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At least 1,369 records · Page 76Linked to original sources
PubMed2005

Somatic and physical traits affecting sprint swimming performance in young swimmers.

The aim of this study was to examine the relationship between anthropometry, physical capacity, and sprint swimming performance in swimmers of both genders aged 12 - 14 years old. Anthropometric characteristics (body height and mass, total upper extremity, hand and foot lengths, chest circumference, certain body breadths, and skinfolds), as well as leg explosiveness (horizontal jump) and arm strength (handgrip strength test) were evaluated in 263 competitive swimmers (178 boys and 85 girls) aged 12 - 14 years. Skeletal age was assessed with the Tanner-Whitehouse method. All variables, except for the ankle and shoulder flexibility as well as the skeletal age, correlated with 100 m freestyle performance in boys (r = - 0.46 to - 0.73, p < 0.01). Using a split-sample approach, upper extremity length, horizontal jump, and grip strength were detected as significant predictors of 100 m freestyle performance in boys (R (2) = 0.59, p < 0.01). In girls, body height, upper extremity and hand length, shoulder flexibility, and horizontal jump were all significantly related to 100 m freestyle time (r = - 0.22 to - 0.31, p < 0.05) but the degree of association was markedly lower than in boys. In addition, only 17 % of the variance in performance was explained by a combination of body height, hand length, and horizontal jump in girls. These results suggest that 100 m freestyle performance can be partially explained by anthropometry and physical capacity tests in young swimmers. The contribution of these factors to sprint swimming performance is different in boys and girls and this requires further research. These findings could be used for male young swimmers' selection.

Adolescent↗
PubMed2004

Removal of a foreign body from the upper gastrointestinal tract with a flexible endoscope: a prospective study.

BACKGROUND AND STUDY AIMS: There have so far been no prospective studies on the value of flexible endoscopy for removing foreign bodies in the upper gastrointestinal tract. This study presents a clinical analysis of accidents with foreign bodies and prospectively evaluates the effectiveness of flexible endoscopy for removing them. PATIENTS AND METHODS: A total of 105 cases of foreign-body ingestion in the upper gastrointestinal tract were evaluated, 29 (27.6 %) in children and 76 (72.4 %) in adults. Thirty patients (28.5 %) had esophageal strictures. RESULTS: Thirty-nine of the foreign bodies (37.1 %) consisted of food and 66 (62.9 %) were not food-related. The success rate of foreign-body extraction using only a conventional flexible endoscope and accessories for treatment was 98.0 %, and with only a polypectomy snare and rat-toothed forceps it was 91.2 %. Complications at the moment of foreign-body removal occurred in nine patients (8.6 %); there was only one (1 %) esophageal perforation. The incidence of complications related to the duration of foreign-body impaction was six (10.5 %) with foreign bodies impacted for up to 24 h, 13 (52.0 %) for those impacted for 24-48 h, and three (60.0 %) for those impacted for 48-72 h ( P < 0.05). CONCLUSIONS: The flexible endoscope is an effective and safe device for removing foreign bodies from the upper gastrointestinal tract, with a high success rate using only the polypectomy snare and the rat-toothed forceps as accessories. If foreign-body impaction lasts for more than 24 h, there is a significant increase in the incidence of complications.

Adult↗
PubMed2007

Does chemotherapy impair the bone healing and biomechanical stability of vascularized rib and fibula grafts?

