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Serkan Uslu and Emel Çetin Özdoğan

Instep kick is one of the most effective kicking techniques in soccer. Lower extremity muscles and joints play a crucial role during instep kick. However, external (EF) and internal focus and their effect on the muscles are still ambiguous. In this study, 13 male adolescent soccer players were included and aimed to hit the targets in internal and EF conditions. Lower extremity muscle activations were measured with surface electromyography, and kinematics were measured with a high-speed video camera. Muscle activations and movement latencies were analyzed in four different phases (backswing, leg cocking, acceleration, and follow-through) of kicking. While 10 out of 13 participants kicked accurately in internal focus, only five out of 13 in EF kicked accurately. Gastrocnemius muscle activations increased significantly in EF in all phases except acceleration. Movement latencies were found 0.07 ± 0.002 s for accurate and 0.05 ± 0.004 s for inaccurate kicks in EF. A correlation has been found between accuracy and movement latency in EF (R = .67). Our results suggest that novices cannot yet coordinate their muscles in EF, cocontraction ratio increases. Therefore, training strategies that aim to reduce the cocontraction ratio can help the athlete increase performance through better motor coordination. Moreover, better motor coordination may be beneficial in preventing injuries (joint stiffness, etc.) caused by increased cocontraction ratio.

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Sarah A. Roelker, Paul DeVita, John D. Willson, and Richard R. Neptune

Skipping has been proposed as a viable cross-training exercise to running due to its lower knee contact forces and higher whole-body energy expenditure. However, how individual muscle forces, energy expenditure, and joint loading are affected by differences in running and skipping mechanics remains unclear. The purpose of this study was to compare individual muscle forces, energy expenditure, and lower extremity joint contact forces between running and skipping using musculoskeletal modeling and simulations of young adults (n = 5) performing running and skipping at 2.5 m·s−1 on an instrumented treadmill. In agreement with previous work, running had greater knee and patella contact forces than skipping which was accompanied by greater knee extensor energetic demand. Conversely, skipping had greater ankle contact forces and required greater energetic demand from the uniarticular ankle plantarflexors. There were no differences in hip contact forces between gaits. These findings further support skipping as a viable alternative to running if the primary goal is to reduce joint loading at the commonly injured patellofemoral joint. However, for those with ankle injuries, skipping may not be a viable alternative due to the increased ankle loads. These findings may help clinicians prescribe activities most appropriate for a patient’s individual training or rehabilitation goals.

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Adam J. Petway, Matthew J. Jordan, Scott Epsley, and Philip Anloague

A systematic search was performed of online databases for any Achilles tendon (AT) injuries occurring within the National Basketball Association (NBA). Video was obtained of injuries occurring during competition and downloaded for analysis in Dartfish. NBA athletes (n = 27) were identified with AT rupture over a 30-year period (1991–2021). Of the 27 NBA athletes found to have AT ruptures (mean age: 29.3 [3.3] y; average time in the NBA: 8.5 [3.8] y), 15 in-game videos were obtained for analysis. Noncontact rupture was presumed to have occurred in 12/13 cases. Eight of the 13 athletes had possession of the ball during time of injury. The ankle joint of the injured limb for all 13 athletes was in a dorsiflexed position during the time of injury (47.9° [6.5°]). All 13 athletes performed a false-step mechanism at time of injury where they initiated the movement by taking a rearward step posterior to their center of mass with the injured limb before translating forward. NBA basketball players that suffered AT ruptures appeared to present with a distinct sequence of events, including initiating a false step with ankle dorsiflexion of the injured limb at the time of injury.

