Influence of high altitude on cerebral blood flow and fuel utilization during exercise and recovery
Notice bibliographique
Résumé
Key points This study assessed the dynamic response of global cerebral blood flow (CBF) and cerebral fuel utilization during and following incremental supine exercise to exhaustion. Global CBF increased more during exercise and recovery at high altitude (HA) compared with sea level (SL) such that cerebral oxygen delivery ( ) was maintained. The increase in cerebral metabolic rate of oxygen during maximal exercise at HA was half the increase observed at SL. Arterial lactate production during exercise at the same absolute intensities was greater at HA compared with SL, but reduced at the same relative intensities. Cerebral carbohydrate uptake (lactate and glucose) is greater than oxygen uptake at HA compared with SL, indicating a shift towards an increased non‐oxidative metabolic utilization. These results suggest that CBF increases to maintain during exercise at HA while changes in arterial lactate concentration and exercise intensity augment the oxidative and non‐oxidative pathways to cerebral metabolism at HA. Abstract We examined the hypotheses that: (1) during incremental exercise and recovery following 4–6 days at high altitude (HA) global cerebral blood flow (gCBF) increases to preserve cerebral oxygen delivery ( ) in excess of that required by an increasing cerebral metabolic rate of oxygen ( ); (2) the trans‐cerebral exchange of oxygen vs . carbohydrates (OCI; carbohydrates = glucose + ½lactate) would be similar during exercise and recovery at HA and sea level (SL). Global CBF, intra‐cranial arterial blood velocities, extra‐cranial blood flows, and arterial–jugular venous substrate differences were measured during progressive steady‐state exercise (20, 40, 60, 80, 100% maximum workload ( W max )) and through 30 min of recovery. Measurements ( n = 8) were made at SL and following partial acclimatization to 5050 m. At HA, absolute W max was reduced by ∼50%. During submaximal exercise workloads (20–60% W max ), despite an elevated absolute gCBF (∼20%, P < 0.05) the relative increases in gCBF were not different at HA and SL. In contrast, gCBF was elevated at HA compared with SL during 80 and 100% W max and recovery. Notwithstanding a maintained and elevated absolute at HA compared with SL, the relative increase in was similar during 20–80% W max but half that of the SL response (i.e. 17 vs . 27%; P < 0.05 vs . SL) at 100% W max . The OCI was reduced at HA compared with SL during 20, 40, and 60% W max but comparable at 80 and 100% W max . At HA, OCI returned almost immediately to baseline values during recovery, whereas at SL it remained below baseline. In conclusion, the elevations in gCBF during exercise and recovery at HA serve to maintain . Despite adequate at HA the brain appears to increase non‐oxidative metabolism during exercise and recovery.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».