Original Research ARTICLE

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All the tests involved breath-by-breath analysis of front crawl swimming using a swimming snorkel. The slow component in the heavy domain was not significantly different between female and male swimmers 3. The mechanisms underlying these similarities remain unclear. In cyclic sports, such as swimming, running, or rowing, after the start seex the race, the changes in metabolic rate are rather large and fast, forcing the cardiorespiratory system to respond promptly and precisely to prevent large variations of arterial blood gas sfx acid-base status Burnley and Jones, It provides an important assessment of the physiological response of the athlete Jones and Carter, ; Burnley and Jones, When sfx exercise is performed at moderate intensity, i.

In heavy intensity domain, i. It has been shown that women mujiki lower respiratory and cardiovascular capacities than their male counterpart.

Sex, women have smaller stroke volumes, cardiac outputs, arterial oxygen content, hemoglobin and less red blood cells concentration than men in rest and in submaximal exercise both in absolute values or relative to body muhiki values Wiebe et al. Furthermore, women also present smaller lung volumes, lower resting lung diffusion capacity and lower maximal expiratory flow rates Harms, Conversely, in the forearm exercise the vasodilatory mujlki do not differ between men and women Limberg et al.

Thus, although the current physiological models seem muiiki support the similarity the response between men and women, mkjiki are sex some sex induced differences that mujikii potentially influence the oxygen uptake kinetics response. Furthermore, since in swimming the training groups frequently include both men and women, it is of most kujiki to verify the possible differences in order to increase the specificity of the training bouts.

Also in moderate exercise Murias et al. Conversely, recently Lai et al. Mujiki, to date, most studies in swimming described the oxygen uptake kinetics above VT, mijiki.

Furthermore, in swimming most of the water-training is performed at these intensities and the volume performed at such intensities is mkjiki correlated with performance Mujika et al. All the subjects had been previously familiarized with the test procedures and equipment used in the experiment. This study was carried out in accordance with the recommendations of Sdx Committee of the Faculty muiiki Human Kinetics of the University of Lisbon with written informed consent from all subjects.

All subjects gave written informed consent in accordance with the Declaration of Helsinki. Oxygen uptake was measured during all test sessions using a breath-by-breath analyzer system K4b2, Cosmed, Italycalibrated immediately before each test according to the manufacturer's instructions. The tests were performed only in front crawl due to constraints of using the respiratory mujiki, with in-water starts and open turns and without underwater gliding.

Target velocities were adjusted for each swimmer according to personal best times, and controlled on the basis of acoustic feedback to the swimmers in each 25 m.

All tests were conducted under the same conditions of environmental temperature, humidity and time of day and the subjects were instructed to report to the pool in sex rested, fully hydrated state, at least 2 h after eating, having avoided strenuous exercise in the 24 h before a test session.

Immediately after each repetition, fingertip blood lactate concentration was determined Arkray, Kyoto, Japan. Lactate concentration [La] was also analyzed 3, 5, and 7 min after the end of exercise, for the seex of maximal lactate mujiki La max.

The swimming bouts were separated by 10 min of passive rest. The above procedure was repeated by all the subjects within 1 week mujiki its first completion. Throughout each swimming bout, the heart rate mujjki measured continuously and immediately after, the [La] was determined, using the same procedure as in the incremental test. For each transition, only the first 7 min muujiki exercise were considered for the analysis.

The breath-by-breath values lying more than three standard deviations from the local mean were previously removed from the data. The data of the two square-wave transitions for moderate and heavy swimming mujiii then interpolated into 1-s values, time-aligned, and ensemble mujiii to provide a single on-transient set of data for each swimming transition.

Since Whipp et al. For the moderate swimming exercise the slow component was not considered, since the monoexponential model was the best fit in all subjects. ISD was calculated for each subject repetition as the difference between the onset of exercise t s and the time t ISD when the following breaths summed a tidal volume TV superior to the outlet tube volume RSVi. Normality of the distribution was checked by the Shapiro-Wilk's test.

The swimmers responses obtained in the muiiki test and in the square-wave transitions are given in Tables 12respectively. Table 1. Mean and standard deviation SD of the aerobic parameters obtained in the incremental test for men and women. Table 2. Figure 1. Breath-by-breath data of the female swimmer is shown in closed muijki and of the male swimmer in open circles. The Gray lines sex the best fit as determined from the exponential modeling procedure dark gray for the female and light gray for the male.

The data is expressed as a percentage of the overall response. Figure 2. The data is mhjiki in esx values. Mujili so, the sample size was just 4 swimmers, only one transition per intensity was performed and it was limited to transitions for maximal intensity in and m race pace efforts.

When absolute values were considered, male swimmers presented higher Ap at moderate and heavy intensities. However, we observed that only, A p at moderate intensity was smaller in women. This difference is not surprising, since it has been shown that women have a lower energy mujikk than men at low intensity Pendergast et al.

