Bicarbonate attenuates arterial desaturation during  maximal exercise in humans

Nielsen, Henning Bay; Bredmose, Per P.; Strømstad, M.; Volianitis, Stefanos; Quistorff, Bjørn; Secher, Niels H.

doi:10.1152/japplphysiol.00398.2000

Cited by 84 publications

(87 citation statements)

References 58 publications

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“…Our findings agree with others in demonstrating an improvement in endurance exercise performance after preventing normally occurring EIAH (36,37). They also are consistent with the effects of inspired hypoxia (1,11,19,25,29,38) and hyperoxia (1,11,19,38) on decreasing and increasing performance, respectively.…”

Section: Eiah Fatigue and Exercise Performance Limitationssupporting

confidence: 92%

“…Our finding of a significant EIAH effect on locomotor muscle fatigue is consistent with the increase in limb muscle V O 2 max induced via hyperoxic-induced elevations in Ca O 2 (28) but was not expected in light of the reports of Nielsen et al (36,37), who found no effect of preventing EIAH during heavy exercise on muscle O 2 saturation, as assessed via near-infrared spectroscopy. However, this method is unable to detect withinregion differences in oxygenation and can only measure up to tissue depths of a few centimeters.…”

Section: Eiah Contributes To Locomotor Muscle Fatiguesupporting

confidence: 90%

“…This proposal is supported by the finding that cycle exercise during chronic severe hypoxia is terminated without evidence of peripheral muscle fatigue, again as inferred by the absence of hypoxic effects on limb muscle EMG activity (26). Furthermore, preventing O 2 desaturation and increasing performance during sustained heavy exercise at sea level did not raise tissue oxygenation in the limb muscle (36,37) but did increase brain tissue O 2 saturation as assessed via near-infrared spectroscopy (36).…”

mentioning

confidence: 87%

“…The desaturation is attributable primarily to a reduced arterial O 2 partial pressure (Pa O 2 ) in some highly fit subjects (17,22,52) or, more universally, to a rightward shift of the O 2 dissociation curve because of a time-and intensity-dependent metabolic acidosis and an increase in body temperature (42,50). EIAH has a detrimental effect on maximal O 2 uptake (V O 2 max ) (16,41) and endurance exercise performance (36,37).…”

mentioning

confidence: 99%

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Effect of exercise-induced arterial hypoxemia on quadriceps muscle fatigue in healthy humans

