Showing papers in "Journal canadien des sciences du sport in 1990"

Injury patterns of female competitive club gymnasts.

Abstract: Gymnast and injury information on 178 competitive female gymnasts was collected through questionnaires and interviews in a 3-year prospective epidemiologic study. The injury rate was 30/100 gymnasts/year, .52 injuries/1000 h. Injury rates excluding risk exposure increased with competitive level, but the top level gymnasts had the lowest rate per 1000 h of practice. Fractures of the wrist, fingers and toes were most common, followed by sprains of ankle and knee. Nearly 40% of the sudden-onset injuries occurred in the floor event. 'Missed move' was most frequently cited as the injury mechanism, while somersaults and handsprings were the most injury-producing moves. Most injuries happened with moves that were basic or moderately difficult and well-established. There was an increased chance of injury when the gymnast had been on the apparatus for an extended period of time. One major source of injury is loss of concentration, and a key to injury prevention may be the reorganization of the practice session.

In defence of discovery learning.

Abstract: The present paper discusses the influence of different training methods--i.e., knowledge of results, preferred frequency, and the availability of a model--on the learning of a complex motor skill, in this case the learning of slalom ski-type movements on a ski-simulator. Results of three experiments performed on this apparatus showed that, although the training methods used influence the course of learning, none of the methods used was actually superior to discovery learning. It is suggested that discovery learning forces the learner to explore the dynamics of the system in which he or she operates, in an iterative way. Possibilities for cooperative working between prescription and discovery learning are discussed.

Personal investment predictors of adolescent motivational orientation toward exercise.

Abstract: The primary purpose of this study was to determine the relationship between the psychosocial components of Personal Investment Theory and exercise behavior among 237 adolescents. Specifically, the adolescents' personal incentives for exercise, perceptions of sense of self, and perceived options for exercise were examined as predictors of physical activity level. A secondary purpose was to determine the interdependence between the components reflecting personal investment and self-reported exercise behavior separately by gender and activity level. Multiple regression analysis revealed that the personal investment variables accounted for 19% of the variance in exercise behavior among male adolescents and 25% of the variance in exercise behavior among female adolescents. Discriminant analysis correctly classified 76.5% of the males and 71.8% of the females as well as 80.4% of high-active adolescents and 73.3% of low-active adolescents on the basis of the three meaning components. Further, the results indicated that the significant predictors of exercise behavior varied as a function of gender as well as the adolescents' level of physical activity.

Use of augmented feedback for the modification of the pedaling mechanics of cyclists.

Abstract: On-line computer representation of forces applied to the pedals during a 90-degree sector of the pedaling cycle were used to train a group of cyclists to alter their pattern of force application while they cycled on a stationary cycle. The subjects rode for 32 min each day for ten days. During these training rides, three cyclists were given augmented feedback on only their pedaling rate, while three other cyclists were presented with augmented, visual feedback on the magnitude of force application in the sector of interest as well as cadence. At the end of the training period it was noted that the experimental group showed significantly reduced pedal forces in the sector of interest while the control group did not. It was concluded that this technique of modifying a well-practised task was an effective one and that it could be used to explore various training modalities and other pedaling styles.

Study of decision-making in squash competition: a computer simulation approach.

Abstract: This paper describes how a computer simulation approach was used to specify some of the cognitive processes underlying decision-making in squash competition. The work presented in this article focused on the cognitive strategy of the defending player when choosing among three categories of preparation. (Total preparation for one particular event, partial preparation in favor of one event, and absence of biased preparation.) The defending player is viewed as in information processing system (IPS) placed in a problem-solving situation, the problem being what decision to reach. There are four steps inherent to the computer simulation approach: (a) obtaining the verbal protocol, (2) analyzing the protocol, (3) computer simulation, and (4) validation. This paper describes how each of those steps have been completed, with a special emphasis being placed on the first step of the procedure, that of obtaining the verbal protocol.

Use of the Borg scale in exercise prescription for overweight youth.

