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1.
Scand J Med Sci Sports ; 28(3): 1193-1200, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28940766

RESUMO

The aim of the study was to compare the effect of skin surface menthol application on rectal temperature (Tre) during prolonged immersion in cool and cold water. We hypothesized that menthol application would lead to a slower Tre decline due to the reduced heat loss as a consequence of the menthol-induced vasoconstriction and that this effect would be attenuated during cold-water immersion. Six male subjects were immersed for 55 minutes in stirred cool (24°C) or cold (14°C) water immediately after attaining a Tre of 38°C by cycling at 60% of maximum heart rate on two occasions: without (ΝM) and with (M) whole-body skin application of menthol cream. Tre, the proximal-distal skin temperature gradient, and oxygen uptake were continuously measured. ANOVA with repeated measures was employed to detect differences among variables. Significance level was set at 0.05. The area under the curve for Tre was calculated and was greater in 24°C M (-1.81 ± 8.22 a.u) compared to 24°C NM (-27.09 ± 19.09 a.u., P = .03, r = .90), 14°C NM (-18.08 ± 10.85 a.u., P = .03, r = .90), and 14°C M (-11.71 ± 12.58 a.u, P = .05, r = .81). In cool water, oxygen uptake and local vasoconstriction were increased (P ≤ .05) by 39 ± 25% and 56 ± 37%, respectively, with menthol compared to ΝM, while no differences were observed in cold water. Menthol application on the skin before prolonged immersion reduces heat loss resulting in a blunted Tre decline. However, such a response is less obvious at 14°C water immersion, possibly because high-threshold cold-sensitive fibers are already maximally recruited and the majority of cold receptors saturated.


Assuntos
Regulação da Temperatura Corporal , Temperatura Corporal , Temperatura Baixa , Mentol/administração & dosagem , Vasoconstrição , Adulto , Frequência Cardíaca , Humanos , Imersão , Masculino , Consumo de Oxigênio , Pele , Temperatura Cutânea , Água , Adulto Jovem
2.
Scand J Med Sci Sports ; 27(12): 1560-1568, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27859725

RESUMO

We hypothesized that menthol application on the skin would enhance vasoconstriction of subjects immersed in cool water, which would reduce heat loss and rectal temperature (Tre) cooling rate. Furthermore, it was hypothesized that this effect would be greater in individuals acclimatized to immersion in 24 °C water, such as swimmers. Seven swimmers (SW) and seven physical education students (CON) cycled at 60% VO2 max until Tre attained 38 °C, and were then immediately immersed in stirred water maintained at 24 °C on two occasions: without (NM) and with (M; 4.6 g per 100 mL of water) whole-body skin application of menthol cream. Heart rate, Tre, proximal-distal skin temperature gradient, oxygen uptake (VO2 ), electromyographic activity (EMG), and thermal sensation were measured. Tre reduction was similar among SW and CON in NM and CON in M (-0.71±0.31 °C in average), while it was smaller for SW in M (-0.37±0.18 °C, P < 0.01). VO2 and heart rate were greater in M compared with NM condition (P = 0.01). SW in M exhibited a shift of the threshold for shivering, as reflected in increased VO2 and EMG activity, toward a higher Tre compared with the other trials. Menthol application on the skin before immersion reduces heat loss, but defends Tre decline more effectively in swimmers than in non-swimmers.


Assuntos
Mentol/administração & dosagem , Temperatura Cutânea/efeitos dos fármacos , Natação/fisiologia , Adulto , Temperatura Corporal , Regulação da Temperatura Corporal , Temperatura Baixa , Eletromiografia , Frequência Cardíaca , Humanos , Imersão , Masculino , Consumo de Oxigênio , Estremecimento , Sensação Térmica , Vasoconstrição , Adulto Jovem
3.
J Sports Med Phys Fitness ; 46(2): 271-80, 2006 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-16823358

