The effect of β-alanine supplementation on neuromuscular performance
Notice bibliographique
Résumé
Carnosine (β-alanyl-L-histidine), a histidine containing dipeptide, is one of the most abundant small-molecular compounds in human skeletal muscle. Supplementation with the rate limiting amino acid, β-alanine, has resulted in significant improvements to high-intensity exercise performance. The role of carnosine as an intracellular pH buffer is undisputable, yet other physiological roles have been proposed, including the potential influence of increased carnosine content on regulation of skeletal muscle calcium (Ca2+) kinetics. The movement of Ca2+ is vital during both skeletal muscle contraction and relaxation phases. The overall aim of this thesis was to investigate the effect of β-alanine supplementation on voluntary and electrically evoked contractile properties of in-vivo human skeletal muscle. To examine this research question, there were several aims of this thesis, initially to examine the effect of β-alanine supplementation on intrinsic in-vivo isometric knee extensor force production and skeletal muscle contractility in both fresh and fatigued human skeletal muscle in young (Studies 1 and 2; Chapters 4 and 5) and older (Study 3; Chapter 6) adults. The distribution of the carnosine molecule across subcellular fractions within rat skeletal muscle tissue was explored, as well as the impact of increased carnosine availability on ATPase activity, a measure associated with skeletal muscle relaxation, estimated by Pi generation. In young adults, 28-days of β-alanine supplementation did not significantly influence voluntary and evoked force responses, or the force-frequency relationship, the in-vivo analogue of the force-Ca2+ relationship, in either fresh (Studies 1 and 2; Chapters 4 and 5) or fatigued (Study 2; Chapter 5) skeletal muscle. Furthermore, older adults experiencing pre-existing declines in skeletal muscle function due to ageing, demonstrated no beneficial effect of 28-days β-alanine supplementation on voluntary or electrically evoked skeletal muscle contractions (Study 3; Chapter 6). In young adults, there was, however, a significant decline in skeletal muscle half-relaxation time (HRT) during electrically evoked octet contractions, resting and potentiated twitches (Studies 1 and 2; Chapters 4 and 5). Two possible steps influence skeletal muscle relaxation speed include the Ca2+ removal from the myoplasm and Ca2+ dissociation from troponin followed by cross-bridge detachment. Based on the in-vivo research, it was proposed that there was a direct or indirect mechanism associated with activity of the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA) pump, the proposed rate-limiting step of muscle relaxation. In-vitro analysis of ATPase activity demonstrated that SERCA activity was unaffected by increased carnosine concentrations, although there was a significant increase in overall ATPase activity (Study 4; Chapter 7). The results in this thesis showed that β-alanine supplementation was effective in improving skeletal muscle HRT in young adults, although not in healthy older adults. The exact mechanism associated with the in-vivo decline in skeletal muscle HRT remains unclear, yet raising the availability of carnosine in-vitro, does increase overall ATPase activity, although not Ca2+-dependent or SERCA activity.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| 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 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 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 source (Gemma direct ou Codex distillé), 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 ».