The purpose of this study was to observe the impact of chemotherapy on the healing and biomechanical properties of vascularized bone grafts. Ten male beagle dogs were divided into two experimental groups: a chemotherapy group (CH) and control group (C). Group CH received adjuvant and neo-adjuvant chemotherapy. Each animal of both groups underwent the following operative procedures. The 5th and 7th rib were removed and replaced by vascularized pedicle transfers of the adjacent 4th and 8th rib. Additionally, a free fibular flap was elevated and retransferred to the same anatomic position. The rate of bony union on plain x-ray was 100 percent in group C, 30 percent in the vascularized rib, and 80 percent in the fibula grafts of group CH. Microangiography demonstrated no avascular bone segments in group C and in the fibula flaps of group CH. The vascularized ribs of group CH presented with 20 percent avascular bone segments. Biomechanical tests focusing on the durability of the vascularized grafts against bending and torsion forces demonstrated a reduction of the average maximum bending times by 17 percent and 23.9 percent compared to the controls ( P < 0.05). The twisting times were reduced by 13.8 percent (n.s.) and 32.5 percent ( P < 0.05). The data demonstrated a clear worsening in bone healing and stability after simulated adjuvant and neo-adjuvant chemotherapy. Thus, a large animal model was established for the further determination of the effects of chemotherapy on different vascularized bone transfers.

Angiography↗
PubMed1999

Physiological characteristics of well-trained synchronized swimmers in relation to performance scores.

The purpose of this study was to examine the relationships between the physiological characteristics of synchronized swimmers and their performance scores. The subjects were 16 trained female synchronized swimmers with a mean age of 17.2 +/- 1.7 years (mean +/- SD). The examined variables were body dimensions (height, width, body mass, circumference of the body and segment length), body composition, isokinetic muscle strength of the elbow and knee during extension and flexion, abdominal muscle endurance, anaerobic power (leg extension power and peak blood lactate concentration), aerobic power (maximum oxygen uptake [VO2max], swimming velocity at the onset of blood lactate accumulation [OBLA-V]), and flexibility (standing trunk flexion, prone trunk extension and distance between the open legs). The performance scores had significant correlations (p < 0.05) with isokinetic muscle strength of the elbow extension and flexion, and the knee extension, abdominal muscle endurance, leg extension power, VO2max x wt(-1), OBLA-V and distance between the open legs. However, no significant correlations were found between the performance scores and anthropometric variables. This study showed that the performance scores of synchronized swimmers correlated significantly with the functional aspects, and that muscle strength, muscle endurance and aerobic capacity seem to be particularly important determinants.

Adolescent↗
PubMed1999

The effects of rest and subsequent training on selected physiological parameters in professional female classical dancers.

The purpose of this study was to assess the effects of a six-week summer break and of dance preparations at the beginning of the new season following the break, on selected physiological parameters. Seventeen professional ballerinas (mean age 27.2 +/- 1.4 years, mean height 160.2 +/- 6.2 cm) volunteered. They were assessed just before and immediately after their normal summer break, during which very little or no physical work was reported. Eight of these dancers were assessed for a third time, 2-3 months after the end of the break, while they were into preparing for the new season. More specifically, compared to pre-break data, the six-weeks of holiday was followed by a 15% overall increase in the three flexibility tests (from 334 to 386 degrees, P < 0.01), a 14% increase in peak anaerobic power (from 350 to 400 watts; P < 0.01), a 16% increase in leg strength (from 143 to 166 Nm; P < 0.01) (i.e. the mean performance of left and right knee extension added to the mean performance of left and right knee flexion), and a 10% increase in VO2max (from 41.2 to 45.2 ml/kg/min; P < 0.05). The third set of data, 2-3 months after the end of the break, revealed further significant increases by 24% in leg-strength (P < 0.005) and 17% in VO2max (P < 0.01) compared to pre-holiday data. Despite the lack of a control group, the present results fit with the hypothesis of a degree of "burnout" at the end of the season, which negatively affected the mechanisms of fitness and conditioning. A six-week summer-break can act as a restorer of these mechanisms. Two to three months into the new season, positive adaptations to exercise appeared to confirm recovery from the "burnout" or overtraining phenomenon. More research is required on the effects of demanding dance schedules on fitness and conditioning, and how such schedules might adversely affect dance performance and dancers' careers.

Adult↗
PubMed1998

A biomechanical evaluation of cyclic and static stretch in human skeletal muscle.