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Dennis W. Klima, Ethan Hood, Meredith Madden, Rachel Bell, Teresa Dawson, Catherine McGill, and Michael Patterson

Concussion screening among collegiate lacrosse athletes is a major safety priority. Although attention has been directed at concussion management following injury, less is known about the association between cognition and balance during preseason screening. The purpose of the study was to assess the relationship between balance and neurocognition among collegiate male lacrosse players and to examine predictive determinants of postural stability. Participants included a convenience sample of 49 male collegiate Division 3 lacrosse players who completed a demographic survey and performed the immediate postconcussion test (ImPACT) and instrumented Sensory Organization Test (SOT). There was a significant association between balance SOT performance and both verbal memory (r = .59, p < .01) and visual motor speed scores (r = .43, p < .05). Significant correlations between verbal memory and SOT Conditions 2, 5, and 6 were also noted (all p < .05). Verbal memory predicted 33% of the variance in the SOT composite balance score (p < .001). Our results indicate a significant relationship exists between postural stability and both verbal memory and visual processing speed among collegiate male lacrosse players and supports vestibulocortical associations. Findings warrant ongoing performance and executive function tracking and can serve as a conduit for integrated sensorimotor and dual-task training.

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Ming Hui Li, Jane Jie Yu, Stephen Heung Sang Wong, Raymond Kim Wai Sum, and Cindy Hui Ping Sit

This study aimed to examine the associations between perceived social support, perceived competence, and physical activity in children with physical and intellectual disabilities during the COVID-19 pandemic. During the third wave of the pandemic in Hong Kong (i.e., July through December 2020), 291 participants age 6–17 years from 27 special schools were included. After controlling for demographic variables, the total variance explained by perceived social support and perceived competence was 24%, F(2, 240) = 12.42, p < .001, with perceived competence having a stronger association with physical activity (β = 0.29, p < .001) than perceived social support (β = 0.07, p = .22). This study highlights two key facilitators for shaping physical activity involvement among children with disabilities during the COVID-19 pandemic.

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Maggie Evans, Kelly J. Rohan, Jonah Meyerhoff, Richard J. Norton, and Jeremy S. Sibold

Mood deterioration in response to exercise cessation is well documented, but moderators of this effect remain unknown. This study tested the hypothesis that physically active individuals with higher levels of cognitive vulnerability (i.e., tendencies toward negative thought content and processes in response to stress or negative mood states) are at greater risk for increased anxiety and depressive symptoms when undergoing exercise cessation. Community adults meeting recommended physical activity guidelines (N = 36) participated in a 4-week prospective, longitudinal study with 2 weeks each of maintained exercise and exercise cessation. Cognitive vulnerability measures included dysfunctional attitudes, brooding rumination, and cognitive reactivity (i.e., change in dysfunctional attitudes over a dysphoric mood induction). Anxiety and depression symptoms increased during exercise cessation. Brooding emerged as a risk factor for increases in tension scores on the Profile of Mood States–Brief during exercise cessation. Future studies should explore brooding as a mediator (i.e., potential mechanism) of exercise-induced mood deterioration.

Open access

Dayuan Xu, Jiwon Park, Jiseop Lee, Sungjune Lee, and Jaebum Park

Gravity provides critical information for the adjustment of body movement or manipulation of the handheld object. Indeed, the changes in gravity modify the mechanical constraints of prehensile actions, which may be accompanied by the changes in control strategies. The current study examined the effect of the gravitational force of a handheld object on the control strategies for subactions of multidigit prehension. A total of eight subjects performed prehensile tasks while grasping and lifting the handle by about 250 mm along the vertical direction. The experiment consisted of two conditions: lifting gravity-induced (1g) and weightless (0g) handheld objects. The weightless object condition was implemented utilizing a robot arm that produced a constant antigravitational force of the handle. The current analysis was limited to the two-dimensional grasping plane, and the notion of the virtual finger was employed to formulate the cause–effect chain of elemental variables during the prehensile action. The results of correlation analyses confirmed that decoupled organization of two subsets of mechanical variables was observed in both 1g and 0g conditions. While lifting the handle, the two subsets of variables were assumed to contribute to the grasping and rotational equilibrium, respectively. Notably, the normal forces of the thumb and virtual finger had strong positive correlations. In contrast, the normal forces had no significant relationship with the variables as to the moment of force. We conclude that the gravitational force had no detrimental effect on adjustments of the mechanical variables for the rotational action and its decoupling from the grasping equilibrium.

