ISSN:0195-9131    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Mitochondrial DNA sequence variation was determined in 46 sedentary young adult males who took part in ergocycle endurance training programs in two laboratories to assess whether mitochondrial DNA variants were associated with individual differences in maximal oxygen uptake (VO2max) and its response to training. VO2maxwas obtained from a progressive ergocycle test to exhaustion. White blood cell mitochondrial DNA was characterized with the restriction fragment length polymorphism (RFLP) technique using 22 restriction enzymes and human mitochondrial DNA as a probe for hybridization, Multiple mitochondrial DNA variants were detected with 15 of the enzymes. Some subjects exhibited many RFLPs. while others showed no variation. These RFLPs (morphs) were generated by base substitutions located in gene regions coding for mitochondrial proteins as well as in the noncoding regions. Carriers of three mitochondrial DNA morphs, two in the subunit 5 of the NADH dehydrogenase gene and one in the tRNA for threonine, had a VO2max(ml.kg−1·min−1) in the untrained state significantly higher than noncarriers, while carriers of one mitochondrial DNA morph in subunit 2 of NADH dehydrogenase had a lower initial VO2max, Endurance training increased VO2maxby a mean of 0.51 of O2, with individual differences ranging from gains of 0.06 to 1.03. After adjustment for training site and initial VO2max, a lower response was observed for three carriers of a variant in subunit 5 of the NADH dehydrogenase detected with Hincll (mean gain of 0.28 l;P< 0.05). These results suggest that sequence variation in mitochondrial DNA may contribute to individual difference in VO2maxand its response to training.

ISSN:0195-9131    

出版商:OVID    

年代:1993

数据来源: OVID

ISSN:0195-9131    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Iron and iron-binding proteins play a critical role in the physiology of many human systems, including the immune system. Intense interval exercise in trained men (mean [SD] age = 31.5 [4.5] yr; VO2max= 64.3 [3.8] ml,kg−1min−1) is associated with significant modulation of iron status parameters. The concentration of red blood cells, hemoglobin, and transferrin all increased significantly immediately post-test (P< 0.01), increases which can largely be attributed to hemoconcentration. Serum iron was elevated by approximately 25% both immediately and 1 h post-test (P< 0.08). Maximum post-test serum iron values (either immediately or 1 h post-test) were significantly elevated with respect to rest (P< 0.01). Transferrin concentration was also significantly elevated at 24 h post-test (P< 0.05). Transferrin saturation was not significantly altered by this protocol (P> 0.10). Despite a trend toward elevation at 24 h post-test, ferritin concentration was not significantly different from the resting value at any sampling point. Intense interval exercise appears to be associated with significant modulation of iron status, the biological importance of which remains to be determined.

ISSN:0195-9131    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The responses of quadriceps femoris muscles to an electrically elicited fatigue test were recorded from both lower extremities of 18 patients who had recently undergone unilateral, anterior cruciate ligament reconstruction. The fatigue test consisted of 40 pps, 13-pulse electrical trains that were repeated once per second for 3 min. The intensity of stimulation was set for each extremity to produce 20% of the maximum voluntary isometric contraction of the uninvolved muscle. The uninvolved quadriceps femoris muscle showed a significantly greater rate of decline in force over the first minute than the involved muscle (0.803% s−1for uninvolved muscle vs 0.620%.s−1for involved muscle). Similarly, the average forces produced over the last minute were significantly lower for the uninvolved than the involved quadriceps femoris muscle (uninvolved = 42.6%, involved = 50.4% of their original forces). These surprising results showed that the involved quadriceps femoris muscles were more endurant than the uninvolved muscles. It is suggested that the increases in endurance of the involved muscle may have been due, in part, to greater recruitment of Type I fibers with electrical stimulation or selective Type II fiber atrophy in the involved muscle.

ISSN:0195-9131    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

To investigate the effect of temperature stress on responses to static-dynamic work in patients with ischemic heart disease (IHD), 10 men with IHD shoveled gravel for 30 min in a warm (29°C), neutral (24°C), and cold (-8°C) environment (on separate days). A pace of 15 lifts. min−1was set, and the load per lift approximated 5.5 kg. Heart rate (HR), oxygen consumption (VO2), and systolic (SBP) and diastolic blood pressures (DBP) were evaluated at 5-min intervals. Arrhythmias and ST-segment depression were evaluated by ambulatory electrocardiographic monitoring. At 30 min, VO2, SBP, and DBP were higher (P< 0.05) in the cold environment, and HR was higher (P< 0.05) in the warm environment compared with the neutral environment. HR increased (P< 0.05) from 5 to 30 min in all three conditions. The increase in HR was greater (P< 0.05) in the warm environment. None of the subjects reported angina or demonstrated electrocardiographic ST-segment changes during shoveling in any environment. The results indicate that low-risk patients with stable IHD show modest temperature-induced alterations in hemodynamic and VO2responses during 30 min of moderate intensity (50–60% of peak VO2) static-dynamic work without adverse electrocardiographic responses or symptomatology.

