Limb blood flow and muscle oxygenation responses during handgrip exercise above vs. below critical force.
Microvasc Res
; 131: 104002, 2020 09.
Article
em En
| MEDLINE
| ID: mdl-32198059
ABSTRACT
This study compared the brachial artery blood flow (QÌBA) and microvascular oxygen delivery responses during handgrip exercise above vs. below critical force (CF; the isometric analog of critical power). QÌBA and microvascular oxygen delivery are important determinants of oxygen utilization and metabolite accumulation during exercise, both of which increase progressively during exercise above CF. However the QÌBA and microvascular oxygen delivery responses above vs. below CF remain unknown. We hypothesized that QÌBA, deoxygenated-heme (deoxy-[heme]; an estimate of microvascular fractional oxygen extraction), and total-heme concentrations (total-[heme]; an estimate of changes in microvascular hematocrit) would demonstrate physiological maximums above CF despite increases in exercise intensity. Seven men and six women performed 1) a 5-min rhythmic isometric-handgrip maximal-effort test (MET) to determine CF and 2) two constant target-force tests above (severe-intensity; S1 and S2) and two constant target-force tests below (heavy-intensity; H1 and H2) CF. CF was 189.3 ± 16.7 N (29.7 ± 1.6%MVC). At end-exercise, QÌBA was greater for tests above CF (S1 418 ± 147 mL/min; S2 403 ± 137 mL/min) compared to tests below CF (H1 287 ± 97 mL/min; H2 340 ± 116 mL/min; all p < 0.05) but was not different between S1 and S2. Further, end-test QÌBA during both tests above CF was not different from QÌBA estimated at CF (392 ± 37 mL/min). At end-exercise, deoxy-[heme] was not different between tests above CF (S1 150 ± 50 µM; S2 155 ± 57 µM), but was greater during tests above CF compared to tests below CF (H1 101 ± 24 µM; H2 111 ± 21 µM; all p < 0.05). At end-exercise, total-[heme] was not different between tests above CF (S1 404 ± 58 µM; S2 397 ± 73 µM), but was greater during tests above CF compared to H1 (352 ± 58 µM; p < 0.01) but not H2 (371 ± 57 µM). These data suggest limb blood flow limitations exist and maximal levels of muscle microvascular oxygen delivery and extraction occur during exercise above, but not below, CF.
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Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Oxigênio
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Consumo de Oxigênio
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Artéria Braquial
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Exercício Físico
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Músculo Esquelético
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Força da Mão
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Força Muscular
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Contração Isométrica
Limite:
Adult
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Female
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Humans
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Male
Idioma:
En
Revista:
Microvasc Res
Ano de publicação:
2020
Tipo de documento:
Article