RESUMEN
Surfers often wear wetsuits while paddling in the ocean. This neoprene covering may be beneficial to upper extremity movement by helping to improve proprioceptive acuity, or it may be detrimental by providing increased resistance. The purpose of this study was to evaluate the effects of wearing a wetsuit on muscle activation, upper extremity motion, heart rate, and oxygen consumption during simulated surfboard paddling in the laboratory. Twelve male, recreational surfers performed two paddling trials at a constant workload on a swim bench ergometer both with and without a wetsuit. Kinematic data and EMG were acquired from the right arm via motion capture, and oxygen consumption and heart rate were recorded with a metabolic cart and heart rate monitor. Wearing a wetsuit had no significant effect on oxygen consumption or heart rate. A significant increase in EMG activation was observed for the middle deltoid but not for any of the other shoulder muscle evaluated. Finally, approximate entropy and estimates of the maximum Lyapunov exponent increased significantly for vertical trajectory of the right wrist (i.e. stroke height) when a wetsuit was worn. These results suggest that a 2mm wetsuit has little effect on the energy cost of paddling at lower workloads but does affect arm motion. These changes may be the result of enhanced proprioceptive acuity due to mechanical compression from the wetsuit.
Asunto(s)
Brazo/fisiología , Movimiento (Física) , Ropa de Protección , Entrenamiento Simulado , Deportes , Adulto , Metabolismo Energético , Frecuencia Cardíaca/fisiología , Humanos , Masculino , Músculo Esquelético/fisiología , Consumo de Oxígeno/fisiologíaRESUMEN
The purpose of this investigation was to test the hypothesis that maternal exercise training during pregnancy enhances endothelial function in offspring at birth. Six-month-old gilts (n = 8) were artificially inseminated and randomized into exercise-trained (n = 4) and sedentary groups (n = 4). Exercise training consisted of 15 weeks of treadmill exercise. The thoracic aorta of offspring were harvested within 48 h after birth and vascular responsiveness to cumulative doses of endothelium-dependent (bradykinin: 10-11-10-6 M) and independent (sodium nitroprusside: 10-10-10-4 M) vasodilators were assessed using in vitro wire myography. Female offspring from the exercised-trained gilts had a significantly greater endothelium-dependent relaxation response in the thoracic aorta when compared with the male offspring and female offspring from the sedentary gilts. The results of this investigation demonstrate for the first time that maternal exercise during pregnancy produces an enhanced endothelium-dependent vasorelaxation response in the thoracic aortas of female offspring at birth.
RESUMEN
Physical activity, exercise training, and fitness are associated with decreased cardiovascular risk. In the context that a risk factor "gap" exists in the explanation for the beneficial effects of exercise on cardiovascular disease, it has recently been proposed that exercise generates hemodynamic stimuli which exert direct effects on the vasculature that are antiatherogenic. In this review we briefly introduce some of the in vitro and in vivo evidence relating exercise hemodynamic modulation and vascular adaptation. In vitro data clearly demonstrate the importance of shear stress as a potential mechanism underlying vascular adaptations associated with exercise. Supporting this is in vivo human data demonstrating that exercise-mediated shear stress induces localized impacts on arterial function and diameter. Emerging evidence suggests that exercise-related changes in hemodynamic stimuli other than shear stress may also be associated with arterial remodeling. Taken together, in vitro and in vivo data strongly imply that hemodynamic influences combine to orchestrate a response to exercise and training that regulates wall stress and peripheral vascular resistance and contributes to the antiatherogenic impacts of physical activity, fitness, and training.
Asunto(s)
Enfermedades Cardiovasculares/prevención & control , Endotelio Vascular/fisiopatología , Ejercicio Físico , Hemodinámica , Músculo Liso Vascular/fisiopatología , Adaptación Fisiológica , Animales , Enfermedades Cardiovasculares/etiología , Enfermedades Cardiovasculares/fisiopatología , Humanos , Estrés MecánicoRESUMEN
The purpose of this investigation was to test the hypothesis that chronic N(G)-nitro-l-arginine methyl ester (l-NAME) treatment produces differential effects on conduit artery and resistance arteriole relaxation responses to endothelium-dependent and -independent vasodilators in arteries that perfuse skeletal muscle of swine. To test this hypothesis, conduit skeletal muscle arteries and second-order skeletal muscle (2A) arterioles were harvested from 14 Yucatan swine that were chronically administered l-NAME and from 16 controls. In vitro assessments of vasorelaxation to increasing doses of acetylcholine (ACH), bradykinin (BK), and sodium nitroprusside (SNP) were performed in both conduit and 2A arterioles. l-NAME treatment produced a significant reduction in both BK and ACH relaxation responses in the conduit arteries. In contrast, the relaxation response and/or sensitivity to SNP were significantly greater in the intact, but not denuded, conduit arterial rings from chronically l-NAME-treated swine. There were no significant effects of chronic l-NAME treatment on vasodilation of skeletal muscle arterioles. These findings suggest (1) that unlike arterioles, skeletal muscle conduit arteries do not functionally compensate for a lack of NO through the upregulation of alternative vasodilator pathways; (2) that the greater relaxation response in conduit arteries of chronically l-NAME-treated swine to SNP can be explained by alterations to the endothelium.
