322,998 research outputs found
Analysis of heart rate and lactate concentrations during coordinative tasks : pilot study in karate kata world champions
No full textKata, the artistic part of karate, requires motor control, rhythm and movement differentiation capacities. When performing in a synchronised manner, kata team members have to make temporal and spatial adaptations to satisfy the requested task. It is not clear whether these coordinative adaptations modify physical output such as heart rate (HR) and blood lactate ([La−]) nor is it known how rapidly top-level athletes adapt. This study examined HR and [La−] outputs in different coordinative tasks and how accurately these tasks were done, in three world champion kata team competitors. In session 1, athletes performed their individual best trial (IM) on Gankaku, the kata that is normally executed during final team events. In sessions 2 and 3, the athletes repeated the kata with temporal and spatial variations (TV10 and TV20, SV1 and SV2). In session 4, one maximal team trial (TM) was performed. There was a decreasing trend in both HR and [La−] across the trials (HR: −2% in TV10, −4.2% in TV20, −2.9% in SV1, −3.2% in SV2; [La−]: −23.6% in TV10, −32.6% in TV20, −18% in SV1, −15.9% in SV2), and between IM and TM (HR −9.9%; [La−] − 21.5%). The coordinative tasks were achieved with a small error (<3%) in all subjects. These results indicate that top-level kata athletes easily adapt to coordinative modifications, with a reduction in HR and [La−]. Although this decline does not compromise the competition results, it also occurs when the performance is executed synchronously in a team
Identification and Quantification of Metabolites of the Fungicide Tebuconazole in Human Urine
No full textTebuconazole (TEB) is a fungicide used in agriculture; the objective of this work was to identify and quantify TEB metabolites in human urine. Samples from seven vineyard workers exposed to TEB were submitted to liquid chromatography interfaced with a triple quadrupole mass spectrometer, equipped with an electron spray source, and a linear ion trap to gain a profile of candidate metabolites. Based on the presence of the ion m/z 70 in the MS/MS spectra, which corresponds to protonated triazole (a specific moiety of TEB), and the isotopic pattern of the molecular ions, typical of molecules with one chlorine atom, hydroxyl and carboxyl derivatives of TEB, that is, TEB-OH and TEB-COOH, were identified as major metabolites, both as free molecules and as glucuronide (Glc) conjugates. The mean molar fractions were 0.67, 0.13, 0.13, and 0.07 for TEB-O-Glc, TEB-OH, TEB-COO-Glc, and TEB-COOH. Urine samples were submitted to hydrolysis with β-glucuronidase, and the free compounds were quantified in the presence of deuterated TEB (TEB-d6) as the internal standard (IS), by multiple reaction monitoring (MRM) mode. The assay was linear in the ranges of 0.2-600 μg/L and 0.1-240 μg/L for TEB-OH and TEB-COOH, respectively; precision, accuracy, and the limit of quantification (LOQ) were <3.1%, 98-103%, and 0.3 μg/L for both analytes. An evaluation of matrix effects showed that the use of TEB-d6 controlled these sources of bias. The urinary levels of TEB-OH and TEB-COOH in specimens collected from farmers exposed to TEB ranged from 10 to 473 and from 3 to 159 μg/L, respectively
Identification of Metabolites of the Fungicide Penconazole in Human Urine
No full textPenconazole (PEN) is a fungicide
used in agriculture that has been
classified as hazardous to humans and the environment. The objective
of this work was to identify PEN urinary metabolites in humans and
propose a biomarker for PEN exposure. Five urine samples were collected
from agricultural workers who worked with and were exposed to PEN.
