Showing papers in "Journal canadien des sciences du sport in 1987"

Kinetics of standing broad and vertical jumping.

Abstract: The purpose of this study was to determine the contributions made by the leg muscle groups to the external mechanical work done in standing broad and vertical jumping. Six subjects were filmed jumping from a force platform. Linked-segment analysis and inverse dynamics methods were used to compute the muscle moments of force and power and work output created by these moments of force. Results support the principle that all three extensor moments of force summate in both types of jumping but that the sequence of contractions was not from proximal muscles to distal as is stated by the continuity principle. Instead all three extensor moments act simultaneously to produce leg extension. The contributions made by the three muscle groups were not the same for the two types of jumps. For the propulsive phase of the standing broad jump the contributions of the hip, knee, and ankle muscles were 45.9%, 3.9%, and 50.2%, respectively, whereas, for the vertical jump the contributions were 40.0%, 24.2%, and 35.8%, respectively. These results indicate that broad jumping utilizes the muscle groups differently than vertical jumping and show the importance of the hip and ankle musculature in the production of external work in jumping.

Participation motivation of Australian children involved in organized sport

Abstract: The purpose of the present study was to examine the participation motives of Australian youth involved in a number of sports, determine any sport differences, and compare the results with North American findings. Four hundred and four male and female youths from 8 to 18 years of age and from five sports participated in the study. Subjects responded to a 27-item sport participation motive questionnaire. Responses indicated that the most important reasons for participation in sport were 'to improve skills,' 'be physically fit,' 'compete,' 'learn new skills; and 'to be challenged.' These reasons were similar to North American findings except for the absence of 'fun' in Australian data. Male and female responses were similar, thus supporting previous research. However, significant differences emerged as a function of age and sport. Younger participants endorsed extrinsic and social motives to a greater degree than older participants. Swimmers considered 'having fun,' 'being with friends,' 'action' and 'excitement' as all of significantly less importance than participants from other sports. Factor analyses suggested four dimensions of participation motivation. These were labelled 'team/achievement,' 'situational,' 'status' and 'fitness.' Factor structures varied in several important instances compared with North American data. This study generally supports previous North American findings, but does suggest cultural differences in participation motivation as well as sport and age differences.

Fluid shifts and hydration state: effects of long-term exercise.

Abstract: During exercise, increased capillary hydrostatic pressure caused by elevation of arterial pressure produces plasma volume shifts from the vascular space to the interstitial fluids. Following a rapid efflux of vascular fluid within minutes of exercise, there is very little further reduction in plasma volume during long-term exercise, suggesting protective mechanisms against loss of circulating blood volume. These mechanisms probably include increasing plasma protein oncotic pressure, differences in peripheral vasoconstriction in active muscles and inactive tissues, and elevated lymph flow. The interaction of these factors provides optimal thermoregulatory and cardiovascular stability. The dynamics of fluids shifts during long-term exercise are altered by hydration state. The hypovolemia caused by dehydration acts to conserve blood volume by reducing the amount of plasma shift and sweat loss during exercise. The consequence is less heat dissipation and greater cardiovascular stability. In contrast, the hypervolemia produced by hyperhydration promotes greater shifts of fluid and sweat loss, resulting in lower body temperature and heart rate during prolonged work. The beneficial effects of hyperdydration and subsequent hypervolemia are manifest in the adaptation of body fluids and electrolytes to exercise training. Thus, with regard to fluid shifts during long-term exercise, training is an effective way to become hyperhydrated and to reduce the limiting effects of working in 'hostile' environments.

Active vs. passive attentional manipulation and multidimensional perceptions of exercise intensity.

Abstract: The purpose of this study was to ascertain whether active (arithmetic problems) or passive (asynchronous music) attention demanding tasks affected undifferentiated ratings of exertion during work of varying intensities. Also, an effort was made to determine which aspect of perceived exertion, (i.e., Fatigue, Task Aversion, and Motivation) as measured by the Physical Activity Questionnaire (PAQ), the attentional manipulation affected most. Twenty-six female subjects performed 5 minutes of work at either 60 or 90% of predicted VO2 Max. During work they were required to solve a constant flow of arithmetic problems, listen to music, or work in an unfilled control condition. Following activity they completed the PAQ and Borg's Scale. A repeated measures MANOVA followed by step-down F tests revealed that the Fatigue factor of the PAQ was the only component significantly (p less than .01) affected by attentional manipulation. A Scheffe test showed that both active and passive manipulation differed from the control (p less than .01), with active manipulation more potent at 90% VO2 Max.

Comparison of physiology and biomechanics of speed skating with cycling and with skateboard exercise.

Abstract: Eight well-trained speed skaters performed three all-out tests during ice speed skating, board skating and cycling. Compared to speed skating, cycling produced significantly higher values of oxygen consumption (57.2 +/- 4.9 vs. 53.9 +/- 4.2 ml/(kg X min], ventilation (111.3 +/- 10.2 vs. 98.8 +/- 7.3 l/min) and respiratory exchange ratio (1.18 +/- 0.13 vs. 1.03 +/- 0.05). This seems to suggest a different demand on the aerobic metabolism during cycling compared to speed skating. Board skating resulted in a significantly higher value of the ventilation (110.0 +/- 8.6 l/min) only. Kinematic analysis showed that during both skating activities the time series of the hip and knee angles, angular velocities and angular accelerations were similar. High peak values, especially of the knee angular acceleration, occur in the short push-off phase. During cycling completely different curves were found. The possible significance of these differences for movement co-ordination and motor unit involvement is discussed. The results show that board skating is a more specific training exercise for speed skating than cycling, at least when training for skating performances lasting 8-10 minutes at most.

