Age and aerobic power: the rate of change in men and women

The historic studies by Robinson and Astrand as well as more recent studies present a fairly uniform rate of decline in VO2max with age at 0.40-0.50 ml X kg-1 X min-1 X year-1 in men. In women the rate of decline appears to be less--approximately 0.20-0.35 ml X kg-1 X min-1 X year-1, at least in cross-sectional studies. Further, there is no clear distinction in the rate of change in VO2max when comparing active and inactive populations. Longitudinal studies varying from 2.5 to 21 to 56 years present a confounding picture. The rate of decline in VO2max varies from 0.04 to 1.43 ml X kg-1 X min-1 X year-1. There is some indication that active individuals decline at a slower rate than inactive persons but the results are not uniform. A possible explanation is that changes in VO2max over the entire age range may be curvilinear, with active individuals declining slowly as long as they maintain a regular exercise program, and sedentary individuals declining at a rapid rate during their 20's and 30's followed by a slower rate of decline of their VO2max as they age further.     

A comparison of high-speed power training and traditional slow-speed resistance training in older men and women

Muscle power, the product of force × velocity, is a critical determinant of function in older adults. Resistance training (RT) at high speed has been shown to improve peak muscle power in this population; however, different functional tasks may benefit from the improvement of power at values other than "peak" values, for example, tasks that require a greater velocity component or a greater force component. This study compared the effect of high-speed RT on muscle performance (peak power [PP] and its components [PP force and PP velocity] and overall peak velocity [VEL]) across a broad range of external resistances. Thirty-eight older men and women were randomized to high-speed power training at 40% of the 1-repetition maximum (1RM) (n = 13 [74.1 ± 6.4 years]); traditional RT at 80% 1RM (n = 13 [70.1 ± 7.0 years]); or control (n = 12 [72.8 ± 4.1 years]). Measures of muscle performance were obtained at baseline and after the 12-week training intervention. Muscle power and 1RM strength improved similarly with both high-speed and traditional slow-speed RT. However, speed-related muscle performance characteristics, PP velocity and overall VEL, were most positively impacted by high-speed power training, especially at lower external resistances. Because gains in speed-related measures with high-speed training compared to traditional RT do not come at the expense of other muscle performance outcomes, we recommend using an RT protocol in older adults that emphasizes high-speed movements at low external resistances.     

Skeletal muscle oxidative capacity in young and older women and men.

It has been suggested that a decline in skeletal muscle oxidative capacity is a general consequence of aging in humans. However, previous studies have not always controlled for the effects of varying levels of physical activity on muscle oxidative capacity. To test the hypothesis that, when matched for comparable habitual physical activity levels, there would be no age-related decline in the oxidative capacity of a locomotor muscle, the postexercise recovery time of phosphocreatine was compared in the tibialis anterior muscle of young [n = 19; 33.8 +/- 4.8 (SD) yr] and older [n = 18; 75.5 +/- 4.5 yr] healthy women and men of similar, relatively low, activity levels. The intramuscular metabolic measurements were accomplished by using phosphorus magnetic resonance spectroscopy. The results indicate that there was no age effect on the postexercise recovery time of phosphocreatine recovery, thus supporting the stated hypothesis. These data suggest that there is no requisite decline in skeletal muscle oxidative capacity with aging in humans, at least through the seventh decade.     

Variations in plasma zinc in older men and women

The study evaluated the biological and analytical variance in plasma zinc from 36 adults 60–88 yr of age. Blood samples were taken by finger-prick from each subject on d 1, 2, 3, 8, and 15. Days 1, 2, and 3 were selected to describe daily variation; 1, 8, and 15 were selected to describe weekly variation. Plasma Zn was analyzed by flame atomic absorption using a microinjection technique. Variation was partitioned into analytical, intraindividual, and interindividual components using analysis of variance. The interindividual variability was generally greater than the intraindividual variability. The variability for plasma zinc was about 30% and was substantially greater than reported for younger populations. This variability could not be attributed to the covariates examined, including zinc intake from food and supplements, serum albumin, and C-reactive protein. The variability would affect the accuracy of plasma zinc status based on a blood sample collected on a single day. With the microtechnique used in this study, 8 sample days would be needed to estimate plasma Zn with 95% confidence level and 20% level of accuracy.     

