Declines in physiological functional capacity with age: a longitudinal study in peak swimming performance.

We followed up swimming performance times of 321 women and 319 men who participated in the US Masters Swimming Championships over a 12-yr period. All swimmers placed in the top 10 in their age group over 3 yr (mean = 5 yr). A random coefficients model for repeated measures was used to derive a line of best fit from a group of regression lines for each subject. Both 50- and 1,500-m swimming performance declined modestly until approximately 70 yr of age, where a more rapid decline was observed in both men and women. Compared with 1,500-m swimming, the 50-m freestyle declined more modestly and slowly with age. The rate and magnitude of declines in swimming performance with age were greater in women than in men in 50-m freestyle; such sex-related differences were not observed in 1,500-m freestyle. Overall, the variability along a population regression line increased markedly with advancing age. The present longitudinal findings indicate that 1) swimming performance declines progressively until age 70, where the decrease becomes quadratic; 2) the rates of the decline in swimming performance with age are greater in a long-duration than in a short-duration event, suggesting a relatively smaller loss of anaerobic muscular power with age compared with cardiovascular endurance; 3) the age-related rates of decline are greater in women than in men only in a short-duration event; and 4) the variability of the age-related decline in performance increases markedly with advancing age.     

Effects of four different single exercise sessions on lipids, lipoproteins, and lipoprotein lipase

The purpose ofthis study was to determine the threshold of exercise energyexpenditure necessary to change blood lipid and lipoproteinconcentrations and lipoprotein lipase activity (LPLA) in healthy,trained men. On different days, 11 men (age, 26.7 ± 6.1 yr; bodyfat, 11.0 ± 1.5%) completed four separate, randomly assigned,submaximal treadmill sessions at 70% maximalO₂ consumption. During eachsession 800, 1,100, 1,300, or 1,500 kcal were expended. Compared withimmediately before exercise, high-density lipoprotein cholesterol(HDL-C) concentration was significantly elevated 24 h after exercise(P < 0.05) in the 1,100-, 1,300-, and 1,500-kcal sessions. HDL-C concentration was also elevated(P < 0.05) immediately after and 48 h after exercise in the 1,500-kcal session. Compared with values 24 hbefore exercise, LPLA wassignificantly greater (P < 0.05) 24 h after exercise in the 1,100-, 1,300-, and 1,500-kcal sessions andremained elevated 48 h after exercise in the 1,500-kcal session. Thesedata indicate that, in healthy, trained men, 1,100 kcal of energyexpenditure are necessary to elicit increased HDL-C concentrations.These HDL-C changes coincided with increased LPLA.

     

Muscle quality. I.Age-associated differences between arm and leg muscle groups

To determine the differences between armand leg muscle quality (MQ) across the adult life span in men andwomen, concentric (Con) and eccentric (Ecc) peak torque (PT) weremeasured in 703 subjects (364 men and 339 women, age range 19-93yr) and appendicular skeletal muscle mass (MM) was determined in thearm and leg in a subgroup of 502 of these subjects (224 men and 278 women). Regression analysis showed that MQ, defined as PT per unit ofMM, was significantly higher in the arm (~30%) than in the legacross age in both genders (P < 0.01). Arm and leg MQ declined at a similar rate with age in men,whereas leg MQ declined ~20% more than arm MQ with increasing age inwomen (P  0.01 andP < 0.05 for Con and Ecc PT,respectively). Moreover, the age-associated decrease in arm MQ wassteeper in men than in women whether Con or Ecc PT was used (bothP < 0.05). Arm MQ as determined byCon PT showed a linear age-related decline in men and women (28 and20%, respectively, P < 0.001),whereas arm MQ as determined by Ecc PT showed a linear age-relateddecline in men (25%, P < 0.001) butnot in women (not significant). In contrast, both genders exhibited anage-related quadratic decline in leg MQ as determined by Con PT(~40%) and Ecc PT (~25%; both P < 0.001), and the rate of decline was similar for men and women. ThusMQ is affected by age and gender, but the magnitude of this effectdepends on the muscle group studied and the type of muscle action (Convs. Ecc) used to assess strength.

