Jürgen Stegemann

Zum Mechanismus der Pulsfrequenzeinstellung durch den Stoffwechsel

ZusammenfassungAm Menschen wird untersucht, wie der Stoffwechsel in einer vom Kreislauf getrennten Muskelgruppe die Pulsfrequenz beeinflußt. Es zeigt sich, daß eine statistisch gesicherte lineare Beziehung zwischen dem O2-Defizit in einer abgebundenen Muskelgruppe und der Erhöhung der Pulsfrequenz besteht. In den Versuchen wurde das O2-Defizit in einer vom Kreislauf isolierten Muskelgruppe auf unterschiedliche Weise erzeugt:1.Durch Variation des abgebundenen Muskelvolumens.2.Durch Variation der Abbindedauer.3.Durch Variation der Stoffwechselintensität in der abgebundenen Muskelgruppe. Es erwies sich für die Steuerung der Pulsfrequenz als gleichgültig, auf welche Weise das O2-Defizit erzeugt wird. Gleiches O2-Defizit hatte bei der gleichen Versuchsperson gleichen Einfluß auf den Pulsfrequenzanstieg. Die Regression zwischen den beiden Größen war bei verschiedenen Versuchspersonen unterschiedlich steil.Die Einwirkung experimentell erzeugter Schmerzen zeigte, daß unter dieser Bedingung das Atemminutenvolumen stark zunimmt. Die CO2-Abgabe steigt an, und auch die Pulsfrequenz nimmt viel stärker zu, als der oben angegebenen Beziehung entspricht.Während die Pulsfrequenz in der Abbindungsperiode fortlaufend ansteigt, sinkt das Atemminutenvolumen entsprechend der verminderten CO2-Abgabe leicht ab. Eine zusätzliche Stimulierung der Atmung aus der abgebundenen Muskulatur konnte in den Versuchen nicht beobachtet werden.SummaryThe response of the heart rate to restriction of the blood flow in muscles detached by ligature from the normal circulation was investigated on humans. A statistically significant relationship between the O2 debt in the ligated muscles and the rise of the heart rate was found. In the experiments O2 debt was produced:1.by variation of the ligated muscle volume;2.by variation of the duration in which the muscles have been ligated;3.by variation of the metabolic rate by slight exercise of the ligated muscles. The rise of the heart rate was not influenced by the way in which this O2 debt was produced. The same O2 debt shows the same increase in heart rate in the same subject. However, different relations of the heart rate to O2 debt were found in different subjects.Induced pain caused a higher ventilation rate with increased CO2 output. With pain the heart rate increased more than without pain related to the same O2 debt.During the period of ligature the heart rate increased continously but the ventilation showed a little decrease corresponding to the reduced CO2 output. There was no additional stimulation of the respiration caused by the ligated muscles.

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 [1a]) 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 1 · min−1 during rest, light ([la] < 2 mmol · 1−1) and moderate ([la] =2–4 mmol · 1−1) 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 (ΔW ⩾ 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 (ΔW=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.

A model for studying the distortion of muscle oxygen uptake patterns by circulation parameters

SummaryThe transmission of muscle oxygen uptake

Der Einfluß einer 6stündigen Immersion in thermoindifferentem Wasser auf die Regulation des Kreislaufs und die Leistungsfähigkeit bei Trainierten und Untrainierten

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On the reliability of the Penaz cuff during systemic and local fingertip vasodilatation at rest and in exercise.

patterns to the pulmonary site is a basically nonlinear process during unsteady state exercise. We were mainly interested in three questions concerning the dynamic relationship between power input and pulmonary

Auslsung peripherer neurogener Atmungs-und Kreislaufantriebe durch Erhhung des CO2-Druckes in greren Muskelgruppen

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