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At least 1,387 records · Page 77Linked to original sources
PubMed2002

Growth status and estimated growth rate of young distance runners.

A mixed-longitudinal design was used to evaluate the growth status (size attained) and estimated growth rate of competitive young distance runners. Twenty-seven male and 27 female distance runners were enrolled in the study based on race performance times. Ages ranged from 8.0 to 15.1 years at initial visit. Twenty males and 16 females were followed at approximate annual intervals for 4 or 5 years. Stature (cm) and body mass (kg) were measured on each occasion and annual growth velocities were estimated. Stature and body mass were plotted relative to age- and sex-specific U.S. reference data, while estimated velocities of stature (cm/yr) and body mass (kg/yr) were plotted relative to age- and sex-specific percentiles from the Zurich Longitudinal Study. Differences in growth pattern between the runners and the reference values were compared statistically with a growth curve estimation regression model. Mean statures of male and female distance runners approximate the reference medians, while mean body masses are slightly below reference medians. Mean stature and body mass also maintain a constant position relative to the reference values in both sexes over time. Estimated velocities for stature and body mass are, on average, similar to age- and sex-specific medians for Swiss youth. Slope values indicate no significant difference in growth patterns between young distance runners and reference values. The findings are consistent with other data indicating that intensive endurance training during childhood and adolescence does not influence size attained and rate of growth in stature and body mass.

Adolescent↗
PubMed2002

Myosin heavy chain composition of single muscle fibers in male distance runners.

The purpose of this study was to characterize the myosin heavy chain (MHC) composition of single muscle fibers from the gastrocnemius of male collegiate distance (DIST; n = 7), middle-distance (MID; n = 6), and recreational runners (REC; n = 6). Additionally, mATPase histochemistry was used to serve as a comparison to previous studies and the single fiber MHC technique. SDS-PAGE of single muscle fibers revealed a higher proportion of MHC I in DIST compared to MID and REC (74.9 +/- 4.3 vs 54.4 +/- 2.8 vs 56.2 +/- 2.9 %, respectively; p < 0.05), less MHC IIa/IIx in DIST compared to MID and REC (0.0 +/- 0.0 vs 6.0 +/- 2.4 vs 15.9 +/- 4.2 %, respectively; p < 0.05), and more total hybrids (I/IIa+IIa/IIx+I/IIa/IIx) in REC than both run groups, DIST and MID (23.0 +/- 3.3 vs 6.2 +/- 1.1 vs 13.2 +/- 2.6 %, respectively; p < 0.05). ATPase histochemistry (pH 4.54) revealed a higher percentage of type I fibers in DIST compared to MID and REC (71.1 +/- 3.1 vs 56.3 +/- 2.5 vs 59.8 +/- 2.3 %, respectively; p < 0.05), a higher percentage of type IIa in MID compared to DIST and REC (43.3 +/- 2.7 vs 28.5 +/- 3.1 vs. 30.2 +/- 3.1 %, p < 0.05), and a higher distribution of type IIb in REC than both run groups (10.0 +/- 2.7 vs 0.4 +/- 0.2 vs 0.4 +/- 0.2 %, p < 0.05). These results suggest that distance running leads to an increase in MHC I expression, training for mid-distance events leads to a prevalence of MHC IIa, and run training leads to a decrease in hybrid fibers.

Adult↗
PubMed2005

[Osteoarthritis from long-distance running?].

Long distance running has become a fashionable recreational activity. This study investigated the effects of external impact loading on bone and cartilage introduced by performing a marathon race. Seven beginners were compared to six experienced recreational long distance runners and two professional athletes. All participants underwent magnetic resonance imaging of the hip and knee before and after a marathon run. Coronal T1 weighted and STIR sequences were used. The pre MRI served as a baseline investigation and monitored the training effect. All athletes demonstrated normal findings in the pre run scan. All but one athlete in the beginner group demonstrated joint effusions after the race. The experienced and professional runners failed to demonstrate pathology in the post run scans. Recreational and professional long distance runners tolerate high impact forces well. Beginners demonstrate significant changes on the post run scans. Whether those findings are a result of inadequate training (miles and duration) warrant further studies. We conclude that adequate endurance training results in adaptation mechanisms that allow the athlete to compensate for the stresses introduced by long distance running and do not predispose to the onset of osteoarthritis. Significant malalignment of the lower extremity may cause increased focal loading of joint and cartilage.

Adult↗
PubMed2006

Intra-cyclic distance per stroke phase, velocity fluctuations and acceleration time ratio of a breaststroker's hip: a comparison between elite and nonelite swimmers at different race paces.

