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Steven W. Barrentine, Tomoyuki Matsuo, Rafael F. Escamilla, Glenn S. Fleisig and James R. Andrews

Previous researchers studying baseball pitching have compared kinematic and kinetic parameters among different types of pitches, focusing on the trunk, shoulder, and elbow. The lack of data on the wrist and forearm limits the understanding of clinicians, coaches, and researchers regarding the mechanics of baseball pitching and the differences among types of pitches. The purpose of this study was to expand existing knowledge of baseball pitching by quantifying and comparing kinematic data of the wrist and forearm for the fastball (FA), curveball (CU) and change-up (CH) pitches. Kinematic and temporal parameters were determined from 8 collegiate pitchers recorded with a four-camera system (200 Hz). Although significant differences were observed for all pitch comparisons, the least number of differences occurred between the FA and CH. During arm cocking, peak wrist extension for the FA and CH pitches was greater than for the CU, while forearm supination was greater for the CU. In contrast to the current study, previous comparisons of kinematic data for trunk, shoulder, and elbow revealed similarities between the FA and CU pitches and differences between the FA and CH pitches. Kinematic differences among pitches depend on the segment of the body studied.

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Josje van Houwelingen, Sander Schreven, Jeroen B.J. Smeets, Herman J.H. Clercx and Peter J. Beek

In this paper, a literature review is presented regarding the hydrodynamic effects of different hand and arm movements during swimming with the aim to identify lacunae in current methods and knowledge, and to distil practical guidelines for coaches and swimmers seeking to increase swimming speed. Experimental and numerical studies are discussed, examining the effects of hand orientation, thumb position, finger spread, sculling movements, and hand accelerations during swimming, as well as unsteady properties of vortices due to changes in hand orientation. Collectively, the findings indicate that swimming speed may be increased by avoiding excessive sculling movements and by spreading the fingers slightly. In addition, it appears that accelerating the hands rather than moving them at constant speed may be beneficial, and that (in front crawl swimming) the thumb should be abducted during entry, catch, and upsweep, and adducted during the pull phase. Further experimental and numerical research is required to confirm these suggestions and to elucidate their hydrodynamic underpinnings and identify optimal propulsion techniques. To this end, it is necessary that the dynamical motion and resulting unsteady effects are accounted for, and that flow visualization techniques, force measurements, and simulations are combined in studying those effects.

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E. Randy Eichner

Sickle cell trait can pose a grave risk for some athletes. In the past few years, exertional sickling has killed nine athletes, including five college football players in training. Exercise-physiology research shows how and why sickle red cells can accumulate in the bloodstream during intense exercise bouts. Sickle cells can “logjam” blood vessels and lead to collapse from ischemic rhabdomyolysis. Diverse clinical and metabolic problems from explosive rhabdomyolysis can threaten life. Sickling can begin in 2-3 minutes of any all-out exertion, or during sustained intense exertion – and can reach grave levels very soon thereafter if the athlete struggles on or is urged on by coaches despite warning signs. Heat, dehydration, altitude, and asthma can increase the risk for and worsen sickling. This exertional sickling syndrome, however, is unique and in the field can be distinguished from heat illnesses. Sickling collapse is a medical emergency. Fortunately, screening and precautions can prevent sickling collapse and enable sickle-trait athletes to thrive in their sports.

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Ludovic Seifert, Dominic Orth, Jérémie Boulanger, Vladislavs Dovgalecs, Romain Hérault and Keith Davids

This study investigated a new performance indicator to assess climbing fluency (smoothness of the hip trajectory and orientation of a climber using normalized jerk coefficients) to explore effects of practice and hold design on performance. Eight experienced climbers completed four repetitions of two, 10-m high routes with similar difficulty levels, but varying in hold graspability (holds with one edge vs holds with two edges). An inertial measurement unit was attached to the hips of each climber to collect 3D acceleration and 3D orientation data to compute jerk coefficients. Results showed high correlations (r = .99, P < .05) between the normalized jerk coefficient of hip trajectory and orientation. Results showed higher normalized jerk coefficients for the route with two graspable edges, perhaps due to more complex route finding and action regulation behaviors. This effect decreased with practice. Jerk coefficient of hip trajectory and orientation could be a useful indicator of climbing fluency for coaches as its computation takes into account both spatial and temporal parameters (ie, changes in both climbing trajectory and time to travel this trajectory).

