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PubMed2006

Effects of fatigue of elbow extensor muscles voluntarily induced and induced by electromyostimulation on multi-joint movement organization.

To investigate the capacity of the central nervous system to integrate and differentiate two different muscular fatigue states, the present study examines the changes on multi-joint movement organization following muscular fatigue of elbow extensor muscles (triceps brachii) induced by voluntary versus electrically induced contractions. Twenty right-handed male volunteers performed throws in the horizontal plane before and after two fatiguing procedures. First, success rate of throws was not affected by fatigue neither after voluntary contractions, nor after electrically induced contractions. Despite similar reductions of the maximal voluntary isometric force and the median frequency of the electromyographic signal following both fatiguing protocols, voluntary contractions induced greater changes in muscle activation, kinematics and kinetics during throws than electrically induced contractions. The changes observed following voluntary contractions are interpreted as a compensatory strategy involving a greater contribution of the wrist. In contrast, the greater activation of the triceps brachii could compensate the weakness of this muscle induced by fatigue without any modification of the initial multi-joint movement organization.

Adult↗

PubMed1999

How efficient are central mechanisms for the learning and retention of coincident timing actions?

We compared the adaptive strategy and retention capacity of a deafferented subject and control subjects when intercepting, with a sliding-throw, an apparent movement coming at various speeds. Subjects were submitted to five practice sessions (30 trials per session) and to a retention test. The throwing kinematics was analysed, and spatial and temporal performance errors were measured. With practice, the deafferented subject showed modifications in movement initiation strategies and throwing patterns. With a slow apparent movement, the deafferented subject's initial behavior was characterized by short movement initiation and movement times. With practice, she showed an important increase in movement time in session 5, allowing longer visual control and leading to better temporal and spatial accuracy than that shown in session 1. In the retention session, the deafferented patient showed a late movement initiation strategy, similar to that of the control subjects. This increased movement initiation time was accompanied by an improved temporal accuracy compared to the deafferented subject's early results. However, spatial accuracy improvement was labile and could not be maintained over the retention interval. At the fast speed, all temporal components of the response, namely, movement initiation time (MIT), movement time (MT), and disk travel time (DTT), were similar for the deafferented and control subjects. Overall, the deafferented subject reduced her temporal error through practice, though without attaining the control subjects' accuracy. However, with a fast-moving stimulus, she showed a deteriorated spatial accuracy, even doubling her spatial errors at retention. In brief, the deafferented subject achieved proper temporal (perceptivo-cognitive) lasting control of her interceptive action, whereas spatial (sensorimotor) regulation raised mnemonic problems.

Afferent Pathways↗

PubMed2001

Evaluation and management of shoulder instability in the elite overhead thrower.

The elite throwing athlete places significant forces on the soft-tissue stabilizers of the shoulder with every pitch. Anterior translation forces can be as high as 40% of body weight and distraction forces as high as 80% body weight during the act of throwing. Injury to the static and dynamic stabilizers can lead to significant pain and loss of function in these athletes. To successfully treat the injured thrower, it is important to accurately diagnose the pathologic process. This article reviews the biomechanics of throwing and pathologic processes seen in the elite thrower. We cover the essentials of the history and physical in this population and conclude with a discussion of the various treatment regimens.

Baseball↗

PubMed2003

Lateral preference profiles and right shift attempt histories of consistent and inconsistent left-handers.

Differences in abilities and preferences exist between left-handers who both write and throw with their left hands (consistent left-handers) and those who write with their left hand but prefer to throw with their right (inconsistent left-handers). It is also known that many left-handers are pressured to switch to right-hand writing, and that these pressures can lead to a right shift attempt. The present study is the first to explore the joint effects of the consistent/inconsistent left-handedness dichotomy, right shift attempt history, and lateral preference profiles. Testing 379 Canadian adults between the ages of 18 and 94 indicated that, while both types of left-handers were equally likely to experience a right shift attempt, the inconsistent left-handers were more likely to successfully switch to right-hand writing. Further analyses revealed that throwing hand was more associated than writing hand with the direction of sidedness for a lateral preference index based upon eye, foot, and ear preferences. More specifically, right-hand throwers were much more likely to have a rightward lateral preference score than were left-hand throwers, regardless of current preferred writing hand. Overall, the results support an hypothesis that the left-handers who are least likely to submit to rightward switch pressures are those with the strongest, most consistent left-sided lateral preference profile.