Skeletal muscle fiber quality in older men and women

Wholemuscle strength and cross-sectional area (WMCSA), andcontractile properties of chemically skinned segments from single fibers of the quadriceps were studied in 7 young men (YM, 36.5 ± 3.0 yr), 12 older men (OM, 74.4 ± 5.9 yr), and 12 olderwomen (OW, 72.1 ± 4.3 yr). WMCSA was smaller in OMcompared with YM (56.1 ± 10.1 vs. 79.7 ± 13.1 cm²; P = 0.031) and in OW (44.9 ± 7.5; P < 0.003) compared with OM. Age-related, but notsex-related, differences in strength were eliminated after adjustingfor WMCSA. Maximal force was measured in 552 type I and 230 type IIAfibers. Fibers from YM (type I = 725 ± 221; type IIA = 792 ± 271 µN) were stronger (P < 0.001) thanfibers from OM (I = 505 ± 179; IIA = 577 ± 262 µN) even after correcting for size. Type IIA fibers were stronger(P < 0.005) than type I fibers in YM and OM but not inOW (I = 472 ± 154; IIA = 422 ± 97 µN).Sex-related differences in type I and IIA fibers were dependent onfiber size. In conclusion, differences in WMCSA explain age-relateddifferences in strength. An intrinsic defect in contractile proteinscould explain weakness in single fibers from OM. Sex-relateddifferences exist at the whole muscle and single fiber levels.

     

Postexercise protein metabolism in older and younger men following moderate-intensity aerobic exercise

Regular aerobic exercise strongly influences muscle metabolism in elderly and young; however, the acute effects of aerobic exercise on protein metabolism are not fully understood. We investigated the effect of a single bout of moderate walking (45 min at approximately 40% of peak O2 consumption) on postexercise (POST-EX) muscle metabolism and synthesis of plasma proteins [albumin (ALB) and fibrinogen (FIB)] in untrained older (n = 6) and younger (n = 6) men. We measured muscle phenylalanine (Phe) kinetics before (REST) and POST-EX (10, 60, and 180 min) using l-[ring-2H5]phenylalanine infusion, femoral arteriovenous blood samples, and muscle biopsies. All data are presented as the difference from REST (at 10, 60, and 180 min POST-EX). Mixed muscle fractional synthesis rate (FSR) increased significantly at 10 min POST-EX in both the younger (0.0363%/h) and older men (0.0830%/h), with the younger men staying elevated through 60 min POST-EX (0.0253%/h). ALB FSR increased at 10 min POST-EX in the younger men only (2.30%/day), whereas FIB FSR was elevated in both groups through 180 min POST-EX (younger men = 4.149, older men = 4.107%/day). Muscle protein turnover was also increased, with increases in synthesis and breakdown in younger and older men. Phe rate of disappearance (synthesis) was increased in both groups at 10 min POST-EX and remained elevated through 60 min POST-EX in the older men. A bout of moderate-intensity aerobic exercise induces short-term increases in muscle and plasma protein synthesis in both younger and older men. Aging per se does not diminish the protein metabolic capacity of the elderly to respond to acute aerobic exercise.     