RESUMO

AIM: The aims of the present study were: a) to determine the anthropometric profile, body composition and somatotype of elite Greek female basketball (B), volleyball (V) and handball (H) players, b) to compare the mean scores among sports and c) to detect possible differences in relation to competition level. METHODS: A total of 518 female athletes, all members of the Greek first National League (A1 and A2 division) in B, V and H sport teams participated in the present study. Twelve anthropometric measures required for the calculation of body composition indexes and somatotype components were obtained according to the established literature. RESULTS: V athletes were the tallest (P<0.001) among the three groups of athletes, had the lowest values of body fat (P<0.001) and their somatotype was characterized as balanced endomorph (3.4-2.7-2.9). B athletes were taller (P<0.01) and leaner (P<0.001) than H players, with a somatotype characterized as mesomorph-endomorph (3.7-3.2-2.4). H athletes were the shortest of all (P<0.01), had the highest percentage of body fat (P<0.001) and their somatotype was mesomorph-endomorph (4.2-4.7-1.8). In comparison with their A2 counterparts the A1 division players were taller (P<0.001) and heavier (P<0.01), but at the same time leaner (P<0.001), and exhibited higher homogeneity in somatotype characteristics (P<0.05). CONCLUSIONS: Anthropometric, body composition and somatotype variables of Greek female elite teamball players varied among sports; selection criteria, hours of training and sport-specific physiological demands during the game could explain the observed differences. More data are certainly needed to define the anthropometric profile of B, V and H female athletes internationally.


Assuntos
Antropometria , Basquetebol , Composição Corporal , Somatotipos , Esportes , Tecido Adiposo/fisiologia , Adulto , Basquetebol/fisiologia , Composição Corporal/fisiologia , Estatura/fisiologia , Índice de Massa Corporal , Peso Corporal/fisiologia , Feminino , Fêmur/anatomia & histologia , Grécia , Humanos , Úmero/anatomia & histologia , Músculo Esquelético/anatomia & histologia , Desempenho Psicomotor/fisiologia , Dobras Cutâneas , Esportes/fisiologia
4.
Am J Physiol ; 276(2): H438-45, 1999 02.
Artigo em Inglês | MEDLINE | ID: mdl-9950843

RESUMO

A universal O2 sensor presumes that compensation for impaired O2 delivery is triggered by low O2 tension, but in humans, comparisons of compensatory responses to altered arterial O2 content (CaO2) or tension (PaO2) have not been reported. To directly compare cardiac output (QTOT) and leg blood flow (LBF) responses to a range of CaO2 and PaO2, seven healthy young men were studied during two-legged knee extension exercise with control hemoglobin concentration ([Hb] = 144.4 +/- 4 g/l) and at least 1 wk later after isovolemic hemodilution ([Hb] = 115 +/- 2 g/l). On each study day, subjects exercised twice at 30 W and on to voluntary exhaustion with an FIO2 of 0.21 or 0.11. The interventions resulted in two conditions with matched CaO2 but markedly different PaO2 (hypoxia and anemia) and two conditions with matched PaO2 and different CaO2 (hypoxia and anemia + hypoxia). PaO2 varied from 46 +/- 3 Torr in hypoxia to 95 +/- 3 Torr (range 37 to >100) in anemia (P < 0.001), yet LBF at exercise was nearly identical. However, as CaO2 dropped from 190 +/- 5 ml/l in control to 132 +/- 2 ml/l in anemia + hypoxia (P < 0.001), QTOT and LBF at 30 W rose to 12.8 +/- 0.8 and 7.2 +/- 0.3 l/min, respectively, values 23 and 47% above control (P < 0.01). Thus regulation of QTOT, LBF, and arterial O2 delivery to contracting intact human skeletal muscle is dependent for signaling primarily on CaO2, not PaO2. This finding suggests that factors related to CaO2 or [Hb] may play an important role in the regulation of blood flow during exercise in humans.


