2,129 research outputs found
Consistency of pacing and metabolic responses during 2000-m rowing ergometry
PURPOSE: This study investigated the pacing strategy adopted and the consistency of performance and related physiological parameters across three 2000-m rowing-ergometer tests.
METHODS: Fourteen male well-trained rowers took part in the study. Each participant performed three 2000-m rowing-ergometer tests interspersed by 3-7 d. Throughout the trials, respiratory exchange and heart rate were recorded and power output and stroke rate were analyzed over each 500 m of the test. At the completion of the trial, assessments of blood lactate and rating of perceived exertion were measured.
RESULTS: Ergometer performance was unchanged across the 3 trials; however, pacing strategy changed from trial 1, which featured a higher starting power output and more progressive decrease in power, to trials 2 and 3, which were characterized by a more conservative start and an end spurt with increased power output during the final 500 m. Mean typical error (TE; %) across the three 2000-m trials was 2.4%, and variability was low to moderate for all assessed physiological variables (TE range = 1.4-5.1%) with the exception of peak lactate (TE = 11.5%).
CONCLUSIONS: Performance and physiological responses during 2000-m rowing ergometry were found to be consistent over 3 trials. The variations observed in pacing strategy between trial 1 and trials 2 and 3 suggest that a habituation trial is required before an intervention study and that participants move from a positive to a reverse-J-shaped strategy, which may partly explain conflicting reports in the pacing strategy exhibited during 2000-m rowing-ergometer trials
Relaxation oscillations, stability, and cavity feedback in a superradiant Raman laser
We experimentally study the relaxation oscillations and amplitude stability
properties of an optical laser operating deep into the bad-cavity regime using
a laser-cooled Rb Raman laser. By combining measurements of the laser
light field with nondemolition measurements of the atomic populations, we infer
the response of the gain medium represented by a collective atomic Bloch
vector. The results are qualitatively explained with a simple model.
Measurements and theory are extended to include the effect of intermediate
repumping states on the closed-loop stability of the oscillator and the role of
cavity feedback on stabilizing or enhancing relaxation oscillations. This
experimental study of the stability of an optical laser operating deep into the
bad-cavity regime will guide future development of superradiant lasers with
ultranarrow linewidths.Comment: 9 pages, 6 figure
Genesis of the Antarctic Slope Current in West Antarctica
The stability of the West Antarctic Ice Sheet (WAIS) depends on ocean heat transport toward its base and remains a source of uncertainty in sea level rise prediction. The Antarctic Slope Current (ASC), a major boundary current of the ocean's global circulation, serves as a dynamic gateway for heat transport toward Antarctica. Here, we use observations collected from the Bellingshausen Sea to propose a mechanistic explanation for the initiation of the westwardâflowing ASC. Waters modified throughout the Bellingshausen Sea by oceanâseaâice and oceanâiceâshelf interactions are exported to the continental slope in a narrow, topographically steered western boundary current. This focused outflow produces a localized front at the shelf break that supports the emerging ASC. This mechanism emphasizes the importance of buoyancy forcing, integrated over the continental shelf, as opposed to local wind forcing, in the generation mechanism and suggests the potential for remote control of melt rates of WAIS' largest ice shelves
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