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At least 829 records · Page 46Linked to original sources
PubMed1995

Effect of complexity of a physical task on estimation of time to complete.

Two studies were performed to examine the effect of the complexity of a physical task on the estimation of the time required for its performance. Different paradigms for the estimation of time (prospective vs retrospective) were used with different methods of estimation (reproduction vs verbal estimation). In Study 1, 32 pairs of adults were asked to throw a ball to each other in different ways. The two groups were distinguished by the motor and cognitive changes required in moving from one task to the next. One group had to perform 10 successive repetitions on each of five kinds of ball throws, while the other had to perform the same number of ball throws but with each type being split into two different successive sets of throws so here the task consisted of changes. In Study 2, 60 children (aged 7 or 8 yr.) were asked to perform a set of basketball tasks. The two groups were distinguished by the pace at which they had to perform the task, slowly or rapidly. The results of the two studies indicated a negative relation between the complexity of the task and the group's estimation of time. The reproductive method yielded shorter estimations than the verbal method. The results indicate that for physical activity the attentional model may well be valid.

Adolescent↗
PubMed2004

Survey of advantages obtained by judoka in competition by level of practice.

In judo, placing the opponent in a situation of uncertainty requires the mastery of several throws. French young judoka learn, respectively, 10, 9, and 8 throws to earn yellow, orange, and green belts. These techniques allow throwing down a judoka in several directions (backward, forward, left and right). To see what happens in competition 82 judoka were observed during regional competitions. The average number of matches was 3.3 +/- 0.5. The average number of successful attack directions was 2.8 +/- 1.3 for 8 children at orange to green belt level; 2.1 +/- 0.7 for 11 children at blue belt level; 2.2 +/- 0.8 for 17 children at brown belt level; 2.8 +/- 0.9 for 20 cadets at brown to black belt level, 2.6 +/- 1.1 for 10 juniors at brown to black belt level, and 3.3 +/- 0.9 for 16 seniors at black belt level. These scores for children with blue and brown belts were significantly different (p=.02) from those of seniors with black belts. Such results imply a nonlinear progression between the technical level (represented by the belt) and the capacity to create uncertainty (the ability to throw down the opponent with at least three techniques in three different directions). Judo is a sport of slow technical maturation; it requires this adaptation before its mastery in competition.

Adolescent↗
PubMed1992

[Type A personality and level of aspiration in preschool children: some basic characteristics of aspiration levels and their modifications by introducing risk-taking and competitive situations].

The purpose of this study was to investigate some characteristics of aspiration levels of Type A preschoolers. Twenty-two Type A and twenty-one Type B subjects selected from 245 preschoolers were given three tasks: ball-throwing task 1, ball-throwing task 2, and ringtoss task. After investigating some basic characteristics of aspiration levels in a standard situation (ball-throwing task 1), risk-taking (ball-throwing task 2) and competitive (ringtoss task) situations were introduced in order to study the modifications of aspiration levels. The results indicated that Type A children showed higher aspiration levels than Type B children, but that no differences of changes in aspiration levels by introducing risk-taking and competitive situations were found between the two types. These results were discussed from the view point of formation of Type A characteristics.

Aspirations, Psychological↗
PubMed1982

Subluxing biceps tendon in the athlete.

Subluxation or dislocation of the long head of the biceps tendon from the bicipital groove is one of the common causes of shoulder disability in the throwing arm of the athlete. This condition has characteristic symptoms; pain on throwing and relieved by rest; palpable snap at a certain point in the arc of motion. The signs are tenderness over the bicipital groove and a reproducible pop in rotation of the humeral head. The diagnosis can be quite secure and is often confirmed by X-rays profiling the bicipital tunnel. The remedy is a relatively nontraumatic operation which removes the biceps tendon from the shoulder and fastens it into the bicipital groove. To take the young athlete who can no longer throw, and by a procedure of short morbidity permit him to throw without inhibition, is very gratifying both to patient and physician. Definitive diagnosis of shoulder lesions in the young athlete is mandatory for any effective treatment.

Adolescent↗
PubMed1994

Laparoscopic knot substitutes. An assessment of techniques of securing sutures through the laparoscope.