     

Age and gender comparisons of muscle strength in 654women and men aged 20-93 yr

Lindle, R. S., E. J. Metter, N. A. Lynch, J. L. Fleg, J. L. Fozard, J. Tobin, T. A. Roy, and B. F. Hurley. Age and gendercomparisons of muscle strength in 654 women and men aged 20-93 yr.J. Appl. Physiol. 83(5): 1581-1587, 1997.To assess ageand gender differences in muscle strength, isometric, concentric (Con),and eccentric (Ecc) peak torque was measured in the knee extensors at aslow (0.52 rad/s) and fast (3.14 rad/s) velocity in 654 subjects (346 men and 308 women, aged 20-93 yr) from the Baltimore LongitudinalStudy of Aging. Regression analysis revealed significant(P < 0.001) age-related reductions in Con and Ecc peaktorque for men and women at both velocities, but no differences wereobserved between the gender groups or velocities. Age explained lossesin Con better than Ecc peak torque, accounting for 30% (Con) vs. 19%(Ecc) of the variance in men and 28% (Con) vs. 11% (Ecc) in women. Toassess age and gender differences in the ability to store and utilizeelastic energy, the stretch-shortening cycle was determined in a subsetof subjects (n = 47). The older women (mean age = 70 yr)showed a significantly greater enhancement in the stretch-shorteningcycle, compared with men of similar age (P < 0.01) andcompared with younger men and women (each P < 0.05). Bothmen and women showed significant declines in muscle quality for Conpeak torque (P < 0.01), but no gender differences were observed. Only the men showed a significant decline in muscle quality(P < 0.001) for Ecc peak torque. Thus both men and women experience age-related losses in isometric, Con, and Ecc knee extensorpeak torque; however, age accounted for less of the variance in Eccpeak torque in women, and women tend to better preserve muscle qualitywith age for Ecc peak torque. In addition, older women have an enhancedcapacity to store and utilize elastic energy compared with similarlyaged men as well as with younger women and men.

     

Grip strength changes over 27yr in Japanese-American men

The aim of thisstudy was to describe changes in grip strength over a follow-up periodof ~27 yr and to study the associations of rate of strength declinewith weight change and chronic conditions. The data are from theHonolulu Heart Program, a prospective population-based studyestablished in 1965. Participants at exam1 were 8,006 men (ages 45-68 yr) who were ofJapanese ancestry and living in Hawaii. At follow-up, 3,741 men (agerange, 71-96 yr) participated. Those who died before the follow-upshowed significantly lower grip-strength values at baseline than didthe survivors. The average annualized strength change among thesurvivors was 1.0%. Steeper decline (>1.5%/yr) wasassociated with older age at baseline, greater weight decrease, andchronic conditions such as stroke, diabetes, arthritis, coronary heartdisease, and chronic obstructive pulmonary disease. The risk factorsfor having very low hand-grip strength at follow-up, here termedgrip-strength disability (21 kg, the lowest 10th percentile), werelargely same as those for steep strength decline. However, theage-adjusted correlation between baseline and follow-up strength wasstrong (r = 0.557, P < 0.001); i.e., those who showedgreater grip strength at baseline were also likely to do so 27 yrlater. Consequently, those in the lowest grip-strength tertile atbaseline had about eight times greater risk of grip-strength disabilitythan those in the highest tertile because of their lower reserve ofstrength. In old age, maintenance of optimal body mass may help preventsteep strength decrease and poor absolute strength.