Adolescent↗

PubMed2000

Shoulder injuries in overhead athletes. The "dead arm" revisited.

The following statements summarize this article: Three distinct categories of Type 2 SLAP lesions exist: (1) anterior, (2) posterior, and (3) combined anteroposterior. Posterior Type 2 SLAP lesions have distinct clinical and anatomic features that distinguish them from anterior Type 2 SLAP lesions. Posterior and combined Type 2 SLAP lesions can be disabling to overhead-throwing athletes because of posterosuperior instability and anteroinferior pseudolaxity. The Jobe relocation test is positive with posterosuperior pain in patients with posterior or combined anterior-posterior Type 2 SLAP lesions and is negative in patients with anterior Type 2 SLAP lesions. Rotator cuff tears are frequently associated with posterior or combined anterior-posterior SLAP lesions, are lesion-location specific, and typically begin from inside the joint as undersurface tears. Repair of posterior SLAP lesions can return overhead-throwing athletes to full overhead athletic functioning. The peel-back mechanism is a likely cause of posterior Type 2 SLAP lesions. To securely repair the posterosuperior labrum to resist torsional peel-back, sulure anchors must be placed posterior to the biceps at the corner of the glenoid. The repair must be protected against external rotation past 0 degree for 3 weeks to avoid undue premature torsional stresses on the repair from the peel-back mechanism. A tight posteroinferior capsule predisposes to Type 2 SLAP lesions in overhead athletes. Shoulders at risk for the dead arm syndrome have a marked loss of internal rotation caused by contracture of the posteroinferior capsule such that less than a 180 degrees arc of rotation is achieved with the arm abducted 90 degrees (the 180 degrees rule). Type 2 SLAP lesions that cause the dead arm syndrome in overhead-throwing athletes are most likely acceleration injuries that occur in late cocking rather than deceleration injuries in follow-through. Rehabilitation of athletes with the dead arm syndrome must include the entire kinetic chain. The root cause of the dead arm syndrome is the Type 2 SLAP lesion.

Athletic Injuries↗

PubMed1998

Spiral fracture of the humerus in a ball thrower.

Spiral fractures of the humerus in ball throwers are rare clinical entities that can be confused with pathologic fractures. These fractures have been reported in various throwing sports, arm wrestling, and hand grenade throwing. They most commonly occur in the distal third of the humerus in young, active individuals. They are often preceded by throwing arm pain. Neurologic sequelae are rare. Herein, a case is presented of spiral fracture of the humerus in a softball player, and the assessment and management of these fractures, as well as their etiologic contrast to stress and pathologic fractures, are reviewed.

Adult↗

PubMedDate not supplied

Technical considerations in knot construction. Part II. Interrupted dermal suture closure.

The purpose of this study was to identify the optimal knot construction for interrupted dermal sutures. A synthetic braided absorbable suture, sizes 3-0 and 5-0, was selected for this evaluation. With reproducible mechanical performance tests, we determined that the construction of secure knots without ears required one additional throw as compared with secure knots with 3-mm ears. The direction of applied tension did not alter knot security, with the exception of granny knots, which required an extra throw when tension was applied parallel to the suture loop. Because interrupted dermal knot construction is accomplished without knot ears and with an applied tension parallel to the wound, one additional throw must be added to the knot to ensure knot security.

Humans↗

PubMed1996

The Effect of Knot Geometry on the Strength of Laparoscopic Slipknots

We evaluated and compared the strength of six extracorporeal slipknots used in laparoscopic surgery as measured with a tensiometer. Two multiple-throw laparoscopic square knots (intracorporeal two-turn flat square knot and extracorporeal sliding square knot) were used as controls. Each knot type was tied five times, and each type tied in random order by the same primary and assisting surgeons using a laparoscopic pelvic surgery training model. A one-way analysis of variance was performed to detect significant differences in knot strengths. The variability in strength for each knot type was determined using Tukey's multiple comparison test. A significant main effect for knot geometry was discovered (p <0.001). The mean knot strengths, 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 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 <0.05) than all slipknots except the 4S and fisherman's knot. These are the strongest laparoscopic slipknots and are the only slipknots that compare in strength with multiple-throw square knots.

Journal Article↗

PubMed2001

Velocity specificity, combination training and sport specific tasks.

