between arterial blood and ear oximetry at the 6-min, 8-min, and maximal exercise sampling times (repeated measures analysis of variance, P < 0.05). The results indicate that ear oximetry overestimates the incidence of EIH and underestimates the oxyhaemoglobin saturation in highly trained cyclists during exercise in comparison with those measurements made from arterial blood.
Frontiers in Physiology
Rowing performance may be enhanced by attenuated metabolic acidosis following bicarbonate (BIC) supplementation. This study evaluated the dose of BIC needed to eliminate the decrease in plasma pH during maximal ergometer rowing and assessed the consequence for change in plasma volume. Six oarsmen performed “2,000-m” maximal ergometer rowing trials with BIC (1 M; 100–325 ml) and control (CON; the same volume of isotonic saline). During CON, pH decreased from 7.42 ± 0.01 to 7.17 ± 0.04 (mean and SD; p < 0.05), while during BIC, pH was maintained until the sixth minute where it dropped to 7.32 ± 0.08 and was thus higher than during CON (p < 0.05). The buffering effect of BIC on metabolic acidosis was dose dependent and 300–325 mmol required to maintain plasma pH. Compared to CON, BIC increased plasma sodium by 4 mmol/L, bicarbonate was maintained, and lactate increased to 25 ± 7 vs. 18 ± 3 mmol/L (p < 0.05). Plasma volume was estimated to decrease by 24 ± 4% in CON, while with...