Introduction Anaerobic thresholds reflect the organism's capacity to produce energy without considerable accumulation of lactate and corresponding increase in acidosis. The predictable value of anaerobic thresholds for distance running performance is firmly established. Determination of anaerobic thresholds is an objective measure of exercise capacity and functional state in healthy subjects and cardiac patients. Endurance athletes including distance runners are known to develop cardiac hypertrophy, which is due to both dilation of cavities and thickening of myocardial walls. Specific sport-related strain can significantly influence left ventricular (LV) adaptation and endurance performance. There are some investigations that have established correlations between maximal oxygen consumption and heart mass of endurance athletes. Interrelations among. Scarce data are presently available regarding the relationship among such exercise capacity parameters as anaerobic thresholds, heart rate (HR) at these thresholds and echocardiographic indices, and to the best of our knowledge no special research on the relationship among echocardiographic parameters and anaerobic thresholds in athletes has been undertaken. Thus, the present study was aimed at comparing echocardiographic parameters and anaerobic thresholds in middle (MDR) and long distance runners (LDR) and determining the relationship among training, exercise capacity and echocardiographic variables. Methods 29 male Caucasian middle (MDR) and 31 long distance runners (LDR) of national level were included into the study. Their weekly training volume in hours was calculated as an average of the prior four weeks. Two increasing intensity treadmill tests, intermittent and continuous ones, were performed by each subject on a treadmill. Intermittent increasing intensity treadmill test consisted of 4 min running bouts interspaced with 4 min passive rest in seated position. Speed was increased by 0.7 km·h-1 until 16 km·h-1 was reached. Treadmill's belt speed then remained constant (16 km·h-1) while inclination was increased by 1 % with each bout. Arterialised fingertip blood samples were analysed within the first 30 s after each running bout. Subjects ran on treadmill a minimal number of times enough to increase blood lactate concentration to more than 4 mmol·l-1. Continuous treadmill exercise test was preceded by 15 min warm-up consisting of 5 min walking at 6 km·h-1 and 10 min jogging at 10 to 12 km·h-1 on treadmill and stretching. Thereafter the subjects completed maximum effort test starting at 9 km·h-1 without slope and working with speed increments of 0.7 km·h-1 each min until 16 km·h-1 speed was reached. The treadmill's belt speed then remained constant at 16 km·h-1 while inclination increased by 1 % each min. HR was continuously recorded during rest and both exercise tests using Polar HR monitor S810. Maximal HR was calculated as the highest average HR of 10 s. Estimated peak oxygen consumption was calculated using standard formula for treadmill running. Standard 2-dimentional Doppler echocardiography was performed with the subjects resting in a left lateral position. LV mass index was calculated dividing LV mass by height in m2.7. Results There were no differences between MDR and LDR with regard to body height, body mass index and systolic or diastolic blood pressure at rest. LDR were slightly older and had greater training experience, but differences were not statistically significant (p>0.05). Body mass (67.2 kg), body surface area and resting HR (54.6 beats/min) were lower, while training weekly volume (9.01 h) was higher in LDR (p<0.05). Anaerobic thresholds as characterized by two lactate turnpoints and oxygen consumption at HR deflection point were higher in the LDR group, but HR at these running intensities were not significantly different (p<0.05). Estimated peak oxygen consumption was similar in both groups, while the difference between peak oxygen consumption and second lactate turnpoint were significantly higher in MDR. Neither absolute nor relative LV end-diastolic diameters differed significantly between the two groups of distance runners (p>0.05; 55.8 mm in MDR and 55.5 mm in LDR). End-diastolic intraventricular septum thickness (9.62 mm in MDR and 10.84 mm in LDR), end-diastolic LV posterior wall thickness (9.83 mm in MDR and 11.02 mm in LDR), total wall thickness, relative LV wall thickness, LV mass (250.4 g in MDR and 292.0 in LDR) and LV mass index were significantly greater in LDR (p<0.05). All the transmitral Doppler indices measured, as well as ejection fraction, were similar in the groups investigated. In general, the variance of all exercise capacity and HR parameters was predictable not more than by 50 % of the variables analysed. Training volume was the best predictor of exercise capacity, while training experience - that of HR parameters. The LV echocardiographic parameters were weak predictors of HR, and exercise capacity parameters especially. Discussion Overall, exercise capacity was related mostly to training volume while HR parameters were rather related to training experience than to LV echocardiographic parameters. The present study evidenced a better LDR aerobic capacity with higher lactate turnpoints, but lower resting and exercise HR as compared with MDR. In general, exercise capacity was related mostly to training volume while HR parameters were related rather to training experience than to LV echocardiographic parameters. Greater LV mass and LV mass index due to greater wall thickness, but not end-diastolic diameter in LDR seems to be of moderate importance for their exercise capacity, which appears to depend more on training volume.
© Copyright 2004 Book of Abstracts - 9th Annual Congress European College of Sport Science, July 3-6, 2004, Clermont-Ferrand, France. All rights reserved.