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PubMed1995

Mechanical loading on the low back in three methods of refuse collecting.

The mechanical loading on the low back was studied in three different current methods of refuse collecting: in polythene bags, two-wheeled mini-containers and large four-wheeled containers. To this end the most prominent activities of each collecting method were performed in a laboratory. On the basis of movement analysis, force measurements and biomechanical modelling, spinal compressive and shear forces were estimated. From these forces and from the frequency of activities during the working day (assessed in a preliminary field study) the low-back stress in each collecting method was evaluated. In the bag-method, peak forces when throwing the bags ranged from 3341 to 5179 N (average compression) and from 284 to 673 N (shear) among the different conditions studied. The act of picking up bags also showed rather high forces (exceeding the NIOSH limit for disc compression in most cases). The frequency of exposure to these forces in the field is rather high (workers pick up and throw on average 807 times each day). The mini-container method compares favourably to the bags method. Peak compressive and shear force in tilting/pushing and pulling mini-containers ranged from 1657 to 2654 N and from 123 to 248 N respectively. Also, the frequency of stressful events in the field is lower in this method. In the large container method extremely high peak forces (e.g. compression ranged from 4991 to 5810 N) were observed in the task of putting the empty container back from street level to sidewalk level (surmounting the kerb). The frequency of activities like pushing, pulling and lifting the large container in the field is much lower compared with activities in the other methods. On the basis of the frequency and magnitude of spinal forces it was concluded that the mini-containers should be preferred to the bags. If kerbs are removed at container places and tasks are performed by two instead of a single person, the large container method would form another good alternative to the stressful task of collecting refuse in bags.

Adult↗

PubMed1978

The effects of success and failure on the patterning of neuromuscular energy.

Weinberg and Hunt (1976) demonstrated that high- and low-anxious subjects differed in their patterning of neuromuscular energy in performance under failure feedback. The present study extends these findings to conditions that involve success feedback. The Sport Competition Anxiety Test and State-Trait Anxiety Inventory were administered to distinguish A-State and A-Trait subjects, while EMG indicated qualitative aspects of throwing. High-and low-trait anxiety subjects received either success, failure, or no feedback. High-anxious subjects performed best under success feedback, and low-anxious subjects performed best after failure feedback. High-anxious subjects used more EMG energy before, during, and after the throw in all conditions, and success feedback was beneficial for high-anxious subjects. The results are discussed in terms of the inter-relationships between efficiency of neuromuscular energy, motor performance, and state anxiety.

Journal Article↗

PubMed1980

The level of organization of the motor schema.

The interpretations of Piaget and Schmidt on the level on which the motor schema is supposedly effective were evaluated in pre-school children of different ages in a throwing task. In an analysis of variance on the accuracy scores, significant main effects for age, sex, and throwing arm were found. Further, the results showed no relationship between accuracy scores with the preferred and non-preferred arm in the younger group, while in the older group a moderate relationship was found. This result was interpreted in terms of structural development and as a warning for studies where Schmidt's variability-of-practice hypothesis is tested.

Journal Article↗

PubMed1984

Sports injuries to the upper extremity. How to recognize and deal with some common problems.

Upper extremity syndromes caused by a single stress or by repetitive microtrauma occur in a variety of sports. The throwing motion, long-distance swimming, bowling, golf, gymnastics, basketball, volleyball, and field events can repetitively stress the hand, wrist, elbow, and shoulder. The biomechanical evaluation of racquet handling, throwing, and swimming motions has progressed considerably, and the future looks promising for better identification and prevention of sports injuries due to stress. These insights will help the physician more adequately understand and treat athletic injuries. As for the present, we must recognize athletic injuries for what they are--debilitating single or repetitive trauma to active persons who want a rapid return to their sport. The goal of both the injured athlete and the treating physician must be 100% recovery; compromise in treatment is not warranted. To achieve the best results, the physician should emphasize to the athlete, coach, and parent that healing is a matter of time.

Arm Injuries↗

PubMed2000

An upper limb kinematic model for the examination of cricket bowling: a case study of Mutiah Muralitharan.

We show how biomechanics can be used to accurately assess spin-bowling techniques (offspin, legspin and topspin) in cricket, under controlled conditions, when the player is suspected of throwing. A 50 Hz six-camera Vicon Motion Analysis system was used to record the movements of markers strategically placed on the upper limb during each of the above bowling actions. A kinematic model of the upper limb, created using Vicon BodyBuilder software, enabled the movements of the upper arm and forearm to be described during each delivery. Selected physical characteristics of the upper limb were also measured. The present 'no ball' law in cricket with reference to throwing states that 'the arm should not be straightened in the part of the delivery that immediately precedes ball release'. The bowler, Mutiah Muralitharan, was shown to maintain a relatively constant elbow angle in the 0.06 s before ball release. Furthermore, this angle changed little from the time that the upper arm was angled vertically downward until ball release during the three spin-bowling actions.

