Canadian journal of applied sport sciences. Journal canadien des sciences appliquees au sport最新文献

Some remarks are tendered on the commonly accepted equations of motion for sprint running. All these involve combinations of one or more exponentials. An alternate form, not discussed in the sports literature, is investigated but though sound, is considered to be mathematically unsuitable. The re-examination of some available data on sprinting suggests that a reformulation of the original differential equation leads to a new solution which is a simple hyperbolic function. This equation may prove a better mathematical model than that commonly accepted as the velocity curve of sprint running. Parameters of the curves are discussed for trainability.

The role of mental practice in motor skill learning is briefly reviewed, and the relationship between mental practice and imagery discussed. A case is made for the importance of considering individual differences for imagery in motor studies investigating mental practice. Studies that have examined imagery ability in the motor domain are outlined, and the reasons are addressed why a consistent relationship between imagery ability and motor performance has failed to emerge. Finally, an approach for investigating imagery ability is suggested. This approach concentrates on the inclusion and interaction of three imagery related variables: the measurement of imagery ability, the task to be performed, and the imagery instructions that are given to the subjects.

Selected temporal events and associated kinematic parameters were studied about the knee and ankle during running using the C.A.R.S. -U.B.C. Triplanar Electrogoniometer, with and without corrective running orthotic devices (CRODs), in ten male runners who displayed compensatory overpronation. Extension and flexion, internal and external rotation plus varus and valgus displacement were recorded at the knee joint, while plantar and dorsi flexion, adduction and abduction plus inversion and eversion were recorded at the foot. CRODs produced a significant decrease (p less than 0.03) in the total amount of foot eversion during the support phase of running. The maximum amounts of support phase foot dorsiflexion and abduction were not altered significantly by CRODs. CRODs produced a significant increase (p less than 0.03) in the amount of plantar flexion occurring after foot strike. The knee was not fully extended at foot strike and up to ten degrees of additional knee extension took place after foot strike, before knee flexion began. None of the absolute time intervals between the achievement of the maximum of the three components of pronation (ankle abduction, eversion and dorsiflexion) and maximum knee flexion or maximum knee internal rotation were significantly altered by CRODs: Significant differences were detected between the left and right legs for several parameters at both the knee and ankle, which the authors believe warrants the separate examination and treatment of each leg when CRODs are to be used to control compensatory overpronation.

The seasonal variation in physiological characteristics of elite male runners was studied. Five middle distance (mean age 21 yrs) and 5 long distance runners (23 yrs), all members of the Swedish national track and field team, participated in treadmill tests on 4 occasions over a period of one year: in January, in May, during the highly competitive summer period and the following January. The maximal oxygen uptake (VO2 max, ml X kg-1 X min-1) increased successively during the season and was significantly (p less than 0.01) higher during the summer than in the winter (74.2 to 77.4 ml X kg-1 X min-1). From the competitive summer period to the second winter the VO2 max (ml X kg-1 X min-1) showed a significant decrease. The absolute value of VO2 max (1/min) was not significantly changed during this one-year period, however. Running economy was evaluated from oxygen uptake determinations at 15 km/h (VO2 15) and 20 km/h (VO2 20). Slightly lower values of VO2 15 and VO2 20 were noted during the season, and after one year VO2 20 was significantly decreased. Such an improvement in running economy with time was also found in a larger group of elite runners (n = 16) when determined from an average of 7 treadmill tests. The running velocity corresponding to a blood lactate concentration of 4 mmol/l increased from January to the summer season. The blood lactate concentration after exhaustion (VO2 max test) increased significantly from January to May.

