Assessment of Pulmonary Function of Kenyan Elite Distance Runners during Rest, Sub-Maximal and Maximal Endurance Exercise
Mwangi, Francis Mundia
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Kenyan middle and long distance runners have performed extraordinarily well, dominating the world over the past four decades. The factors that contribute to their prowess in endurance races are not yet determined. Pulmonary limitations to endurance performance have been reported among non-Kenyan runners but the extent Kenyan runners experience or overcome these limitations had not been investigated. The purpose of this study was to assess pulmonary function parameters of Kenyan elite runners in relation to endurance exercise performance and compare with predicted values. Fifteen (10 male, 5 female) purposively selected elite Kenyan runners were instrumented in baseline spirometry and an incremental treadmill test to exhaustion at a moderate altitude (1,600 m.a.s.l.). Spirometric variables measured included forced vital capacity (FVC), forced expiratory volume in one second (FEV1), forced expiratory volume in one second as a proportion of forced vital capacity (FEV1/FVC) and maximum inspiratory pressure (MIP). Respiratory measures obtained during treadmill test included tidal volume (Vt), breathing frequency (Fb), minute ventilation (VE), oxygen consumption (VO2), carbon dioxide production (VCO2) and respiratory exchange ratio (RER). Arterial blood gases (ABG) data; arterial oxygen partial pressure (PaO2), arterial oxygen saturation (SaO2), arterial partial pressure of carbon dioxide (PaCO2), alveolar to arterial oxygen partial pressure difference (A-aDO2) and acidosis (pH) were obtained from blood samples taken from radial artery at the end of every exercise stage via indwelling cannula. Repeated measures ANOVA and t tests were run to examine the various measurements at different exercise intensities using statistical package for social sciences. One sample t test on participants’ spirometric variables’ percentage of predicted values showed that they were not significantly different from commonly used predicted values (p >.05). Absolute VO2 peak values for males (3.50±.26) and females (2.26±.26) [L/min] were significantly higher than the predicted values (p = .001). Relative VO2 max formales (64.4±4.9) and females (48.1±4.9) [ml/kg/min] rated superior and excellent respectively on cardio-respiratory fitness classification norms. ABG data showed that the runners experienced only moderate levels of exercise-induced arterial hypoxemia (EIAH) (SaO2 = 89.4±4.6%[male], 91.5±2.2%[female], 89.9±4.1[total]% and A-aDO2 = 24.5±4.7[male], 20.1±10.7[female], 23.39±6.39[total] mmHg) at maximal endurance exercise. Respiratory compensation (partial) for metabolic acidosis was evident (PaCO2 = 34.15±3.44 mmHg, pH = 7.30±.08[total]). Bicarbonate ions (HCO3) recorded the most consistent decline and highest effect size (Eta sqd = .724) while change in oxygen content in the blood (CaO2) recoded the least (Eta sqd = .072). Stepwise regression showed that VE was the most significant predictor of VO2 and speed at sub-maximal exercise level. The study concluded that most Kenyan distance runners’ baseline pulmonary function values are comparable to commonly used reference values. However, the runners’ respiratory system is able to cope with demands of superior oxygen consumption during endurance running. The runners experience moderate level hypoxemia during sub-maximal and maximal endurance exercise. Strategies to alleviate excessive acidosis are recommended for improving performance during endurance training and competitions. Further investigations are needed to determine the source of the differences in pulmonary function among distance runners, and the effects on endurance race performances.