Utilização do esforço percebido na determinação da velocidade crítica em corrida aquática

Abstract

The linear relation between exercise intensity and the increase rate of the neuromuscular activity assessed by electromyography allows the estimation of the fatigue threshold, which would be the intensity that could be maintained indefinitely without presenting increase on the electromyography signals along time. It has been hypothesized that the subjetive perception of exertion would behave similarly to the neuromuscular activity and that a perceived exertion threshold (PET) identified similarly to the electromyographic fatigue threshold could coincide with the critical velocity (CritV). Thirteen individuals from both genders (23.0 ± 2.5 years), in a 15 m long x 2.5 m deep swimming pool performed three deep water running exhaustive tests for the determination of the parameters of the critical velocity model, reporting the perceived exertion (6-20 points in Borg scale) each 15 m. For the PET identification, the straight lines inclination coefficients of the increase on the perceived exertion in time (ordinate) and the velocities used (abscissa) were adjusted into a linear function that provided a point in the velocity axis where, theoretically, the perceived exertion would be indefinitely stable. The CritV was estimated through the equations used in the critical velocity model. For comparison purposes of the CritV and PET estimations and their associations, the repeated measures analysis of variance ANOVA was used (p < 0.05) and the Pearson correlation was calculated. The data obtained for the CritV determination fulfilled the criteria adopted for the model's validity and CritV and PET presented no statistical difference (0.23 ± 0.02 m/s x 0.24 ± 0.03 m/s), being significantly correlated (r = 0.85). These results suggest that the PET seems to represent the maximum exercise intensity in which the physiological and psychophysical variables would attain stability and that this index may be used in the CritV determination.

Independência temporal das respostas do esforço percebido e da freqüência cardíaca em relação à velocidade de corrida na simulação de uma prova de 10km

“…Moreover, Gibson et al (30) suggested that the processing of the perceived exertion is also altered by cognitive signals, such as the memory of a training session previously conducted and the motivation at the moment of the task. Thereby, we believe that differently from other studies in which there was the control of contextual variables that may interfere in the PE (9,11,22) , the intention to exercise to the limit in real situations of sports practice, leads to a time dissociation of the PE with the HR and with the exercise intensity.…”

“…Thus, it is probable that the recreational runners have constantly adjusted the υ _ in a manner inverse to the contribution of the glycolytic system, at least up to the one before the last lap. It is known that with the participation of the glycolytic system in protocols with continuous load, an increase of the PE proportional to the anaerobic mobilization rate is observed (11) . However, such discourse should be cautiously interpreted, since in the present investigation no measurement of this physiological variable was taken.…”

“…Concerning the PE, it has been widely associated to a process of sensory interaction of the physiological adjustments originated from the metabolic demand imposed by the physical exertion (8,11,22) . However, information about the main physiological stimuli (central or peripherical) is still inconclusive.…”

“…Therefore, the results of some studies pointed to the possibility of the use of the monitoring of the HR to represent the physiological demand in tasks predominantly aerobic (5)(6)(7) . Besides the HR, the scale of perceived exertion (PE) presented by Borg (8) has also been widely used in the control (9)(10) and in the indirect determination of fulfillment of continuous cycle tasks (11) and intermittent (12) with aerobic predominance. The use of this scale is based on the premise that the physiological adjustments promoted by the physical stress produce measurable sensory signals which are able to alter the subjective perception of exertion.…”

Respostas de lactato, esfor&#231;o percebido, frequ&#234;ncia card&#237;aca, triptofano, prolactina e &#225;cidos graxos &#224; s&#233;rie de nata&#231;&#227;o na velocidade cr&#237;tica

“…Nakamura et al (2005), observaram em treze indivíduos de ambos os sexos (23,0 ± 2,5 anos), em percentuais superiores à VC, que o EP aumentava em função do tempo a uma taxa proporcional à intensidade na corrida aquática. O menor valor de correlação (tau = 0,544) encontrado no presente estudo entre o EP e a [LA] pode ser explicado pelo papel do EP no controle da tolerância às demandas da intensidade do exercício: parece que nem sempre o EP pode aumentar em função do incremento da [LA] (acidose metabólica) em uma série de treinamento intervalado (ALBERTUS et al, 2005;CREWE;TUCKER;NOAKES, 2008).…”