Exercise During Extreme Hypoxia

Hanel, Birgitte; Worm, L.; Secher, N. H.; Perko, G.; Kjær, Michael

doi:10.1249/00005768-199205001-00945

Cited by 3 publications

(7 citation statements)

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“…The finding that MAP was at the resting level during functional electrical stimulation with epidural anaesthesia, is in agreement with the hypothesis that MAP is stimulated by reflex mechanisms arising by chemical stimulation of thin afferent nerve fibres in muscle during exercise (Mitchell et al 1977, Sinoway & Prophet 1990. This hypothesis has primarily been developed from animal experiments (Coote et al 1971, McCloskey & Mitchell 1972, Mitchell et al 1977, but is supported by human studies in which the MAP response to cycling was reduced by lumbar epidural anaesthesia (Fernandes et , Hanel et al 1992, Strange et al 1993). Furthermore, in man the post-exercise decline in MAP is delayed if muscle blood supply is interrupted, and this inhibition can be abolished by sensory nervous blockade (Freund et al 1979, Fernandes et al 1990).…”

Section: Discussionsupporting

confidence: 80%

Cardiovascular and ventilatory responses to electrically induced cycling with complete epidural anaesthesia in humans

Kjær

Perko

Secher

et al. 1994

Acta Physiologica Scandinavica

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Cardiovascular and ventilatory responses to electrically induced dynamic exercise were investigated in eight healthy young males with afferent neural influence from the legs blocked by epidural anaesthesia (25 ml 2% lidocaine) at L3-L4. This caused cutaneous sensory anaesthesia below T8-T9 and complete paralysis of the legs. Cycling was performed for 22.7 +/- 2.7 min (mean, SE) (fatigue) and oxygen uptake (VO2) increased to 1.90 +/- 0.13 1 min-1. Compared with voluntary exercise at the same VO2, increases in heart rate (HR) (135 +/- 7 vs. 130 +/- 9 beats min-1) and cardiac output (16.9 +/- 1.1 vs. 17.3 +/- 0.91 min-1) were similar, and ventilation (54 +/- 5 vs. 45 +/- 41 min-1) was higher (P < 0.05). In contrast, the rise in mean arterial blood pressure during voluntary exercise (93 +/- 4 (rest) to 119 +/- 4 mmHg (exercise)) was not manifest during electrically induced exercise with epidural anaesthesia [93 +/- 3 (rest) to 95 +/- 5 mmHg (exercise)]. As there is ample evidence for similar cardiovascular and ventilatory responses to electrically induced and voluntary exercise (Strange et al. 1993), the present results support the fact that the neural input from working muscle is crucial for the normal blood pressure response to exercise. Other haemodynamic and/or humoral mechanisms must operate in a decisive manner in the control of HR, CO and VE during dynamic exercise with large muscle groups.

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Section: Discussionsupporting

confidence: 80%

Cardiovascular and ventilatory responses to electrically induced cycling with complete epidural anaesthesia in humans

Kjær

Perko

Secher

et al. 1994

Acta Physiologica Scandinavica

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“…It is possible that central command could provide all of the stimulus for increased sympathetic tone during dynamic exercise with epidural anaesthesia. Such an interpretation would be consistent with the results of the pilot study by Freund et al (1979), but not with those of Kjar et al 1989, Fernandes et al (1990, Hanel et al (1992) and Strange et al (1992). In these studies involving a large muscle mass, afferent input from the working muscle dominates cardiovascular regulation during dynamic exercise.…”

Section: Post-exercise Ischaemiasupporting

confidence: 60%

“…This is a combination that is difficult to explain. The blockade used by Freund et al (1979) resulted in a much greater reduction in strength than did the anaesthesia in our study, or that of Fernandes et al (1990), Kjaer et al (1989) and Hanel et al (1992). Perhaps the subjects of Freund et al (1979) were actually performing a type of exercise which simulates repeated static contractions.…”

Section: Post-exercise Ischaemiamentioning

confidence: 41%

“…However, during post-exercise ischaemia, the rating of perceived pain was lower during epidural blockade than during control (Table 1). DISCUSSION An important finding of this study was that 1 % lidocaine in contrast to 0 25 % bupivacaine (Kjaer et al 1989;Fernandes et al 1990;Hanel et al 1992), 0-5 % bupivacaine and 2 % lidocaine (Strange et al 1992) does not affect the pressor response to dynamic exercise in man. This occurred even though the cold pressor response of the foot was abolished and the pain associated with the test was reduced during epidural anaesthesia.…”