Abstract: Twenty overweight children, ages 9-15 years, participated in a study on the usefulness of the Borg 6-20 perceived exertion (RPE) scale as a means for exercise prescription. As a criterion measure, they cycled at four intensities, based on pre-determined % peak power, giving RPE ratings at each load. During two return visits subjects were asked to set the resistance on the ergometer (cycle tasks) and to walk or run around an oval track (track tasks) at intensities they perceived as RPE = 7, 10, 13 and 16. HR-on-RPE regressions were compared among the criterion, cycle and track tasks. Cycle and track lines differed from the criterion (p less than .001). Subjects were, however, able to discriminate among each of the RPE prescriptions on the cycle. They overestimated intensities on the track tasks. We conclude that overweight children need additional instruction in using the Borg scale for exercise prescription.

Oxygen uptake and heart rate responses to treadmill and water running

Abstract: The relationship between heart rate (HR) and oxygen uptake (VO2) was assessed during treadmill running and during running-like motions in water without ground support. Athletes self-selected easy, moderate and hard efforts during water running. While there was a linear relationship between HR and VO2 in both exercise conditions, there was considerable between-subject variability of the slope and intercept of the linear regressions. These data are taken to indicate that HR for a given VO2 during water compared to land running is influenced in large part by the skill of the athlete in the water running activity.

The effects of elastic tights on the post-exercise response.

Abstract: It has previously been demonstrated that graduated compression stockings will affect the post-exercise venous lactate profile. To determine the effects of elastic tights on venous lactate levels and the post-exercise response, eight males completed three exercise bouts on a motor driven treadmill. Each subject ran on the treadmill for up to three minutes at 110% of his VO2max. The conditions for the three exercise bouts were: elastic tights worn during exercise and recovery, elastic tights worn only during exercise, and no elastic tights worn during exercise or recovery. Oxygen consumption, heart rates and venous blood samples, for lactate and hematocrit determination, were obtained at rest and at 5, 15 and 30 min post-exercise. Analysis revealed no significant differences (p greater than 0.05) in any of the above variables between the three trials at any of the measurement times. These results indicate that the use of elastic tights will not significantly affect the post-exercise response or circulating lactate levels.

Bone tissue and physical activity.

Abstract: Bones provide more than just a structural framework for the body. In reality, bone is a multifunctional tissue dependent on, and sensitive to, a wide variety of biological, biochemical and biomechanical stimuli. This complex system is highly responsive to the mechanical stresses imposed by gravity and muscular contractions. Animal studies as well as human cross-sectional and longitudinal studies all point to the importance of weight-bearing physical activity and mechanical loading as the prime modalities in the preservation of skeletal integrity. Lack of weight-bearing activity is extremely harmful to the skeleton. Loss of skeletal density in individuals subjected to various types of immobilization or under conditions of weightlessness is well documented. The role of physical activity in the maintenance of skeletal integrity is a topic of considerable current interest when the increasing incidence of skeletal fragility in the elderly is taken into account.

Human body composition.

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Concentric and eccentric quadriceps torque in pre-adolescent males.

Abstract: The purpose of this study was to evaluate the applicability of using the Kin Com (Chattecx Corp., Chattanooga, TN) isokinetic machine to measure concentric and eccentric quadriceps torque in a group of 12 healthy male volunteers aged 10-12 years. Each individual was tested by an experienced physiotherapist using a 60 degree per second velocity mode according to our standardized protocol. Average and peak torque values for concentric and eccentric contractions of the quadriceps were recorded; based upon the best of three maximum effort trials on each lower extremity. Retesting was performed on a randomly selected sub-group in an identical manner two weeks later. Our results showed no statistically significant difference between the original and retest values using the method error of repeated measurements and paired t-test analyses. Eccentric peak torque was greater on average than concentric. This was significant with p-values of 0.01 for the non-dominant quadriceps and 0.002 for the dominant side (paired t-test). There was no significant difference between the dominant and non-dominant sides. In conclusion, eccentric muscle testing has been reliably quantitated for the first time in children. This study has shown a practical and reproducible method of quantitative muscle strength assessment.