Asunto(s)
Arterias/efectos de los fármacos , Arteriolas/efectos de los fármacos , Endotelio Vascular/fisiología , Músculo Esquelético/irrigación sanguínea , Óxido Nítrico Sintasa de Tipo III/antagonistas & inhibidores , Vasodilatación/efectos de los fármacos , Acetilcolina/farmacología , Animales , Arterias/enzimología , Arteriolas/enzimología , Presión Sanguínea/efectos de los fármacos , Arteria Braquial/efectos de los fármacos , Arteria Braquial/enzimología , Bradiquinina/farmacología , Relación Dosis-Respuesta a Droga , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/enzimología , Inhibidores Enzimáticos/farmacología , Femenino , Arteria Femoral/efectos de los fármacos , Arteria Femoral/enzimología , Miembro Anterior/irrigación sanguínea , Regulación Enzimológica de la Expresión Génica , Miembro Posterior/irrigación sanguínea , Concentración 50 Inhibidora , NG-Nitroarginina Metil Éster/farmacología , Óxido Nítrico Sintasa de Tipo III/genética , Óxido Nítrico Sintasa de Tipo III/metabolismo , Nitroprusiato/farmacología , Flujo Sanguíneo Regional , Porcinos , Porcinos Enanos , Factores de Tiempo , Vasodilatadores/farmacologíaRESUMEN
Shear rate is significantly lower in the superficial femoral compared with the brachial artery in the supine posture. The relative shear rates in these arteries of subjects in the upright posture (seated and/or standing) are unknown. The purpose of this investigation was to test the hypothesis that upright posture (seated and/or standing) would produce greater shear rates in the superficial femoral compared with the brachial artery. To test this hypothesis, Doppler ultrasound was used to measure mean blood velocity (MBV) and diameter in the brachial and superficial femoral arteries of 21 healthy subjects after being in the supine, seated, and standing postures for 10 min. MBV was significantly higher in the brachial compared with the superficial femoral artery during upright postures. Superficial femoral artery diameter was significantly larger than brachial artery diameter. However, posture had no significant effect on either brachial or superficial femoral artery diameter. The calculated shear rate was significantly greater in the brachial (73 +/- 5, 91 +/- 11, and 97 +/- 13 s(-1)) compared with the superficial femoral (53 +/- 4, 39 +/- 77, and 44 +/- 5 s(-1)) artery in the supine, seated, and standing postures, respectively. Contrary to our hypothesis, our current findings indicate that mean shear rate is lower in the superficial femoral compared with the brachial artery in the supine, seated, and standing postures. These findings of lower shear rates in the superficial femoral artery may be one mechanism for the higher propensity for atherosclerosis in the arteries of the leg than of the arm.
Asunto(s)
Arteria Braquial/fisiología , Arteria Femoral/fisiología , Postura , Adulto , Velocidad del Flujo Sanguíneo , Presión Sanguínea , Arteria Braquial/diagnóstico por imagen , Femenino , Arteria Femoral/diagnóstico por imagen , Frecuencia Cardíaca , Hemorreología , Humanos , Flujometría por Láser-Doppler , Masculino , Valores de Referencia , Flujo Sanguíneo Regional , UltrasonografíaRESUMEN
The relationship between skeletal muscle intracellular PO(2) (iPO(2)) and progressive muscular work has important implications for the understanding of O(2) transport and utilization. Presently there is debate as to whether iPO(2) falls progressively with increasing O(2) demand or reaches a plateau from moderate to maximal metabolic demand. Thus, using (1)H magnetic resonance spectroscopy of myoglobin (Mb), we studied cellular oxygenation during progressive single-leg knee extensor exercise from unweighted to 100% of maximal work rate in six active human subjects. In all subjects, the Mb peak at 73 ppm was not visible at rest, whereas the peak was small or indistinguishable from the noise in the majority of subjects during progressive exercise from unweighted to 50-60% of maximum work rate. In contrast, beyond this exercise intensity, a Mb peak of consistent magnitude was discernible in all subjects. When a Mb half saturation of 3.2 Torr was used, the calculated skeletal muscle PO(2) was variable before 60% of maximum work rate but in general was relatively high (>18 Torr, the measurable PO(2) with the poorest signal-to-noise ratio, in the majority of cases), whereas beyond this exercise intensity iPO(2) fell to a relatively uniform and invariant level of 3.8 +/- 0.5 Torr across all subjects. These results do not support the concept of a progressive linear fall in iPO(2) across increasing work rates. Instead, this study documents variable but relatively high iPO(2) from rest to moderate exercise and again confirms that from 50-60% of maximum work rate iPO(2) reaches a plateau that is then invariant with increasing work rate.