摘要:

Inorganic phosphate (Pi) supplementation has been reported to provide ergogenic benefits, though the research findings are inconsistent. Several confounding influences may explain these results, including mode of exercise, exercise intensity, dietary intake, daily biological fluctuations, type of supplement, administered dose of the supplement, washout period, length of loading period, fitness level of subjects, blood volume alterations, and sample collection and analysis techniques. This review provides a critical analysis of the methodological difficulties that may contribute to the equivocal research findings pertaining toPisupplementation.Key words: ergogenic aid, athletic performance, methodological critique

ISSN:1066-7814    

DOI:10.1139/h94-001

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Mitochondrial biogenesis (synthesis) has been observed to occur in skeletal muscle in response to chronic use. It also occurs in cardiac muscle during growth and hypertrophy, and it may be impaired during the aging process. This review summarizes the literature on the processes of mitochondrial biogenesis at the biochemical and molecular levels, with particular reference to striated muscles. Mitochondrial biogenesis involves the expression of nuclear and mitochondrial genes and the coordination of these two genomes, the synthesis of proteins and phospholipids and their import into the organelle, and the incorporation of these lipids and proteins into their appropriate locations within the matrix, inner or outer membranes. The emphasis is on the regulation of these events, with information derived in part from other cellular systems. Although descriptions of mitochondrial content changes in heart and skeletal muscle during altered physiological states are plentiful, much work is needed at the molecular level to investigate the regulatory processes involved. A knowledge of biochemical and molecular biology techniques is essential for continued progress in the field. This is a promising area, and potential new avenues for future research are suggested.Key words: heart, skeletal muscle, gene expression, heme metabolism, protein import

ISSN:1066-7814    

DOI:10.1139/h94-002

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

This study examined the relationship of oxygen pulse (O2pulse) to stroke volume (SV) and arterio-venous oxygen difference [diff] during submaximal cycle exercise in untrained (UG) and trained (TG) males. Fourteen volunteers in each group completed an incrementalmax test and a submaximal test at 60%max to determine cardiac output (Q) via CO2rebreathing., Q, and heart rate (HR) were used to calculate SV anddiff. There were no significant differences (p >.05) between the two groups for O2pulse, SV, anddiff during submaximal exercise. Stroke volume index (SVI) was significantly higher (p <.05) in the TG. O2pulse was significantly related to SV and SVI (p <.05) but not todiff in both groups. Regression equations for predicting SV from O2pulse for UG and TG wereY = 6.81X + 26.7,SE = 21.4,r = 0.84, andY = 10.33X - 32.3,SE = 14.2,r = 0.71, respectively. These results suggest that O2pulse can be used to predict SV during submaximal cycle exercise in untrained and trained men.Key words: cardiac performance, exercise, training status

ISSN:1066-7814    

DOI:10.1139/h94-003

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Six young men weight trained 3 days∙week−1for 19 weeks, on each day doing 3 warm-up sets of 20 repetitions followed by 1 set each at 15-20, 10-15, and 7-10 RM (Day 1), 3 sets at 15-20 RM (Day 2), and 1 set at 15-20 and 2 sets at 10-15 RM (Day 3) of a seated bilateral leg press exercise. Training increased (P < 0.05) the maximal single leg press lift (1-RM, 26%) and knee extensor cross-sectional area (12%). Arterial (brachial artery catheter) and esophageal (probe) pressure responses were measured before and after training as subjects did sets of as many repetitions as possible up to 20 reps with 50, 70, 80, 85, and 87.5% 1-RM. After training, peak values of systolic pressure attained during a set (Mpre/post, mm Hg) were significantly (P < 0.05) increased at 85% (325/360,10.8%) 1-RM. Peak diastolic pressure increased significantly at 50 (136/151, 11.0%), 70 (185/200, 8.1%), and 80% (215/234, 8.8%). Peak esophageal pressure increased significantly at 80% (71/91, 28.2%) 1-RM. For a given absolute weight lifted, all responses were markedly reduced after training. It is concluded that weight training can (a) increase the peak arterial and esophageal pressure responses attained during maximal weight lifting exercise, and (b) reduce the arterial and esophageal pressure responses to lifting the same absolute weight.Key words: weight training, systolic pressure, diastolic pressure, esophageal pressure, Valsalva maneuv

ISSN:1066-7814    

DOI:10.1139/h94-004

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The purpose of the study was to develop a minimum physical fitness standard for Canadian Forces personnel, 35 years and older, based on common criteria for physically demanding tasks. A random sample of 100 men and 76 women performed the Exercise Prescription (EXPRES) test and five physically demanding tasks that simulate common military tasks, while restricted, for safety reasons, to 90% maximal predicted heart rate. Results indicated poor predictive power, as variances ranged from 5 to 55% between EXPRES fitness scores and task performance. With approval from an expert panel, the 75th percentile score for each task was selected as the cutting criterion. The passing-group data were converted to Z-scores in order to determine the 5th percentile from each EXPRES item: these scores became the EXPRES fitness standard. The minimum fitness standard had a greater impact on women than on men but was representative of the passing groups for both sexes.Key words: occupational selection standards, employee selection, personnel selection, screening, job related performance tests

ISSN:1066-7814    

DOI:10.1139/h94-005

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

In order to compare the physiological and psychological responses to various levels of eccentric exercise, 7 active men (25 ± 5 yrs) exercised for 60 min on separate days at 60% of apparatus specificmax using downhill jogging (−5% 60DH), level jogging (60J), and cycling (60C). Virtually all of the responses to 60DH fell between 60J and 60C. Heart rate, O2pulse, and respiratory exchange ratio were significantly different among modes, with the responses during 60DH falling between those during 60J and 60C. Fat energy expenditure during the 60-min exercise bout was significantly higher during 60J, followed by 60DH and then 60C. Ratings of perceived exertion followed the order of 60C > 60DH > 60J. Vigor and fatigue scores on the Profile of Mood States also followed a hierarchy that paralleled the physiological responses. These results suggest that downhill jogging elicits physiological and psychological responses that are between those elicited by level jogging and cycling.Key words: energy expenditure, fat energy expenditure, ratings of perceived exertion, eccentric contractions

ISSN:1066-7814    

DOI:10.1139/h94-006

出版商:NRC Research Press    

年代:1994

数据来源: NRC

ISSN:1066-7814    

DOI:10.1139/h94-007

出版商:NRC Research Press    

年代:1994

数据来源: NRC

ISSN:1066-7814    

DOI:10.1139/h94-008

出版商:NRC Research Press    

年代:1994

数据来源: NRC

ISSN:1066-7814    

DOI:10.1139/h94-009

出版商:NRC Research Press    

年代:1994

数据来源: NRC