The relationship between anaerobic power and isokinetic torque outputs.

Abstract: Optimal peak and mean power outputs were determined from a 30s anaerobic cycle ergometer test and compared to the isokinetic peak torque outputs for hip and knee flexion and extension. Fifteen male physical education students, mean age 20.9 yrs., mean weight 73.2 kg, performed several 30s all-out ergometer rides to determine individual power curves for the calculation of peak and mean power outputs. Isokinetic exercise at 30 degrees X s-1 for knee flexion and extension and 180 degrees X s-1 for hip and knee flexion and extension was also performed. The peak and mean power outputs were 11.66 and 9.29 watts X kg-1 respectively. Mean power correlated with isokinetic peak torque at 180 degrees X s-1 for knee flexion (r = 0.96) and extension (r = 0.87) and for hip flexion (r = 0.71) and extension (r = 0.68). Due to the significant contribution of knee and hip flexion and extension movements at 180 degrees X s-1, high intensity sports may benefit from incorporation of such movements at high velocities into resistance training programs.

Non-surgical management of overuse knee injuries in runners.

Abstract: Seventy-three injured runners (45 men, 28 women) who presented with 83 running-induced overuse knee injuries were managed conservatively. The regimens utilized focused on quadriceps and hamstring muscle retraining and the control of functional overpronation. Patello-femoral pain syndrome (42 cases) was by far the most common problem. The next most common problems were iliotibial band friction syndrome (10), patellar tendonitis (9) and popliteal tendonitis (5). The most frequent etiological factor was a sudden increase in training mileage. Following the initial visit and at regular intervals throughout the recovery phase, quadriceps and hamstring capacities were determined on a Cybex II isokinetic unit at 60 degrees/second and 180 degrees/second. Significant differences (p less than 0.01) in Cybex scores were observed between strong and weak extremities in males and females for both muscle groups at both velocities. The mean Cybex scores and the differences with muscle groups between strong and weak legs for the subjects were similar to those reported for healthy non-athletes. The treatment protocol followed four basic principles: control of pain; rebuilding of muscle strength and endurance; improvement of bio-mechanical efficiency and gradual reintroduction of training. No significant changes in the differences between strong and weak leg Cybex scores occurred between the initial and final evaluations, except in the male group when the hamstrings were evaluated at 60 degrees/second (p less than 0.01). In the 82 cases managed non-surgically, 1 poor, 8 fair, 36 good and 37 excellent results were obtained. The authors believe that the significance of disturbance in quadriceps and hamstring function to the etiology of overuse knee injuries may be increased in runners who over-pronate.

A study of carbohydrate loading techniques used by marathon runners.

Abstract: Carbohydrate loading techniques were studied in a survey of 76 marathon runners. It was found that these runners practised a variety of methods that they believed would achieve carbohydrate loading. Analysis of records of food use showed that the diets actually used by runners did not reach the level of carbohydrate specified in the high carbohydrate phase of the glycogen loading regimens reported in the literature. It is suggested that in a free-living situation, without specific instructions or a knowledge of nutrition and food composition, runners are limited in their ability to achieve the dietary requirements of carbohydrate loading.

Inhibition of exercise-induced blood prolactin response by acute hypoxia.

Abstract: Prolactin (PRL) secretion is regulated by a variety of factors, most of them being known for their enhancing effects on blood PRL levels. This study describes the inhibitory influence of an acute exposure to hypoxia (14.5% O2) on the blood PRL response induced by graded maximal exercise in eight trained male subjects.

The effects of salbutamol on pulmonary function in cyclists exposed to ozone: a pilot study.

Abstract: In order to determine the effects of an inhaled bronchodilator on the acute effects of ozone exposure on competitive cyclists, three subjects exercised on a stationary cycle ergometer for one hour in 0.34 +/- 0.02 ppm ozone, 29.8 +/- 0.3 degrees C. and 36.5 +/- 0.5% relative humidity under three experimental conditions. The initial test involved no pre-medication and served as a control. Using a double blind protocol the subjects were either given a placebo or salbutamol (200 micrograms via aerosol) prior to the second and third exposures. Pre- and post-exercise pulmonary function tests demonstrated a reduction in forced vital capacity (FVC) and forced expiratory volume in one second (FEV1), however, the magnitude of this reduction was not changed by the administration of salbutamol. These data suggest that pre-treatment with salbutamol is ineffective in reducing or eliminating pulmonary discomfort or respiratory dysfunction.

Sprint start reaction time: on the advisability of sensory vs motor sets.

Abstract: Currently, the available literature cannot provide definitive advice as to whether a sensory or a motor set will provide the faster reaction times. Two reasons have been proposed for the apparently incompatible results--and these were examined here. The first reason holds that the traditional motor set instructions were inappropriate because they misdirected subjects' attention to output execution which, in turn, resulted in prolonged RTs. Second, spontaneous set preferences (i.e., the set preferred at the time of reporting for the experiment) may influence which enforced set (sensory vs motor) yields the faster latency and, hence, sampling may have contributed to the different conclusions offered in past work. The present data supported the second but not the first proposal. The optimal set is that most practised by the individual.