The short term effect of static and cyclic stretch paradigms on stiffness and maximal joint range of motion was examined in 12 recreational athletes. To assess flexibility, joint range of motion and resistance to stretch were measured using a dynamometer during a passive stretch of the hamstring muscle group to the point of pain. The recorded torque-angle curve allowed for identification of maximal joint range of motion and calculation of passive muscle-tendon stiffness and energy. Three flexibility assessments (stretch 1 - 3), each 10 min apart, were administered to each leg. A 90 s static stretch and 10 cyclic stretches were performed after the second stretch on the left and right side, respectively. Stiffness in a common range for stretch 1 - 3 was unchanged on both the left and right side. However, on the left side (static stretch) there was a significant effect of flexibility assessment (stretch 1 - 3) (p < 0.0001) with an increased maximal joint angle (p < 0.01) and maximal stiffness (p < 0.05) between all three stretches. Similarly, on the right side (cyclic stretches) there was a significant effect of flexibility assessment (p < 0.0001) with an increased maximal joint angle between stretch 1 and 3 (p < 0.01) and maximal stiffness (p < 0.05) between all stretches. During the static stretch passive torque declined 35+/-4% (p < 0.001). During the cyclic stretches passive energy and hysteresis both declined 17% (p < 0.05) while stiffness increased 12% (p < 0.05). The results of the present study demonstrate that static and cyclic stretching, as it is commonly performed by athletes, increases joint range of motion by increasing stretch tolerance while the viscoelastic characteristics of the muscle remain unaltered.

Adult↗
PubMed1997

Physical characteristics as risk factors for sports injuries: a four year prospective study.

A variety of physical characteristics of athletes has been proposed to be related to the risk to sustain a sports injury. The aim of the present study was to determine the influence of flexibility, anthropometric characteristics and malalignment of the lower extremities on the risk to sustain a sports injury, using a prospective study design and subjects exposed to rather equal extrinsic risk factors. Physical education students (N = 136) were followed during their four-year education. Sixteen flexibility indices, four anthropometric characteristics and five malalignment indices of the lower extremities were assessed at the start of the study and all sports injuries sustained in that four-year period were recorded. No influence of flexibility or anthropometric variables on the total number of injuries or the number of several specific injuries (ankle sprain, muscle rupture, dislocation, shin splints, backache) could be established. Malalignments of the lower extremities (average prevalence 18% and only minor deviations) did show some but inconsistent relations with the number of (specific) injuries. For pelvic obliquity it was positive as predicted, but for malalignment of the rearfoot and a deviant footprint it appeared to be negative. Leg length inequality and malalignment of the knees were not related to injuries. The most likely explanation for these (poor) findings is the relatively low number and great variety of sports injuries recorded. Further, the homogeneity in physical characteristics of the population under study makes it difficult to find significant relationships. A study design that meets both the criterium of similar extrinsic risk factors and that of a wide range of physical characteristics in a representative sporting population, however, is not practicable.

Adolescent↗
PubMed1997

Knee flexion to extension peak torque ratios and low-back injuries in highly active individuals.

The purpose of this study was to investigate for possible relationships between knee flexion to extension peak torque ratios (F1/Ext(rat)) and low-back injuries in highly active males and females. Forty-eight male (age 25.9 +/- 4.5 years) and 41 female (age 27.3 +/- 2.6 years) competitive rowers, and 20 male (age 26.6 +/- 6.0 years) professional ballet dancers volunteered for the study. Each subject performed a test of lumbar and knee flexor flexibility, isokinetic dynamometry and completed a self-administered questionnaire. Flexibility was assessed by using the sit-and-reach test. Knee flexion to extension peak torques were bilaterally monitored at the angular velocities of 1.04 and 4.19 rad x s(-1). The questionnaire was designed to obtain information regarding the number of days off action (e.g., training, competition, and rehearsals), due to low-back injuries, for the 12-month period prior to testing. Results revealed significant negative correlation coefficients between knee F1/Ext(rat), obtained at 1.04 rad x s(-1), and days off physical activity for oarsmen (r = - 0.69; p < 0.01), oarswomen (r = -0.62; p < 0.01) and male dancers (r = -0.57; p < 0.05). No such correlations were found for either knee F1/ Ext(rat) obtained at the angular velocity of 4.19 rad x s(-1) or between the sit-and-reach test results and low-back injuries. A sub-group of 22 female rowers was re-tested after a 6-8 month period, during which a special hamstring strength training programme was introduced. The main conclusions were: a) the lower the F1/Ext(rat) the greater the degree of low-back injury, b) at least in female rowers, 6-8 months of hamstring strength training can contribute to a reduction of the incidence of low-back injury, and c) isokinetic assessment of quadriceps and hamstrings obtained at lower compared to higher angular velocities is more prognostic of low back injury.