     

Regional deposition of inhaled particles in human lungs: comparison between men and women

We measured detailed regional depositionpatterns of inhaled particles in healthy adult male(n = 11; 25 ± 4 yr of age) and female (n = 11; 25 ± 3 yr of age)subjects by means of a serial bolus aerosol delivery technique formonodisperse fine [particle diameter(D_p) = 1 µm] and coarse aerosols(D_p = 3 and 5 µm). The bolus aerosol (40 ml half-width) was delivered to a specificvolumetric depth (Vp) of the lung ranging from 100 to 500 ml with a50-ml increment, and local deposition fraction (LDF) was assessed for each of the 10 local volumetric regions. In all subjects, the deposition distribution pattern was very uneven with respect to Vp,showing characteristic unimodal curves with respect to particle sizeand flow rate. However, the unevenness was more pronounced in women.LDF tended to be greater in all regions of the lung in women than inmen for D_p = 1 µm. For D_p = 3 and 5 µm, LDF showed a marked enhancement in the shallow region of Vp  200 ml in women compared with men(P < 0.05). LDF in women wascomparable to or smaller than those of men in deep lung regions of Vp > 200 ml. Total lung deposition was comparable between men and womenfor fine particles but was consistently greater in women than men forcoarse particles regardless of flow rates used: the difference rangedfrom 9 to 31% and was greater with higher flow rates(P < 0.05). The results indicatethat 1) particledeposition characteristics differ between healthy men and women undercontrolled breathing conditions and2) deposition in women is greaterthan that in men.

     

A 33-yr follow-up of peak oxygen uptake and related variables of former physical education students

Åstrand, Per-Olof, Ulf Bergh, and ÅsaKilbom. A 33-yr follow-up of peak oxygen uptake and relatedvariables of former physical education students. J. Appl. Physiol. 82(6): 1844-1852, 1997.In 1949, 27 female and 26 male physical education students were studied at amean age of 22 and 25 yr, respectively. They were restudied in 1970 and1982. Measurements included oxygen uptake, heart rate, and pulmonaryventilation during submaximal and maximal exercise on a cycle ergometerand treadmill. After 21 yr, peak aerobic power was significantlyreduced, from 2.90 to 2.18 l/min and from 4.09 to 3.28 l/min for womenand men, respectively. After another 12 yr, the 1970 maxima were notreduced further. From 1949 to 1982 there was a decrease in peak heartrate from 196 to 177 beats/min in women and from 190 to 175 beats/minin men (P < 0.05). Highest pulmonaryventilation did not change significantly. At an oxygen uptake of 1.5 l/min, the heart rate was the same in 1949 as in 1982. In conclusion,the physical fitness level of the subjects was well above average forthese ages. From 1970 to 1982 there was no decline in the average peakaerobic power, a finding possibly related to increased habitualphysical activity.

     

Fiber type and citrate synthase activity in the human gastrocnemius and vastus lateralis with aging

The purpose ofthis study was to determine whether enzymatic and histochemicalcharacteristics of human skeletal muscle are altered with aging.Tissues from the vastus lateralis (VL) and gastrocnemius were analyzedfor citrate synthase (CS) activity and fiber type in 55 sedentary men(age range 18-80 yr). In this population, CS activity in thegastrocnemius was negatively related to age(r = 0.32,P < 0.05); there was no relationshipin the VL. Treadmill-determined maximal oxygen consumption waspositively related (r = 0.40, P < 0.05) to CS in the gastrocnemiusbut not in the VL. CS activity in the gastrocnemius was 24% lower inthe oldest (60 yr, n = 10) vs. theyoungest (30 yr; n = 12) men; therewas no change in CS activity in the VL with aging. No changes in fibertype were evident with age in either muscle. These data suggest areduction in oxidative enzyme activity in human skeletal muscle withthe aging process; this relationship may be muscle-group specific.

