Canadian journal of sport sciences = Journal canadien des sciences du sport最新文献

This study investigated the effects of many years of bodybuilding on muscular strength and endurance. Eight bodybuilders (BB), 4 males and 4 females, and 8 controls (C), 4 males and 4 females, performed a muscle fatigue test (MFT) consisting of 25 maximal leg extensions at angular velocities of 180 and 300 degrees/s. The results for strength showed that at both the slow and fast contraction speeds, BB were significantly stronger than C and males were significantly stronger than females. For muscular endurance the results showed that at the slow contraction speed the torques and torque decline were greater in the BB than in the C, and greater in the males than the females. At the faster contraction speed, torque decline was similar in all groups while torques for the BB and male-C were similar and significantly greater than the torques for the female-C. The ratio of torques (fast/slow) for both strength and muscular endurance showed a main effect due to training status which supported the velocity specificity hypothesis. However, when the relative torques over the 25 contractions at both speeds were looked at, no velocity specificity occurred for muscular endurance. The data suggest a definite velocity specificity for the strength factor in BB whereas the same conclusion is not as clear for the muscular endurance factor.

This study evaluated the blood lactate (LA) response to stepping exercise, specifically the Canadian Aerobic Fitness Test (CAFT). It also compared the correlation between either LA or heart rate (HR) at a given stage of the CAFT and directly measured maximal aerobic power (VO2max). A total of 137 male Canadian Forces (CF) personnel between the ages of 18 and 53 years participated in this study. The LA concentration after each stage of the CAFT was measured in all subjects from blood sampled from the fingertip. Seventy-eight of these subjects also had their VO2max measured directly during a maximal treadmill run. The results showed that increasing stages of the CAFT were associated with exponentially increasing LA. At Stage 5, LA concentration ranged from 1.0 to 7.0, with a mean of 2.6 mmol.L-1, while HR ranged from 72 to 192 with a mean of 132 beats. When the LA and HR measures at Stage 5 of the CAFT were compared for their ability to predict VO2max, the correlation between lactate and VO2max was -0.71 (p less than .001); between HR and VO2max it was -0.36 (p less than .01). These results suggest that LA is a better predictor of VO2max than HR.

This study observed oxygen consumption (VO2), heart rate (HR), and rating of perceived exertion (RPE) during both maximal and submaximal exercise tests on a conventional Monark cycle ergometer and a new Velodyne ergometer. The Velodyne uses the subject's own bicycle attached to an electrically braked roller, which regulates power output. Trained male cyclists performed maximal exercise tests on both ergometers (N = 7) and two submaximal tests on each of three identical Velodynes and a Monark (N = 6). VO2, HR and RPE were measured during the submaximal and maximal tests. Data were analyzed via multiple repeated-measures ANOVA. No differences were found across cycles during the maximal or submaximal tests. The results indicate that the Monark and the Velodyne ergometers elicited similar physiologic and perceptual responses and that the Velodyne can be a viable alternative to the conventional Monark ergometer.

The use of androgenic-anabolic steroids (AAS) for enhancing athletic performance and body image is widespread. An increasing number of elite and recreational athletes of varying ages and athletic pursuits are using AAS. Sophisticated patterns of AAS use are supported by unethical and illegal distribution channels. Various testosterone-derived preparations attempt to manipulate pharmacological characteristics in an effort to maximize anabolic potential while minimizing androgenic effects. Although anecdotal and theoretical information suggests that AAS have positive ergogenic properties, the experimental evidence is equivocal. In addition to the ethical and legal implications of using AAS, there are diverse, though often reversible, medical and behaviour ramifications. In an effort to control and discourage AAS use, relevant sport governing bodies have implemented various testing and educational programs with undetermined success.

Participation in physical activity may influence health outcomes, so its quantification is important. There is little data on adolescent physical activities. Recall of physical activity in the preceding year was obtained from a birth cohort of 799 fifteen-year-old adolescents in New Zealand using a modified version of the Minnesota Leisure Time Activities Questionnaire. Mean total participation times were relatively high, with 612 hrs/year (1.68 hrs/day) for males and 401 hrs/year (1.1 hrs/day) for females. Individual total participation ranged from less than a minute to 6.5 hrs/day. Over 10% more females than males reported netball, equestrian activities, and dancing, and at least 10% more males reported cricket, rugby, fishing, soccer, squash, golf, and surfing. Ranked by mean participation time, equestrian activity was highest for females and walking was highest for males. Cycling and swimming represented the largest proportion of total group participation time. The sample will be followed up at age 18 years.