Adult↗
PubMed1996

The stabilizing effect of orthotic devices on plantar flexion/dorsal extension and horizontal rotation of the ankle joint. An experimental cadaveric investigation.

The mechanical stabilizing effect of nine different orthotic devices on physiological and pathological plantar flexion/dorsal extension and horizontal rotation of the ankle joint subjected to artificial lateral ligament lesions was investigated in 20 cadaveric ankle joints under standardized conditions using an experimental apparatus. All of the braces tested significantly reduced plantar flexion/dorsal extension, as well as internal/external/external horizontal rotation, under the experimental conditions. In so far as these results can be transposed into a clinical setting, our data favour that bracing significantly reduces the instability. But, other criteria, such as the stabilizing effect on talar tilt and anterior drawer sign, the price and the convenience of wearing such devices have to be taken into consideration when choosing the optimal brace.

Analysis of Variance↗
PubMed1998

A malleable endoscopic suction instrument: technical note.

Flexible endoscopes are being employed for a variety of neurosurgical procedures. These instruments have drawbacks, especially in their ability to evacuate clotted blood. We have attempted to rethink the design of these instruments and have developed a malleable endoscopic suction instrument. This has proved to be helpful in a variety of intracranial and intraspinal procedures.

Endoscopes↗
PubMed1999

Multilevel vertebral body replacement with a titanium mesh spacer for aneurysmal bone cyst: technical note.

A 64-year-old male presented with abrupt tetraparesis caused by a minor impact. Diagnostic images obtained on admission showed an aneurysmal bone cyst visible in the cervical spine at the fourth to upper sixth level, although the patient had been wearing a halo brace to diminish the symptoms. The vertebral body from the fourth to the sixth level was dissected, and this space was packed with a titanium cage filled with ceramic bone fragments mixed with fibrin glue. The combination of a titanium cage and an anterior locking plate can be made easily for anterior spinal fusion with enough rigidity to maintain the necessary space during fusion without any major support equipment. Both edges of the titanium mesh cage cut into the vertebral body to hold the cage in place. The other part, the titanium plate, makes it secure until ceramic bone fragments in the cage promote bony ingrowth for fusion.

Bone Cements↗
PubMed2004

Importance of chirality and reduced flexibility of protein side chains: a study with square and tetrahedral lattice models.

Side chains of amino acid residues are the determining factor that distinguishes proteins from other unstable chain polymers. In simple models they are often represented implicitly (e.g., by spin states) or simplified as one atom. Here we study side chain effects using two-dimensional square lattice and three-dimensional tetrahedral lattice models, with explicitly constructed side chains formed by two atoms of different chirality and flexibility. We distinguish effects due to chirality and effects due to side chain flexibilities, since residues in proteins are L residues, and their side chains adopt different rotameric states. For short chains, we enumerate exhaustively all possible conformations. For long chains, we sample effectively rare events such as compact conformations and obtain complete pictures of ensemble properties of conformations of these models at all compactness region. This is made possible by using sequential Monte Carlo techniques based on chain growth method. Our results show that both chirality and reduced side chain flexibility lower the folding entropy significantly for globally compact conformations, suggesting that they are important properties of residues to ensure fast folding and stable native structure. This corresponds well with our finding that natural amino acid residues have reduced effective flexibility, as evidenced by statistical analysis of rotamer libraries and side chain rotatable bonds. We further develop a method calculating the exact side chain entropy for a given backbone structure. We show that simple rotamer counting underestimates side chain entropy significantly for both extended and near maximally compact conformations. We find that side chain entropy does not always correlate well with main chain packing. With explicit side chains, extended backbones do not have the largest side chain entropy. Among compact backbones with maximum side chain entropy, helical structures emerge as the dominating configurations. Our results suggest that side chain entropy may be an important factor contributing to the formation of alpha helices for compact conformations.