Left ventricular dimensions of 11 successful male college basketball players engaged in pre-season conditioning (mean age, 20.3 years) and 13 tall healthy male controls (mean age, 21.6 years) were studied by echocardiography. Left ventricular internal dimension (LVIDd, mm), posterior wall thickness (PWT, mm), septal thickness (ST, mm), and calculated left ventricular mass (LV mass, g) in the athletes were within or only slightly in excess of echocardiographic normal limits and mean values were not significantly different from the control group. LVIDd (mm/m2 body surface area) was significantly lower in the athletes. However, five guard-type players displayed significantly greater mean values for PWT and LV mass compared to six taller forwards/centers with linear body builds. It was concluded that left ventricular hypertrophy is not a common characteristic of college basketball players. It was hypothesized that cardiac dimensions of young men may vary independently of gross body size in relation to somatotype or other anthropometric variables.

The purpose of this study was to compare various physical and performance characteristics of two elite groups of athletes, the 1980 U.S. Women's National Volleyball Team and the collegiate players who composed the 1979 U.S. Women's University Games Volleyball Team. The characteristics compared were age, height, weight, body composition determined via hydrostatic weighing, vertical jumping distance, vertical jumping height, maximal oxygen consumption, heart rate max and respiratory exchange ratio. Significant differences (p less than 0.05) in age (23 +/- 2.6 yr. and 21.5 +/- 0.7 yr.), percent of body fat (11.7 +/- 3.7% and 18.3 +/- 3.4%), and vertical jumping distance (52.4 +/- 4.5 cm and 45.5 +/- 6.4 cm), between the two teams were demonstrated, with the National Team being significantly older, having a lower percentage of body fat and possessing a larger vertical jumping distance. These results indicate trainers of elite (national and international caliber) women volleyball players should consider including techniques to reduce percentage of body fat and increase vertical jumping distance.

The reliability and concurrent validity of a simple questionnaire to assess leisure time physical activity has been investigated on 306 self-selected healthy adults of both sexes (163 M; 143 F). Values of body fat (BF) and maximum oxygen intake (VO2 max) expressed as percentiles of appropriate age and sex categories were used as criteria of validity for the questionnaire. BF and VO2 max were predicted from the Durnin and Womersley skinfold equations, and the laboratory version of the Canadian Home Fitness Test respectively. The strongest correlation was between VO2 max (percentile) and reported strenuous exercise (r = 0.35). The optimum discriminant function for VO2 max was based on a combination of reported strenuous and light activity. This yielded a correct 2-way classification of 69% of the subjects. A combination of sweat-inducing and moderate exercise yielded a correct 2-way classification of BF for 66% of subjects. The reliability coefficients for the optimum discriminant functions classifying VO2 max and BF were 0.83 and 0.85 respectively. We conclude that this simple instrument has potential value for the assessment of leisure time exercise behavior, offering the possibility of examining changes in behavior following the implementation of health and physical fitness promotion programmes in the community.

This study compared measurements which were considered traditionally to reflect alactacid and lactacid components of anaerobic metabolism. Subjects (men (N = 9) and women (N = 5)) on one occasion performed an exhaustive cycle ergometer ride at VO2 max and had peak lactate and O2 debt (fast and slow components) determined. On a second occasion, they performed a Wingate test. All data were normalized for body weight. Very few correlations were found between O2 debt or peak lactate and the peak power, mean power and power decrease of the Wingate test. In particular, both peak lactate and the fast O2 debt component had low, nonsignificant correlations with either peak or mean power. The study failed to support the traditional assumptions that both tests are quantifying the same anaerobic energy systems.

Two studies were carried out to investigate the utility of an interactionist approach to motivating involvement in an exercise program. In both studies the Self-Motivation Scale (Dishman, Ickes and Morgan, 1980) was used to classify program participants according to their level of self-motivation. Participants for each category were then assigned to experimental or control conditions. A decision balance-sheet technique was the treatment intervention in the first study while a structured social support intervention was implemented in the second study. In both cases, the motivational treatment resulted in an improvement in program attendance but there was no effect due to level of self-motivation nor its interaction with the treatment. The results are interpreted as being consistent with a situationist perspective of behavior; however, the need for further research using an interactionist approach is emphasized. Implications for exercise practice are discussed.