Advanced interventional laparoscopy has required the development of new methods of securing sutures as alternatives to the three-throw reef knot. A tensiometer was designed to measure the forces required for distraction of various knots or securing devices with different sutures. A three-throw reef knot was used as a control. Each device was tested 15 times, and the tension at which the "knot" slipped was recorded. Titanium clips (Ligaclip, Ethicon), locking polydioxanone clips (Absolok and Lapra-ty, Ethicon), malleable collars, Roeder knots and biocompatible glue (Histoacryl, B Braun Melsungen AG) were all assessed. Sutures secured with Ligaclips, Absolok clips and glue were significantly weaker than the three-throw reef knot. Sutures secured with malleable collars and Lapra-ty clips were as strong as the three-throw reef knot and have potential for use as knot substitutes.

Enbucrilate↗
PubMed1998

[Fodder flinging in cattle].

When cattle fling fodder, this is, in many respects, an undesirable behaviour: fodder is wasted, the interior of the shed is dirtied and the slatted floor is compromised in its function. Through behavioural observation, it should therefore be examined which are the determining factors for fodder throwing. Two breeds of cattle (Simmenthal and Brown Swiss) were examined to establish how often the animals fling fodder within 60 minutes in the medium-tie-stall and the short-tie-stall system and receiving varied feeding (green fodder and grass silage). Fodder throwing occurs amongst the two examined breeds, in both housing systems and amongst animals of all ages. The percentage of fodder flinging of Simmenthal cows was higher in the medium-tie-stall than in the short-tie-stall system (16.8% and 8.3%; p < 0.01). During the initial period following the start of feeding, the throwing frequency was at its highest. Fodder throwing animals had a significantly higher blinking frequency (a sign of excitement) than those not flinging fodder (p < 0.01). The reasons for food flinging and its possible effects on the fodder were not checked. Nevertheless, consideration was given to the meaning of this behaviour pattern. It would seem it is not a behaviour disorder. It could be that food flinging is the result of a learning process to control an itch caused by the husbandry system.

Animal Feed↗
PubMed1990

Some biomechanical considerations of polytetrafluoroethylene sutures.

The biomechanical performance of polytetrafluoroethylene (PTFE) sutures has been compared with that of polypropylene sutures, the standard to which other sutures used in vascular and cardiac surgery are compared. The PTFE is supple and has no plastic memory, while the polypropylene suture is stiff and retains its plastic memory. In addition, the rate of creep encountered in the PTFE suture was significantly less than that of the polypropylene suture. The knotting profiles for knot security for either a square, granny, or surgeon's knot for polypropylene sutures were three throws each. In contrast, knot security with either a square or granny PTFE knot was accomplished with seven throws; six throws were needed for a secure surgeon's knot. The breaking strength of the unknotted and knotted PTFE sutures was approximately one half as great as that for the unknotted and knotted polypropylene sutures. Knot construction significantly reduced the breaking strength of polypropylene sutures but did not alter the breaking strength of PTFE sutures. The percent elongation experienced by both sutures before breakage did not differ significantly. The elasticity, as measured by work recovery, for the polypropylene suture was greater than that for the PTFE suture. On the basis of its unique biomechanical performance characteristics, the PTFE suture should have an important place in vascular and cardiac surgery.

Physical Phenomena↗
PubMed1990

Use of carbon dioxide laser in improving knot security in polyester sutures.

Knot slippage continues to be a serious concern in surgery. This study explored the possibility of improving knot performance by exposing it to radiation from a CO 2 laser. The specimens were mounted in a special device and exposed in a predetermined position for precisely controlled lengths of time. In the first set of experiments, the welding of ends was examined in nylon and polyester sutures. Although the welding was easily achieved, the joint was found brittle and its strength lower than that of a surgical knot. In the next set of experiments, the work was performed at a more fundamental level using oriented, high density, polyester films. The results showed that up to a certain level of exposure the tensile properties did not change, but beyond it a rapid decay took place. Shear tests on polyester sutures twisted together and then exposed to various levels of energy indicated that a bond of maximum strength developed at this exposure. Mersilene sutures of size 3/0 containing a two throw square knot when exposed to energy of this level produced optimal results. The knot strength increased by about 16% (from 13.4 N unexposed to 15.6 N exposed) and the slippage often known to occur in a two-throw knot was completely absent. This work performed under standard atmospheric conditions provided a direction for greatly enhancing the performance of a two-throw knot in terms of both the security and the strength.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1979

Biomechanical study of the pitching elbow.