The aim of this study was to compare the intra-cyclic velocity graphs of breaststroke swimmers at two skill levels in relation to their movement phases. Two groups of nine male swimmers were videotaped underwater at three swimming race paces corresponding to their actual competitive times for the 200-m, 100-m and 50-m breaststroke. Their forward intra-cyclic hip velocity was recorded with a velocity-meter. The breaststroke cycle was divided into four phases: leg propulsion, leg-arm lag phase, arm propulsion, and arm and leg recovery. From the velocity-time data, the following parameters were computed: an index of velocity fluctuations (IVF), the distance covered during each stroke phase, and an acceleration-deceleration time ratio (ADTR). The main results showed that in both groups of swimmers, when the race pace increased, the distance covered during the leg-arm lag phase decreased, while the other swimming phases remained stable. When expressed in relative values, the percentage of distance covered during the leg-arm lag phase decreased. In nonelite swimmers, the percentage of distance covered in the other stroke phases increased significantly, while only a tendency was noted in the elite group. Elite swimmers demonstrated a higher ADTR at the 50-m pace than at their 100-m and 200-m paces. An inter-group comparison showed that elite swimmers had higher values for the IVF and ADTR, which indicated their capacity to accelerate to boost the swim and highlighted the relevancy of these factors to discriminate skill level.

Acceleration↗
PubMed1994

Body-mass-modified running economy and step length in elite male middle- and long-distance runners.

To minimize the influence of body mass on oxygen uptake (VO2) during running, submaximal and maximal VO2 should preferentially be expressed as ml.kg-0.75.min-1. In this study, the levels of such body-mass-modified running economy were investigated at different velocities in elite runners and related to step lengths and anthropometric measures. Twenty-six Swedish National Team middle- and long-distance runners performed submaximal (4 velocities) and maximal treadmill tests. In 17 runners repeated (2-4) tests were performed within 6 months. The maximal oxygen uptake (VO2max; 214 vs 202 ml.kg-0.75.min-1) and running velocity at 4 mmol.l-1 blood lactate were higher in the long- (n = 12) than in the middle-distance group (n = 14). The oxygen uptake at 15 km.h-1 (VO2 15) was lower (129 vs 138 ml.kg-0.75.min-1, p < 0.01) and the VO2/velocity slope higher in the long-distance runners, with similar VO2 18 in the two groups. Step lengths at 18 (168 vs 173 cm) and 15 km.h-1 did not differ significantly between the groups, but the increase in step length per km.h-1 velocity raise was greater in the middle-distance runners. Step lengths at these velocities were positively related to body mass and stature, negatively to relative leg length. Stature and leg length were greater in runners displaying low VO2 15, whereas no corresponding difference was seen for VO2 18. The figures for running economy at 15 and 18 km.h-1 were poorly related to the concomitantly determined step lengths at the respective velocities.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Reduced training volume and intensity maintain aerobic capacity but not performance in distance runners.

It has recently been shown that a 70% reduction in training volume, while maintaining training intensity, results in the maintenance of VO2 max and 5 km running performance in distance runners. The purpose of this study was to examine the effects of a 4 wk reduction in training volume and intensity in distance runners. Ten well-conditioned males (VO2max = 63.4 +/- 1.3 ml.kg-1 x min-1) underwent 4 wks of base training (BT) at their accustomed training distance (71.8 +/- 3.6 km.wk-1) and intensity (76% of total distance > 70% VO2max). Training volume (-66%), frequency (-50%), and intensity (all running < 70% VO2max) were then decreased for a 4 wk reduced training period (RT). Treadmill VO2max was unchanged with RT (p > 0.05) as were resting plasma volume, estimated from haemoglobin and haematocrit levels, and resting heart rate (HR). Submaximal treadmill exercise VO2 (l.min-1), ventilation and HR were also unchanged, however, submaximal exercise RER and blood lactate accumulation following 4 mins at 95% VO2max (8.39 vs 9.89 mmol.l-1) were significantly elevated by RT (p < 0.05). Estimated percent body fat also increased (10.4% vs 11.8%) (p < 0.05). Five km race completion time significantly increased from 16.6 +/- 0.3 mins at week 4 of BT to 16.8 +/- 0.3 mins (12 seconds) at week 4 of RT. Nine of the 10 subjects were slower after RT. It is concluded that aerobic capacity was maintained in these runners, despite the combined reduction in training volume and intensity. However, it appears that training intensity during RT is important for the maintenance of 5 km running performance.

Adult↗
PubMed1995

Neuromuscular differences between volleyball players, middle distance runners and untrained controls.

