Sixteen men completed four trials at random as follows: (Trial A) performance of a single bout of resistance exercise preceded by placebo ingestion (vitamin C); (Trial B) ingestion of 1,500 mg L-arginine and 1,500 mg L-lysine, immediately followed by exercise as in Trial A; (Trial C) ingestion of amino acids as in Trial B and no exercise; (Trial D) placebo ingestion and no exercise. Growth hormone (GH) concentrations were higher at 30,60, and 90 min during the exercise trials (A and B) compared with the resting trials (C and D) (p < .05). No differences were noted in [GH] between the exercise trials. [GH] was significantly elevated during resting conditions 60 min after amino acid ingestion compared with the placebo trial. It was concluded that ingestion of 1,500 mg arginine and 1,500 mg ly sine immediately before resistance exercise does not alter exercise-induced changes in [GH] in young men. However, when the same amino acid mixture is ingested under basal conditions, the acute secretion of GH is increased.
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Richard R. Suminski, Robert J. Robertson, Fredric L. Goss, Silva Arslanian, Jie Kang, Sergio DaSilva, Alan C. Utter and Kenneth F. Metz
Ben D. Kern, Kim C. Graber, Amelia Mays Woods and Tom Templin
Physical education teachers have been criticized for not implementing progressive or innovative instruction resulting in enhanced student knowledge and skills for lifetime participation in physical activity. Purpose: To investigate how teachers with varying dispositions toward change perceive socializing agents and teaching context as barriers to or facilitators of making pedagogical change. Methods: Thirty-two teachers completed a survey of personal dispositions toward change and participated in in-depth interviews. Results: Teachers perceived that students’ response to instructional methods and student contact time (days/week), as well as interactions with teaching colleagues and administrators influenced their ability to make pedagogical changes. Teachers with limited student contact time reported scheduling as a barrier to change, whereas daily student contact was a facilitator. Change-disposed teachers were more likely to promote student learning and assume leadership roles. Conclusion: Reform efforts should include consideration of teacher dispositions and student contact time.
Anne Sofie B. Malling, Bo M. Morberg, Lene Wermuth, Ole Gredal, Per Bech and Bente R. Jensen
The authors examined the associations between the performance of upper- and lower-extremity motor tasks across task complexity and motor symptom severity, overall disease severity, and the physical aspects of quality of life in persons with Parkinson’s disease. The performance was assessed for three lower-extremity tasks and two upper-extremity tasks of different levels of complexity. The motor symptoms and overall disease severity correlated significantly with all motor tasks with higher correlation coefficients in the complex tasks. Thus, the strength of the association between disease severity or severity of motor symptoms and motor performance is task-specific, with higher values in complex motor tasks than in simpler motor tasks. Mobility-related and activity-of-daily-living-related quality of life correlated with lower-extremity tasks of low and medium complexity and with the complex upper-extremity task, respectively; this suggests that Parkinson’s Disease Questionnaire-39 is capable of differentiating between the impact of gross and fine motor function on quality of life.
Janina M. Prado-Rico and Marcos Duarte
The goal of this work was to investigate body weight distribution during relaxed and quiet (constrained) standing tasks. Forty-one healthy, young adults performed relaxed and quiet standing tasks, and they stood with each leg on a separate force plate. The weight distribution asymmetry across time was computed as the difference between the right and left vertical force time series. The subjects presented a small average across time asymmetry during relaxed and quiet standing. However, during relaxed standing, the subjects alternated between postures, and, as a result, they were largely asymmetrical over time (instant by instant). Two unexpected results that the authors found for the relaxed standing task were that women were more asymmetrical over time than men and that there were two preferential modes of weight distribution.
Manuel E. Hernandez, Erin O’Donnell, Gioella Chaparro, Roee Holtzer, Meltem Izzetoglu, Brian M. Sandroff and Robert W. Motl
Functional near-infrared spectroscopy was used to evaluate prefrontal cortex activation differences between older adults with multiple sclerosis (MS) and healthy older adults (HOA) during the performance of a balance- and attention-demanding motor task. Ten older adults with MS and 12 HOA underwent functional near-infrared spectroscopy recording while talking, virtual beam walking, or virtual beam walking while talking on a self-paced treadmill. The MS group demonstrated smaller increases in prefrontal cortex oxygenation levels than HOA during virtual beam walking while talking than talking tasks. These findings indicate a decreased ability to allocate additional attentional resources in challenging walking conditions among MS compared with HOA. This study is the first to investigate brain activation dynamics during the performance of balance- and attention-demanding motor tasks in persons with MS.