Medial-tension injuries of the pitching elbow are well recognized. One contributing factor is the extreme valgus which has been noted to occur during the acceleration phase of throwing. It is hypothesized that breaking pitches generate higher medial loading because of the pronation and supination required to impart spin to the ball. The pitching motion is a complex action of all body segments to produce maximum linear and angular acceleration of the ball. The purpose of this study was to correlate elbow loading with pitching style. We measured the forearm segment for axial and tangential (varus-valgus plane) acceleration using accelerometers attached to the forearm and hand. Muscle activity was measured by EMG. Forearm rotation was assessed by stroboscopic photography. Despite different delivery styles when throwing breaking pitches, each pitcher demonstrated patterns of muscle activity and acceleration which were similar. Deceleration forces were lower than acceleration forces. Pronation and supination were documented and contribute to the direction of ball spin. Accelerometers can be used to evaluate pitching mechanics. We suggest that the main factors causing an elbow injury are the amount of throwing and the force with which the ball is thrown.

Baseball↗
PubMed1988

Plasma lecithin: cholesterol acyltransferase activity in elite athletes from selected sports.

The activity of lecithin: cholesterol acyltransferase (LCAT) and the plasma lipoprotein concentrations of elite athletes from 8 selected sports (volleyball, judo, sprinting, wrestling, throwing, cycling, water polo and tennis) were determined and compared with those of a sedentary control group. Plasma LCAT activity levels in the athletes were significantly 2.2-7.0 times higher than in the controls in most sports (p less than 0.01). Judo, sprinting, wrestling and throwing had comparable LCAT values while tennis, volleyball and cycling were considerably higher. HDL-C concentration was significantly higher than controls in the water polo (p less than 0.05), cycling and volleyball (p less than 0.01) groups. Percentage lipoprotein distribution in the athletes in all sports except tennis, throwing and wrestling were similar to the controls. The differences among groups in LCAT activity may be related to the effect of physical exercise and training adaptations to lipid metabolism. This may be of importance when judging the benefit of exercise for atherosclerosis protection.

Adult↗
PubMed1995

Sexual orientation and performance on sexually dimorphic motor tasks.

Performance of homosexual and heterosexual men and women on two motor tasks which reliably demonstrate sex differences in opposite directions was examined. A Throw-to-Target Task and the Purdue Pegboard were administered to undergraduate students matched for age and program of study. A two-way ANOVA (Sex x Sexual Orientation) of the Throw data showed a significant interaction, F(1, 90) = 16.22, p < or = 0.001, and a trend for an effect of sex, F(1, 90) = 3.72, p < 0.06. Heterosexual men outperformed heterosexual women, whereas gay men threw less accurately and lesbians tended to throw more accurately than their heterosexual counterparts. Differences in sports history or hand strength did not account for these effects. Analysis of the Pegboard scores found no interaction or main effect of sexual orientation, but the effect of sex was significant, F(1,63) = 7.01, p < or = 0.02. Regardless of sexual orientation, women outperformed men and this difference remained significant even when a measure of finger size was partialed out. This study provides new evidence suggesting an association between sexual orientation and motor-performance profiles. As with cognitive tasks, the motor-performance profiles of homosexuals are composites of some male-typical and some female-typical abilities. To the extent that sociological factors have been controlled, the study suggests that both sexual orientation and motor/cognitive predispositions may have early biological contributions.

Adult↗
PubMed2003

[Biomechanical investigations for the development of a SLAP-II-lesion].