Whether velocity-specific resistance training is important for improving functional sporting performance was investigated by studying the effect of isoinertial training velocity on netball chest pass throwing velocity. Twenty-one female netball players were randomly assigned to a strength-trained group (80% 1RM - average training velocity = .308 m/s), power-trained group (60% 1RM - average training velocity = .398 m/s) and a control group. Resistance training was combined with sport specific motion training for both groups over a ten-week training duration. Pre- and post-training testing revealed that the training velocity associated with the strength-trained group produced significantly greater improvement in mean volume of weight lifted (85kg) and mean power output (13.25 W) as compared to the power and control groups (P< 0.05). The strength-trained and power-trained groups significantly improved netball throw velocity by 12.4% and 8.8% respectively. There was no significant difference between the two groups. The validity of velocity-specific training and subsequent adaptations to improve functional sporting performance appears highly questionable, due to the disparity between training velocity and actual movement velocity (11.38 m x s(-1)) for a given sport specific task such as the netball throw it was proposed that the repeated intent to move an isoinertial load as rapidly as possible coupled with performance of the sport-specific movement promote efficient coordination and activation patterns. Such mechanisms might be more important determinants of sport-specific high velocity adaptation.

Acceleration↗

PubMed1990

Coordination of a multi-joint movement in normal humans and in patients with cerebellar dysfunction.

The contribution of the cerebellar cortex to coordination of a multi-joint throwing movement was studied by measuring various movement and EMG parameters while normal control subjects and patients with cerebellar cortical atrophy threw a ball at a target. Although patients did not throw as accurately as controls, several coordination measurements were normal in the patients. These included parameters used by us to assess elbow-wrist coordination and the coordination of hand opening with activation of more proximal arm muscles. Postural support for the movement at the shoulder was also normal in that the shoulder was not pushed backwards by the reaction forces resulting from the rapid forward acceleration of the forearm and hand. In contrast, however, patients were unable to coordinate the muscles so as to produce the same hand direction from trial to trial when throwing at the same target. In addition, EMG onset times were abnormal in the antagonist muscles relative to agonist EMG bursts and kinematic parameters of the movement. In conclusion, our patients with cerebellar cortical atrophy showed abnormalities in visual-motor coordination, in that they were unable to consistently produce the appropriate hand direction in response to a visual target. Agonist-antagonist relationships were also impaired. Other aspects of coordination, such as the relative timing of EMG onsets of agonist muscles, even when these were active at different joints, were normal.

Adult↗

PubMed2004

Perceiving distance: a role of effort and intent.

Perceiving egocentric distance is not only a function of the optical variables to which it relates, but also a function of people's current physiological potential to perform intended actions. In a set of experiments, we showed that, as the effort associated with walking increases, perceived distance increases if the perceiver intends to walk the extent, but not if the perceiver intends to throw. Conversely, as the effort associated with throwing increases, perceived distance increases if people intend to throw to the target, but not if they intend to walk. Perceiving distance combines the geometry of the world with our behavior goals and the potential of our body to achieve these goals.

Adult↗

PubMed2005

Evaluation of exercise performance in healthy Turkish adolescents.

In this study, exercise performance was evaluated in 259 healthy adolescents by using some tests. The purpose of the study was to investigate exercise performance and cardiorespiratory capacity in both adolescent boys and girls. The following tests were applied to all children: ball throw with right and left hands, vertical jump, long jump without prior motion, pull up (repetition number), flexibility, and agility (set repetition number) tests. Additionally, heart rate and systolic and diastolic blood pressures were measured. Applied spirometric tests were as follows: vital capacity, forced vital capacity, forced expiration volume in the first second, ventilation volume, maximum volunteer ventilation and respiration frequency. This study found that heart rate was statistically significantly higher in females than males (p < .05). There was also a statistically significant difference in vital capacity, forced vital capacity and forced expiratory volume in the first second (in both measured and predicted values) between males and females (p < .05). Additionally, it was found that there were statistically significant differences in the 60 and 200 meters races, maximal pull up, maximal sit up, vertical jump, standing long jump, ball throwing with right hand, horizontal bar, and agility between the male and female groups (p < .05). In conclusion, the findings showed that although females were superior in the 60 and 200 meter race, males were superior in agility, horizontal bar, ball throwing with right hand, long jump, and vertical jump.

