ISSN:1066-7814    

DOI:10.1139/h93-001

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The purposes of this review are to summarize studies of cross-sections of autopsied whole muscles from previously physically healthy males and to focus on the cause of the ageing atrophy. The ageing atrophy begins around 25 years of age and thereafter accelerates. This is caused mainly by a loss of muscle fibres, and to a lesser extent by a reduction in fibre size, mostly of the proportion of the fibre area in the muscle cross-section occupied by type 2 (fast-twitch) fibres. In muscle from old subjects, there is a significant increase in the number of enclosed fibres, indicating an increased incidence of fibre type grouping, a loss of motor neurons in the spinal cord, and a reduction in the number of functioning motor units. These findings strongly suggest a combination of a progressive denervation process and an altered physical activity level as the two major mechanisms underlying the effects of normal ageing on human muscle. These changes have obvious implications for old individuals and their participation in physical activity and in sports, which must be accommodated in rehabilitation regimes or in training programmes.Key words: ageing, microscopy, muscles, physiological adaptation

ISSN:1066-7814    

DOI:10.1139/h93-002

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

This study identifies the quickest recovery between consecutive anaerobic tests to maintain power output (PO) on the repeated test. Sixteen male cyclists finished three sessions of max rpm initial and repeated 45-s cycling tests at 53.9 N. Tests were separated by 6, 9, or 12 min of recovery cycling (80 rpm, 9.8 N). Results showed no significant differences in PO between initial tests (M = 578.5 ± 50 watts). PO was significantly less on the 6-min repeated test (M = 551.2 ± 51) compared to the 9- (M = 575.1 ± 53) and 12-min tests (M = 581.7 ± 49.9) (p > 0.05). Net blood lactate [HLa] (repeated test-recovery) was significantly related to net PO (repeated test-initial test) on the 9- (r = 0.60,p < 0.05) and 12-min (r = 0.64,p < 0.001) trials, but not on the 6-min trial (r = 0.35,p = 0.19). In summary, at least 9 min of recovery cycling maintains PO on a repeated 45-s cycling test. Elevated [HLa] at the onset of high-intensity sprint exercise is moderately associated with PO on repeated cycle ergometer tests.Key words: anaerobic exercise, cycling, power output, blood lactate, exercise recovery

ISSN:1066-7814    

DOI:10.1139/h93-003

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The advantage of active over passive recovery from long and intermediate duration exercise is well documented. Success has been attributed to metabolite washout and/or lactate (La) utilization by the active musculature. This study was designed to determine whether active recovery was superior to passive rest during short duration, high intensity performance. On 4 separate days, six athletes performed a set of eight 6-s power tests separated by 30-s recovery intervals under two recovery conditions. Recovery conditions involved either sitting passively on the bike (P) or actively pedaling (A) at 60 rpm using 1 kg resistance. A MANOVA on peak power (PP), fatigue rate (F), and total work (TW) showed a significant difference due to recovery condition,F(3, 169);p <.0001. Separate ANOVAs revealed that PP (A = 1192.85 watts, P = 1134.57 watts;p <.0001) and TW (A = 6.59 kJ, P = 6.23 kJ; p <.0001) differed significantly between conditions. No difference was found for F (A = 80.12 watts∙sec−1, P = 79.80 watts∙sec−1). Results indicate that active recovery provides superior performance to passive rest in repeated short-term, high intensity power activities.Key words: recovery, cycle ergometry, anaerobic p

ISSN:1066-7814    

DOI:10.1139/h93-004

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The hyperbolic relationship between power output (P) and time to exhaustion (t) is described ast = W′/(P- θPA). The purpose of this study was to determine the stability of estimations of estimates of θPAand W′, said to reflect maximal sustainable power and anaerobic capacity, respectively. Thirteen women and 13 men performed five bouts of cycling exercise to exhaustion. Individual θPAand W′ were calculated from the results of these five bouts (Trial 1). These procedures were repeated (Trial 2). For both sexes, Trial 2 estimates of θPAwere 5 to 6% higher than Trial 1 estimates, but they were highly correlated. Mean W′ estimates were the same in Trials 1 and 2, with higher trial-to-trial correlations in the men than in the women.Key words: critical power, power asymptote, endurance, cycle ergometry, gender