Longitudinal tracking of muscular power changes of NCAA Division I collegiate women gymnasts

Gymnastics relies upon power as a critical component of sports-specific fitness. The purpose of this study was to monitor long-term training adaptations in the power of National Collegiate Athletics Association Division I women gymnasts. Twenty members of a women's gymnastic team (aged 18-22) were tracked over 3 years with the first year a baseline year of testing. Whole body power for the counter-movement (CMJ) and squat (SJ) vertical jump was obtained via force plate analyses at 2 assessment time points during each year (February and November). Results showed significant (p < or = 0.05) and continued increases in peak power output in the CMJ and SJ at each biannual assessment. Improvements of 46% (+1010 W) for the CMJ and 43% (+900 W) for the SJ were observed at the end of the tracking period. Peak power for the CMJ and SJ were recorded at 3210 W (+/-350 W) and 3000 W (+/-152 W), respectively. Associated improvements in the time to peak power of 36% (-0.239 second) and 38% (-0.151 second) were also found for the CMJ and SJ. There were no significant changes in body mass or total skinfold thickness, however, a shift toward improved fat free mass (i.e., lean muscle mass) was apparent. These data underscore the importance that specificity, and more importantly power development, should play in the conditioning of collegiate women gymnasts' training programs.     

Frequency and duration of interval training programs and changes in aerobic power.

This study was designed to ascertain whether 7- and 13-wk interval training programs with training frequencies of 2 days/wk would produce improvement in maximal aerobic power (VO2max) comparable to that obtained from 7- and 13-wk programs of the same intensity consisting of 4 training days/wk. Sixty-nine young healthy college males were used as subjects. After training, there was a significant increase in VO2max (bicycle ergometer, open-circuit spirometry) that was independent of both training frequency and duration. However, there was a trend for greater gains after 13 wk. Maximal heart rate (direct lead ECG) was significantly decreased following training, being independent of both training frequency and duration. Submaximal VO2 did not change with training but submaximal heart rate decreased significantly with greater decreases the more frequent and longer the training. Within the limitations of this study, these results indicate that: 1) maximal stroke volume and/or maximal avO2 difference, principle determinants of VO2max, are not dependent on training frequency nor training duration, and 2) one benefit of more frequent and longer duration interval training is less circulatory stress as evidenced by decreased heart rate, during submaximal exercise.     

Circadian changes in salivary constituents and conductivity in women and men.

Circadian rhythms in salivary [glucose], [Na+], [K+] and conductivity were measured in 2 age groups of men (men A, 20-45 years and men B, 46-60 years) and 8 different states of fertility in women (normally menstruating, taking oral contraceptives, pregnant, lactational amenorrhea, lactational amenorrhea and taking oral contraceptives, lactating and menstruating, menopausal, and post-menopausal). Unstimulated whole saliva (2-3 ml) was collected every 3 h over a 48 h span. Analysis of Spearman Rank Correlations indicated significant circadian rhythms (significant positive coefficients) for all groups of [Na+] (mean = 0.577 +/- 0.040) and conductivity (mean = 0.410 +/- 0.050). There was no evidence of differences in prominence of rhythm across groups for [Na+] and conductivity. [K+] showed less evidence of rhythms and much greater variability between groups (mean correlation coefficient = 0.198 +/- 0.055). Rhythms in [glucose] (mean correlation coefficient = 0.409 +/- 0.051) were evident in all groups except men B (0.016), menopausal women (0.151) and post-menopausal women (0.310). Model analysis of the data showed no discernible rhythmic trend with age for either conductivity, [Na+] or [K+], where any differences were explainable by the group characteristics. The rhythm in [glucose] showed a significant weakening with age over all groups (F-ratio = 7.46**), and was different between men A and men B (F-ratio = 6.95**). It was concluded that circadian rhythms were present in whole unstimulated saliva for conductivity and [Na+] and that these rhythms were independent of reproductive state, whereas circadian rhythms in [K+] were dependent on reproductive state. Circadian rhythms for [glucose] were dependent on age. The loss of a rhythm in [glucose] with age indicates that glucose, Na+ and K+ are not linked in their entry into saliva. The influence of entry and reabsorption on the final concentrations of glucose, Na+ and K+ in saliva is discussed.     

Skeletal muscle contractile and noncontractile components in young and older women and men.