Arm↗

PubMed2004

Talent identification and early development of elite water-polo players: a 2-year follow-up study.

The processes of talent detection and early development are critical in any sport programme. However, not much is known about the appropriate strategies to be implemented during these processes, and little scientific inquiry has been conducted in this area. The aim of this study was to identify variables of swimming, ball handling and physical ability, as well as game intelligence, which could assist in the selection process of young water-polo players. Twenty-four players aged 14-15 years underwent a battery of tests three times during a 2-year period, before selection to the junior national team. The tests included: freestyle swim for 50, 100, 200 and 400 m, 100-m breast-stroke, 100-m 'butterfly' (with breast-stroke leg motion), 50-m dribbling, throwing at the goal, throw for distance in the water, vertical 'jump' from the water, and evaluation of game intelligence by two coaches. A comparison of those players eventually selected to the team and those not selected demonstrated that, 2 years before selection, selected players were already superior on most of the swim tasks (with the exception of breast-stroke and 50-m freestyle), as well as dribbling and game intelligence. This superiority was maintained throughout the 2 years. Two-way tabulation revealed that, based on baseline scores, the prediction for 67% of the players was in agreement with the final selection to the junior national team. We recommend that fewer swim events be used in the process of selecting young water-polo players, and that greater emphasis should be placed on evaluation of game intelligence.

Achievement↗

PubMed2006

Comparison of kinematics in skilled and unskilled arms of the same recreational baseball players.

We examined mechanisms of coordination that enable skilled recreational baseball players to make fast overarm throws with their skilled arm and which are absent or rudimentary in their unskilled arm. Arm segment angular kinematics in three dimensions at 1000 Hz were recorded with the search-coil technique from the arms of eight individuals who on one occasion threw with their skilled right arm and on another with their unskilled left arm. Compared with their unskilled arm, the skilled arm had: a larger angular deceleration of the upper arm in space in the forward horizontal direction; a larger shoulder internal rotation velocity at ball release (unskilled arms had a negative velocity); a period of elbow extension deceleration before ball release; and an increase in wrist velocity with an increase in ball speed. It is suggested that some of these differences in arm kinematics occur because of differences between the skilled and unskilled arms in their ability to control interaction torques (the passive torque at one joint due to motion at adjacent joints). It is proposed that one reason unskilled individuals cannot throw fast is that, unlike their skilled counterparts, they have not developed the coordination mechanisms to effectively exploit interaction torques.

Acceleration↗

PubMed1999

Morphological variation analysis of the repeatability of soccer offensive schemes.

A landmark-based statistical method, morphological variation analysis, for the quantification of the repeatability in the arrangement of body segments during the execution of sport actions has recently been developed. A two-dimensional shape is produced and its morphology is studied. The method was used to measure the within-team variability of the relative positions of players during the execution of offensive schemes in soccer. Two junior soccer teams of different technical abilities (semi-professional vs. amateur), each playing two standardized offensive schemes of different difficulty (easier: throw-in; more difficult: wing attack) were filmed. Each scheme was repeated 25 (semi-professionals) or 10 (amateurs) times. For each repetition, the position of the players in a single significant frame was analysed using morphological variation analysis. The reproducibility of both schemes was higher among the semi-professionals than among the amateurs (two-way analysis of variance, P<0.005). The repeatability of the players' relative positions was related to the difficulty of the scheme and the technical level of the team. Among the amateurs, the throw-in was more reproducible than the wing attack (Student's t-test, P<0.005). The method not only allows the quantification of collective (team) coordination, but also the separation of the influence of individual players.

Adolescent↗

PubMed1989

The effectiveness of an interactive videodisc qualitative assessment training program.

This study was designed to investigate the effect of an interactive videodisc motor skill assessment training program on the development of preservice and inservice teachers' qualitative assessment proficiency on two motor skills: the overhand throw and catch. Twenty-seven preservice and 27 inservice physical education teachers were randomly assigned to one of three treatment conditions: interactive videodisc (IVD), teacher-directed (TD), or self-directed (SD). Motor skill qualitative assessment accuracy was evaluated on a pre- and post-test basis using a 50-item motor skill assessment accuracy test (10 performances rated on 5 components) for each skill. Analysis of covariance results indicated significant main effects for treatment for both skills. Post hoc tests revealed that for the overhand throw, the IVD and TD groups were superior to the SD group but not different from each other. For the catch, the IVD group was found to be superior to both the TD and SD groups. These findings are discussed in relation to the advantages of interactive videodisc in terms of efficiency and user independence and with comparable findings in other educational applications.

Adult↗

PubMed1995

Expert-novice differences in cognitive and skill execution components of youth baseball performance.