Volleyball players, middle distance runners and non-athletes (n = 10/group) were tested to determine whether neuromuscular differences existed between groups and to clarify the roles of factors involved in maximal power production. The runners were leaner than controls, while the volleyball players were taller, heavier and had larger thigh volumes than the other groups. The volleyball players had higher absolute cycle ergometer power than both middle distance (26%) and control (15%) groups, but differences disappeared when expressed relative to body mass or thigh volume. Volleyball athletes were also stronger than both middle distance (51, 52%) and control subjects (33, 35%) for isokinetic leg extension and plantar flexion respectively (0-4.19 rad.s-1). In leg press they were stronger than middle distance (32%) and control subjects (36%) for only the isometric and 1.05 rad.s-1 contraction. The volleyball players also had higher rates of isometric torque development than the other groups, however nerve conduction velocity did not vary. Vastus lateralis biopsy samples revealed no differences in percent Type II muscle fibers, or fiber cross-sectional area between groups, yet volleyball athletes had larger Type II/I fiber area ratio than controls (15%). Both strength, rate of torque development and power were related to muscle and muscle fiber size variables, but not fiber distribution or nerve conduction velocity. The size of type II muscle fibers seemed to be especially important since this was the only variable related to power when adjusted for body size.

Adult↗
PubMed1987

Muscle fiber composition and enzyme activities in elite female distance runners.

This study has attempted to describe the fiber composition and respiratory potential in the leg (gastrocnemius) muscle of highly trained, elite female distance runners. As noted, many of these women were competing successfully in middle-distance (1500-3000 m) rather than long distance (10 km and marathon) events. This fact appears to explain many of the differences observed between these "elite female runners" and the "elite male runners" studied in the 1975 Dallas study (6). With the exception of differences in muscle fiber areas, the female runners appear to show the same enzyme adaptations to endurance training that have been reported for male runners. The most notable finding of this study was the remarkable similarity of muscle fiber composition and enzyme activity for male and female runners when matched according to their preferred competitive distance.

Capillaries↗
PubMed1981

Early post-infarction angina. Ischemia at a distance and ischemia in the infarct zone.

We studied two forms of post-infarction angina: ischemia at a distance (angina with new electrocardiographic changes distant from the acute infarct) and ischemia in the infarct zone (angina with new electrocardiographic changes limited to the leads originally involved by the acute infarct). Seventy patients with early post-infarction angina were followed for an average of six months; 43 had ischemia at a distance, and 27 had ischemia in the infarct zone. Mortality in the entire group was 56 per cent, but it was 72 per cent (31 of 43 patients) among those with ischemia at a distance and 33 per cent (nine of 27) among those with ischemia in the infarct zone (P less than 0.005). Post-infarction angina identifies patients with high mortality; among such patients, ischemia at a distance may represent an especially high-risk subset of patients with large areas of viable but jeopardized myocardium who could benefit from aggressive intervention.

Aged↗
PubMed2005

Distance measurements between paramagnetic centers and a planar object by matrix Mims electron nuclear double resonance.

Frequency-domain electron nuclear double resonance (ENDOR), two time-domain electron nuclear double resonance techniques, and electron spin echo envelope modulation spectroscopy are compared with respect to their merit in measurements of small hyperfine couplings to nuclei with intermediate gyromagnetic ratio such as 31P. The frequency-domain Mims ENDOR experiment is found to provide the most faithful line shapes. In the limit of long electron-nuclear distances of more than 0.5 nm, sensitivity of this experiment is optimized by matching the first interpulse delay to the transverse relaxation time of the electron spins. In the same limit, Mims ENDOR efficiency scales inversely with the sixth power of distance. Hyperfine splittings as small as 33 kHz can be detected, corresponding to an electron-31P distance of 1 nm. In systems, where a certain kind of nuclei is distributed in a plane, measurements of intermolecular hyperfine couplings can be analyzed in terms of a distance of closest approach of a paramagnetic center to that plane. By applying this technique to spin-labeled lipids in a fully hydrated lipid bilayer it is found that for a fraction of lipids, chain tilt angles can be 25 degrees larger than the mean tilt angle of the lipid chains. This model of all-trans hydrocarbon chains with a broad distribution of tilt angles is also consistent with orientation selection effects in high-field ENDOR spectra.

Journal Article↗
PubMed2005

Using fluorescence resonance energy transfer to measure distances along individual DNA molecules: corrections due to nonideal transfer.