     

Twenty-year follow-up of aerobic power and body composition of older track athletes

Pollock, Michael L., Larry J. Mengelkoch, James E. Graves,David T. Lowenthal, Marian C. Limacher, Carl Foster, and Jack H. Wilmore. Twenty-year follow-up of aerobic power and body composition of older track athletes. J. Appl.Physiol. 82(5): 1508-1516, 1997.The purpose wasto determine the aerobic power (maximal oxygen uptake) and bodycomposition of older track athletes after a 20-yr follow-up (T3). At 20 yr, 21 subjects [mean ages: 50.5 ± 8.5 yr at initialevaluation (T1), 60.2 ± 8.8 yr at 10-yr follow-up (T2), and 70.4 ± 8.8 yr at 20-yr follow-up (T3)] were divided into threeintensity groups: high (H; remained elite; n = 9); moderate (M; continuedfrequent moderate-to-rigorous endurance training;n = 10); and low (L; greatly reducedtraining; n = 2). All groupsdecreased in maximal oxygen uptake at each testing point (H, 8 and15%; M, 13 and 14%; and L, 18 and 34% from T1 to T2 and T2 to T3,respectively). Maximal heart rate showed a linear decrease of~5-7beats · min¹ · decade¹ and was independentof training status. Body weight remained stable for the H and M groupsand percent fat increased ~2-2.5%/decade. Although fat-freeweight decreased at each testing point, there was a trend for those whobegan weight-training exercise to better maintain it. Cross-sectionalanalysis at T3 showed that leg strength and bone mineral density weregenerally maintained from age 60 to 89 yr. Those who performed weighttraining had a greater arm region bone mineral density than those whodid not. These longitudinal data show that the physiological capacitiesof older athletes are reduced despite continued vigorous enduranceexercise over a 20-yr period (~8-15%/decade). Changes in bodycomposition appeared to be less than those shown for the healthysedentary population and were related to changes in training habits.

     

Longitudinal changes in aerobic power in older men and women.

The purpose of this study was to describe the longitudinal (10 yr) decline in aerobic power [maximal O(2) uptake (Vo(2 max))] and anaerobic threshold [ventilatory threshold (T(Ve))] of older adults living independently in the community. Ten years after initial testing, 62 subjects (34 men, mean age 73.5 +/- 6.4 yr; 28 women, 72.1 +/- 5.3 yr) achieved Vo(2 max) criteria during treadmill walking tests to the limit of tolerance, with T(Ve) determined in a subset of 45. Vo(2 max) in men showed a rate of decline of -0.43 ml.kg(-1).min(-1).yr(-1), and the decline in Vo(2 max) was consequent to a lowered maximal heart rate with no change in the maximum O(2) pulse. The women showed a slower rate of decline of Vo(2 max) of -0.19.ml.kg(-1).min(-1).yr(-1) (P < 0.05), again with a lowered HR(max) and unchanged O(2) pulse. In this sample, lean body mass was not changed over the 10-yr period. Changes in Vo(2 max) were not significantly related to physical activity scores. T(Ve) showed a nonsignificant decline in both men and women. Groupings of young-old (65-72 yr at follow-up) vs. old-old (73-90 yr at follow-up) were examined. In men, there were no differences in the rate of Vo(2 max) decline. The young-old women showed a significant decline in Vo(2 max), whereas old-old women, initially at a Vo(2 max) of 19.4 +/- 3.1 ml.kg(-1).min(-1), showed no loss in Vo(2 max). The longitudinal data, vs. cross-sectional analysis, showed a greater decline for men but similar estimates of the rates of change in women. Thus the 10-yr longitudinal study of the cohort of community-dwelling older adults who remained healthy, ambulatory, and independent showed a 14% decline in Vo(2 max) in men, and a smaller decline of 7% in women, with the oldest women showing little change over the 10-yr period.     

Influence of diet and exercise on skeletal muscle and visceral adipose tissue in men

