RESUMEN
Observations of athletes in seated and standing cycling positions in laboratory and field settings have led to the perception that they produce different outputs. The purpose of this study was to determine whether there are differences in power output and physiological responses between seated and standing positions of athletes during 3 consecutive Wingate tests. Seven (n = 7) elite-level speedskaters completed 3 x 30-second Wingate tests (resistance = 7.5% body weight) with 3.5 minutes of recovery between each test in both seated and standing positions. During the recovery period, athletes pedaled against no resistance in the seated position. Testing was randomized and separated by at least 48 hours. Power output, heart rate, blood lactate, and muscle oxygenation data were collected. Statistical analysis of comparable tests (i.e., seated Wingate test 1 [WinD1] compared with standing Wingate test 1 [WinU1]; WinD2:WinU2; WinD3:WinU3) revealed no significant differences between the seated and standing variables. Position during a short-duration maximal-effort exercise test on a stationary bike did not produce statistically different results in power, maximal heart rate, blood lactate, or muscle oxygenation. As no differences were detected between positions, practitioners can allow subjects to choose their position. Also, if a subject rises out of the seat during a "seated" test, this change may not affect the subject's physiological variables. However, transitioning from one position to the other during the test is not advised due to the possible chance of injury. It should be acknowledged that there may be reasons for stipulating one position over another (e.g., injuries, leg length).
Asunto(s)
Ciclismo/fisiología , Prueba de Esfuerzo/métodos , Postura/fisiología , Patinación/fisiología , Adolescente , Adulto , Femenino , Frecuencia Cardíaca/fisiología , Humanos , Lactatos/sangre , Masculino , Consumo de Oxígeno/fisiologíaRESUMEN
We describe in situ neutron reflectivity (NR) and RAIRS studies of the chemical modification of films of a polypyrrole-based conducting polymer derived from the pentafluorophenyl ester of poly(pyrrole-N-propanoic acid) (PFP) electrodeposited on electrode surfaces. We explore the role of the solvent in controlling the rate of reaction with solution-based nucleophiles (amines, which react with the ester to form amides). By varying the identity of the solvent (water vs acetonitrile) and the neutron contrast (deuteration), we find that both the identity of the solvent and its population within the film are paramount in determining chemical reactivity and electroactivity. IR signatures allow monitoring of the reaction of solution-based amine-tagged species such as amino-terminated poly(propylene glycol), ferrocene ethylamine, and lysine with film-based ester functionalities: the carbonyl bands show ester/amide interconversion and some hydrolysis to acid. Time-dependent spectral analysis shows marked variations in reaction rate with (i) (co-)polymer composition (replacement of some fluorinated ester-functionalized pyrrole with unfunctionalized pyrrole), (ii) the solvent to which the polymer film is exposed, and (iii) the rate of polymer deposition. NR data provide solvent profiles as a function of distance perpendicular to the interface, the variations of which provide an explanation for film reactivity patterns. Homopolymer films are relatively hydrophobic, thus hindering reaction with species present in water solutions. Incorporating pyrrole groups raises the solvent population-dramatically for water-thereby facilitating entry and reaction of aqueous-based lysine. Changing film deposition rate yields films with different absolute levels of solvent and reactivity patterns that are dependent on the size of the reactant molecules: more rapid deposition of polymer gives films with a more open structure leading to a higher solvent content and thence increased reactivity. These results, supported by XPS and AFM data, allow assembly of composition-structure-reactivity correlations, in which the controlling feature is film solvation.