PHD-Department of Recreation Management & Exercise Science

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Browsing PHD-Department of Recreation Management & Exercise Science by Author "Mwangi, Francis Mundia"

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    Assessment of Pulmonary Function of Kenyan Elite Distance Runners during Rest, Sub-Maximal and Maximal Endurance Exercise
    (2014-02-22) Mwangi, Francis Mundia; Onywera, V.O.; Boit, Michael K.; Sheel, W.
    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.
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    Effects of different arm actions on performance in long distance running among Kenyan athletes
    (2011-11-02) Mwangi, Francis Mundia
    This study investigated the effects of different arm actions on cardio-respiratory parameters and stride patterns during the steady phase of long distance running. Mean values of working heart rate (WHR), recovery heart rate (RHR), percentage of maximum oxygen consumption (% VOZ max), ventilation rate (VR), and rating of perceived exertion (RPE) were used to estimate physiological demands and the energy cost of running with different arm actions. This helped to evaluate and compare their effects on running economy (RE). Ten elite Kenyan endurance athletes of both sexes were selected through purposive sampling procedures and tested in ten sub-maximal treadmill trial runs, each trial performed with different arm action for 15 minutes at a speed corresponding to individual's 80% running effort. Their working and recovery heart rates were monitored (using Polar heart rate monitor), as well as the rating of perceived exertion (using Borg Scale of perceived exertion), ventilation rate (VR) and stride rate (SR) during each trial and the values recorded after every five minutes. The Cooper test was used to estimate participants' VOz max. Regression equations were used to estimate percentage of maximum oxygen consumption and kilocalories expended (Kcl) from working heart rate values. ANOVA with Repeated Measures was used to analyze the data, using the SPSS software. Significant difference was observed in WHR, % VOz max, Kcl, RPE, and SR at p < .05. Intraclass Correlation Coefficient (R) analysis of individuals' trial-to-trial test values showed high reliability for all the variables measurements and procedures (WHR; 98, RHR; .83, RPE; .83, VR, .99, SR; .90, % VOZ max; .98, Kcl; .97). Medium effect size was observed; Omega Squared (cot) = .20. The study concluded that arm action consisting of about ±20 degrees oscillation of the hands around 90 degrees angle at the elbow is more economical than running with arms held at 90 degrees angle at the elbows (one recommended by most biomechanics authors), and that different arm actions have different effects on the various components of running mechanics. The study recommended that arm action consisting of'about 30 degrees elbow angle range of oscillation -arm action involving oscillation of elbow angles from 70 degrees (on foreswing) 100 degrees (on backswing), be adopted by distant runners for optimum performance.