Assuntos
Débito Cardíaco/fisiologia , Exercício Físico/fisiologia , Perna (Membro)/irrigação sanguínea , Oxigênio/sangue , Vasoconstrição/fisiologia , Adulto , Anemia/sangue , Anemia/fisiopatologia , Artérias/fisiologia , Epinefrina/sangue , Humanos , Hipóxia/sangue , Hipóxia/fisiopatologia , Ácido Láctico/sangue , Ácido Láctico/metabolismo , Masculino , Músculo Esquelético/metabolismo , Norepinefrina/sangue , Consumo de Oxigênio/fisiologia , Fluxo Sanguíneo Regional/fisiologia
5.
Acta Physiol Scand ; 162(3): 421-36, 1998 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-9578388

RESUMO

Regional limb blood flow has been measured with dilution techniques (cardio-green or thermodilution) and ultrasound Doppler. When applied to the femoral artery and vein at rest and during dynamical exercise these methods give similar reproducible results. The blood flow in the femoral artery is approximately 0.3 L min(-1) at rest and increases linearly with dynamical knee-extensor exercise as a function of the power output to 6-10 L min[-1] (Q= 1.94 + 0.07 load). Considering the size of the knee-extensor muscles, perfusion during peak effort may amount to 2-3 L kg(-1) min(-1), i.e. approximately 100-fold elevation from rest. The onset of hyperaemia is very fast at the start of exercise with T 1/2 of 2-10 s related to the power output with the muscle pump bringing about the very first increase in blood flow. A steady level is reached within approximately 10-150 s of exercise. At all exercise intensities the blood flow fluctuates primarily due to the variation in intramuscular pressure, resulting in a phase shift with the pulse pressure as a superimposed minor influence. Among the many vasoactive compounds likely to contribute to the vasodilation after the first contraction adenosine is a primary candidate as it can be demonstrated to (1) cause a change in limb blood flow when infused i.a., that is similar in time and magnitude as observed in exercise, and (2) become elevated in the interstitial space (microdialysis technique) during exercise to levels inducing vasodilation. NO appears less likely since NOS blockade with L-NMMA causing a reduced blood flow at rest and during recovery, it has no effect during exercise. Muscle contraction causes with some delay (60 s) an elevation in muscle sympathetic nerve activity (MSNA), related to the exercise intensity. The compounds produced in the contracting muscle activating the group IIl-IV sensory nerves (the muscle reflex) are unknown. In small muscle group exercise an elevation in MSNA may not cause vasoconstriction (functional sympatholysis). The mechanism for functional sympatholysis is still unknown. However, when engaging a large fraction of the muscle mass more intensely during exercise, the MSNA has an important functional role in maintaining blood pressure by limiting blood flow also to exercising muscles.


Assuntos
Músculo Esquelético/irrigação sanguínea , Músculo Esquelético/fisiologia , Esforço Físico/fisiologia , Vasodilatação/fisiologia , Humanos , Músculo Esquelético/inervação , Fluxo Sanguíneo Regional/fisiologia , Sistema Nervoso Simpático/fisiologia
6.
Am J Physiol ; 273(4): H1787-93, 1997 10.
Artigo em Inglês | MEDLINE | ID: mdl-9362244

RESUMO

We hypothesized that reducing arterial O2 content (CaO2) by lowering the hemoglobin concentration ([Hb]) would result in a higher blood flow, as observed with a low PO2, and maintenance of O2 delivery. Seven young healthy men were studied twice, at rest and during two-legged submaximal and peak dynamic knee extensor exercise in a control condition (mean control [Hb] 144 g/l) and after 1-1.5 liters of whole blood had been withdrawn and replaced with albumin [mean drop in [Hb] 29 g/l (range 19-38 g/l); low [Hb]]. Limb blood flow (LBF) was higher (P < 0.01) with low [Hb] during submaximal exercise (i.e., at 30 W, LBF was 2.5 +/- 0.1 and 3.0 +/- 0.1 l/min for control [Hb] and low [Hb], respectively; P < 0.01), resulting in a maintained O2 delivery and O2 uptake for a given workload. However, at peak exercise, LBF was unaltered (6.5 +/- 0.4 and 6.6 +/- 0.6 l/min for control [Hb] and low [Hb], respectively), which resulted in an 18% reduction in O2 delivery (P < 0.01). This occurred despite peak cardiac output in neither condition reaching >75% of maximal cardiac output (approximately 26 l/min). It is concluded that a low CaO2 induces an elevation in submaximal muscle blood flow and that O2 delivery to contracting muscles is tightly regulated.