Section: Post-exercise Ischaemiamentioning

confidence: 60%

“…In one subject there was no block of the post-exercise ischaemic response and a normal blood pressure response to dynamic exercise, and this agrees with our present study. In one subject there was a partial block of the post-exercise ischaemic response and an attenuation of the blood pressure response to dynamic exercise (Kjaer et al 1989;Fernandes et al 1990;Hanel et al 1992). However, in two subjects there was complete block of the post-exercise ischaemic response and a normal increase in blood pressure during dynamic exercise.…”

Section: Post-exercise Ischaemiamentioning

confidence: 99%

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The effect of epidural anaesthesia with 1% lidocaine on the pressor response to dynamic exercise in man.

Friedman

Brennum

Sztuk

et al. 1993

The Journal of Physiology

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SUMMARY1. In order to examine the sensitivity to local anaesthetics of afferent neural feedback from working muscle during dynamic exercise, sixteen subjects cycled for 12 min before and after epidural anaesthesia using 1 % lidocaine. The presence of afferent neural blockade was verified by elimination of the blood pressure response to a cold pressor test, laser-induced evoked potentials and increases in pain detection and tolerance thresholds of the foot. Conversely, epidural anaesthesia had no effect on these variables in the unblocked skin areas or on electrically evoked potentials in blocked or unblocked skin.2. During dynamic exercise, heart rate increased as did mean arterial pressure and cardiac output. Mean arterial pressure remained at the exercise level during post-exercise ischaemia, but heart rate and cardiac output decreased while total peripheral resistance increased. Epidural anaesthesia did not significantly affect these variables during rest, dynamic exercise, post-exercise ischaemia or recovery.3. The results of this study show that, in order to affect blood pressure during dynamic exercise, epidural anaesthesia must block the pressor response to postexercise ischaemia. The implication of these data is that complete or almost complete block of group III and/or group IV muscle afferents is necessary to inhibit the pressor response to dynamic exercise in man.

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Neural control of cardiovascular responses and of ventilation during dynamic exercise in man.

Strange

Secher

Pawelczyk

et al. 1993

The Journal of Physiology

115

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SUMMARY1. Nine subjects performed dynamic knee extension by voluntary muscle contractions and by evoked contractions with and without epidural anaesthesia. Four exercise bouts of O min each were performed: three of one-legged knee extension (10, 20 and 30 W) and one of two-legged knee extension at 2 x 20 W. Epidural anaesthesia was induced with 0-5 % bupivacaine or 2 % lidocaine. Presence of neural blockade was verified by cutaneous sensory anaesthesia below T8-T10 and complete paralysis of both legs.2. Compared to voluntary exercise, control electrically induced exercise resulted in normal or enhanced cardiovascular, metabolic and ventilatory responses. However, during epidural anaesthesia the increase in blood pressure with exercise was abolished. Furthermore, the increases in heart rate, cardiac output and leg blood flow were reduced. In contrast, plasma catecholamines, leg glucose uptake and leg lactate release, arterial carbon dioxide tension and pulmonary ventilation were not affected. Arterial and venous plasma potassium concentrations became elevated but leg potassium release was not increased.3. The results conform to the idea that a reflex originating in contracting muscle is essential for the normal blood pressure response to dynamic exercise, and that other neural, humoral and haemodynamic mechanisms cannot govern this response. However, control mechanisms other than central command and the exercise pressor reflex can influence heart rate, cardiac output, muscle blood flow and ventilation during dynamic exercise in man.

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Exercise During Extreme Hypoxia

Cited by 3 publications

References 0 publications

Cardiovascular and ventilatory responses to electrically induced cycling with complete epidural anaesthesia in humans

Cardiovascular and ventilatory responses to electrically induced cycling with complete epidural anaesthesia in humans

The effect of epidural anaesthesia with 1% lidocaine on the pressor response to dynamic exercise in man.

Neural control of cardiovascular responses and of ventilation during dynamic exercise in man.

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