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Damien Clement and Vanessa R. Shannon

Context:

According to the buffering hypothesis, social support moderates the harmful effects of stress and, in turn, indirectly affects injured athletes’ health and well-being. Previous research suggests that perceptions of social support influence athletes’ psychological reactions, as well as their rehabilitation adherence, but additional research in this area is warranted.

Objective:

To examine injured athletes’ perceptions regarding satisfaction, availability, and contribution for each of the 8 types of social support.

Design:

Descriptive.

Setting:

Mid-Atlantic Division II and III institutions.

Participants:

49 injured athletes.

Main Outcome Measures:

Social support was assessed using a modified version of the Social Support Survey.

Results:

Injured athletes were significantly more satisfied with social support provided by athletic trainers (ATCs) than that provided by coaches and teammates. In addition, injured athletes reported that social support provided by ATCs contributed significantly more to their overall well-being. Athletes reported several significant differences regarding satisfaction and contribution to well-being among the 8 different types of social support.

Conclusions:

Injury, an unavoidable part of sport, is often accompanied by negative psychological reactions. This reaction may have a negative influence on an athlete’s experience of injury and rehabilitation. Findings suggest that perceptions of social support provided by ATCs have the greatest influence on injured athletes’ rehabilitation and well-being.

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Paige Guild, Monica R. Lininger and Meghan Warren

Clinical Scenario: Female college student-athletes (SA) often experience time loss from musculoskeletal injuries to the lower extremities. This can lead to lengthy rehabilitation, expensive medical bills, and declines in health-related quality of life. Identifying at-risk athletes prior to the start of an athletic season may allow coaches or athletic trainers to prescribe an injury prevention program. Clinical Question: In female college SA, are preseason single leg hop (SLH) scores associated with identifying those at risk for lower-extremity musculoskeletal injuries? Summary of Key Findings: Five prospective cohort studies in female SA scored athletes on the SLH prior to the start of the athletic sport season. One of 5 studies found an association of SLH with injury risk. An additional 2 studies found that the SLH as part of a battery of functional performance tests was associated with injury risk in some anatomic locations (eg, thigh/knee), but not overall injury risk. Clinical Bottom Line: Methodological limitations of the reviewed studies limits a final conclusion, and there is insufficient evidence to determine if the SLH should be used as a sole functional performance test to identify at-risk female SA; it may be useful as part of a battery of functional performance tests for female college SA. Strength of Recommendation: All studies were prospective cohort studies (level 3).

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Vishveshwar R. Mantha, António J. Silva, Daniel A. Marinho and Abel I. Rouboa

The aim of the current study was to analyze the hydrodynamics of three kayaks: 97-kg-class, single-rower, flatwater sports competition, full-scale design evolution models (Nelo K1 Vanquish LI, LII, and LIII) of M.A.R. Kayaks Lda., Portugal, which are among the fastest frontline kayaks. The effect of kayak design transformation on kayak hydrodynamics performance was studied by the application of computational fluid dynamics (CFD). The steady-state CFD simulations where performed by application of the k-omega turbulent model and the volume-of-fluid method to obtain two-phase flow around the kayaks. The numerical result of viscous, pressure drag, and coefficients along with wave drag at individual average race velocities was obtained. At an average velocity of 4.5 m/s, the reduction in drag was 29.4% for the design change from LI to LII and 15.4% for the change from LII to LIII, thus demonstrating and reaffirming a progressive evolution in design. In addition, the knowledge of drag hydrodynamics presented in the current study facilitates the estimation of the paddling effort required from the athlete during progression at different race velocities. This study finds an application during selection and training, where a coach can select the kayak with better hydrodynamics.