An experiential perspective on the motivational features of exercise and lifestyle.

Abstract: The purpose of this study was to describe the cognitive, emotional and behavioral concomitants of direction, intensity and persistence for exercise in individuals displaying different levels of exercise involvement. In order to attain this goal, 78 one-hour interviews were conducted with individuals who were either autonomous exercisers, fitness program enrollees, fitness program dropouts or sedentary individuals. Subjects were asked to describe their thoughts, feelings and behaviours, before, during and after a workout, and trained interviewers used probes to further tease out aspects of direction, intensity and persistence. Findings were content-analyzed to detect significant trends. Results revealed that autonomous exercisers differed from individuals with less active lifestyles in several ways: participation motives were geared mainly toward fitness-health; the aspect they enjoyed the most about their participation was the task itself; they did not need to do any planning to ensure that they regularly attended their workouts; they expended a moderately high amount of effort and intensity in pursuing their exercise; they conceded that sometimes they missed workouts simply out of fatigue and that they felt that something was missing in their life when they did not exercise. By contrast, other types of exercisers displayed different profiles. These findings replicate and extend data available in the literature and thus support the viability of qualitatively conceptualizing and assessing motivation in exercise settings.

Lower extremity preference and knee extensor torques in intercollegiate soccer players.

Abstract: The purpose of this study was to determine whether lower extremity preference influenced the relationship between the dominant and nondominant knee extensors of intercollegiate soccer players. Twelve recreational athletes and 12 soccer players completed isometric contractions at 60 degrees flexion, and concentric-eccentric contraction cycles at angular velocities of 60 degrees and 180 degrees/s through a range of motion from 90 degrees to 10 degrees knee flexion. Although the soccer players demonstrated greater peak and average torques, and greater differences between their dominant and nondominant legs, they responded similarly to recreational athletes during isometric, concentric and eccentric contractions and produced similar torque-velocity patterns. The concentric/eccentric ratios were similar for both legs and both groups, and decreased as angular velocity increased. The nondominant/dominant ratios of the soccer players, however, were significantly lower than those of the recreational athletes when calculated using peak torque (p less than .02) and nearly so when calculated using average torque (p less than .08). Nondominant/dominant ratios were not affected by the type of contraction or by the angular velocity. Further study is required to determine whether the small asymmetry (about 7%) in knee extensor strength of the soccer players is significant with respect to performance or injury rates, or may be inconsequential.

Assessment of occupational fitness in the context of human rights legislation.

Abstract: The potential applications of occupational fitness assessment are briefly reviewed in the general context of recent human rights legislation. Limiting tasks in an industrial process must be examined, and bona fide occupational requirements must be defined in terms of psychomotor ability and physiological capacity. Heavy work may demand a high level of aerobic power, muscular strength, or tolerance of adverse environments. Such criteria can define an action limit, above which the task must be redesigned, or workers must be specially selected and trained. The courts may accept the results of field performance tests more readily than laboratory measurements of aerobic power or muscular strength. However, neither type of test currently has the reliability and validity needed to characterize the individual, or to distinguish a good worker from a poor worker. If the concern is public safety, employment must thus be based upon average data for a given population, while if the concern is employment equity, the only recourse seems a probationary period of employment.

Muscle fibre area, fibre type & capillarization in male and female body builders.

Abstract: The effects of long-term strength training on skeletal muscle fibre characteristics were evaluated in nine body builders (BB) (five males and four females) and ten control subjects (six females and four males). Muscle fibre area, percentage fibre type, and capillary supply were compared between the BB and controls as well as between the males and females with a two-way analysis of variance design. For the fast-twitch fibre area (FTa), the BB had larger areas than the controls, and males had larger areas than females. The analysis for the slow-twitch fibre areas (STa) showed only a training effect; BB had a larger STa than controls. The FTa in the untrained females and the female BB were similar to their STa; in contrast, both male groups had significantly larger FTa than STa. The BB had significantly more capillaries per fibre than the control groups but the number of capillaries/mm2 were similar in all groups. The results suggest that prolonged training in the female BB hypertrophies both the FT and ST fibres. The female BB realized the same increase in capillary per fibre ratio (#cap/f) as the male BB. However, the larger area of the FT fibres compared to the ST fibre seen in both male groups was not observed in either female group.

