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Ross H. Sanders and Peter C. Owens

Many golf coaches refer to a focal point or “hub” of a golf swing and encourage players to imagine the clubhead rotating about this point. The purpose of this study was to locate the hub of the swings of elite (handicaps 0–5) and novice golfers. Six novice and six elite players (all male) each performed 10 swings with the 3-wood provided. Motions of reflective markers attached to the vertex and chin of the subject and three points along the shaft of the club were recorded on videotape. The position of the hub at sampled instants during the swing was defined by the intersection of normals to the clubhead path. Among elite players the hub was not fixed and the pattern of hub movement was consistent. The radius of the hub to the clubhead reached a maximum near impact. Novice players tended to achieve maximum radius after impact and the hub patterns were inconsistent.

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Peter J. Worthington, Mark A. King and Craig A. Ranson

The aim of this study was to identify the key aspects of technique that characterize the fastest bowlers. Kinematic data were collected for 20 elite male fast bowlers with 11 kinematic parameters calculated, describing elements of fast bowling technique that have previously been linked to ball release speed. Four technique variables were identified as being the best predictors of ball release speed, explaining 74% of the observed variation in ball release speed. The results indicate that the fastest bowlers have a quicker run-up and maintain a straighter knee throughout the front foot contact phase. The fastest bowlers were also observed to exhibit larger amounts of upper trunk flexion up to ball release and to delay the onset of arm circumduction. This study identifies those technique variables that best explain the differences in release speeds among fast bowlers. These results are likely to be useful in both the coaching and talent identification of fast bowlers.

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Clara Teixidor-Batlle, Carles Ventura Vall-llovera, Justine J. Reel and Ana Andrés

within the sport culture, it is essential to have valid screening tools available to coaches, sports psychologists, athletic trainers, and other stakeholders to identify at-risk athletes ( Pope, Gao, Bolter, & Pritchard, 2015 ). Initially, weight pressures screening instruments were sport specific, for

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Annamari Maaranen, Judy L. Van Raalte and Britton W. Brewer

skills regardless of the feeling, such as when pressured by coaches, has been described as a factor that increases the severity of the problem, and pressure from an upcoming competition or performance has been identified as a trigger of the balking phase of flikikammo among some athletes ( Day et

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Volker Nolte

The purpose of this investigation was to clarify the effects of blade design and oar length on performance in rowing. Biomechanical models and equations of motion were developed to identify the main forces that affect rowing performance. In addition, the mechanical connection between the propelling blade force and the force that the rower applies on the handle was established. On this basis it was found that the blade design and oar dimensions play a significant role on the rowing performance. While rowers have found empirically that larger and/or hydrodynamically more efficient blade shapes need to be rowed with shorter oars, this article explains this tendency from a biomechanical point of view. Based on the presented evidence, it can be concluded that shorter oars will allow rowers to improve the propelling forces without increasing the handle forces. These findings explain tendencies that started with the introduction of new blade shapes in 1991. A 2 × 2 factorial ANOVA was used to test the significance of the oar shortenings that occurred with the introduction of larger blade surfaces while international record times improved during all those years. Consequently, the findings of this investigation encourage coaches to further experiment with shorter oars and oar manufacturers to continue their blade development that would lead to even shorter oars, with the goal of continuous rowing performance improvements.

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Max C. Stuelcken, René E.D. Ferdinands and Peter J. Sinclair

This study aimed to investigate the bowling techniques of female fast bowlers and identify any association between a history of low back pain (LBP) and the movement patterns of the thorax relative to the pelvis during the delivery stride of the bowling action. Three-dimensional kinematic data were collected from 26 elite Australian female fast bowlers using an eight-camera Vicon motion analysis system. Nineteen bowlers used a mixed action, 6 bowlers used a semiopen action, and 1 bowler used a side-on action. Fourteen bowlers had a history of LBP. Eight of these 14 bowlers used a mixed action, and bowlers with more shoulder counterrotation were no more likely to have a history of LBP. Bowlers with a history of LBP positioned the thorax in more left lateral flexion relative to the pelvis between 73–79% of the delivery stride, and moved the thorax through a significantly greater range of lateral flexion relative to the pelvis during the delivery stride compared with bowlers with no history of LBP. This information will give coaches and support staff a better understanding of female bowling technique and may facilitate better screening practices for elite female cricketers.

