No description available.

A path π = (v1, v2, ⋯ , vk+1) in a graph G = (V,E) is a downhill path if for every i, 1 ≤ i ≤ k, deg(vi) ≥ deg(vi+1), where deg(vi) denotes the degree of vertex vi ∈ V. The downhill domination number equals the minimum cardinality of a set S ⊆ V having the property that every vertex v ∈ V lies on a downhill path originating from some vertex in S. We investigate downhill domination numbers of graphs and give upper bounds. In particular, we show that the downhill domination number of a graph is at most half its order, and that the downhill domination number of a tree is at most one third its order. We characterize the graphs obtaining each of these bounds.

For coaches to qualitatively analyze the performance of sport skills as executed by their students, they must possess an internal image of the desired skill against which to make comparisons (Hoffman, 1983; Pinheiro & Simon, 1992). Leas and Chi (1993) have indicated that there are differences between novice and expert swimming coaches in the internal image of the freestyle stroke. They further reported group differences in their ability to diagnose errors in movement form. Study 1 extended that investigation to include a beginning and advanced skill in downhill snow skiing. Two groups of downhill ski instructors (n=8) certified at Level II (n=4) and Examiner status (n=4) were compared on their knowledge of the prototypical versions of the wedge and open parallel turns. They were subsequently tested on their ability to diagnose errors in incorrectly performed videotape versions of those turns. Two Level H instructors internalized the skill similarly to the level of the Examiners on their knowledge of the prototypical skills, while the other two instructors did not appear to have constructed the same type of prototypical model. On the wedge turn diagnostic task, Level II instructors misdiagnosed 50% of the primary errors in student performance compared to a perfect performance by Examiners. On the open parallel diagnostic task, performance across groups was similar for the primary error. It was suggested that the open parallel level of skiing is similar to the skiing ability of Level II instructors, which may have enhanced their ability to better diagnose the errors associated with that skill compared to the wedge turn. In Study 2, participants prescribed exercises for the errors identified in Study 1. Results indicated that exercises primarily addressed errors in the same order as they were prioritized. The lesson plans of Level II participants, however, attempted to address 35% more errors than Examiners. The use of part-task teaching methods, used by seven of eight participants, was subsequently addressed and theoretical implications were discussed. A possible theory of expertise explaining group differences was described. / Graduation date: 1999

No description available.

An acute bout of unaccustomed eccentric exercise causes prolonged strength loss and delayed onset muscle soreness (DOMS) for several days. Chronic dietary supplementation with polyphenols, from pomegranates, has been shown to accelerate recovery following eccentric exercise, but the optimal dose is unknown. The purpose of this study was to determine the effect of dietary supplementation with different doses of pomegranate juice concentrate (PJC) on muscular strength, power, and soreness throughout a 96-hour time period following an acute bout of eccentric exercise. Healthy recreationally active males (n=45) were assigned to one of three treatment groups: Once-daily PJC (1x), twice-daily PJC (2x), or placebo (PLA) supplementation over a period of eight days. A 1x dose of PJC provided approximately 650 mg GAE. On day four of each treatment, subjects performed downhill running intervals (-10% grade) over a 40-minute period followed by 40 repetitions of eccentric elbow flexion at 100% of concentric 1-RM. Muscle soreness of arms and legs, maximal isometric strength of the elbow flexors (EF) and knee extensors (KE), vertical jump height (VJ[subscript height]) maximal cycling power (P[subscript max]), and 10-meter sprint velocity (V[subscript 10m]) were assessed pre-exercise and 2, 24, 48, 72, 96 hours post-exercise. Additionally, maximal instantaneous power (IP[subscript max]), maximal velocity (V[subscript max]), maximal torque (T[subscript max]), and torque at 0° (T0) were assessed on the inertial load power cycle pre-exercise and 24, 48, 72, 96 hours post-exercise. Throughout the 96-hours post-exercise, isometric EF strength was significantly higher in 1x and 2x groups as compared to PLA (main treatment effect, 83.6 ± 2.7% vs. 85.6 ± 1.9% vs. 78.4 ± 1.8%, respectively; p < 0.001). Isometric KE strength was significantly higher in 1x and 2x groups as compared to PLA (main treatment effect, 93.9 ± 1.5% vs. 91.6 ± 1.5% vs. 87.1 ± 1.8%, respectively; p < 0.001). Both VJ and V10m were significantly higher in 1x compared to PLA (main treatment effect, 99.9 ± 0.9% vs. 98.0 ± 1.0%, respectively, p = 0.037; 100.0 ± 0.8% vs. 97.8 ± 0.7%, respectively, p = 0.003). Muscle soreness and Pmax, were similar at all time points between groups. We conclude that dietary supplementation with 1x or 2x PJC results in higher isometric strength values compared to placebo for EF and KE muscles during the 96-hour period after an acute bout of eccentric exercise. / text

A four second eccentric squat test (EST) specific to the sport of alpine skiing was developed and standardized. Eighteen men aged 21-30 with one year resistance training experience participated in this study. The reliability of the EST and various jump tests was calculated and the relationship between EST and SSC performance was examined through the correlation of jump test variables and EST performance. The EST was observed to be highly reliable (ICC 0.99). The kinematic characteristics of the EST were closely related to those of alpine skiing. The reliability of the jump test performance variables ranged from low to high (ICC 0. 10-0.90). Investigators should be aware that the reliability of force and power measures can be confounded by changes in jump strategy between jump test trials. The relationship between slow eccentric strength and SSC performance was dependent on whether the jump was performed for maximal height or minimum contact time. / School of Physical Education