Ross, Robert, John Rissanen, Heather Pedwell, JenniferClifford, and Peter Shragge. Influence of diet and exercise onskeletal muscle and visceral adipose tissue in men. J. Appl. Physiol. 81(6): 2445-2455, 1996.Theeffects of diet only (DO) and diet combined with either aerobic (DA) orresistance (DR) exercise on subcutaneous adipose tissue (SAT), visceraladipose tissue (VAT), lean tissue (LT), and skeletal muscle (SM) tissue were evaluated in 33 obese men (DO, n = 11; DA, n = 11; DR,n = 11). All tissues were measured byusing a whole body multislice magnetic resonance imaging (MRI) model.Within each group, significant reductions were observed for bodyweight, SAT, and VAT (P < 0.05). Thereductions in body weight (~10%) and SAT (~25%) and VAT volume (~35%) were not different between groups(P > 0.05). For alltreatments, the relative reduction in VAT was greater than in SAT(P < 0.05). For the DA and DR groupsonly, the reduction in abdominal SAT (~27%) was greater(P < 0.05) than thatobserved for the gluteal-femoral region (~20%). Conversely, thereduction in VAT was uniform throughout the abdomen regardless oftreatment (P > 0.05). MRI-LT andMRI-SM decreased both in the upper and lower body regions for the DO group alone (P < 0.05). PeakO₂ uptake (liters) wassignificantly improved (~14%) in the DA group as was muscularstrength (~20%) in the DR group (P < 0.01). These findings indicate that DA and DR result in a greaterpreservation of MRI-SM, mobilization of SAT from the abdominal region,by comparison with the gluteal-femoral region, and improved functionalcapacity when compared with DO in obese men.

     

Effects of resistance training and chromium picolinate on body composition and skeletal muscle in older men

The effects of chromium picolinate (CrPic)supplementation and resistance training (RT) on skeletal muscle size,strength, and power and whole body composition were examined in 18 men(age range 56-69 yr). The men were randomly assigned(double-blind) to groups (n = 9) thatconsumed either 17.8 µmol Cr/day (924 µg Cr/day) as CrPic or alow-Cr placebo for 12 wk while participating twice weekly in ahigh-intensity RT program. CrPic increased urinary Cr excretion~50-fold (P < 0.001). RT-inducedincreases in muscle strength (P < 0.001) were not enhanced by CrPic. Arm-pull muscle power increased withRT at 20% (P = 0.016) but not at 40, 60, or 80% of the one repetition maximum, independent of CrPic.Knee-extension muscle power increased with RT at 20, 40, and 60%(P < 0.001) but not at 80% of onerepetition maximum, and the placebo group gained more muscle power thandid the CrPic group (RT by supplemental interaction,P < 0.05). Fat-free mass(P < 0.001), whole body muscle mass(P < 0.001), and vastus lateralistype II fiber area (P < 0.05)increased with RT in these body-weight-stable men, independent ofCrPic. In conclusion, high-dose CrPic supplementation did not enhancemuscle size, strength, or power development or lean body mass accretionin older men during a RT program, which had significant, independenteffects on these measurements.

     

Age and gender dependency of baroreflex sensitivity in healthy subjects

Laitinen, Tomi, Juha Hartikainen, Esko Vanninen, LeoNiskanen, Ghislaine Geelen, and Esko Länsimies. Age andgender dependency of baroreflex sensitivity in healthy subjects.J. Appl. Physiol. 84(2): 576-583, 1998.We evaluated the correlates of baroreflex sensitivity (BRS) inhealthy subjects. The study consisted of 117 healthy, normal-weight,nonsmoking male and female subjects aged 23-77 yr. Baroreflexcontrol of heart rate was measured by using the phenylephrinebolus-injection technique. Frequency- and time-domain analysis of heartrate variability and an exercise test were performed. Plasmanorepinephrine, epinephrine, insulin, and arginine vasopressinconcentrations and plasma renin activity were measured. In theunivariate analysis, BRS correlated with age(r = 0.65,P < 0.001), diastolic blood pressure(r = 0.47, P < 0.001), exercise capacity(r = 0.60, P < 0.001), and the high-frequency component of heart rate variability (r = 0.64, P < 0.001). There was also asignificant correlation between BRS and plasma norepinephrine concentration (r = 0.22,P < 0.05) and plasma renin activity (r = 0.32, P < 0.001). According to themultivariate analysis, age and gender were the most importantphysiological correlates of BRS. They accounted for 52% ofinterindividual BRS variation. In addition, diastolic blood pressureand high-frequency component of heart rate variability were significantindependent correlates of BRS. BRS was significantly higher in men thanin women (15.0 ± 1.2 vs. 10.2 ± 1.1 ms/mmHg, respectively;P < 0.01). Twenty-four percent ofwomen >40 yr old and 18% of men >60 yr old had markedly depressedBRS (<3 ms/mmHg). We conclude that physiological factors, particularly age and gender, have significant impact on BRS in healthysubjects. In addition, we demonstrate that BRS values that have beenproposed to be useful in identifying postinfarction patients at highrisk of sudden death are frequently found in healthy subjects.