Samples were analyzed by liquid chromatography coupled with hybrid
triple quadrupole-linear ion trap mass spectrometry, with the source
operating in the electrospray ionization mode. Metabolites previously
identified in animal studies were searched as possible metabolites
in humans. Candidate metabolites were first identified by multiple
reaction monitoring following the protonated molecular ions that generated
the protonated triazole moiety, which is expected to be present in
all PEN metabolites; second, the isotopic patterns of the molecular
ions were checked for consistency with the presence of two chlorine
atoms; third, the full mass spectra were evaluated for consistency
with the molecular structure. Seven different oxidized metabolites
were found, both in the free and glucuronide conjugate forms. The
major metabolite was the monohydroxyl-derivative PEN-OH (median molar
fraction approximately 0.92 as a sum of free and glucuronide conjugated
form). The product of further oxidation was the carboxyl-derivate
PEN-COOH (median molar fraction approximately 0.03). After hydrolysis
with β-glucuronidase, the free compounds were quantified in
the presence of deuterated PEN as an internal standard; PEN-OH levels
ranged from 230 to 460 μg/L, and PEN-COOH levels ranged from
5.2 to 16.7 μg/L. We propose a pathway for PEN metabolism in
humans and suggest PEN-OH, after hydrolysis of glucuronide conjugates,
as a biomarker for monitoring human exposure to PEN
Relationships between swimming style and dry-land strength in breaststroke
No full textIn breaststroke, at each arm action corresponds one leg kick; therefore, compared to the other strokes (front crawl, backstroke and butterfly), the contribution of the lower limbs is more important. However, it can be observed that the same distance can be covered at similar velocities with different stroke length (SL) and, as a consequence, stroke rate (SR). Hence, it seems that breaststroke swimmers can use different styles to achieve their goals. Therefore, the assessment of upper and lower limbs strength becomes very important along with the style being used during breaststroke performance. Twenty-four male and twenty female national-level breaststroke swimmers were divided in two groups for each gender, according to their SR (low-SR and high-SR). They performed 100 m breaststroke all-out performance in a 50 m swimming pool. SR, SL and velocity (v) were measured. To assess upper and lower limbs strength, swimmers underwent dry-land chin-up and jump & reach tests. Dry-land tests did not correlate to v (p > 0.05). SL inversely correlated to chin-up and directly correlated to jump & reach (p < 0.01). Regardless to the gender, low-SR had lower chin-up results than high-SR (males 0.19 ± 0.03 vs. 0.24 ± 0.04 nr kg-1, p < 0.01; females 0.13 ± 0.02 vs. 0.15 ± 0.03 nr kg-1, p < 0.05) and jumped higher than high-SR (males 31.74 ± 0.50 vs. 25.11 ± 0.55 % height, p < 0.001; females 22.93 ± 0.33 vs. 20.54 ± 0.63 % height, p < 0.01) swimmers. Despite many factors are involved in determining swimming performance, upper and lower limbs strength seems to be linked to a different breaststroke style in our group of swimmers
Erratum: Correlation between two propulsion efficiency indices in front crawl Swimming Sport (Sci Health) (2009) vol. 5 (43))
No full textHydrodynamic skills in young swimmers : repeatability of some gliding tests
No full textINTRODUCTION. Analysis conducted in swimming competitions of distances up to 400m pointed out that the first 15m play an important role for the result of the entire performance. Hence the hydrodynamic ability to glide underwater in a streamline position should not be neglected during training, especially in young competitors. AIM The purpose of this study was to identify some tests to evaluate gliding skills in young swimmers, which might be repeatable and correlated to their performances in 15m crawl and breaststroke. MATERIAL AND METHODS Fifteen males (M, mean±SD, age 16.5±1.9 years, height 180±8 cm, body mass 69.3±11.3 kg) and sixteen females (F, mean±SD, age 15.6±1.5 years, height 170±6 cm, body mass 57.4±6.3 kg) at national level were tested. After familiarisation, participants were positioned on a starting block and asked to dive and swim for 15m crawl (CR) and 15m breaststroke (BR) in two different trials. Later subjects underwent a series of hydrodynamic tests such as: diving and gliding underwater in a streamline position for 8m (DG), pushing off from the wall