According to Statistics Canada (2013), downhill skiing participation rates have declined from 14% in 1992 to 6% in 2010. Finding ways to counteract this decline by revitalizing interest in downhill skiing is necessary to avoid further negative effects on the economic sustainability of the ski industry in Canada. This study proposes a reliable and valid measuring instrument to identify current factors that affect ski participation among various segments of skier groups. An online questionnaire is developed using extended Shank and Lyberger’s (2015) sports consumption model. It consists of five sections. Data were collected in the winter of 2019 from a convenience sample of 150 university students (targeting 30 participants for each: non-skiers, former-, low-, moderate-, and high-frequency skiers). Reliability was tested using a test(T1)-retest(T2) method among the same participants with a 14-day interval, calculating correlations. Of the initial 64 items, only 29 showed sufficient reliability. Generally speaking, the internal and external factors showed higher correlations, while the situational factors showed very low correlations and all 15 situational items had to be dropped. The results revealed that internal constraints influence former and low-frequency skiers more than higher-frequency skiers and that all current skiers, particularly in the high-frequency group, were strongly driven by internal facilitators such as positive perceptions. Family and financial constraint as an external, facilitating factor appear to be equally important among all groups of ski participants. Culture, another external factor, acts as a constraint on non-skiers, former skiers and low-frequency skiers, but has significantly less effect on high-frequency skiers. Former skiers are most affected by financial constraints, although this factor is also a constraint for other groups, if to a lesser extent.

Chronic exercise has been recommended as a strategy for preventing several diseases associated with lifestyle such as heart disease, hypertension, osteoporosis and type II diabetes. Although regular physical exercise has benefits for health, all sports practitioners, and even sedentary people, have already feel delayed onset muscle soreness (DOMS) once, characterized by discomfort in skeletal muscle. As the most DOMS generator, acute eccentric exercise induce fatigue, strength reduction and performance impairment. Despite some researches demonstrating reactive oxygen species (ROS) in this context, there are few information about purine degradation as well as transient receptor potential vanilloid 1 (TRPV1) on DOMS development. In this context, animals performed a downhill running test (eccentric exercise) on treadmill until exhaustion for histologic evaluation, mechanical allodynea, strength force test and biochemical analysis. The results showed an increase in mechanical allodynea and ADP, AMP, uric acid and TRPV1 immunoreactivity levels. In conclusion, the results support the contribution of ROS and the participation of purine and TRPV1 on delayed onset muscle soreness. / O exercício físico crônico tem sido recomendado como estratégia para a prevenção de diversas doenças associadas ao estilo de vida, como doenças cardíacas, hipertensão, osteoporose e diabetes tipo 2. Embora o exercício físico regular traga benefícios para a saúde, todos os praticantes de atividade física e esporte e, até mesmo indivíduos sedentários, já experimentaram alguma vez na vida um episódio de dor muscular tardia (DMT), caracterizada pela sensação de desconforto na musculatura esquelética. Como grande gerador de DMT, destaca-se o exercício excêntrico agudo que induz fadiga, redução de força e perda de desempenho. Apesar de diversos estudos demonstrando a participação das espécies reativas de oxigênio neste quadro, pouco se sabe sobre a participação da degradação das purinas bem como a participação dos receptores de potencial transitório vaniloide 1 (TRPV1) no desenvolvimento da dor muscular tardia. Para tanto, os ratos wistar machos realizaram teste de downhill em esteira (exercício excêntrico) até a exaustão. Após foram analisados os danos histológicos nos músculos gastrocnêmio e sóleo, Outro set de animais após a exaustão foram avaliados nos testes de alodinea mecanica na pata traseira direita, teste funcional de força nas pastas dianteiras e análises bioquímicas no músculo gastrocnêmio. Os resultados demonstram aumento na alodinea, na carbonilação protéica, nos níves de ADP, AMP, ácido úrico, além de elevar os níveis de immureatividade do receptor TRPV1 e atividade da xantina oxidase. Esses dados apontam uma possível contribuição das espécies reativas de oxigênio, da degradação de purinas e dos receptores TRPV1 na dor muscular tardia.

Degree constraints on the vertices of a path allow for the definitions of uphill and downhill paths. Specifically, we say that a path P = vi, v2,⋯ vk+1 is a downhill path if for every i, 1 ≤ i ≤ k, deg(vi) ≥ deg(v1+1). Conversely, a path π = u1, u2,⋯ uk+1 is an uphill path if for every i, 1 ≤ i ≤ k, deg(ui) ≤ deg(ui+1). The downhill domination number of a graph G is the minimum cardinality of a set S of vertices such that every vertex in V lies on a downhill path from some vertex in S. The uphill domination number is defined as expected. We give a polynomial time algorithm to find a minimum downhill dominating set and a minimum uphill dominating set for any graph.

Placing degree constraints on the vertices of a path yields the definitions of uphill and downhill paths. Specifically, we say that a path π = v1, v2, ⋯ vk+1 is a downhill path if for every i, 1 ≤ i ≤ k, deg(v1) ≥ deg(vi+1). Conversely, a path π = u1, u2, ⋯ uk+1 is an uphill path if for every i, 1 ≤ i ≤ k, deg(u1) ≤ deg(ui+1). The downhill domination number of a graph G is defined to be the minimum cardinality of a set S of vertices such that every vertex in V lies on a downhill path from some vertex in S. The uphill domination number is defined as expected. We explore the properties of these invariants and their relationships with other invariants. We also determine a Vizing-like result for the downhill (respectively, uphill) domination numbers of Cartesian products.