     

One- and two-year change in body composition as measured by DXA in a population-based cohort of older men and women.

Changing body composition has been suggested as a pathway to explain age-related functional decline. No data are available on the expected changes in body composition as measured by dual-energy X-ray absorptiometry (DXA) in a population-based cohort of older persons. Body composition data at baseline, 1-yr follow-up, and 2-yr follow-up was measured by DXA in 2,040 well-functioning black and white men and women aged 70-79 yr, participants of the Health, Aging, and Body Composition Study. After 2 yr, a small decline in total body mass was observed (men: -0.3%, women: -0.4%). Among men, fat-free mass and appendicular lean soft tissue mass (ALST) decreased by -1.1 and -0.8%, respectively, which was masked by a simultaneous increase in total fat mass (+2.0%). Among women, a decline in fat-free mass was observed after 2 yr only (-0.6%) with no change in ALST and body fat mass. After 2 yr, the decline in ALST was greater in blacks than whites. Change in total body mass was associated with change in ALST (r = +0.58 to +0.70; P < 0.0001). Among participants who lost total body mass, men lost relatively more ALST than women, and blacks lost relatively more ALST than whites. In conclusion, the mean change in body composition after a 1- to 2-yr follow-up was 1-2% with a high interindividual variability. Loss of ALST was greater in men compared with women, and greater in blacks compared with whites, suggesting that men and blacks may be more prone to muscle loss.     

Leg mass and lower body negative pressure tolerance in men and women

To explore the hypothesis that lower body musclemass correlates with orthostatic tolerance, 18 healthy volunteers (age18-48 yr; 10 men, 8 women) underwent a graded lower body negativepressure (LBNP) protocol consisting of six, 5-min stages of suction up to 60 mmHg in 10-mmHg increments. Forearm blood flow, heart rate, andblood pressure were measured, and forearm vascular resistance wascalculated. Leg muscle mass was assessed by dual-energy X-ray absorptiometry. All subjects received standard intravenous hydration for at least 8 h before the study. Six men and four women completed allstages of LBNP. Four men and four women developed presyncopal symptoms,including marked bradycardia and/or hypotension, at LBNP levelsof 30 mmHg (n = 2; 1 man, 1 woman), 40 mmHg (n = 2; 1 man, 1 woman), and 50 mmHg (n = 4; 2 men, 2 women). Thepresyncopal subjects had leg muscle masses ranging from 19.5 to 25.2 kgin men and from 11.7 to 16.6 kg in women. In subjects who completed allstages of LBNP, leg muscle mass ranged from 17.5 to 24.1 kg in men andfrom 10.4 to 18.0 kg in women. Leg muscle mass did not differ betweenpresyncopal subjects and those who completed the protocol. Furthermore,there were no differences in the hemodynamic responses to LBNP betweensubjects with low vs. high leg mass. These data suggest that leg musclemass is not a critical determinant of LBNP tolerance in otherwisehealthy men and women.

