European journal of applied physiology
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Eur. J. Appl. Physiol. · May 2005
Clinical Trial Controlled Clinical TrialKinetics of oxygen uptake during arm cranking with the legs inactive or exercising at moderate intensities.
The purpose of this study was to compare the kinetics of oxygen uptake (VO(2)) during arm cranking with the legs inactive or exercising. Each subject (n = 8) performed three exercise protocols: 6-min arm cranking at an intensity of 60% of peak oxygen uptake (VO(2peak), AC(60)) and 6-min combined arm cranking and leg cycling in which AC(60) was added to on-going leg cycling at an intensity of 20% or 40% of VO(2peak) (LC(20) and LC(40): AC(60)LC(20) and AC(60)LC(40), respectively). After the onset of arm cranking, VO(2) tended to increase until the end of arm cranking in all of the three exercise modes. ⋯ There were no significant differences in the effective VO(2) time constant, partial O(2) deficit, and the difference between the values of VO(2) measured at 3 and 6 min in the three exercise modes. The present results indicate that the amplitude of the increase in VO(2) is reduced during arm cranking with the legs exercising, that this reduction becomes greater with increases in the intensity of leg cycling, and that the rate of increase in VO(2) is not affected by the additional muscle mass of the legs exercising below moderate intensities. The decrease in the amplitude of increase in VO(2) might be caused by reduction in oxygen supply to the exercising arms due to large muscle mass and/or overlaps of activity of stabilizing muscles during combined arm and leg exercise.
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Hyperventilation prior to breath-hold diving increases the risk of syncope as a result of hypoxia. Recently, a number of cases of near-drownings in which the swimmers did not hyperventilate before breath-hold diving have come to our attention. These individuals had engaged in prolonged exercise prior to breath-hold diving and it is known that such exercise enhances lipid metabolism relative to carbohydrate metabolism, resulting in a lower production of CO(2) per amount of O(2 )consumed. ⋯ A similar pattern was observed after breath-holding under resting conditions, i.e., a lower end-tidal P O(2) and P CO(2) after exercise (PPE) compared to control conditions. Our findings demonstrate that under the conditions of a relatively low RER following prolonged exercise, breath-holding is terminated at a lower P O(2) and a lower P CO(2) than under normal conditions. This suggests that elevated lipid metabolism may constitute a risk factor in connection with breath-holding during swimming and diving.
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Eur. J. Appl. Physiol. · Dec 2004
Diffusive sensitivity to muscle architecture: a magnetic resonance diffusion tensor imaging study of the human calf.
The aim of this study was to examine the diffusive properties of adjacent muscles at rest, and to determine the relationship between diffusive and architectural properties, which are task-specific to muscles. The principle, second, and third eigenvalues, trace of the diffusion tensor, and two anisotropic parameters, ellipsoid eccentricity (e) and fractional anisotropy (FA), of various muscles in the human calf were calculated by diffusion tensor imaging (DTI). Linear correlations of the calculated parameters to the muscle physiological cross-sectional area (PCSA), which is proportional to maximum muscle force, were performed to ascertain any linear relation between muscle architecture and diffusivity. ⋯ A strong correlation was also found between PCSA and the third eigenvalue, e, and FA. A mathematical derivation revealed a linear relationship between PCSA and the third eigenvalue as a result of their dependence on the average radius of all fibers within a single muscle. These findings demonstrated the ability of DTI to differentiate between functionally different muscles in the same region of the body on the basis of their diffusive properties.
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Eur. J. Appl. Physiol. · Oct 2004
Clinical Trial Controlled Clinical TrialInfrared thermography for examination of skin temperature in the dorsal hand of office workers.
Reduced blood flow may contribute to the pathophysiology of upper extremity musculoskeletal disorders (UEMSD), such as tendinitis and carpal tunnel syndrome. The study objective was to characterize potential differences in cutaneous temperature, among three groups of office workers assessed by dynamic thermography following a 9-min typing challenge: those with UEMSD, with ( n=6) or without ( n=10) cold hands exacerbated by keyboard use, and control subjects ( n=12). Temperature images of the metacarpal region of the dorsal hand were obtained 1 min before typing, and during three 2-min sample periods [0-2 min (early), 3-5 min (middle), and 8-10 min (late)] after typing. ⋯ Controls further increased mean temperature by 0.1 degrees C ( t-test, P=0.001) at 3-5 min post-typing before a late temperature decline of -0.3 degrees C ( t-test, P=0.04), while cases without cold hands showed no change from initial post-typing mean temperature rise during middle or late periods. In contrast, subjects with keyboard-induced cold hands had no change from initial post-typing temperature until a decrease at the late period of -0.3 degrees C ( t-test, P=0.06). Infrared thermography appears to distinguish between the three groups of subjects, with keyboard-induced cold hand symptoms presumably due, at least partially, to reduced blood flow.
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Eur. J. Appl. Physiol. · Sep 2004
Assessment of the efficiency of warming devices during neonatal surgery.
This study assessed the relative efficiency of different warming devices (surgical sheets covering the body and a tubegauze on the head, forced-air warming, warming mattress) commonly used to prevent body hypothermia during neonatal surgery. Dry heat losses were measured from a thermal manikin, which simulated a low-birth-weight neonate of 1,800 g. The manikin's surface temperatures (35.8 degrees C) corresponded to those of neonates nursed in closed incubators. ⋯ Heat losses were reduced by 7.9 W when combining the warming mattress and Bair Hugger. The heat loss from the head of the covered manikin was reduced from 4.5 W to 3.9 W when the head was covered with the tubegauze. Our data indicate that forced-air warming is more effective than conductive warming in preventing neonatal hypothermia during abdominal operations.