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Heiko Wagner, Kim Joris Boström, Marc H.E. de Lussanet, Myriam L. de Graaf, Christian Puta, and Luis Mochizuki

Because of the redundancy of our motor system, movements can be performed in many ways. While multiple motor control strategies can all lead to the desired behavior, they result in different joint and muscle forces. This creates opportunities to explore this redundancy, for example, for pain avoidance or reducing the risk of further injury. To assess the effect of different motor control optimization strategies, a direct measurement of muscle and joint forces is desirable, but problematic for medical and ethical reasons. Computational modeling might provide a solution by calculating approximations of these forces. In this study, we used a full-body computational musculoskeletal model to (a) predict forces measured in knee prostheses during walking and squatting and (b) study the effect of different motor control strategies (i.e., minimizing joint force vs. muscle activation) on the joint load and prediction error. We found that musculoskeletal models can accurately predict knee joint forces with a root mean squared error of <0.5 body weight (BW) in the superior direction and about 0.1 BW in the medial and anterior directions. Generally, minimization of joint forces produced the best predictions. Furthermore, minimizing muscle activation resulted in maximum knee forces of about 4 BW for walking and 2.5 BW for squatting. Minimizing joint forces resulted in maximum knee forces of 2.25 BW and 2.12 BW, that is, a reduction of 44% and 15%, respectively. Thus, changing the muscular coordination strategy can strongly affect knee joint forces. Patients with a knee prosthesis may adapt their neuromuscular activation to reduce joint forces during locomotion.

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Lara Pomerleau-Fontaine, Gordon A. Bloom, and Danielle Alexander

The majority of research on the coach–athlete relationship has been explored from the perspective of able-bodied athletes. The purpose of this study was to explore wheelchair basketball athletes’ perceptions of the coach–athlete relationship. Timelining and semistructured interviews were conducted with six wheelchair basketball athletes, and data were analyzed using a reflexive thematic analysis. Athletes highlighted the important role that parasport coaches played in fostering an enjoyable wheelchair basketball environment and valued coaches who displayed expertise regarding their athletes’ equipment and had personal parasport athletic experiences. Additionally, athletes identified personal preferences, including coaches who addressed sex differences and maintained professional relationships at the national level as contributing factors to the coach–athlete relationship. The current results benefit both parasport coaches and athletes by providing a portrayal of coaching behaviors, characteristics, and expertise that not only influence the parasport coach–athlete dyad but also affect the well-being and athletic development of parasport athletes.

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Qian Qi Lai, Darwin Gouwanda, and Alpha A. Gopalai

Balance control is essential for postural adjustment in physical activities. This study investigates the behavior of human postural control and the coordination and adaptation strategy of hip, knee, and ankle when standing on an unstable surface. Twenty participants were recruited. Four different conditions were investigated: a quiet bipedal stance with eyes open and eyes closed, and standing on an unstable surface with eyes open and eyes closed. Other than the joint angle, the standard body sway measures, such as sway area and sway velocity, were computed. A nonlinear time series measure, that is, sample entropy, was used to determine the regularity of the time series and body adaptability to change and perturbation. The results show that the body sway increases as the difficulty increases. This study also confirms the coordination of the hip, knee, and ankle to maintain body balance on the unstable surface by decreasing the joint angle and adopting a lower posture. Even though the individual joint has lower sample entropy value and is deemed to be rigid and less adaptive to perturbation, the postural control exhibits higher sample entropy value, particularly in the anterior–posterior direction, and has the ability to stabilize the body by manipulating the joints simultaneously. These outcomes suggest that an unstable surface not only challenges the human postural control, but also reduces the hip, knee, and ankle adaptability to perturbation, thus making it a great tool to train body balance.