ISSN:0195-9131    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Plasma ferritin (F) concentrations were measured (range 12–245 ng. ml−1) as an indicator of iron status in 24 male and 45 female healthy, nonanemic athletes. Usual food intake was assessed using a self-completed but supervised food frequency questionnaire. Linear regression was applied to determine the relationship between log F (as data was skewed) and average daily intake of iron (Fe). meat (M), protein (Pr), carbohydrate (CHO), fat (Fa), fiber (Fi). and kilojoules (Kj). There were negative correlations between F and each of Kj (P< 0.01) and CHO (P< 0.001) and a positive correlation between F and Pr/Kj (P< 0.01). No significant relationship existed between F and any of Fe. M, Fa, or Fi. These data suggest that iron or meat intake may not be important determinants of iron status in these athletes. Instead, the percentage of protein in the diet may be more influential on F. as may the (negative) effect of Kj and CHO intake, or at least their reflection of energy expenditure.

ISSN:0195-9131    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The relationship of fractures to physical activity and growth velocity in stature and metacarpal II bone dimensions was investigated in adolescent Belgian boys, Peak fracture incidence occurred between 12 and 14 yr of age and preceded the age at peak height velocity. The peak fracture rate occurred during mid adolescence (\pm 2 SD of the age at peak height velocity) and was twice as high as the rates before and after this period, The majority of fractures occurred during active participation in sports and general physical activities. The age at peak growth velocity for metacarpal cortical thickness, an indirect measure of bone mineral content, was about 6 months later than the ages at peak height velocity and peak growth velocity for metacarpal length. Peak fracture incidence occurred during a period when the amount of time spent in sports physical activity was low compared with later years. A lag in cortical bone thickness and mineralization, relative to linear skeletal growth, and unknown factors associated with active participation in sports, rather than an increase in the amount of physical activity, appear to be the predominant factors associated with the increased fracture incidence in Belgian boys during the growth spurt.

ISSN:0195-9131    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Previous studies linked muscular fatigue with a decrease in blood pH. This study investigated if the means of altering pH affected the extent of muscular fatigue. Drug-induced and exercise-induced acidosis were compared to test the hypothesis that exercise-induced acidosis impairs subsequent muscular performance more than chemically induced acidosis. In eight male subjects acidosis was induced by ingesting 0.3 g.kg−1ammonium chloride (AC) for one trial, by upper body exercise (UBE) for another trial, and after placebo (PL) treatment. They then completed a performance test (PT) of 50 maximal, bilateral isokinetic knee extensions. Whole blood pH before (pHpre) and after (pHpost) the PT was 7.412, 7.264, and 7.261 for PL, UBE, and AC, respectively; both AC and UBE decreased pH similarly compared with PL. Peak torque and total work during the PT were similar for PL and AC, and were significantly greater than after UBE. Six subjects performed a fourth trial after combined AC and UBE treatments causing a pHpreof 7.081, but there was no greater performance impairment than that caused by UBE alone. The results dissociate the extent of the impairment from the magnitude of the disruption in blood pH.

ISSN:0195-9131    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The effects of anabolic-androgenic steroid administration and exercise training on various aspects of hepatic function were investigated in sedentary and trained (treadmill for 12 wk) male and female rats treated orally with fluoxymesterone or methylandrostanolone (2 mg.kg−1body weight, 5 d.wk−1for 8 wk). The mean values of serum alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, total and direct bilirubin, and total- and high-density lipo-protein-cholesterol remained within normal range in all groups of male animals. The same is true for female rats, except for an increase in alkaline phosphatase activity in the steroid-treated groups. Hepatic microsomal aniline p-hydroxylase activity was reduced in male and increased in female rats by either steroid, whereas no significant effect was detected on 7-ethoxycoumarin deethylase activity. The levels of cytochrome P-450 and cytochrome b5were markedly decreased by the anabolic-androgenic steroid treatment in male rat microsomes, but neither the steroid administration nor exercise training induced significant changes in the cytochrome levels of female rat livers. Taking into account the significant increase in microsomal protein yield elicited by fluoxymesterone or methylandrostanolone treatment both in males and females, it is noteworthy that the total mono-oxygenase activities and cytochrome P-450 content, expressed on a per gram liver basis, were significantly increased in female whereas they were apparently unchanged in male rats. In conclusion, the present data show that the prolonged ingestion of high doses of anabolic-androgenic steroids, either with or without concurrent exercise training, can modify in a sex-dependent manner the capacity of rat liver to metabolize drugs without affecting classical serum indicators of hepatic function.

ISSN:0195-9131    

出版商:OVID    

年代:1993

数据来源: OVID