Single molecule fluorescence resonance energy transfer has been extensively used to measure distance changes and kinetics in various biomolecular systems. However, due to complications involving multiple de-excitation pathways of the dyes, the absolute inter-dye distance information has seldom been recovered. To circumvent this we directly probe the relative variations in the quantum yield of individual fluorophores. B-DNA was used as a scaffold to position the donor (Cy3 or TMR) at precise distances from the acceptor (Cy5) within the Forster radius. We found that the variation in the Cy3 quantum yield is approximately 5 times larger than that of TMR. By taking into account the molecule-to-molecule variability in the acceptor/donor quantum yield ratio, the apparent fluorescence resonance energy transfer efficiencies were scaled to yield the theoretical values. We obtained very good agreement with a physical model that predicts distances along B-DNA.

Carbocyanines↗
PubMed1999

Estimator reliability and distance scaling in stereoscopic slant perception.

When a horizontal or vertical magnifier is placed before one eye, a frontoparallel surface appears slanted. It appears slanted away from the eye with horizontal magnification (geometric effect) and toward the eye with vertical magnification (induced effect). According to current theory, the apparent slant in the geometric and induced effects should increase with viewing distance. The geometric effect does scale with distance, but there are conflicting reports as to whether the induced effect does. Ogle (1938 Archives of Ophthalmology 20 604-623) reported that settings in slant-nulling tasks increase systematically with viewing distance, but Gillam et al (1988 Perception & Psychophysics 44 473-483) and Rogers et al (1995 Perception 24 Supplement, 33) reported that settings in slant-estimation tasks do not. We re-examined this apparent contradiction. First, we conducted two experiments whose results are consistent with the literature and thus replicate the apparent contradiction. Next, we analyzed the signals available for stereoscopic slant perception and developed a general model of perceived slant. The model is based on the assumption that the visual system knows the reliability of various slant-estimation methods for the viewing situation under consideration. The model's behavior explains the contradiction in the literature. The model also predicts that, by manipulating eye position, apparent slant can be made to increase with distance for vertical, but not for horizontal, magnification. This prediction was confirmed experimentally.

Adult↗
PubMed2002

Absolute and relative effects of similarity and distance on grouping.

Four experiments are reported, the aim of which was to explore the achromatic-colour and distance relations that determine the probability of achromatic surfaces grouping perceptually. The first two experiments were performed to test Wertheimer's conjecture that similarity and dissimilarity of achromatic colours jointly determine grouping. The results indicate that only similarity of achromatic colours determines grouping. Data from the other two experiments show that grouping is determined by absolute, relative, and Gillam's distances. These findings agree with previous literature showing that different algorithms or mechanisms determine grouping by similarity and grouping by distance. Additionally, these findings show that the single factor of grouping by distance also depends on multiple algorithms or mechanisms.

Form Perception↗
PubMed2005

Single molecule high-resolution colocalization of Cy3 and Cy5 attached to macromolecules measures intramolecular distances through time.

Here we present a technique called single-molecule high-resolution colocalization (SHREC) of fluorescent dyes that allows the measurement of interfluorophore distances in macromolecules and macromolecular complexes with better than 10-nm resolution. By using two chromatically differing fluorescent molecules as probes, we are able to circumvent the Rayleigh criterion and measure distances much smaller than 250 nm. The probes are imaged separately and localized individually with high precision. The registration between the two imaging channels is measured by using fiduciary markers, and the centers of the two probes are mapped onto the same space. Multiple measurements can be made before the fluorophores photobleach, allowing intramolecular and intermolecular distances to be tracked through time. This technique's lower resolution limit lies at the upper resolution limit of single molecule FRET (smFRET) microscopy. The instrumentation and fluorophores used for SHREC can also be used for smFRET, allowing the two types of measurements to be made interchangeably, covering a wide range of interfluorophore distances. A dual-labeled duplex DNA molecule (30 bp) was used as a 10-nm molecular ruler to confirm the validity of the method. We also used SHREC to study the motion of myosin V. We directly observed myosin V's alternating heads while it walked hand-over-hand along an actin filament.

Animals↗
PubMed2002

Zinc finger as distance determinant in the flexible linker of intron endonuclease I-TevI.

