Biomedical subjects

E J Schabort

Publications and source records attributed to E J Schabort.

3 recordsLinked to original sources

PubMed1998

Reproducibility of self-paced treadmill performance of trained endurance runners.

The reproducibility of performance in a laboratory test impacts on the statistical power of that test to detect changes of performance in experiments. The purpose of this study was to determine the reproducibility of performance of distance runners completing a 60 min time trial (TT) on a motor-driven treadmill. Eight trained distance runners (age 27 +/- 7yrs, peak oxygen consumption [VO2peak] 66 +/- 5 ml x min(-1) x kg(-1), mean +/- SD) performed the TT on three occasions separated by 7-10 days. Throughout each TT the runners controlled the speed of the treadmill and could view current speed and elapsed time, but they did not know the elapsed or final distance. On the basis of heart-rate, it is estimated that the subjects ran at an average intensity equivalent to 80-83% of VO2peak. The distance run in 1 h did not vary substantially between trials (16.2 +/- 1.4 km, 15.9 +/- 1.4 km, and 16.1 +/- 1.2 km for TTs 1-3 respectively, p = 0.5). The coefficient of variation (CV) for individual runners was 2.7% (95% Cl = 1.8-4.0%) and the test-retest reliability expressed as an intraclass correlation coefficient was 0.90 (95% Cl = 0.72-0.98). Reproducibility of performance in this test was therefore acceptable. However, higher reproducibility is required for experimental studies aimed at detecting the smallest worthwhile changes in performance with realistic sample sizes.

Adult↗

PubMed1998

A new reliable laboratory test of endurance performance for road cyclists.

PURPOSE: The purpose of this study was to devise and evaluate a laboratory test of cycling performance that simulates the variable power demands of competitive road racing. The test is a 100-km time trial interspersed with four 1-km and four 4-km sprints. METHODS: On three occasions separated by 5-7 d, eight endurance-trained cyclists (peak oxygen uptake 5.0 +/- 0.7 L.min-1, peak power output 411 +/- 43 W, mean +/- SD) performed the test on their own bikes mounted on an air-braked Kingcycle ergometer. Subjects were free to regulate their power output but were asked to complete each sprint and the full distance as quickly as possible. The only feedback given to the cyclists during each test was elapsed distance. RESULTS: In the first test, time for the 100 km and mean times for the 1-km and 4-km sprints were 151:42 +/- 10:36, 1:16 +/- 0:06, and 5:31 +/- 0:16 min:s, respectively; these times improved by 1.6-2.2% in the second test, but there was little further improvement in the third test (0.7 to -0.5%). The between-test correlation for 100-km time was 0.93 (95% CI 0.79 to 0.98), and the within-cyclist coefficient of variation was 1.7% (95% CI 1.1 to 2.5%). Mean sprint performance showed similar good reliability (within-subject variation and correlations for the 1-km and 4-km sprint times of 1.9%, 2.0%, 0.93, and 0.81, respectively). CONCLUSIONS: The high reliability of this laboratory test will make the test useful for research on performance of competitive road cyclists.

Adult↗

PubMed1997

Carbohydrate-loading and exercise performance. An update.

This review suggests that there is little or no effect of elevating pre-exercise muscle glycogen contents above normal resting values on a single exhaustive bout of high-intensity exercise lasting less than 5 minutes. Nor is there any benefit of increasing starting muscle glycogen content on moderate-intensity running or cycling lasting 60 to 90 minutes. In such exercise substantial quantities of glycogen remain in the working muscles at the end of exercise. However, elevated starting muscle glycogen content will postpone fatigue by approximately equal to 20% in endurance events lasting more than 90 minutes. During this type of exercise, exhaustion usually coincides with critically low (25 mmol/kg wet weight) muscle glycogen contents, suggesting the supply of energy from glycogen utilisation cannot be replaced by an increased oxidation of blood glucose. Glycogen supercompensation may also improve endurance performance in which a set distance is covered as quickly as possible. In such exercise, high carbohydrate diets have been reported to improve performance by 2 to 3%.

Dietary Carbohydrates↗