and gliding underwater in a streamline position for 8m (PG), pushing off from the wall, gliding and swimming crawl for 12.5m (PGC), pushing from the wall, gliding and swimming breaststroke for 12.5m (PGB), sculling while floating on the back for 10m (SC). Time was recorded and all tests were repeated five times on the same day and again on a different day to assess their repeatability. RESULTS Repeatability was assessed through intraclass correlation coefficient (ICC: DG=0.90 vs 0.84, PG=0.89 vs 0.88, PGC=0.85 vs 0.81, PGB=0.88 vs 0.76, SC=0.84 vs 0.63, M and F respectively). M performed significantly better than F in all trials (mean±SD, CR=6.16±0.4 vs 6.88±0.2 s, BR=7.74±0.4 vs 8.58±0.5 s, DG=2.16±0.3 vs 2.61±0.2 s, PG=4.10±0.6 vs 4.62±0.6 s, PGC=5.27±0.2 vs 6.06±0.2 s, PGB=7.07±0.4 vs 8.08±0.5 s, SC=9.52.±0.7 vs 10.60±0.6 s , p<0.02, M and F respectively). Tests significantly correlated with both CR (CR vs DG r=0.83, CR vs PG r=0.68, CR vs PGC r=0.93, CR vs PGB r=0.76, p<0.01) and BR (BR vs DG r=0.77, BR vs PG r=0.67, BR vs PGC r=0.84, BR vs PGB r=0.83, p<0.01) performances. CONCLUSIONS The tests carried out on the groups were repeatable and the male group performed better than the female group. According to the literature, these gliding tests correlated well with the performance in 15m crawl and breaststroke, factors which highly influence the results in sprint competitions
Visual feedback and motor control in swimming and walking
No full textIntroduction. In swimming, sensory-perception is strictly related to the so called “feel of the water” and to the ability in reducing the drag forces. Anyway the visual feedback, that has a basic role in the motor control and learning and that supports the swimmers in displacements along a straight direction when they swim in a lane, does not attend so easily in open water events. This study aimed to analyze the consequences of a visual deprivation both in walking exercise and in swimming. Methods 20 young swimmers, aged 8 to 11 years, participated to the study. After a familiarization to perform the trials at low to middle intensity, subjects underwent three tests both in visual feedback (VF) and in visual deprivation (VD) conditions: 25m front crawl and 25m backstroke in a double-wide lane set; 25m walking along a line in a gymnasium set. They were surveyed: i) stroke length (SL) and stroke rate in the first 10m of the swim tests (i.e. until no deviations were detected); ii) amplitude (PA) and frequency of the path in the first 10m of the walking test; iii) velocity (v) in the first 10m; iv) deviations of displacements from the straight direction; v) limbs dominance, vi) side of breathing in the 25m crawl. Results SL and PA significantly lowered (p<0.05) in VD (SL crawl: 1.8±0.27 vs 0,97±0.26, m/stroke; SL backstroke: 1.41±0.37 vs 1.16±0.25, m/stroke; PA: 1.16±0.19 vs 0.76±0.17, m; VF vs VD, respectively). In VD the velocities also decreased (Crawl: from 0.87±0.09 to 0.76±0.22, m/s; Backstroke: from 0.87±0.17 to 0.75±0.16, m/s; Walking: from 0.93±0.21 to 0.70±0.19, m/s; VF vs VD, respectively). Furthermore, subjects showed significant correlations between the side of the deviation and: 1) the side of breathing in the 25m crawl (p<0.01); 2) the lower limb dominance (p<0.01). Discussion There is evidence that visual deprivation significantly decreased the velocity of the displacements, both in swimming and in walking. The main effect of this deceleration is that the amplitude of SL and PA (i.e. the cinematic variables most related to the motor control and to the technical skills management) shortened. Visual deprivation probably induced subjects to displace more carefully, dropping the intensity of the actions in both the environments. The correlations between the side of the deviations and either the side of breathing in the 25m crawl and the lower limb dominance show that symmetry of the actions highly affects the spatial guidance. It can be concluded that in young swimmers, even in a simple task such as displacing at low to middle velocity for short distance, visual deprivation significantly modifies the output of the movements. References Novàk, J. (1982). Swimming direction and visual control. V Congress in Biomechanics and medicine in swimming (Amsterdam, Netherlands). Champaign, IL: Human Kinetics, 345-347
Efectos de rendimiento de la brazada y de la patada en el estilo braza en dos categorías juveniles de natación agonística
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