To examine the influences of age, gender, and habitual physical activity level on human skeletal muscle composition, we developed a relatively simple magnetic resonance imaging method for the quantitation of leg anterior compartment contractile and noncontractile content. We studied 23 young (11 women and 12 men, 26-44 yr old) and 21 older (10 women and 11 men, 65-83 yr old) healthy adults. Analysis was by two-factor (age, gender) ANOVA. Physical activity, quantitated by three-dimensional accelerometer worn about the waist for 1 wk, was not different between groups. Men had larger contractile and noncontractile cross-sectional areas (cm(2)) than women, with no gender effect on percent noncontractile area. Young subjects had larger contractile areas and smaller absolute (cm(2)) and relative (percent total) noncontractile areas than older subjects. There was a significant linear relationship between physical activity and percent noncontractile area in older (r = -0.68, P = 0.002) but not young subjects. These data demonstrate a more than twofold increase in the noncontractile content of locomotor muscles in older adults and provide novel support for physical activity as a modulator of this age-related change in muscle composition.     

Modeling developmental changes in strength and aerobic power in children

The present studyexamined two contrasting multilevel model structures to describe thedevelopmental (longitudinal) changes in strength and aerobic power inchildren: 1) an additive polynomial structure and 2) a multiplicativestructure with allometric body size components. On the basis of themaximum log-likelihood criterion, the multiplicative "allometric"model was shown to be superior to the additive polynomial model whenfitted to the data from two published longitudinal studies and toprovide more plausible solutions within and beyond the range ofobservations.The multilevel regression analysis ofstudy 1 confirmed that aerobic powerdevelops approximately in proportion to body mass,m^1/3. Theanalyses from study 2 identified asignificant increase in quadriceps and biceps strength, in proportionto body size, plus an additional contribution from age, centered atabout peak height velocity (PHV). The positive "age" term forboys suggested that at PHV the boys were becoming stronger in thequadriceps and biceps in relation to their body size. In contrast, thegirls' age term was either negligible (quadriceps) or negative(biceps), indicating that at PHV the girls' strength was developing inproportion to or, in the case of the biceps, was becoming weaker inrelation to their body size.

     

High-speed power training: a novel approach to resistance training in older men and women. A brief review and pilot study

Over the past century, increases in both longevity and the number of older adults in the U.S.A. have given rise to greater numbers of functionally limited and disabled older adults. This has resulted in a decline in the quality of life of our elderly population, as well as an increased burden on our health care system. Resistance training (RT) with a strengthening component has traditionally been recommended to improve health and physical functioning in older adults. Muscle power (force x velocity), or the ability to produce force rapidly, has recently emerged as an important predictor of functioning in older men and women and has been the current focus of many RT studies. In this review, the physiological changes that contribute to the declines in muscle strength and power with aging will first be examined, followed by a discussion of the prevailing theories behind the use of traditional RT in older men and women. The rationale for high-velocity RT will then be explored, and the recent literature on novel training interventions designed to improve muscle power in older adults will be discussed. Finally, some preliminary evidence demonstrating the benefits of high-velocity power training in older men and women will be presented.     