The superior labral-biceps-tendon-complex forms an anatomical and functional unit and combines static and dynamic elements of shoulder stability. At present, only theoretical hypotheses exist on the etiology of the microtraumatic SLAP-II-lesion. To gain further insight into this, an instrument was developed to simulate throwing motions such as the late-cocking/early acceleration phase as well as deceleration/follow-through. Sixteen freshly frozen shoulder specimens were tested, varying the loads on the biceps tendon (25 N, 50 N, 100 N) and the compression of the humeral head against the glenoid (25 N, 50 N, 80 N). Each shoulder had to run through a certain number of cycles during the particular phase of throwing. The tests were stopped after a SLAP-II-lesion was observed, or after a limit of 15,000 cycles. Every 1,000 cycles the results of the tests were checked arthroscopically. A SLAP-II-lesion developed in only 10% of the specimens during the acceleration/ late cocking phase whereas in the deceleration/ follow-through phase 83% developed such a lesion. According to our results, the deceleration/follow-through of the throwing motion seems to be responsible for creating microtraumatic SLAP-II-lesions. One reason is the loss of the centering function of the long head of the biceps tendon during total internal rotation, another is the increased posterosuperior translation of the humeral head in this position, which leads to a non-physiological contact, creating lesions in this area due to the large sheering forces.

Acceleration↗
PubMed2006

Optimum surgical suture material and methods to obtain high tensile strength at knots: problems of conventional knots and the reinforcement effect of adhesive agent.

BACKGROUND: Strong suture material and a firmly tight knot that never loosens are necessary for tendon suture, but the appropriate combination of suture materials and the methods to make a knot are matters of uncertainty. METHODS: The tensile strength of four conventional tendon suture materials (Surgilon, Ethibond, Ethilon, PDS II) and newly developed FiberWire were examined. An experienced orthopedic surgeon formed surgical knots with USP2 wire (0.5-0.599 mm in diameter) by making loops and then pulled them at 20 mm/min using Instron. RESULTS: With the conventional surgical suture method (the addition of one throw on a surgeon's knot), Surgilon proved to have the highest tensile strength (163.6 +/- 6.5 N). Other suture materials, when tied under the same conditions, slipped and did not reach the ultimate tensile strength. When four additional throws were made, FiberWire provided the highest tensile strength (316.6 +/- 12.2 N) among the five suture materials tested (others were 140-200 N). When an adhesive agent, cyanoacrylate, was applied to a knot, PDS II provided the highest tensile strength (182.0 +/- 10.1 N). CONCLUSIONS: Our study suggests three suitable combinations of suture materials and methods for suture knot formation, depending on the site of surgery, that provide optimum treatment outcomes. Surgilon provides the most stable strength for general suture techniques. FiberWire is the strongest suture material for a site where a large number of throws is clinically possible. PDS II provides a strong suture when combined with cyanoacrylate reinforcement.

Adhesives↗
PubMed1990

Mechanical performance of square knots and sliding knots in surgery: comparative study.

Various square knots, sliding knots, and surgeon's knots in mono- and multifilament suture material of different diameters were tested with respect to knot strength and knot security. Loop holding capacity of knots varied from 37.2 to 149.8 N, depending on the kind of knot, knot configuration, kind of suture, suture structure, and suture dimension. On the whole, square knots proved to be more reliable than sliding knots. Knot performance of surgeon's knots was not better than that of square knots. Knot security of three-throw sliding knots and two-throw square knots and surgeon's knots was rather poor. These knots cannot be recommended for clinical use. In smaller diameter mono- and multifilament suture material, knot performance of sliding knots that contained one extra throw was identical to that of square knots. It is concluded that the outcome of the comparison of square knots and sliding knots depends on knot configuration, suture material, and suture size. The implications of these laboratory findings for clinical use are discussed.

Evaluation Studies as Topic↗
PubMed1996

The effect of knot geometry on the strength of laparoscopic slip knots.

OBJECTIVE: To evaluate and compare the strength of six different knot geometries used in laparoscopic slip knots. METHODS: The strength of six extracorporeal slip knots used in laparoscopic surgery was measured using a tensiometer. Two multiple-throw laparoscopic square knots (the intracorporeal two-turn flat square knot and the extracorporeal sliding square knot) were used as controls. Each knot type was tied five times, and each type was tied in random order by the same primary and assisting surgeons using a laparoscopic pelvic surgery training model. One-way analysis of variance was performed to detect significant differences in knot strengths, and the variability in knot strength for each knot type was determined by Tukey's multiple comparison test. RESULTS: A statistically significant effect for knot geometry was identified. The mean knot strengths +/- standard deviation (SD), measured in newtons, from strongest to weakest, were: 4S knot (28.01 +/- 11.45), fisherman's knot (22.45 +/- 6.89), modified Roeder knot (19.86 +/- 9.30), Roeder knot (15.77 +/- 7.02), Weston knot (7.28 +/- 7.96), and Duncan knot (6.55 +/- 0.95). The mean knot strengths for the multiple-throw control square knots were as follows: intracorporeal two-turn flat square knot (41.21 +/- 2.69) and extracorporeal sliding square knot (27.81 +/- 16.27). The intracorporeal two-turn flat square knot (control) was significantly stronger (P < .05) than all slip knots except the 4S and fisherman's knot. CONCLUSION: The 4S and fisherman's knots are the strongest laparoscopic slip knots and are the only slip knots similar in strength to multiple-throw square knots.