Previous research has shown that experts exhibit superior response selection and skill execution during performance in youth sport. The purpose of this study was to examine differences in cognitive and skill execution components of game performance in young baseball players (N = 159) with varying levels of expertise. Three levels of expertise (low-, average-, and high-skilled players) were identified at each age level (7, 8, 9, and 10 years of age). Game performance was videotaped, and measures of skill execution (throwing accuracy, throwing force, fielding, catching, batting average, and batting contact) and cognitive components (positioning, decisions) were developed from observational analysis. The results indicated that baseball skill execution during game play maximally discriminated expertise levels.

Analysis of Variance↗

PubMedDate not supplied

Percentage decline in masters superathlete track and field performance with aging.

Masters athletic records in track and field events, published in September 1999, were analyzed to evaluate the percentage decline in maximum physiological performance with increasing age. Records were normalized using the 30s age records as the baseline and studied through to the 90s age range. Track running records declined with age in a curvilinear fashion [y = 1-exp((T-T0)/tau)] whereas the walking and field events declined in a linear manner [y = alpha (T-T'0)]. There were significant differences in the rates of percentage decline in the running events over various distances for both males and females, and significant differences between males and females. Decline with aging was greater for females, and for the longer or endurance running events. There were no differences in the rates of declining function for any of the walking events, and the only jumping event to show a significant difference was the high jump performance, which showed the slowest decline. The walking events declined more slowly than the running events, which declined more slowly than the jumping events. Because of the changes in the weights, heights, and distances at different ages, for both males and females, it was not possible to directly compare rates of decline in the various throwing and hurdling events. The strength-dependent throwing events and the pole vault showed the greatest rates of decline with age. In general terms, men's performance declined to 75% of peak performance in sprint events by the early 70s, in the longer track distances by mid to late 60s, and in field events by mid to late 50s. Women's performance declined to a similar extent by their mid 60s in track events, and by late 40s to early 50s in field events. Some of these differences may be due to differences in training effort and/or other competitive aspects, such as the numbers of athletes involved in the sport, and such differences may be reduced in the future with a more professional approach to these events.

Adult↗

PubMed2004

Influence of pelvis rotation styles on baseball pitching mechanics.

Efficient, sequential timing is essential for upper level pitching. Interestingly, pitchers vary considerably in timing related elements of pitching style including pelvis rotation, arm cocking, stride leg behaviour, and pitch delivery time. The purpose of this study was to determine whether relationships exist among these elements by examining the overall style of pitchers exhibiting different pelvis rotation patterns. Pitching styles were defined by pelvis orientation at the instant of stride foot contact. Pitchers demonstrating a pelvis orientation greater than 30 degrees were designated as 'early rotators', while pitchers demonstrating a pelvis orientation less than 30 degrees were designated as 'late rotators'. Kinematic and temporal differences were associated with the two styles. During the arm cocking phase, early rotators showed significantly greater shoulder external rotation at the instant of stride foot contact, earlier occurrence of maximum pelvis rotation angular velocity, and shorter time taken to complete the phase. However, by the instant of maximum shoulder external rotation, early and late rotators appeared remarkably similar as no significant difference occurred in pelvis and arm orientations. Therefore, it appears that early and late rotators used different methods to achieve similar results, including throwing velocity. Significant differences in throwing arm kinetics were also found for 10 of the 11 measures in the study. As the pelvis assumed a more open position at stride foot contact, maximum kinetic values were found to both decrease in magnitude and occur at an earlier time within the pitch.

Adolescent↗

PubMed2005

Determination of critical parameters among elite female shot putters.

The aim of this study was to determine if critical parameters for elite performance could be identified among a population of female shot putters. The performance of seven of the top women shot putters competing at the 2002 USA National Championships was examined. Video data were captured using two Panasonic 60 Hz cameras and the best throws of each athlete were digitized and analyzed using a Peak Motus three-dimensional motion analysis system. Thirty variables were examined for their effect on the distance of the throw. Correlation analysis indicated that measured distance was positively correlated with release speed (r = 0.97, p < 0.0003) and shoulder-hip separation (r = 0.72, p < 0.06) and negatively correlated with release angle (r = -0.74, p < 0.056), rear knee angle at rear foot touchdown (r = -0.93, p < 0.003) and rear knee angle at release (r = -0.76, p < 0.047). Greater knee flexion angle at both rear foot touch down and release along with a neutral shoulder-hip angle at release were identified as the most critical parameters for success among this sample of elite women shot putters. The unique observation about the knee positions at specific events should assist in new training and coaching developments.

Biomechanical Phenomena↗

PubMed1953

Studies on entry and egress of poliomyelitic infection. VI. Centrifugal spread of the virus into peripheral nerve with notes on its possible implications.