A comparison of adductor pollicis fatigue in older men and women

Sex differences in fatigue resistance of the adductor pollicis (AP) muscle were studied in 24 older adults who were divided into three groups: 12 older men (69.8 +/- 4.60 years), 6 older women not on hormone replacement therapy (HRT) (70.2 +/- 4.02 years), and 6 older women on HRT (68.7 +/- 6.47 years). Fatigue in the AP muscle was induced using an intermittent (5 s contraction, 5 s rest) submaximal voluntary contraction (50% of maximal voluntary contraction (MVC)) protocol, which was continued until exhaustion (i.e., when subjects could either no longer maintain a 5-s contraction at 50% MVC or when the MVC was deemed to be lower than the target force). There was no effect of HRT on MVC or time to fatigue (TTF); therefore, the older women were pooled as one subject group. At baseline, men were stronger than women for MVC (75.9 +/- 18.8 N in men vs. 56.8 +/- 10.0 N in women; P < 0.05) and evoked twitch force (7.3 +/- 1.7 N in men vs. 5.2 +/- 0.8 N in women; P < 0.05). There was no difference in TTF between men and women (14.77 +/- 7.06 min in men vs. 11.53 +/- 4.91 min in women; P > 0.20), nor was there a significant relationship between baseline muscle force and TTF (r = 0.14). There was also no difference in the pattern of fatigue and recovery between the men and women. These results suggest that there is no difference in endurance or fatigue characteristics of the AP muscle in men and women over the age of 65 years, and that baseline muscle force does not predict fatigue resistance in this muscle.     

Validity of methods of body composition assessment in young and older men and women.

We examined the validity of percent body fat (%Fat) estimation by two-compartment (2-Comp) hydrostatic weighing (Siri 2-Comp), 3-Comp dual-energy X-ray absorptiometry (DEXA 3-Comp), 3-Comp hydrostatic weighing corrected for the total body water (Siri 3-Comp), and anthropometric methods in young and older individuals (n = 78). A 4-Comp model of body composition served as the criterion measure of %Fat (Heymsfield 4-Comp; S. B. Heymsfield, S. Lichtman, R. N. Baumgartner, J. Wang, Y. Kamen, A. Aliprantis, and R. N. Pierson Jr., Am. J. Clin. Nutr. 52: 52-58, 1990.). Comparison of the Siri 3-Comp with the Heymsfield 4-Comp model revealed mean differences of /= r = 0.997, total error values 相似文献   

The impact of experimental instruction on changes in EEG power during verbal creative thinking in men and women

Features of EEG pattern during verbal creative thinking depending on experimental instruction were studied in men and women. Spectral power density was analyzed in six frequency bands (4-30 Hz). Performance of a creative task produced an increase in the power of theta (4-6 Hz) and beta2 (20-40 Hz) components and decrease in the power of alpha (8-13 Hz) and betal (13-20 Hz). Changes in the alpha and betal bands were observed, predominantly, in the posterior areas, whereas power of the thetal and beta2 bands increased in the anterior areas. Independently of instruction, women demonstrated greater synchronization in the theta1 band than men, whereas in men the desynchronization in the alpha2 band (10-13 Hz) was more pronounced. When the subjects were instructed to create original sentences, a widespread decrease in the EEG power was observed in the band of 8-30 Hz as compared to instruction "to create sentences". Thus, the instruction-related changes in EEG power were not gender-specific. They may reflect neural activity mediating selective attention.     

Endurance training in older men and women II. Blood lactate response to submaximal exercise

Seven men and four women (age 63 +/- 2 yr, mean +/- SD, range 61-67 yr) participated in a 12-mo endurance training program to determine the effects of low-intensity (LI) and high-intensity (HI) training on the blood lactate response to submaximal exercise in older individuals. Maximal oxygen uptake (VO2max), blood lactate, O2 uptake (VO2), heart rate (HR), ventilation (VE), and respiratory exchange ratio (R) during three submaximal exercise bouts (65-90% VO2max) were determined before training, after 6 mo of LI training, and after an additional 6 mo of HI training. VO2max (ml X kg-1 X min-1) was increased 12% after LI training (P less than 0.05), while HI training induced a further increase of 18% (P less than 0.01). Lactate, HR, VE, and R were significantly lower (P less than 0.05) at the same absolute work rates after LI training, while HI training induced further but smaller reductions in these parameters (P greater than 0.05). In general, at the same relative work rates (ie., % of VO2max) after training, lactate was lower or unchanged, HR and R were unchanged, and VO2 and VE were higher. These findings indicate that LI training in older individuals results in adaptations in the response to submaximal exercise that are similar to those observed in younger populations and that additional higher intensity training results in further but less-marked changes.