Bioelectric impedance methods for the estimation of body composition.

Abstract: The present use of bioelectric impedance is based upon the greater electrolyte content and conductivity of fat-free mass (FFM). The limitation of the whole body impedance approach may be the use of S2/R as an index of the conductive volume of the body. The use of body lengths that closely resemble the actual length of the conductor rather than stature can improve predictions of FFM. Theoretically, the specific resistivity approach to bioelectric impedance also provides a means of circumventing this problem. Another alternative is the estimation of whole body composition or the composition of body segments from measurements of the lengths and resistances of the segments and the use of the phase angle of the whole body and or body segments. Possible alternative methods for the use of bioelectric impedance would be the measurement of the composition of body segments, the determination of specific resistivities so that estimates of FFM can be calculated without the need for regression equations and the determination of the use of different current frequencies in measuring body composition with bioelectric impedance.

Meeting carbohydrate and fluid needs in soccer.

Abstract: If a hard game of soccer is played under warm conditions, there are conflicting demands for carbohydrate and for fluid replenishment, with both variables having a potential influence upon competitive performance. The present review examines evidence concerning the extent of carbohydrate depletion during soccer play, its potential impact upon play, and the optimum choice of beverage for minimizing physiological problems. Players should be prepared for competition by eating a good mixed diet; this should assure a daily intake of at least 8 g of carbohydrate per kilogram of body mass. Although theoretical arguments favour the use of glucose/polymer drinks, in practice, these do not offer any great advantage relative to water or a dilute glucose solution. Some 500 mL of water or a low-concentration carbohydrate preparation can usefully be drunk in the thirty minutes immediately prior to a game, with a further 500 mL drink of the same fluid being taken at half time. During the recovery period following a soccer match, it is useful to increase the salt content of meals, and again to provide a good mixed diet with an emphasis upon carbohydrates.

Postexercise proteinuria in rowers.

Abstract: Exercise performance, glomerular filtration rate (GFR), and urinary filtration of proteins during static pool rowing and cycling to exhaustion were studied in trained rowers. The peak VO2 and heart rate were higher during rowing than during cycling. There was a reduction in plasma volume and an increase in lactate concentration after exercise; however, no significant difference was noted between rowing and cycling in either case. Postexercise proteinuria was increased 8 and 11 times, and albuminuria 25 and 20 times after rowing and cycling exercises, respectively. There was no difference between these exercises in terms of protein or albumin excretion. There was no change in postexercise GFR. Albumin clearance was increased 18 and 20 fold after rowing and cycling, respectively. A significant, but low correlation, r = 0.56, was noted between albumin excretion and postexercise blood lactate concentration. Thus, no difference in the effect on kidney response was found between static pool rowing and cycling to exhaustion in these athletes.

Perceptions of competence in physical education students.

Abstract: This study sought to validate the Self-Perception Profile for College Students (Neemann and Harter, 1986) by investigating the perceived competence of physical education students as compared to students enrolled in other academic programs Group One comprised 114 physical education students Group Two consisted of 209 subjects enrolled in other academic programs The Self-Perception Profile for College Students was administered to all subjects Five scales (athletic, scholastic, social acceptance, appearance, and global self-worth) were analyzed Factor analysis and internal consistency measures provided psychometric support for the scales Separate ANOVAs calculated for each scale revealed that physical education students had higher perceptions of athletic competence than the other students Males had higher perceptions of athletic and appearance competence, whereas females had higher perceived social acceptance These findings are discussed in terms of psychometric issues, and the relationship between perceived competence and motivational patterns

Relationship between the starting age of training and physical fitness in old age.