Adolescent↗

PubMed1997

Maximizing performance feedback effectiveness through videotape replay and a self-controlled learning environment.

This study was designed to examine whether participants who could control the schedule of performance feedback (KP) would learn differentially from those who received a rigid feedback schedule while learning a complex task. Participants (N = 48) were randomly assigned to self-controlled KP (SELF), summary KP (SUMMARY), yoked control (YOKE), or knowledge of results only (KR) conditions. Data collection consisted of an acquisition phase and a 4-day retention phase during which right-handed participants performed a left-handed ball throw. Overall, throwing form improved across trial blocks during acquisition, with the SUMMARY, SELF, and YOKE groups showing more improvement than the KR group. During retention, the SELF group retained a higher level of throwing form and accuracy in comparison to the other groups. Results suggest that when given the opportunity to control the feedback environment, learners require relatively less feedback to acquire skills and retain those skills at a level equivalent to or surpassing those who are given more feedback but receive it passively.

Biofeedback, Psychology↗

PubMedDate not supplied

A model of suture-induced urolithiasis with urographic control in the bladder of the rat.

The characteristics of a model of urolithiasis in the bladder of male Wistar rats were evaluated. Two techniques were compared: one knot of suture material through the bladder wall, or 15-throw knots inside the bladder. Rats were randomly assigned to one of six groups, according to the technique and suture material used (polyester, silk, or chromic catgut). An excretory urogram was performed at days 30, 60, and 90. At the moment of positive radiographic diagnosis, animals were sacrificed and stones were obtained. All rats were sacrificed at day 90 regardless of the x-ray results. Variables evaluated were average days to a positive urogram, average weight of all uroliths, and percentage of animals developing urolithiasis throughout the study. There were no statistical differences between groups for the average weight of stones, which ranged from 0.008 to 1.502 g for individual cases. All three materials were more lithogenic with the 15-throw knot inside technique. No significant differences were detected for lithogenesis criteria between suture materials. X-ray dispersion spectroscopy evidenced calcium phosphate composition of two stones from chromic catgut, and magnesium phosphate composition of two stones from chromic catgut, two from silk, and two from polyester. Neo-epithelization over the suture was confirmed microscopically in bladders with the one-throw technique. We conclude that (1) this is an effective model of urolithiasis, with predictability in time, composition, and amount of stone formation; (2) the presence of more suture material inside the bladder is more lithogenic; and (3) excretory urograms are highly sensitive and specific for the noninvasive diagnosis of bladder urolithiasis.

Animals↗

PubMed2004

Is there geographical variation in human handedness?

Right- and left-handed individuals are present in all cultures. However, while it is known that handedness is a heritable trait, little is known about how handedness varies between populations-and without this knowledge, the significance of the left/right polymorphism is hard to interpret. We reviewed the literature to assess the extent of geographical variation of throwing or hammering handedness. These two tasks were chosen because they are present in all known cultures (unlike, for example, writing), and make sense within the context of several adaptive theories on the origin of laterality, or maintenance of handedness polymorphism, which state that tool or weapon manipulation are pivotal. A total of 81 samples were found with primary data on throwing or hammering handedness, spanning 14 countries and concerning more than 1,214,000 individuals studied between 1922 and 1998. A global logistic regression was performed to assess the significance of the country of the study, controlling for several potentially confounding variables (date of the study, sex and age of individuals). Country always had a significant effect, consistent with substantial geographical variation of throwing and hammering handedness. Curiously, left-handedness frequency estimates for a given country were not always consistent across datasets, perhaps due to missing variables, such as educational level or socio-economic status. Results are discussed in the context of the evolution of handedness and the significance of the current polymorphism.

Biological Evolution↗

PubMed2002

Kinematic and kinetic comparisons between American and Korean professional baseball pitchers.