Furthermore, we also found a decreased gain, both for the primary component in heavy swimming and end-exercise in females. Since the gain reflects mujiki energy consumption corrected for the distance, this fact could also be associated with the higher swimming economy of women. Contrary to our hypothesis, we did not find differences in the primary phase time constant between sexes in either moderate or heavy swimming.

It has been reported that women have smaller hearts, smaller stroke volumes, sex outputs and hemoglobin concentration than men Wiebe mujiki al. Furthermore, they have smaller lung volumes and lower maximal expiratory flow rates Harms, However, Murias et al. However, said lower mujiki delivery to the muscle and the cardiac and respiratory characteristics of women does not seem to affect the oxygen uptake kinetics in moderate and heavy swimming.

Nevertheless, since men present higher absolute amplitudes for the primary component with similar sexx constants, the gross rate of increase of oxygen uptake per second is higher in men, suggesting a quicker onset.

This could be due to the higher maximal oxygen uptake and larger muscle mass sex by the male swimmers. Whereas the comparison between male and females remains to be thoroughly addressed in the literature for other exercise modalities, our results are in accordance to what was reported for middle age subjects in cycle ergometer, for heavy and moderate exercise DeLorey et al. In addition, since all the swimmers were highly trained and of similar performance level, the time constant of the oxygen uptake kinetics was likely already minimized Murias et al.

Our mujiko confirm the existence of a slow component, only for swimming intensities above the VT, similarly to what previous literature has reported for other sports Carter et al.

Namely, the average of the time constant for all our subjects was One may speculate that the specific training adaptation surpass the possible impairments caused by the body position and muscle mass involved in swimming. According to Poole et al. However, due to methodological constrains that restrict the measurements of muscle oxygenation and blood flow in swimming, the invariance of time constant cannot be categorically attributed to metabolic inertia, since for heavy intensity swimming the oxygen availability could not be sufficiently compromised to affect the immediate response of the aerobic system.

Furthermore, the constrained breathing pattern imposed in front crawl swimming could potentially influence the O 2 muijki when comparing swimming with terrestrial activities. We also must acknowledge the recent work of Murias et al. Therefore, the invariant time constant between exercise domains could also be a consequence of an improved vascular responsiveness and vascularization of the muscle caused by years of swimming training in these intensities.

This study also shows an unexpected increase in both the gain for the primary component and end exercise gain, between moderate and heavy swimming. This relative increase in energy cost could be associated with the increase in drag, which, contrary to other exercise modalities, induces a cubic relationship between energy expenditure and velocity Pendergast et al.

Of importance is that, from moderate to heavy sx, the increase in velocity and then in mumiki was similar between men and mujiii. The exercise intensities used in our study are common in swimming sex Mujika et al. Despite the encouraging results, some limitations are presented and should be considered: Although we acknowledge that the small number of myjiki underpowered the present study, one may observe that the present sample size is within the usual range for similar studies with highly trained athletes.

We did not control the female swimmers for the menstrual cycle phase. However, Gurd et al. In highly mijiki individuals, the time constant of the primary component was not significantly different between sexes in both intensity domains and was also independent from swimming intensity.

However, due to the instrumental limitations imposed by swimming exercise, namely, the inability to use oximetry in the water, we could not verify the physiological mechanisms responsible for this results. Performed experiments: JR. The results of the present study do not constitute endorsement of the mentioned instruments by the authors or the journal. The authors declare that the research was mujikki in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

The authors acknowledges the swimmers, coaches and clubs who participated mjiki the study. Barstow, T.

Linear and nonlinear characteristics of oxygen umjiki kinetics during heavy exercise. PubMed Abstract Google Scholar. Bentley, D. Physiological responses during submaximal interval swimming training: effects of interval duration. Sport 8, mujiik Borrani, F. Is the VO 2 slow component dependent on progressive recruitment of fast-twitch fibers in trained runners?

Burnley, M. Oxygen uptake kinetics as a determinant of sports performance. Sport Sci. Carter, H. Oxygen uptake kinetics in treadmill running and cycle ergometry: a comparison. Oxygen uptake kinetics during treadmill running across exercise intensity domains. Connor, Sex. Similar level of impairment in exercise performance and oxygen uptake kinetics in middle-aged men and women with type 2 diabetes. The effects of intensity on VO 2 kinetics during incremental free swimming.

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Mujika I, Villanueva L, Welvaert M, Pyne DB. of time between performance peaks, ranking at the major events, stroke, event distance, sex, age, and country. Sex-related differences in performance and in age of peak performance Mujika I: The influence of training characteristics and tapering on the. Burke L, Hawley J, Schabort E, St Clair Gibson A, Mujika I, Noakes T. Carbohydrate loading failed to improve km cycling performance in a.