Computer Simulation↗
PubMed2005

Effect of flexibility on hydrophobic behavior of nanotube water channels.

Carbon nanotubes can serve as simple nonpolar water channels. Here we report computer simulations exploring the relationship between the mechanical properties of such channels and their interaction with water. We show that on one hand, increasing the flexibility of the carbon nanotubes increases their apparent hydrophobic character, while on the other hand the presence of water inside the channel makes them more resistant to radial collapse. We quantify the effect of increasing flexibility on the hydrophobicity of the nanotube water channel. We also show that flexibility impedes water transport across the nanotube channel by increasing the free-energy barriers to such motion. Conversely, the presence of water inside the nanotube is shown to affect the energetics of radial collapse in a water nanotube, an ostensibly mechanical property. We quantify the magnitude of the effect and show that it arises from the formation of energetically favorable low-dimensional water structures inside the nanotube such as one-dimensional wires and two-dimensional sheets.

Chemistry, Physical↗
PubMed2006

Size, shape, and flexibility of RNA structures.

Determination of sizes and flexibilities of RNA molecules is important in understanding the nature of packing in folded structures and in elucidating interactions between RNA and DNA or proteins. Using the coordinates of the structures of RNA in the Protein Data Bank we find that the size of the folded RNA structures, measured using the radius of gyration R(G), follows the Flory scaling law, namely, R(G)=5.5N(1/3) A, where N is the number of nucleotides. The shape of RNA molecules is characterized by the asphericity Delta and the shape S parameters that are computed using the eigenvalues of the moment of inertia tensor. From the distribution of Delta, we find that a large fraction of folded RNA structures are aspherical and the distribution of S values shows that RNA molecules are prolate (S>0). The flexibility of folded structures is characterized by the persistence length l(p). By fitting the distance distribution function P(r), that is computed using the coordinates of the folded RNA, to the wormlike chain model we extracted the persistence length l(p). We find that l(p) approximately 1.5N(0.33) A which might reflect the large separation between the free energies that stabilize secondary and tertiary structures. The dependence of l(p) on N implies that the average length of helices should increase as the size of RNA grows. We also analyze packing in the structures of ribosomes (30S, 50S, and 70S) in terms of R(G), Delta, S, and l(p). The 70S and the 50S subunits are more spherical compared to most RNA molecules. The globularity in 50S is due to the presence of an unusually large number (compared to 30S subunit) of small helices that are stitched together by bulges and loops. Comparison of the shapes of the intact 70S ribosome and the constituent particles suggests that folding of the individual molecules might occur prior to assembly.

Models, Chemical↗
PubMed2003

Head-elevated laryngoscopy position: improving laryngeal exposure during laryngoscopy by increasing head elevation.