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Matthew T.G. Pain

Bilateral deficit is well documented; however, bilateral deficit is not present in all tasks and is more likely in dynamic activities than isometric activities. No definitive mechanism(s) for bilateral deficit is known but an oft cited mechanism is lower activation of fast twitch motor units. The aim of this study was to produce comparable and consistent one and two legged drop jumps to examine bilateral deficit in elite power athletes and elite endurance athletes. Seven power athletes and seven endurance athletes performed single and double leg drop jumps from a range of heights that equalized loading per leg in terms of: height dropped, energy absorbed, and momentum absorbed. Force and motion data were collected at 800 Hz. Bilateral deficit for jump height, peak concentric force, and peak concentric power were calculated. Power athletes had a significantly greater (P < .05) bilateral deficit for jump height and peak power, possibly due to power athletes having more fast twitch motor units, however, endurance athletes generally had a bilateral surfeit which could confound this inference. Results indicate that equalizing loading by impulse per leg is the most appropriate and that a consistent drop height can be obtained with a short 10 minute coaching session.

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Mostafa Yaghoubi, Mohamad Mahdi Esfehani, Hossein Asghar Hosseini, Yaser Alikhajeh and Sarah P. Shultz

The aim of this study was to compare muscle activity patterns between inexperienced and experienced water polo players while taking an overhead shot. The study was carried out with a group of 12 water polo players and an inexperienced group of 10 healthy participants. Signals were recorded by surface electromyography from six different muscles. The average and standard deviation of the normalized electrical activity, time to peak, time broadness, and muscle sequencing during the overhead shot were determined for each muscle in both groups and compared with each other. In water polo players, the normalized electrical activities of triceps brachii, pectoralis major, and wrist flexors were greater than other muscles, while in the inexperienced group the triceps brachii specifically played an important role. There was minimal activation of the middle deltoid and biceps brachii in water polo players. Increased times to peak and time broadness of muscles were found in the inexperienced group compared to experienced water polo players; this difference may be explained by different neuromuscular proprioception. Only experienced water polo players activated the observed muscles in a specific sequence, from proximal to distal. Therefore, coaches should emphasize smooth and quick transitions from proximal to distal segments, with less importance placed on individual muscle strengthening.

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Andrew A. Dingley, David B. Pyne and Brendan Burkett

Disabilities in Paralympic swimming could impact a swimmer’s ability to execute an effective swim-start. We examined how swim-start performance differed between severity and type of physical disability. Swim-starts were measured in 55 elite Paralympic swimmers from eight different Paralympic classes; S14, S13, S10-S6, S3 grouped as no- (classes S13 & S14), low- (S9 & S10), mid- (S7 & S8) or high- (≤ S6) severity of physical disability and also by type of physical disability (upper, lower, and palsy) to provide meaningful comparisons. The swimmer’s competitive level was determined by the international point score (IPS). Swimmers with no physical disability were significantly faster in most swim-start phases compared with those with physical disabilities, as were swimmers with low-severity disabilities compared with the mid- and high-severity groups. Block velocity was highly negatively correlated (r = –0.57 to –0.86) with 15-m swimming time for all groups except high-severity disabilities. Free-swim velocity is a priority area for improving swim-starts for swimmers regardless of disability, given large correlations between this measure and IPS. Swimmers with lower body or high-severity disabilities spent a smaller percentage of time overall in the underwater phase. Assessment of four specific phases of the swim-start highlight distinctive priorities for coaches working with Paralympic swimmers in an applied biomechanical manner.

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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.