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Tomoyuki Matsuo, Tsuyoshi Matsumoto, Yoshiyuki Mochizuki, Yoshihiro Takada and Kenji Saito

Baseball coaches train pitchers to keep their shoulder abduction at 90º during delivery, because this angle is believed to maximize ball speed and reduce the stress on the throwing arm. In fact, however, the shoulder abduction angle for some pitchers, including professional pitchers, deviates from 90º. There likely are reasons for such deviation. The purposes of this study, therefore, were to investigate the effects of shoulder abduction angle on ball velocity and on the injury-related joint kinetic variable, and to determine why the shoulder abduction angle varies among pitchers. Eleven professional pitchers were videotaped with two high-speed cameras. The resulting kinematic data were used to simulate several pitching motions by varying the shoulder abduction angle from the actual angle. Maximum wrist velocity was used as a reasonable approximation of ball velocity. Elbow varus torque was used as a kinetic variable. The square torque for the throwing arm and torque change for the throwing arm were used to investigate the cause of the variation. It was found that the shoulder abduction angle of 90º did not always maximize wrist velocity nor minimize elbow varus torque. The actual shoulder abduction angle for each pitcher was highly consistent with the angle that minimized both square torque and torque change. The results suggested that the proficient throwers in this study moved their pitching arm so as to minimize mechanical cost while at the same time optimizing performance.

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Jaebin Shim, Deanna H. Smith and Bonnie L. Van Lunen

Clinical Scenario:

Over the past decade, sport-related concussions have received increased attention due to their frequency and severity over a wide range of athletics. Clinicians have developed return-to-play protocols to better manage concussions in young athletes; however, a standardized process projecting the length of recovery time after concussion has remained an elusive piece of the puzzle. The recovery times associated with such an injury once diagnosed can last anywhere from 1 wk to several months. Risk factors that could lead to protracted recovery times include a history of 1 or multiple concussions and a greater number, severity, and duration of symptoms after the injury. Examining the possible relationship between on-field or sideline signs and symptoms and recovery times would give clinicians the confident ability to properly treat and manage an athlete’s recovery process in a more systematic manner. Furthermore, identifying factors after a head injury that may be predictive of protracted recovery times would be useful for athletes, parents, and coaches alike.

Focused Clinical Question:

Which on-field and sideline signs and symptoms affect length of recovery after concussion in high school and college athletes?

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Jamie R. Skaggs, Elizabeth R. A. LaGuardia Joiner, Milo Sini, Tishya A.L. Wren, Regina P. Woon and David L. Skaggs

Context:

A commonly encountered clinical scenario in athletic training is determining what body position is best for pulmonary recovery after strenuous training. Coaches often advise athletes to put their hands behind their heads following rigorous training, but this practice has no scientific support.

Objective:

The purpose of this study is to determine how arm and body position affects ventilation in high school athletes. Our hypothesis is that a position in which the athlete is bent forward with the hands on the knees maximizes ventilation.

Design:

Case series.

Methods:

Seventeen healthy members of a high school track team, 8 females and 9 males with a mean age of 16.3 years (range: 14.6–18.5 years), performed a maximal voluntary ventilation (MVV) test using a portable spirometer in three different positions: standing with (1) hands behind the head, (2) arms at the sides, and (3) leaning forward with hands resting on the knees.

Results:

The MVV performed with hands on knees (120.2 ± 5.9 L/min) was significantly higher than the MVV performed with hands at sides (109.3 ± 7.0 L/min; p = .004) and with hands behind head (114.1 ± 5.9 L/min; p = .03). The MVV performed with hands behind head and with arms at side did not differ significantly (p = .20).

Conclusions:

This is the first study examining the best body position to maximize ventilation in athletes. Leaning forward and placing the hands on the knees led to a significantly greater MVV compared with standing with the arms at the side and standing with the hands behind the head.