Abstract: The purpose of this study was to test the hypothesis that older persons can minimize the reduction in physical fitness with aging if they start training before approximately 50 years of age, beyond which strength decline has been reported to become more pronounced. Maximal values for isometric strength, dynamic strength and speed of movement of the biceps brachii and quadriceps muscles, back-lift strength, and predicted oxygen uptake (VO2max = VO2max) were measured in 39 male subjects who were 60-68 years old. Four groups were studied: T26, T45, T56, and untrained. The T26 group had been training (jogging 10 km.day-1, 5 days.wk-1 at 10 km.h-1) since before their mid-thirties (mean 26 years), the T45 group since their forties (mean 45 years), the T56 group since their fifties (mean 56 years), and the untrained group had never taken part in any systematic training. Collectively, the T26 and T45 groups had significantly (p less than 0.05) higher values for muscle strength, speed of contraction, and VO2max than the T56 and/or untrained group(s). However, no differences were observed between the T26 and T45 groups. The results support a relation between the starting age of training and the age-dependent decline of physical fitness. Thus, the hypothesis is accepted.

Attributions for rapid or slow recovery from sports injuries.

Abstract: Sport participants (n = 276) stated the most likely cause of rapid or slow recovery from injury and rated that causal factor along several dimensions. Examination of the open-ended responses suggested that four general types of attributions were utilized by the athletes: personal factors, injury-related factors, treatment-related factors, and situational factors. Analysis of dimensional ratings indicated: (a) causes of slow recovery were consistently perceived as less stable, controllable, global, and intentional than causes of rapid recovery; (b) causes of slow recovery were sometimes perceived as more internal than causes of rapid recovery; and (c) physical self-esteem interacted with gender to influence dimensional ratings of the attributions. These findings were discussed in relation to the motivational significance of causal interpretations during recovery and in relation to the model of stress and athletic injury presented by Andersen and Williams (1988).

Evaluation of an indoor standardized obstacle course for Canadian infantry personnel.

Abstract: This study compared performance on an indoor standardized obstacle course (ISOC) to laboratory measures of fitness recognized as important in the performance of infantry tasks. The course involves 19 obstacles consisting of running, crawling, scaling, pulling, lifting, carrying and pushing activities arranged in sequential order. Forty-three healthy males between 21 and 31 years of age participated in the study. Performance scores on the ISOC were found to be significantly (p less than 0.01) and positively correlated to maximal aerobic power (MAP), muscular strength and endurance and anaerobic lactic power, and negatively correlated to indices of body fat. Stepwise multiple regression analysis indicated that 81% of the variance in ISOC performance time was accounted for by MAP, a strength index, anaerobic lactic power and sum of four skinfolds.

Semitendinosus repair augmentation of acute anterior cruciate ligament rupture.

Abstract: The semitendinosus tendon has been used since 1980 by the senior author (JPM) to augment anterior cruciate ligament repair surgery in cases of acute rupture There are two major criticisms of this technique: first, the semitendinosus tendon lacks adequate tensile strength functionally to replace the normal anterior cruciate ligament; and second, the semitendinosus is an important hamstring muscle, the loss of which has the potential to weaken the dynamic control of the knee Objective measurement of success or failure of this procedure is provided by KT1000 arthrometer laxity testing for static recovery of stability, and by Cybex isokinetic dynamometer testing of peak torque and fatigue index to evaluate muscular rehabilitation Thirty-seven patients were examined using these techniques in a standardized protocol at least two years after surgery Results show excellent return of static stability and near-normal recovery of strength and endurance of quadriceps and hamstring muscles

Risk exposure and incidence of injuries in school physical education at different activity levels.