The purpose of this study was to quantify and compare kinematic, temporal, and kinetic characteristics of American and Korean professional pitchers in order to investigate differences in pitching mechanics, performance, and injury risks among two different cultures and populations of baseball pitchers. Eleven American and eight Korean healthy professional baseball pitchers threw multiple fastball pitches off an indoor throwing mound positioned at regulation distance from home plate. A Motion Analysis three-dimensional automatic digitizing system was used to collect 200 Hz video data from four electronically synchronized cameras. Twenty kinematic, six temporal, and 11 kinetic variables were analyzed at lead foot contact, during the arm cocking and arm acceleration phases, at ball release, and during the arm deceleration phase. A radar gun was used to quantify ball velocity. At lead foot contact, the American pitchers had significantly greater horizontal abduction of the throwing shoulder, while Korean pitchers exhibited significantly greater abduction and external rotation of the throwing shoulder. During arm cocking, the American pitchers displayed significantly greater maximum shoulder external rotation and maximum pelvis angular velocity. At the instant of ball release, the American pitchers had significantly greater forward trunk tilt and ball velocity and significantly less knee flexion, which help explain why the American pitchers had 10% greater ball velocity compared to the Korean pitchers. The American pitchers had significantly greater maximum shoulder internal rotation torque and maximum elbow varus torque during arm cocking, significantly greater elbow flexion torque during arm acceleration, and significantly greater shoulder and elbow proximal forces during arm deceleration. While greater shoulder and elbow forces and torques generated in the American pitchers helped generate greater ball velocity for the American group, these greater kinetics may predispose this group to a higher risk of shoulder and elbow injuries.

Adult↗

PubMed1999

Shoulder proprioception: latent muscle reaction times.

PURPOSE: The purpose of this study was to identify electromyographic (EMG) differences in the latent muscle reaction timing (LMRT) of the rotator cuff between trained overhead throwers and control subjects in response to sudden internal rotation perturbation (P < or = 0.05). METHODS: Subjects included 15 trained overhead throwers (male intercollegiate baseball players) and 15 untrained subjects (males not active in competitive throwing sports). Subjects were tested while seated, with their dominant glenohumeral joint positioned in 90 degrees abduction/external rotation (scapular plane), their elbow flexed to 90 degrees, and their forearm placed in the perturbation device. Rotator cuff LMRT was assessed as they tried to decelerate a variably timed, sudden internal rotation force. EMG sampling (2000 Hz, 2-s duration) began immediately before perturbation. RESULTS: Trained throwers had slower infraspinatus (P = 0.011) and teres minor (P = 0.024) LMRT and decreased supraspinatus (P = 0.001) and posterior deltoid (P = 0.0001) muscle activation duration compared with control subjects. CONCLUSIONS: These results suggest that the rotator cuff muscles of trained throwers may be downregulated in response to sudden internal rotation perturbation. Although these adaptations would enable greater internal rotation velocities during overhead throwing, they may also contribute to glenohumeral joint pathology. The identification of changes in rotator cuff LMRT in response to sudden internal rotation perturbation suggests an area of acquired neuromuscular imbalance warranting consideration by those involved in the rehabilitation and conditioning of the overhead throwing athlete.

Adolescent↗

PubMed2002

Physical performance responses during 72 h of military operational stress.

PURPOSE: To characterize the impact of prolonged work, underfeeding, and sleep deprivation (i.e., sustained operations; SUSOPS) on physical and occupational related performance during military operational stress. METHODS: Ten male soldiers were tested on days 1 (D1), 3 (D3), and 4 (D4) of a control and an experimental week that included prolonged physical work (total daily energy expenditure approximately 4,500 kcal x d(-1)), underfeeding (approximately 1,600 kcal x d(-1)), and sleep deprivation (approximately 2 h x d(-1)). Body composition was measured with dual-energy x-ray absorptiometry (DEXA). Ballistic power was assessed by 30 repetitive squat jumps and bench-press throws. Military-relevant occupational performance was evaluated with a 10-min box lift, obstacle course, grenade throw, rifle marksmanship, and a 25-min wall-build task. RESULTS: Fat-free mass (-2.3%) and fat mass (-7.3%) declined (P </= 0.05) during SUSOPS. Squat-jump mean power (-9%) and total work (-15%) declined (P </= 0.05) during SUSOPS. Bench-press power output, grenade throw, and marksmanship for pop-up targets were not affected. Obstacle course and box-lift performances were lower (P </= 0.05) on D3 but showed some recovery on D4. Wall building was approximately 25% lower (P </= 0.05) during SUSOPS. CONCLUSION: Decrements in performance during SUSOPS are primarily restricted to tasks that recruit muscles that are over-utilized without adequate recovery. General military skill tasks and occupational physical performance tasks are fairly well maintained.

Adaptation, Physiological↗