Romer

Haverkamp²,

Lovering³

et al. 2006

American Journal of Physiology-Regulatory, Integrative and Comp

116

126

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-The effect of exercise-induced arterial hypoxemia (EIAH) on quadriceps muscle fatigue was assessed in 11 male endurance-trained subjects [peak O 2 uptake (V O2 peak) ϭ 56.4 Ϯ 2.8 ml⅐kg Ϫ1 ⅐min Ϫ1 ; mean Ϯ SE]. Subjects exercised on a cycle ergometer at Ն90% V O2 peak to exhaustion (13.2 Ϯ 0.8 min), during which time arterial O 2 saturation (SaO 2 ) fell from 97.7 Ϯ 0.1% at rest to 91.9 Ϯ 0.9% (range 84 -94%) at end exercise, primarily because of changes in blood pH (7.183 Ϯ 0.017) and body temperature (38.9 Ϯ 0.2°C). On a separate occasion, subjects repeated the exercise, for the same duration and at the same power output as before, but breathed gas mixtures [inspired O2 fraction (FIO 2 ) ϭ 0.25-0.31] that prevented EIAH (Sa O 2 ϭ 97-99%). Quadriceps muscle fatigue was assessed via supramaximal paired magnetic stimuli of the femoral nerve (1-100 Hz). Immediately after exercise at FI O 2 0.21, the mean force response across 1-100 Hz decreased 33 Ϯ 5% compared with only 15 Ϯ 5% when EIAH was prevented (P Ͻ 0.05). In a subgroup of four less fit subjects, who showed minimal EIAH at FIO 2 0.21 (SaO 2 ϭ 95.3 Ϯ 0.7%), the decrease in evoked force was exacerbated by 35% (P Ͻ 0.05) in response to further desaturation induced via FI O 2 0.17 (SaO 2 ϭ 87.8 Ϯ 0.5%) for the same duration and intensity of exercise. We conclude that the arterial O 2 desaturation that occurs in fit subjects during high-intensity exercise in normoxia (Ϫ6 Ϯ 1% ⌬Sa O 2 from rest) contributes significantly toward quadriceps muscle fatigue via a peripheral mechanism. magnetic stimulation; low-and high-frequency fatigue; quadriceps twitch force; voluntary activation; peripheral fatigue; central fatigue EXERCISE-INDUCED ARTERIAL HYPOXEMIA (EIAH), defined as a reduced arterial HbO 2 saturation below preexercise levels, occurs during sustained, heavy-intensity exercise to exhaustion in a significant number of healthy subjects (9). The desaturation is attributable primarily to a reduced arterial O 2 partial pressure (Pa O 2 ) in some highly fit subjects (17, 22, 52) or, more universally, to a rightward shift of the O 2 dissociation curve because of a time-and intensity-dependent metabolic acidosis and an increase in body temperature (42,50). EIAH has a detrimental effect on maximal O 2 uptake (V O 2 max ) (16, 41) and endurance exercise performance (36, 37).Multiple "peripheral" and "central" mechanisms have been proposed to explain how arterial hypoxemia limits endurance exercise performance. There is potential for reduced O 2 transport to cause limb muscle fatigue during heavy exercise via an effect of hypoxia on Ca 2ϩ uptake and Ca 2ϩ release by the sarcoplasmic reticulum (10). Changes in the intracellular environment may impair Ca 2ϩ cycling and other excitation/ contraction processes. Alternatively, an inability of the sarcolemma and T tubule to conduct repetitive action potentials may indirectly reduce Ca 2ϩ cycling. The possibility that such peripheral processes are involved in exercise limitation during hypoxemia is suggested by the finding that...

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Section: Eiah Fatigue and Exercise Performance Limitationssupporting

confidence: 92%

Section: Eiah Contributes To Locomotor Muscle Fatiguesupporting

confidence: 90%

mentioning

confidence: 87%

mentioning

confidence: 99%

See 2 more Smart Citations

Effect of exercise-induced arterial hypoxemia on quadriceps muscle fatigue in healthy humans

Romer

Haverkamp²,

Lovering³

et al. 2006

American Journal of Physiology-Regulatory, Integrative and Comp

116

126

View full text Add to dashboard Cite

show abstract

“…Moderate exercise is associated with a small increase in Pa CO 2 that would be considered to support the increase in CBF and MCA V mean (49). On the other hand, intense exercise is associated with a reduction in Pa CO 2 because ventilation increases exponentially with work rate as pH decreases (66). Accordingly, intense exercise is accomplished despite a decreasing CBF and MCA V mean (49,51,55,88) that interferes with adequate oxygenation of the brain (Fig.…”