Aaron England, Timothy Brusseau, Ryan Burns, Dirk Koester, Maria Newton, Matthew Thiese and Benjamin Chase
In adult performers, research suggests that mental representations (MRs) mediate performance of skilled movement. During adolescence, cortical brain areas responsible for generating MRs develop rapidly along with limb size, which, together, may affect movement and movement representations. The aim of this study was to examine the relationship between adolescent MRs and free-throw shooting expertise. Using structural dimensional analysis of MRs, skilled (n = 11) and less skilled (n = 11) participants sorted free-throw submovements according to their relatedness in movement execution. Data were analyzed using a hierarchical cluster analysis, factor analysis, and invariance test to examine between-group cluster comparisons. Cluster solutions for the skilled and less skilled participants were significantly variant (λ = 0.56). This method of measuring MRs distinguished expertise-related differences in MRs in an adolescent population. Findings may influence methods in which practitioners detect motor-planning faults, track development, and provide feedback to trainees.
Matthew J. Major, José L. Zavaleta and Steven A. Gard
Investigations have begun to connect leg prosthesis mechanical properties and user outcomes to optimize prosthesis designs for maximizing mobility. To date, parametric studies have focused on prosthetic foot properties, but not explicitly longitudinal stiffness that is uniquely modified through shock-absorbing pylons. The linear spring function of these devices might affect work performed on the body center of mass during walking. This study observed the effects of different levels of pylon stiffness on individual limb work of unilateral below-knee prosthesis users walking at customary and fast speeds. Longitudinal stiffness reductions were associated with minimal increase in prosthetic limb collision and push-off work, but inconsistent changes in sound limb work. These small and variable changes in limb work did not suggest an improvement in mechanical economy due to reductions in stiffness. Fast walking generated greater overall center of mass work demands across stiffness conditions. Results indicate limb work asymmetry as the prosthetic limb experienced on average 61% and 36% of collision and push-off work, respectively, relative to the sound limb. A series-spring model to estimate residuum and pylon stiffness effects on prosthesis energy storage suggested that minimal changes to limb work may be due to influences of the residual limb which dominate the system response.
Layne Case and Joonkoo Yun
Despite the rising interest in intervention for children with autism spectrum disorder, the extent to which interventions are effective on gross motor outcomes is currently unknown. The purpose of this study was to analyze the effect of different intervention approaches on gross motor outcomes among children with autism spectrum disorder using meta-analysis. A total of 18 studies met the inclusion criteria for quantitative analysis. Pre- and posttest means and SDs were extracted to calculate effect sizes. Potential moderator variables were chosen based on important intervention characteristics. The results suggest that interventions have a large effect on gross motor outcomes among children with autism spectrum disorder (δ = 0.99, SE = 0.19, p < .001, 95% confidence interval [0.62, 1.36]). The interventions that were 16 total hours or longer had a significantly larger effect than those less than 16 hr. In addition, the interventions in experimental settings had significantly larger effects than the interventions in practical settings. Future interventions should consider intensity, including not only the duration of the intervention but also the intensity in which specific intervention goals are targeted.
Aaron Derouin and Jim R. Potvin
Functional knee braces are frequently prescribed by physicians to ameliorate the function of individuals with anterior cruciate ligament (ACL) injuries. These braces have been shown in the literature to potentially enhance knee stability by augmenting muscle activation patterns and the timing of muscle response to perturbations. However, very few techniques are available in the literature to quantify how those modifications in lower-limb muscle activity influence stability of the knee. The aim of the present study was to quantify the effect of an off-the-shelf functional knee brace on muscle contributions to knee joint rotational stiffness in ACL-deficient and ACL-reconstructed patients. Kinematic, electromyography, and kinetic data were incorporated into an electromyography-driven model of the lower extremity to calculate individual and total muscle contributions to knee joint rotational stiffness about the flexion–extension axis, for 4 independent variables: leg condition (contralateral uninjured, unbraced ACL injured, and braced ACL injured); knee flexion (5°–10°, 20°–25°, and 30°–35°); squat stability condition (stable and unstable); and injury status (ACL deficient and ACL reconstructed). Participants had significantly higher (P < .05, η 2 = .018) total knee joint rotational stiffness values while wearing the brace compared with the control leg. A 2-way interaction effect between stability and knee flexion (P < .05, η 2 = .040) for total joint rotational stiffness was also found.