Biomedical subjects

M L Fysh

Publications and source records attributed to M L Fysh.

4 recordsLinked to original sources

PubMed2002

A comparison of two time-domain analysis procedures in the determination of .VO(2) kinetics by pseudorandom binary sequence exercise testing.

The purpose of this study was to apply and compare two time-domain analysis procedures in the determination of oxygen uptake (.VO(2)) kinetics in response to a pseudorandom binary sequence (PRBS) exercise test. PRBS exercise tests have typically been analysed in the frequency domain. However, the complex interpretation of frequency responses may have limited the application of this procedure in both sporting and clinical contexts, where a single time measurement would facilitate subject comparison. The relative potential of both a mean response time (MRT) and a peak cross-correlation time (PCCT) was investigated. This study was divided into two parts: a test-retest reliability study (part A), in which 10 healthy male subjects completed two identical PRBS exercise tests, and a comparison of the .VO(2) kinetics of 12 elite endurance runners (ER) and 12 elite sprinters (SR; part B). In part A, 95% limits of agreement were calculated for comparison between MRT and PCCT. The results of part A showed no significant difference between test and retest as assessed by MRT [mean (SD) 42.2 (4.2) s and 43.8 (6.9) s] or by PCCT [21.8 (3.7) s and 22.7 (4.5) s]. Measurement error (%) was lower for MRT in comparison with PCCT (16% and 25%, respectively). In part B of the study, the .VO(2) kinetics of ER were significantly faster than those of SR, as assessed by MRT [33.4 (3.4) s and 39.9 (7.1) s, respectively; P<0.01] and PCCT [20.9 (3.8) s and 24.8 (4.5) s; P<0.05]. It is possible that either analysis procedure could provide a single test measurement of .VO(2) kinetics; however, the greater reliability of the MRT data suggests that this method has more potential for development in the assessment of .VO(2) kinetics by PRBS exercise testing.

Adult↗

PubMed2001

The test-retest reliability of gas exchange kinetics in humans using a pseudo random binary sequence exercise test.

The purpose of this study was to compare the test-retest reliability of oxygen uptake (VO2) kinetics with carbon dioxide output (VCO2) kinetics using a pseudo random binary sequence (PRBS) exercise test. A reliable test of gas exchange kinetics would have the potential of being applied as a sports fitness test. Ten healthy male subjects agreed to participate in the study and all subjects completed two identical PRBS exercise tests (test 1 and test 2), separated by a 30 min period of inactivity. Three consecutive 300 s PRBS cycles were completed in each test with 20 s exercise intensity changes between 25 and 85 W using an electrically braked cycle ergometer. Fourier analysis was computed for frequencies 3.3, 6.7 and 10 mHz. Statistical analysis by two-way ANOVA with repeated measures did not reveal significant differences between test 1 and test 2 for either VO2 kinetics or VCO2 kinetics. Static gain of VO2 for test 1 [9.11 (SD 0.59) ml.min-1.W-1] and test 2 [9.23 (SD 0.64) ml.min-1.W-1] did not differ significantly between tests. The 95% limits of agreement for VCO2 kinetics displayed increased variability in comparison to VO2 kinetics at each frequency of amplitude ratio and phase shift. Systematic bias ranged between 0% and 4%, except at frequency 10 mHz of VCO2 kinetics phase shift which showed a 10% bias for slower VO2 kinetics in test 2. It is possible that the increased variability of VCO2 kinetics compared to VO2 kinetics might be attributable to a lower signal to noise ratio in VCO2 kinetics, variations in ventilation or the storage mechanisms of CO2. The lower variability of VO2 kinetics compared with VCO2 kinetics suggests that the PRBS test of VO2 kinetics has the greater potential for further development as an indicator of aerobic fitness.

Adult↗

PubMed2000

Exercise testing in children: an alternative approach.

In recent years there has been a call for new methods of evaluating the cardiorespiratory responses of children to exercise that complement their everyday exercise patterns. One potential method would be to use a sub-maximal, intermittent, pseudo-random binary sequence (PRBS) exercise test protocol to measure oxygen uptake kinetics (VO2 kinetics). Ten children of mean (SD) age 10.8 (+/- 1.5) years completed a 20 - 50 W cycle ergometer protocol of 17-min duration. An estimate of alveolar oxygen uptake (VO2) was calculated on a breath-by-breath basis. The VO2 kinetic parameters were expressed in the frequency domain as amplitude ratio and phase delay using standard Fourier techniques. Analysis was restricted to the frequency range 2.2 to 8.9 mHz. The mean (SD) amplitude ratio responses decreased from 10.33 (+/- 0.73) to 7.42 (+/- 0.99) ml min(-1) W(-1) and the mean phase delay increased from -26.78 degrees (+/- 6.37 degrees) to -81.93 degrees (+/- 10.45 degrees) over the frequency range 2.2-8.9 mHz. Significant correlations (p < 0.05) were found between chronological age and amplitude ratio (r = 0.68 and 0.62), and chronological age and phase delay (r = -0.62 and -0.69) at the frequencies of 2.2 and 4.4 mHz, respectively. No significant correlations were found between VO2 kinetics and stature or VO2 kinetics and body mass. The observations demonstrated the use of the PRBS technique to measure VO2 kinetics in the frequency domain in children. This approach may be a useful addition to the tests that are used to quantify the oxygen uptake responses to exercise in children.

Child↗

PubMed1999

VO2 kinetics determined by PRBS techniques differentiate elite endurance runners from elite sprinters.

The aim of the study was to examine whether a measure of oxygen uptake (VO2) kinetics could differentiate between 12 elite male endurance (3000-10,000 m) runners and 12 elite male sprint (100-400 m) runners using a pseudo random binary sequence (PRBS) exercise protocol. All exercise tests were performed on an electrically braked cycle ergometer at a constant pedal frequency of 1 Hz. The PRBS exercise intensities alternated between 25 W and 85 W for three consecutive PRBS cycles of 300 s. VO2 was measured breath-by-breath and results were analysed by Fourier techniques in the frequency domain. Blood lactate concentrations taken pre and post testing were below 2 mM. Significantly greater amplitude components were observed in the endurance runners than sprinters at frequencies 6.7 mHz (6.71 +/- 1.09 and 5.47 +/- 0.95 ml x min(-1) x W(-1), respectively) P<0.05 and 10 mHz (4.97 +/- 0.98 and 3.56 +/- 0.69 ml x min(-1) x W(-1) respectively) P<0.01. Phase shift components were significantly shorter in the endurance runners compared to the sprinters at frequency 3.3 mHz (-35.45 +/- 4.31 and -41.26 +/- 5.82 degrees respectively) P<0.05. The results of this study show that VO2 kinetics are differentially faster in elite endurance runners than in elite sprinters. This supports the development of the PRBS technique as a test of sports performance.

Adult↗