ISSN:1066-7814    

DOI:10.1139/h93-005

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Team handball players (N = 118) underwent a number of cognitive tests to examine how much of their decision making (DM) ability, as measured through responses to game slides projected to them for 2 seconds under low and high exertion levels (i.e., walking and running), was accounted for by cognitive components. A stepwise multiple linear regression indicated that experience was the most pronounced predictor of DM capacity in both exertion conditions. In the walking condition, concentrational consistency, avoidance of concentrational mistakes, and short-term memory, together with experience, produced a multipleRof 0.48 with decision making. In the running condition, choice reaction time (CRT), intelligence, and short-term memory, together with experience, correlated 0.46 with DM. These differences in cognitive abilities, as predictors of DM under walking and running conditions, are discussed in terms of information processing models and other cognitive processes.Key words: cognition, decision making, information processing

ISSN:1066-7814    

DOI:10.1139/h93-006

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Many clinical factors influence the 1-year prognosis in myocardial infarction (MI) patients. The most important clinical determinants are the left ventricular dysfunction, myocardial ischemia, and complex ventricular arrhythmias. Some authors have found an independent prognostic value of complex ventricular arrhythmias, while others consider that ventricular arrhythmias predict future cardiac events only if associated with low ejection fractions. Other factors that have 1-year prognostic value are the following: a previous MI, a history of angina at least 3 months preceding the infarct, postmyocardial angina, and the criteria that indicate to the practitioner whether MI patients are medically ineligible for stress testing. There still remain controversies in regard to the predictive value of certain variables such as the site, type, and extension of the MI, the presence of complex ventricular arrhythmias, exercise-induced hypotension, ST segment elevation, and the electrical provocation of dangerous arrhythmias.Key words: cardiac rehabilitation, postinfarct mortality and morbidity, cardiac events predictors, postinfarct prognostic stratification

ISSN:1066-7814    

DOI:10.1139/h93-007

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Performance on fitness and back related isometric strength tests, as well as the response to a lifestyle questionnaire, were related to the subsequent occurrence of back injuires in 119 nurses. In all, 22% of subjects sustained injuries during the 18-month study. Injured nurses were more likely to be from high-risk wards and to have received worker's compensation pay for past back injuries. Fitness and lifestyle characteristics did not differ significantly between injured and not-injured groups. Using backward stepwise logistic regression, a model was developed that accounted for 41% of the variability between groups and predicted 67% of those injured. Prior compensation pay, smoking status, and job satisfaction were the most useful discriminators. It was concluded, however, that the fitness and lifestyle parameters measured did not effectively predict back injury in nurses.Key words: fitness assessment, isometric strength, job satisfaction, job selection criteria, smoking status

ISSN:1066-7814    

DOI:10.1139/h93-008

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Three studies were performed to evaluate the effects of jet lag on factors associated with sport performance. In Study 1, members of the USA Women's Soccer Team traveled to Taiwan; in Study 2, North American students and faculty traveled to Western Europe; and in Study 3, European students traveled to North America. After travel, there was disruption of mood state and a reduction in dynamic strength; peak 5-s power and 30-s work capacity were reduced for 2 days (5-s power: 9.8 vs. 9.0 vs. 9.0 W∙kg−1; 30-s work capacity: 213 vs. 199 vs. 201 J∙kg−1). In these studies, mood state, anaerobic power and capacity, and dynamic strength were affected by rapid transmeridianal travel, and even highly trained athletes suffered from jet lag. However, effects of travel on the variables tested were essentially eliminated after 3 or 4 days.Key words: circadian rhythm, anaerobic power, anaerobic capacity, mood, tr

ISSN:1066-7814    

DOI:10.1139/h93-009

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

This study investigated the retention of strength gained after resistance training, while performing aerobic endurance training. Following a 10-week resistance training program (three times a week) that included maintenance aerobic endurance training (twice a week), 18 varsity oarswomen were matched on strength and randomly assigned to two groups: Group 1 performed maintenance resistance training once a week and Group 2 performed resistance training twice a week. Both groups performed endurance training four times a week during the 6-week maintenance resistance training program. There was a significant increase in strength (multiple-RM test) for three upper and three lower body exercises after the initial 10-week resistance training program. A further significant increase in two exercises (inclined leg press and knee flexion) were observed after 6 weeks of maintenance resistance training and endurance training in both groups. No further significant increases were observed in the four other exercises during maintenance strength training. These latter findings occurred at the same time that VO2max and ventilation threshold increased. These results suggest that strength gains can be maintained with resistance training once or twice a week while focusing on improving aerobic endurance performance without compromising the latter.Key words: repetition maximum, ventilation threshold, endurance performance

ISSN:1066-7814    

DOI:10.1139/h93-010

出版商:NRC Research Press    

年代:1993

数据来源: NRC