Abstract: Pupils in the age range of 14-19 years in the schools of a municipality in Sweden were observed prospectively for one year for acute injuries during school physical education (n = 2089). Pupils registered in the Injury Surveillance System for an acute injury sustained during physical education classes and treated by a physician were interviewed. The number of observed injuries was 53. The incidence rate as a ratio of injury and estimated time of activity has been calculated. Physical activity during leisure time was investigated by a mailed questionnaire to a random sample of 7% of the population in the same age range. Levels of physical activity during leisure time of the injured pupils were related to activity levels in the whole population. An increased risk of injury (7 times) was found in pupils with a low activity level, compared to those with a medium or high level, and the risk of injury in females with a sedentary life style was 10 times as high as in active females.

Force-time data acquisition system for sprint starting.

Abstract: A device for the acquisition of horizontal forces in the sprint start was designed and tested on the basis of linearity, hysteresis, and the force-time curves. The force measuring device was built to resemble and function as a regular starting block while measuring the reaction force from the push off. The linearity test produced a correlation coefficient of 0.99; the hysteresis was 1.0% of the full scale force block output; and the frequency response test displayed an average error of 6% in terms of amplitude and no discernable phase shift effect at a 6 Hz loading frequency. The force-time curves produced were consistent with previous results and did not differ greatly upon comparison with a force plate. All these results were within acceptable limits.

Expert assessment of the national coaching certification program (NCCP) theory component.

Abstract: The purpose of this study was to determine if the educational objectives of the revised national coaching certification theory program (NCCP) represent the important and necessary skills needed to be an effective coach in both contemporary and future Canadian society. A study sample of experts in coach education in Canada (n = 75) agreed to participate in the investigation which was based on a research protocol known as the Delphi technique. Results of the study indicate that coach education experts in Canada generally agreed with the educational objectives at each level of the program in both the present and the futures data. Further, the experts seemed to favour a socio-psychological orientation to the curriculum content at level 1 and level 2 and a balance between the biophysical and the socio-psychological sports science areas at level 3.

Effect of an exercise program on the perception of exertion in males at retirement.

Abstract: To describe the association between perception of exertion and exercise, 138 men at retirement, mean age 62.7 years, were studied before and after a one-year program of exercise. VO2max and ratings of perceived exertion (RPE) using the Borg psychophysical scale were determined by a continuous exercise treadmill protocol to fatigue. The men were randomly assigned to an exercise program (n = 69) or control (n = 69). The program consisted of walking or jogging for 30 min, 3 times per week for one year. After training, the activity group showed a significant improvement in VO2max (12%). Linear regression analysis was used to relate RPE to selected physiological measurements for control and activity groups. The equations for the before and after training relationships were compared. Changes in the relationship of RPE vs VO2 and Ve, after training, were not significant for the activity group. However, the control group showed significant changes in these relationships at one year post retirement. For VO2 and Ve, ratings were 1-2 units higher than at time of retirement. Results indicate that perception of a physical task normally changes at retirement such that a given amount of exertion may seem subjectively greater. Results also suggest that a structured exercise program is successful at maintaining perception of task at pre-retirement levels. This maintenance of a low rating of perception may retard a reluctance to be physically active which often accompanies ageing.

Metabolic fatigue and the performance of visual tasks

Abstract: The aim of this study was to analyse the effects of different types of metabolic fatigue, induced by anaerobic alactacid, anaerobic lactacid, sub-maximal aerobic, and maximal aerobic efforts, on the performance of a sensory task (peripheral threshold detection), a sensory-motor task (coincidence-anticipation), and a cognitive task (recall in central vision). Each of three experimental groups performed one of the above-mentioned tasks under all types of fatigue. Running bouts on a treadmill were used to induce the different types of fatigue. Results show that performance in peripheral vision improves with all types of effort. For coincidence-anticipation, only constant error is affected by anaerobic alactacid and maximal aerobic efforts; the former producing a change in behavior from lateness to anticipation, whereas the latter significantly reduces lateness. Finally, performance in the cognitive task is significantly disturbed by the maximal aerobic exercise. It is suggested that, while sensory and adaptive behaviors improve with previous physical work, cognitive behavior is handicapped by highly demanding activities, that is, activities requiring aerobic maximal efforts.