Assuntos
Anemia/fisiopatologia , Sistema Cardiovascular/fisiopatologia , Exercício Físico , Doença Aguda , Adulto , Anemia/sangue , Débito Cardíaco/fisiologia , Veia Femoral , Hemoglobinas/análise , Humanos , Perna (Membro)/irrigação sanguínea , Masculino , Músculo Esquelético/irrigação sanguínea , Oxigênio/sangue , Consumo de Oxigênio/fisiologia , Fluxo Sanguíneo Regional/fisiologia
7.
Am J Physiol ; 272(6 Pt 2): H2655-63, 1997 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-9227543

RESUMO

Hypoxia affects O2 transport and aerobic exercise capacity. In two previous studies, conflicting results have been reported regarding whether O2 delivery to the muscle is increased with hypoxia or whether there is a more efficient O2 extraction to allow for compensation of the decreased O2 availability at submaximal and maximal exercise. To reconcile this discrepancy, we measured limb blood flow (LBF), cardiac output, and O2 uptake during two-legged knee-extensor exercise in eight healthy young men. They completed studies at rest, at two submaximal workloads, and at peak effort under normoxia (inspired O2 fraction 0.21) and two levels of hypoxia (inspired O2 fractions 0.16 and 0.11). During submaximal exercise, LBF increased in hypoxia and compensated for the decrement in arterial O2 content. At peak effort, however, our subjects did not achieve a higher cardiac output or LBF. Thus O2 delivery was not maintained and peak power output and leg O2 uptake were reduced proportionately. These data are consistent then with the findings of an increased LBF to compensate for hypoxemia at submaximal exercise, but no such increase occurs at peak effort despite substantial cardiac capacity for an elevation in LBF.


Assuntos
Sistema Cardiovascular/fisiopatologia , Exercício Físico , Hipóxia/fisiopatologia , Joelho/fisiopatologia , Músculos/fisiopatologia , Adaptação Fisiológica , Adulto , Débito Cardíaco , Humanos , Perna (Membro)/irrigação sanguínea , Masculino , Consumo de Oxigênio , Fluxo Sanguíneo Regional
8.
Artigo em Inglês | MEDLINE | ID: mdl-8162927

RESUMO

In order to determine the level of hypoxemia which is sufficient to impair maximal performance, seven well-trained male cyclists [maximum oxygen consumption (VO2max) > or = 5 l.min-1 or 60 ml.kg-1.min-1] performed a 5-min performance cycle test to exhaustion at maximal intensity as controlled by the subject, under three experimental conditions: normoxemia [percentage of arterial oxyhemoglobin saturation (%SaO2) > 94%], and artificially induced mild (%SaO2 = 90 +/- 1%) and moderate (% SaO2 = 87 +/- 1%) hypoxemia. Performance, evaluated as the total work output (Worktot) performed in the 5-min cycle test, progressively decreased with decreasing % SaO2 [mean (SE) Worktot = 107.40 (4.5) kJ, 104.07 (5.6) kJ, and 102.52 (4.7) kJ, under normoxemia, mild, and moderate hypoxemia, respectively]. However, only performance in the moderate hypoxemia condition was significantly different than in normoxemia (P = 0.02). Mean oxygen consumption and heart rate were similar in the three conditions (P = 0.18 and P = 0.95, respectively). End-tidal partial pressure of CO2 was significantly lower (P = 0.005) during moderate hypoxemia compared with normoxemia, and ventilatory equivalent of CO2 was significantly higher (P = 0.005) in both hypoxemic conditions when compared with normoxemia. It is concluded that maximal performance capacity is significantly impaired in highly trained cyclists working under an % SaO2 level of 87% but not under a milder desaturation level of 90%.


Assuntos
Exercício Físico/fisiologia , Hipóxia/fisiopatologia , Adulto , Teste de Esforço , Frequência Cardíaca/fisiologia , Humanos , Hipóxia/sangue , Masculino , Oxigênio/sangue , Consumo de Oxigênio/fisiologia , Respiração/fisiologia , Volume de Ventilação Pulmonar/fisiologia
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