     

Catecholamine response during 12days of high-altitude exposure (4,300m) in women

We have previously demonstrated thatacclimatization to high altitude elicits increased sympathetic nerveactivity in men. The purpose of this investigation was todetermine 1) whether women respondin a similar manner as found previously in men and 2) the extent to which menstrualcycle phase influences this response. Sixteen eumenorrheic women (age,23.6 ± 1.2 yr; weight, 56.2 ± 4.3 kg) were studied at sea leveland during 12 days of high-altitude exposure (4,300 m) in either theirfollicular (F; n = 11) or luteal (L;n = 5) phase. Twenty-four-hour urinesamples were collected at sea level and during each day at altitude.Catecholamines were determined by high-performance liquidchromatography with electrochemical detection. Compared with sea-levelvalues, urinary norepinephrine excretion increased significantly duringaltitude exposure, peaking on days4-6. Thereafter, levels remained constantthroughout the duration of altitude exposure. The magnitude of thisincrease was similar between the F (138%) and L (93%)phase. Urinary epinephrine levels were elevated onday 2 of altitude exposure comparedwith sea-level values for both F and L subjects (93%). Thereafter, urinary epinephrine excretion returned to sea-level values, and nodifferences were found between F and L subjects. Plasma catecholamine content was consistent with urinary values and supports the concept ofan elevation in sympathetic activity over time at altitude. Mean anddiastolic blood pressure as well as heart rate adjustments to highaltitude correlated significantly with urinary norepinephrine excretionrates. It was concluded that 1)urinary and plasma catecholamine responses to 12 days of high-altitudeexposure in women are similar to those previously documented to occurfor men; 2) whereas no differencesin catecholamine levels were observed between F- and L-phaseassignments, for a given urinary norepinephrine excretion rate, bloodpressure and heart rates were lower for F vs. L subjects; and3) several cardiovascularadaptations associated with high-altitude exposure correlated with 24-hurinary norepinephrine excretion rates and thus sympathetic nerveactivity.

     

Greater rate of decline in maximal aerobic capacity with age in endurance-trained than in sedentary men.

To determine the relation between habitual endurance exercise status and the age-associated decline in maximal aerobic capacity [i.e., maximal O(2) consumption (Vo(2 max))] in men, we performed a well-controlled cross-sectional laboratory study on 153 healthy men aged 20-75 yr: 64 sedentary and 89 endurance trained. Vo(2 max) (ml. kg(-1). min(-1)), measured by maximal treadmill exercise, was inversely related to age in the endurance-trained (r = -0.80) and sedentary (r = -0.74) men but was higher in the endurance-trained men at any age. The rate of decline in Vo(2 max) with age (ml. kg(-1). min(-1)) was greater (P < 0.001) in the endurance-trained than in the sedentary men. Whereas the relative rate of decline in Vo(2 max) (percent decrease per decade from baseline levels in young adulthood) was similar in the two groups, the absolute rate of decline in Vo(2 max) was -5.4 and -3.9 ml. kg(-1). min(-). decade(-1) in the endurance-trained and sedentary men, respectively. Vo(2 max) declined linearly across the age range in the sedentary men but was maintained in the endurance-trained men until approximately 50 yr of age. The accelerated decline in Vo(2 max) after 50 yr of age in the endurance-trained men was related to a decline in training volume (r = 0.46, P < 0.0001) and was associated with an increase in 10-km running time (r = -0.84, P < 0.0001). We conclude that the rate of decline in maximal aerobic capacity during middle and older age is greater in endurance-trained men than in their sedentary peers and is associated with a marked decline in O(2) pulse.     

Is there evidence for an age-related reduction in metabolic rate?

To determinewhether the age-related reduction in basal metabolic rate (BMR) isexplained by a quantitative and/or qualitative change in thecomponents of lean tissue, we conducted a cross-sectional study ingroups of young (n = 38, 18-35yr) and older (n = 24, 50-77 yr)healthy individuals. BMR was measured by indirect calorimetry. Bodycomposition was obtained by using dual-energy X-ray absorptiometry (DEXA), which permitted four compartments to be quantified [bone mineral mass, fat mass (FM), appendicular lean tissue mass(A_LTM), and nonappendicular leantissue mass (NA_LTM)].Absolute BMR and A_LTM were lower,whereas FM was significantly higher in the older, compared with young,subjects. BMR, adjusted for differences in FM,A_LTM, andNA_LTM, was significantly lower inthe older subjects by 644 kJ/day. In separate regression analyses ofBMR on body compartments, older subjects had significantly lowerregression coefficients for A_LTMand NA_LTM, compared with youngsubjects. Hence, the age-related decline in BMR is partly explained bya reduction in the quantity, as well as the metabolic activity, ofDEXA-derived lean tissue components.

