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Biomedical subjects

H G Wunderlich

Publications and source records attributed to H G Wunderlich.

6 recordsLinked to original sources
PubMed1994

Postural effect on cardiac output, oxygen uptake and lactate during cycle exercise of varying intensity.

Owing to changes in cardiac output, blood volume distribution and the efficacy of the muscle pump, oxygen supply may differ during upright and supine cycle exercise. In the present study we measured, in parallel, circulatory (heart rate, stroke volume, blood pressure) and metabolic parameters (oxygen uptake, lactic acid concentration [la]) during incremental-exercise tests and at constant power levels ranging from mild to severe exercise. In supine position, cardiac output exceeded the upright values by 1.0-1.5 l.min-1 during rest, light ([la] < 2 mmol.l-1) and moderate ([la] = 2-4 mmol.l-1) exercise. At higher exercise intensities the cardiac output in an upright subject approached and eventually slightly exceeded the supine values. For both rest-exercise transitions and large-amplitude steps (delta W > or = 140 W) the cardiac output kinetics was significantly faster in upright cycling. The metabolic parameters (VO2 and [la]) showed no simple relationship to the circulatory data. In light to moderate exercise they were unaffected by body position. Only in severe exercise, when cardiac output differences became minimal, could significant influences be observed: with supine body posture, [la] started to rise earlier and maximal power (delta W = 23 W) and exercise duration (64 s) were significantly reduced. However, the maximal [la] value after exercise was identical in both positions. The present findings generally show advantages of upright cycling only for severe exercise. With lower workloads the less effective muscle pump in the supine position appears to be compensated for by the improved central circulatory conditions and local vasodilatation.

Adult↗
PubMed1994

Prediction of individual oxygen uptake on-step transients from frequency responses.

Power-oxygen uptake (VO2) frequency responses can be used to predict VO2 responses to arbitrary exercise intensity patterns. It is still an open question for which range of exercise intensities such computed VO2 response patterns yield valid predictions. In the present study, we determined the power-VO2 frequency response of nine sports students by means of pseudo-randomised switching between 20 W and 80 W during upright and supine cycle exercise. Starting from a baseline of 20 W each subject also performed sustained step increases to 40 W, 80 W, 120 W, and 160 W in both positions. The individual VO2 step responses were then compared with the expected VO2 time-courses predicted on the basis of the individual VO2 frequency responses. The comparison showed a close agreement for the 20 W-40 W and 20 W-80 W steps in both positions. With larger step amplitudes the VO2 kinetics became increasingly slower than the predicted VO2 time course in both positions. During additional ramp tests (10 W.30 s-1) whole blood lactic acid concentration [la-]b tended to be higher in the supine position at exercise intensities higher than 160 W. The mean power at 4 mmol.l-1 [la-]b amounted to 234 (SD 32) W and 253 (SD 44) W (P < 5%) in the supine and the upright position, respectively. The maximal oxygen uptake relative to body mass was not found to be significantly different [upright, mean 57 (SD 10) ml.(min.kg)-1; supine, mean 54 (SD 10) ml.(min.kg)-1].(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

VO2 kinetics determined by PRBS-technique and sinusoidal testing.

The PRBS-technique is a useful tool to investigate muscle VO2 kinetics within the aerobic range. However, the validity of this kind of multi-frequent testing may be limited by non-linearities generated by the circulatory and pulmonary system. To check for such non-linear effects we compared the frequency responses computed from the multi-frequent PRBS with the results of pure sinusoidal testings (periods between 75 s and 450 s). Both methods show a good agreement for periods in the range between 113 s and 450 s. For shorter periods the results slightly diverged. The harmonic analyses of the sinusoidal data indicate increased stimulation of higher harmonics with increase in frequency. It is concluded that the VO2 in the lower frequency range shows only little, if any, influence of the circulatory and pulmonary system. Differences between the methods in the higher frequency range may be caused by non-linearities at the same or even lower frequencies. Therefore, periods shorter than 100 s are not suitable for assessing the muscle VO2 kinetics.

Adult↗
PubMed1992

Dynamic linearity of VO2 responses during aerobic exercise.

The multifrequent pseudorandom binary sequence (PRBS) technique is a useful tool for studying oxygen uptake (VO2) kinetics within the aerobic range. However, the validity of this multifrequent test may be limited by nonlinearities generated by the circulatory and pulmonary system. To check for such nonlinear effects, we compared the frequency responses computed from two PRBS protocols with the results of pure sinusoidal frequencies varying in amplitude and mean values (periods between 50 s and 450 s). According to our results the VO2 frequency response does not seem to depend on the type of testing--PRBS or sine--or the changes within each test, i.e. mean power and power amplitude of the sine tests and the switching frequency of the PRBS. In the range of higher frequencies small differences between the test conditions may have been obscured by the greater scatter of dynamic responses. It was concluded that the VO2 frequency response was quasi-linear for periods down to the least 100 s. However, even in this range nonlinearities can be provoked by rest-exercise transitions, by a varying contribution of lactate or by an insufficient noise reduction.

Adult↗
PubMed1990

[Evaluation of air hygiene in health resorts].

Concerning the maintenance and restoration of health in patients being subjected to health resort treatment, the spas play an important role. Therefore, legal provisions in this field establish the elimination of unfavourable environmental conditions, as air pollution, for instance. The geographical situation of a health resort exercises influences on its air quality considered in terms of hygiene. This is linked with different atmospheric and bioclimatic conditions in various regions. The major source of air pollution in a health resort is represented by housing and the communal area, by traffic on the roads and partly by industry. Instructions for measuring and evaluating of pollutants are given. Furthermore, various possibilities for improving the air quality in health resorts are mentioned.

Air Pollutants↗