Female↗
PubMed1995

Optimizing arthroscopic knots.

Arthroscopic repairs, such as those for shoulder instability, are commonly performed. However, the failure rate after arthroscopic repair appears to be higher than with open surgery. These failures may relate to the challenge of tying secure knots arthroscopically. Many knots tied arthroscopically commonly consist of an initial slip knot to remove slack, and a series of half-hitches. Half-hitches, instead of square throws, are difficult to avoid and result when asymmetrical tension is applied to the strands. For this reason, the security of knots tied arthroscopically may not be equivalent to square knots and a greater rate of failure may occur. The purpose of this study was to determine (1) the security of various arthroscopic knots under cyclic and peak loading conditions, (2) how the surgeon can modify the method or sequence of half-hitch throws to minimize knot slippage or breakage, and (3) whether using an arthroscopic knot pusher affects the security of the same knot tied by hand. The most secure knot configurations were achieved by reversing the half-hitch throws and alternating the posts. These knots performed significantly better than all other knots tested (P < .002). Thus the surgeon can control the holding capacity and minimize suture loop displacement by proper alternation of the tying strands and reversal of the loop when placing the hitches.(ABSTRACT TRUNCATED AT 250 WORDS)

Arthroscopy↗
PubMed2004

Internal impingement: findings on magnetic resonance imaging and arthroscopic evaluation.

PURPOSE: The purpose of this study was to examine preoperative shoulder magnetic resonance imaging (MRI) and intraoperative arthroscopic findings in throwing athletes with a clinical diagnosis of internal impingement. TYPE OF STUDY: Retrospective review. METHODS: A retrospective review of the surgical indications for 769 shoulder arthroscopic procedures performed from 1997 to 2000 revealed 9 throwing athletes with a diagnosis of severe internal impingement. Each had failed treatment that included a minimum of 3 months of rehabilitation. Preoperative MRIs in all 9 were read by a fellowship-trained musculoskeletal radiologist blinded to the operative findings. Findings at arthroscopy were culled from the operative reports. RESULTS: On both MRI and at arthroscopy, all 9 athletes had posterosuperior labral lesions, 1 had a humeral head articular cartilage lesion, and 1 had a SLAP lesion. Additional findings on MRI included humeral head edema, subchondral cystic changes, posterosuperior glenoid sclerosis, and rotator cuff tendonopathy predominantly in the infraspinatus. At arthroscopy, there were additional findings of articular-sided partial rotator cuff tears not shown on MRI. CONCLUSIONS: Both MRI and arthroscopic findings described labral and humeral head articular cartilage lesions. These findings may be indicative of internal impingement in throwing athletes. LEVEL OF EVIDENCE: Level III, diagnostic.

Adult↗
PubMed2004

Biomechanics of the elbow in sports.

In throwing activities, the elbow is sometimes stressed to its biomechanical limits. In this article, forces, torques, angular velocities, and muscle activity about the elbow are reviewed for the baseball pitch, the football pass, the javelin throw, the windmill softball pitch, the tennis serve, and the golf swing. The elbow goes through rapid extension in baseball pitching (about 2400 degrees/s) and rapid flexion in the javelin throw (about 1900 degrees/s). During baseball pitching, the elbow joint is subject to a valgus torque reaching 64 Nm, and requires proximal forces as high as 1000 N to prevent elbow distraction. The ulnar collateral ligament (UCL) rupture in baseball pitching, lateral epicondylitis in the tennis backhand, and other injury mechanisms are also discussed.

Baseball↗