     

Muscle quality. II. Effects of strength training in 65-to 75-yr-old men and women

To determine theeffects of strength training (ST) on muscle quality (MQ,strength/muscle volume of the trained muscle group), 12 healthy oldermen (69 ± 3 yr, range 65-75 yr) and 11 healthy older women (68 ± 3 yr, range 65-73 yr) were studied before and after aunilateral leg ST program. After a warm-up set, four sets ofheavy-resistance knee extensor ST exercise were performed 3 days/wk for9 wk on the Keiser K-300 leg extension machine. The men exhibitedgreater absolute increases in the knee extension one-repetition maximum(1-RM) strength test (75 ± 2 and 94 ± 3 kg before andafter training, respectively) and in quadriceps muscle volume measuredby magnetic resonance imaging (1,753 ± 44 and 1,955 ± 43 cm³) than the women (42 ± 2 and 55 ± 3 kg for the 1-RM test and 1,125 ± 53 vs.1,261 ± 65 cm³ forquadriceps muscle volume before and after training, respectively, inwomen; both P < 0.05). However,percent increases were similar for men and women in the 1-RM test (27 and 29% for men and women, respectively), muscle volume (12% forboth), and MQ (14 and 16% for men and women, respectively).Significant increases in MQ were observed in both groups in the trainedleg (both P < 0.05) and in the 1-RMtest for the untrained leg (both P < 0.05), but no significant differences were observed between groups,suggesting neuromuscular adaptations in both gender groups. Thus,although older men appear to have a greater capacity for absolutestrength and muscle mass gains than older women in response to ST, the relative contribution of neuromuscular and hypertrophic factors to theincrease in strength appears to be similar between genders.

     

Muscle protein metabolism in female swimmers after a combination of resistance and endurance exercise

Tipton, Kevin D., Arny A. Ferrando, Bradley D. Williams, andRobert R. Wolfe. Muscle protein metabolism in female swimmers after a combination of resistance and endurance exercise.J. Appl. Physiol. 81(5):2034-2038, 1996.There is little known about the responses ofmuscle protein metabolism in women to exercise. Furthermore, the effectof adding resistance training to an endurance training regimen on netprotein anabolism has not been established in either men or women. Thepurpose of this study was to quantify the acute effects of combinedswimming and resistance training on protein metabolism in femaleswimmers by the direct measurement of muscle protein synthesis andwhole body protein degradation. Seven collegiate female swimmers wereeach studied on four separate occasions with a primed constant infusionofring-[¹³C₆]phenylalanine(Phe) to measure the fractional synthetic rate (FSR) of the posteriordeltoid and whole body protein breakdown. Measurements were made over a5-h period at rest and after each of three randomly ordered workouts:1) 4,600 m of intense interval swimming (SW); 2) a whole bodyresistance-training workout with no swimming on that day (RW); and3) swimming and resistance training combined (SR). Whole body protein breakdown was similar for all treatments (0.75 ± 0.04, 0.69 ± 0.03, 0.69 ± 0.02, and 0.71 ± 0.04 µmol ^· min^{1 ·} kg¹for rest, RW, SW, and SR, respectively). The FSR of the posterior deltoid was significantly greater (P < 0.05) after SR (0.082 ± 0.015%/h) than at rest (0.045 ± 0.006%/h). There was no significant difference in the FSR after RW(0.048 ± 0.004%/h) or SW (0.064 ± 0.008%/h) from rest or fromSR. These data indicate that the combination of swimming and resistanceexercise stimulates net muscle protein synthesis above resting levelsin female swimmers.