Section: Regulation Of Cbf During Exercisementioning

confidence: 99%

Cerebral blood flow and metabolism during exercise: implications for fatigue

Secher¹,

Seifert²,

Lieshout³

2008

Journal of Applied Physiology

297

281

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Secher NH, Seifert T, Van Lieshout JJ. Cerebral blood flow and metabolism during exercise, implications for fatigue. J Appl Physiol 104: 306 -314, 2008. First published October 25, 2007 doi:10.1152/japplphysiol.00853.2007.-During exercise: the Kety-Schmidt-determined cerebral blood flow (CBF) does not change because the jugular vein is collapsed in the upright position. In contrast, when CBF is evaluated by 133 Xe clearance, by flow in the internal carotid artery, or by flow velocity in basal cerebral arteries, a ϳ25% increase is detected with a parallel increase in metabolism. During activation, an increase in cerebral O 2 supply is required because there is no capillary recruitment within the brain and increased metabolism becomes dependent on an enhanced gradient for oxygen diffusion. During maximal whole body exercise, however, cerebral oxygenation decreases because of eventual arterial desaturation and marked hyperventilation-related hypocapnia of consequence for CBF. Reduced cerebral oxygenation affects recruitment of motor units, and supplemental O 2 enhances cerebral oxygenation and work capacity without effects on muscle oxygenation. Also, the work of breathing and the increasing temperature of the brain during exercise are of importance for the development of so-called central fatigue. During prolonged exercise, the perceived exertion is related to accumulation of ammonia in the brain, and data support the theory that glycogen depletion in astrocytes limits the ability of the brain to accelerate its metabolism during activation. The release of interleukin-6 from the brain when exercise is prolonged may represent a signaling pathway in matching the metabolic response of the brain. Preliminary data suggest a coupling between the circulatory and metabolic perturbations in the brain during strenuous exercise and the ability of the brain to access slow-twitch muscle fiber populations. ammonium; central fatigue; cerebral blood flow; cerebral metabolic ratio; glucose; glycogen; lactate; oxygen; temperature DURING EXERCISE, THERE IS hyperbolic relationship between work intensity and endurance, and A. V. Hill used the relationship to demonstrate that energy turnover can be taken to represent a continuous provision of energy supplemented by an energy store (56). Yet, it is the brain that makes the decision when to slow down or to stop exercise, and from that perspective fatigue is of central origin. Obviously, cerebral metabolism becomes affected if exercise has a duration that lowers blood glucose (74), and, equally, the low O 2 tension faced during mountaineering (47) affects brain function. Perturbation of cerebral metabolism is, however, not restricted to situations where the arterial glucose and O 2 levels are reduced. Recent investigations (3,65,70,90) indicate that also at sea level maximal exercise may be associated with so-called central fatigue as indicated by lower voluntary activation than the force elicited during evoked contractions.The purpose of this review is to address cerebral metabolism in ...

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Red Blood Cell Volume and the Capacity for Exercise at Moderate to High Altitude

Jacobs

Lundby

Robach³

et al. 2012

Sports Med

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Hypoxia-stimulated erythropoiesis, such as that observed when red blood cell volume (RCV) increases in response to high-altitude exposure, is well understood while the physiological importance is not. Maximal exercise tests are often performed in hypoxic conditions following some form of RCV manipulation in an attempt to elucidate oxygen transport limitations at moderate to high altitudes. Such attempts, however, have not made clear the extent to which RCV is of benefit to exercise at such elevations. Changes in RCV at sea level clearly have a direct influence on maximal exercise capacity. Nonetheless, at elevations above 3000 m, the evidence is not that clear. Certain studies demonstrate either a direct benefit or decrement to exercise capacity in response to an increase or decrease, respectively, in RCV whereas other studies report negligible effects of RCV manipulation on exercise capacity. Adding to the uncertainty regarding the importance of RCV at high altitude is the observation that Andean and Tibetan high-altitude natives exhibit similar exercise capacities at high altitude (3900 m) even though Andean natives often present with a higher percent haematocrit (Hct) when compared with both lowland natives and Tibetans. The current review summarizes past literature that has examined the effect of RCV changes on maximal exercise capacity at moderate to high altitudes, and discusses the explanation elucidating these seemingly paradoxical observations. DOI: https://doi.org/10.2165/11632440-000000000-00000Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-69166 Accepted Version Originally published at: Jacobs, Robert A; Lundby, Carsten; Robach, Paul; Gassmann, Max (2012). Red blood cell volume and the capacity for exercise at moderate to high altitude. Sports Medicine, 42 (8) clear. Certain studies demonstrate either a direct benefit or decrement to exercise capacity in 34 response to an increase or decrease, respectively, in RCV; whereas, other studies report Andean natives often present with a higher percent hematocrit (Htc) when compared to both 39 lowland natives and Tibetans. The current review summarizes past literature that has examined 40 the effect of RCV changes on maximal exercise capacity at moderate to high altitudes, and 41 discusses the explanation elucidating these seemingly paradoxical observations.

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Bicarbonate attenuates arterial desaturation during maximal exercise in humans

Cited by 84 publications

References 58 publications

Effect of exercise-induced arterial hypoxemia on quadriceps muscle fatigue in healthy humans

Effect of exercise-induced arterial hypoxemia on quadriceps muscle fatigue in healthy humans

Cerebral blood flow and metabolism during exercise: implications for fatigue

Red Blood Cell Volume and the Capacity for Exercise at Moderate to High Altitude

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