We have demonstrated a progressive centrifugal migration of poliomyelitis virus from the CNS into various peripheral ganglia and into peripheral nerves, including their distal portions. This phenomenon appears to be a regular occurrence in experimental animals, and is similar to that found in two other neurotropic infections, rabies and Borna disease. Viremia appears to be secondary to primary neural infection. The presence of virus in the lumen of the alimentary tract appears to be secondary to primary neural infection and not to viremia, and to be associated with the centrifugal spread of virus in peripheral nerves. The presence of virus in "extraneural" tissues is not per se referable to infection of their constituent cells but rather to infection of their supplying nerves or, in some instances, to their content of virus-bearing blood. The finding of virus in the vagus nerve may throw light on some of the electrocardiographic changes noted in certain cases of human poliomyelitis. The presence of virus in peripheral nerves may throw light on the etiology of the most frequent clinical manifestations of human poliomyelitis, localized pain and tenderness.

Animals↗

PubMed2006

Handedness is associated with asymmetries in gyrification of the cerebral cortex of chimpanzees.

Gyrification of the cerebral cortex reflects complexity in cortical folding during development of the brain. In this paper, we evaluated whether chimpanzees show asymmetries in gyrification and if variation in gyrification asymmetries were associated with handedness. Magnetic resonance images were obtained in a sample of 76 chimpanzees, and gyrification measures were obtained from 10 equally spaced slices of the cortex. Asymmetry quotients (AQs) in gyrification were compared for 4 measures of handedness including reaching, coordinated bimanual actions, manual gestures, and throwing. Overall, the chimpanzees showed significant differences between the right and left hemispheres that were region specific. Significant differences in AQ's were found in right- and nonright-handed chimpanzees for throwing and, to a lesser degree, for manual gestures. Increasing age was associated with increasing gyrification in the prefrontal regions, particularly in female chimpanzees. The results indicate that variation in gyrification between hemispheres is associated with functional measures of laterality in chimpanzees.

Aging↗

PubMed1978

Kinematic and electromyographic differences between men and women during skill acquistion: a preliminary study.

The purpose of this preliminary study was to examine kinematic and muscular differences between male and female subjects during acquisition of a novel throwing skill. The task consisted of an underhand ball toss for accuracy and involved 10 male and 10 female subjects who each practiced the task for 104 trials during one sitting. A high speed 16 mm camera was used to gather the cinematographic data, and surface electrodes monitored the electrical output of the anterior and posterior portions of the deltoid muscle. Statistical analysis revealed significant differences between male and female subjects in 1) integrated electrical activity of the posterior portion of the deltoid muscle, 2) premovement activity of both the anterior and posterior portions of the deltoid muscle, 3) peak velocity of the movement, and 4) velocity of the limb at ball release. Differences may exist between men and women in kinematic and muscular modifications occurring during the acquisition of a novel throwing skill.

Adolescent↗

PubMed2000

Patterns of glenohumeral joint laxity and stiffness in healthy men and women.

PURPOSE: The purpose of this study was to identify gender-related differences in glenohumeral (GH) joint laxity, stiffness, and generalized joint hypermobility in healthy men and women. METHODS: Fifty-one healthy men and women were tested for generalized joint hypermobility, and anterior-posterior (AP) joint laxity and stiffness using a single-group factorial design. RESULTS: Women exhibited significantly more anterior joint laxity (men 8.3 +/- 2.2 mm vs women 11.4 +/- 2.8 mm, P < 0.001) and less anterior joint stiffness (men 20.5 +/- 5.0 N x mm(-1) vs women 16.3 +/- 4.2 N x mm(-1), P < 0.01) than men. Men had significantly more posterior joint laxity than anterior (Ant 8.3 +/- 2.2 mm vs Post 9.6 +/- 2.9 mm; P < 0.001), and women also had significantly less anterior joint stiffness than posterior [Ant 16.3 +/- 4.2 N x mm(-1) vs Post 22.1 +/- 6.9 N x mm(-1); P < 0.01], Women also demonstrated significantly more generalized joint hypermobility than men (men 1.0 +/- 1.7 vs women 2.9 +/- 2.1; P = 0.02). CONCLUSIONS: Our findings may indicate a possible increased risk for instability in women, especially those participating in sports that require repetitive overhead-throwing motion. Future investigations should seek to determine the contribution of increased GH joint laxity and decreased joint stiffness to various injury states and examine these variables in other populations such as overhead-throwing athletes.

Adult↗

PubMed1985

A new, fast surgical knot for skin closures.

A modified surgeon's knot is proposed. Tying is based on twisting the throws instead of laying them down flat. The second (granny) throw is snugged against the first in a locking manner. The knot is tied rapidly by needleholder and is particularly useful for skin sutures with monofilament thread.

Dermatologic Surgical Procedures↗