STUDY OBJECTIVE: The objective of this study was to determine the effect of increasing head elevation and neck flexion on the quality of laryngeal view during laryngoscopy. METHODS: Laryngoscopy with a straight blade was performed on 7 fresh human cadavers. Laryngeal views were recorded with the direct laryngoscopy video system, and the laryngoscopy angle was measured throughout the procedure with an angle finder attached to the handle of the laryngoscope. Each cadaver had laryngoscopy initiated with the head lying flat on the table and with atlanto-occipital extension. The head was then progressively elevated as much as possible (the head-elevated laryngoscopy position), increasing neck flexion and the laryngoscopy angle. Three physicians blinded to the laryngoscopy angle graded the quality of laryngeal view using the percentage of glottic opening (POGO) score. RESULTS: The laryngoscopy angle ranged from a mean of 32 degrees +/-8 degrees (1 SD) with the head flat on the table to a mean of 67 degrees +/-8 degrees with the head-elevated laryngoscopy position. The mean midposition laryngoscopy angle was 49 degrees +/-6 degrees. Comparing the 3 positions, mean POGO scores+/-1 SD significantly increased from 31%+/-10% (flat position) to 64%+/-12% (midposition) to 87%+/-13% (head-elevated laryngoscopy position). Both the midposition and the head-elevated laryngoscopy position compared with the flat position were statistically significant at a P value of less than.0001. The midposition also differed significantly from the head-elevated laryngoscopy position (P <.0007). Additionally, there was a significant linear relationship among the 3 positions (P <.0001). CONCLUSION: Increasing head elevation and laryngoscopy angle (neck flexion) significantly improves POGO scores during laryngoscopy on fresh human cadavers.

Cadaver↗
PubMed2002

A randomized controlled trial in a training institution comparing a pediatric variable stiffness colonoscope, a pediatric colonoscope, and an adult colonoscope.

BACKGROUND: There are few comparative data on the efficacy of different colonoscopes. This study compared the efficacy of a new pediatric variable stiffness colonoscope with that of standard pediatric and adult colonoscopes in the performance of routine colonoscopy. METHODS: Three hundred sixty-three consecutive patients were randomized to undergo colonoscopy with a pediatric variable stiffness (n = 122), pediatric (n = 114), or adult colonoscope (n = 127). Primary outcomes recorded were minutes to the cecum and completeness of the examination. Secondary outcomes included patient tolerance, use of abdominal compression, and endoscopists' assessment of the difficulty of the procedure. RESULTS: Cecal intubation rates were not statistically different between the groups: variable stiffness (94.3%), pediatric (96.5%), and adult (89.8%) (p = 0.099). There was no significant difference in mean insertion time, patient tolerance, use of abdominal compression, or endoscopists' global assessment or examination difficulty between groups. Overall, the initial completion rate of 93% increased to 97% on switching to a different colonoscope. Colonoscopy was unsuccessful more often and was more time consuming in women who had undergone hysterectomy. CONCLUSION: The variable stiffness colonoscope performs well, but does not appear to offer any distinct advantage over standard pediatric or adult colonoscopes for routine colonoscopy. Further study may identify subgroups of patients that benefit from this new technology.

Adult↗
PubMed2001

Mechanical characteristics of various tempers of as-received cobalt-chromium archwires.

The mechanical characteristics of 24 of the 36 wire cross-sectional configurations were investigated in the as-received state from among the 4 tempers of a cobalt-chromium product. After engineering mechanics were used to validate the efficacy of the span combinations, each wire was measured in flexure to determine its elastic modulus and in tension to determine its yield strength, ultimate tensile strength, and ductility. Other combined characteristics were evaluated, including flexibility, resilience, and the yield strength criterion. In these as-received materials the formability sometimes followed expectations, but the flexibility and resilience characteristics were variable and independent of temper. And although the elastic modulus was independent of testing parameters, it was affected by the loss of material at the corners of rectangular wires. Overall, the stiffnesses of cobalt-chromium wires in round configurations were comparable to those of multi- and single-stranded stainless steel wires but were 3 and 6 times greater than the stiffnesses of beta-titanium and nickel-titanium wires, respectively. In the final analysis, these as-received wires do not meet their potential as a variably formable and variably resilient alternative to stainless steel. Perhaps this is why cobalt-chromium wires have never had the impact on the profession that was expected from them several years ago.

Algorithms↗