I-TevI, the phage T4 td intron-encoded endonuclease, recognizes a lengthy DNA target and initiates intron mobility by introducing a double-strand break in the homing site. The enzyme uses both sequence and distance determinants to cleave the DNA 23-25 bp upstream of the intron insertion site. I-TevI consists of an N-terminal catalytic domain and a C-terminal DNA-binding domain separated by a long, flexible linker. The DNA-binding domain consists of three subdomains: a zinc finger, a minor-groove binding alpha-helix, and a helix-turn-helix. In this study, a mutational analysis was undertaken to assess the roles of these subdomains in substrate binding and cleavage. Surprisingly, the zinc finger is not required for DNA binding or catalysis. Rather, the zinc finger is a component of the linker and directs the catalytic domain to cleave the homing site at a fixed distance from the intron insertion site. When the cleavage site (CS) is shifted outside a given range, wild-type I-TevI defaults to the fixed distance, whereas zinc-finger mutants have lost the distance determinant and search out the displaced cleavage sequences. Although counterintuitive, a protein containing a 19-aa deletion of the zinc finger can extend further than can wild-type I-TevI to cleave a distant CS sequence, and a Cys-to-Ala mutant of the ligands for zinc, nominally a longer protein, can retract to cleave at a closer CS sequence. Models are presented for the novel function of the zinc finger, as a molecular constraint, whereby intramolecular protein-protein interactions position the catalytic domain by "catalytic clamp" and/or "linker-organizer" mechanisms.

Base Sequence↗
PubMed2003

Long-distance root-to-shoot transport of phytochelatins and cadmium in Arabidopsis.

Phytochelatin synthases (PCS) mediate cellular heavy-metal resistance in plants, fungi, and worms. However, phytochelatins (PCs) are generally considered to function as intracellular heavy-metal detoxification mechanisms, and whether long-distance transport of PCs occurs during heavy-metal detoxification remains unknown. Here, wheat TaPCS1 cDNA expression was either targeted to Arabidopsis roots with the Arabidopsis alcohol dehydrogenase (Adh) promoter (Adh::TaPCS1/cad1-3) or ectopically expressed with the cauliflower mosaic virus 35S promoter (35S::TaPCS1/cad1-3) in the PC-deficient mutant cad1-3. Adh::TaPCS1/cad1-3 and 35S::TaPCS1/cad1-3 complemented the cadmium, mercury, and arsenic sensitivities of the cad1-3 mutant. Northern blot, RT-PCR, and Western blot analyses showed Adh promoter-driven TaPCS1 expression only in roots and thus demonstrated lack of long-distance TaPCS1 mRNA and protein transport in plants. Fluorescence HPLC analyses showed that under Cd2+ stress, no PCs were detectable in cad1-3. However, in Adh::TaPCS1/cad1-3 plants, PCs were detected in roots and in rosette leaves and stems. Inductively coupled plasma atomic emission spectrometer analyses showed that either root-specific or ectopic expression of TaPCS1 significantly enhanced long-distance Cd2+ transport into stems and rosette leaves. Unexpectedly, transgenic expression of TaPCS1 reduced Cd2+ accumulation in roots compared with cad1-3. The reduced Cd2+ accumulation in roots and enhanced root-to-shoot Cd2+ transport in transgenic plants were abrogated by l-buthionine sulfoximine. The presented findings show that (i) transgenic expression of TaPCS1 suppresses the heavy-metal sensitivity of cad1-3, (ii) PCs can be transported from roots to shoots, and (iii) transgenic expression of the TaPCS1 gene increases long-distance root-to-shoot Cd2+ transport and reduces Cd2+ accumulation in roots.

Aminoacyltransferases↗
PubMed1980

Role of minimization of chemical distances between amino acids in the evolution of the genetic code.

The allocation of codons in the genetic code makes possible a moderate minimization of the chemical distances between pairs of neighboring amino acids in the code. However, the code is neither a global nor a local optimum with respect to distance minimization. These findings do not support the physicochemical postulate that distance minimization was a major factor shaping the evolution of the genetic code. They agree with the coevolution theory, which proposes that genetic code evolution was predominantly determined by the concession of codons from precursor to product amino acids in an expansion of the code to accommodate new varieties of amino acids, with distance minimization playing a subsidiary role in deciding the choice of codons to be acquired by the product amino acids from the codon domains of the precursor amino acids.

Amino Acids↗
PubMed1986

Distance between substrate sites on the Na-glucose cotransporter by fluorescence energy transfer.

Covalent fluorescent probes were used to label the rabbit intestinal brush border Na+-glucose cotransporter at the putative glucose and Na+ binding sites, and a steady-state fluorescence energy transfer technique was used to measure the distance between the two binding sites. In both intact brush border membrane vesicles and partially purified soluble protein, the distance (R2/3) between the Na+ and glucose sites was approximately equal to 35 A. This distance was the same with four different donor/acceptor pairs with different transfer efficiencies, by donor quantum yield measurements, or sensitized acceptor fluorescence. The fact that the Na+ site and glucose site probes bind to a 75-kDa polypeptide, copurify with the same isoelectric point (pI 5.3) and retain function, and exhibit energy transfer indicates that the sites are on the same 75-kDa polypeptide. The large distance between the Na+ and glucose site probes raises questions about simple models of frictional interactions between the two substrates during the transport cycle.

Animals↗