Can dual energy X-ray absorptiometry provide a valid assessment of changes in thigh muscle mass with strength training in older adults?

OBJECTIVE: To determine how dual-energy X-ray absorptiometry (DXA) compares to computed tomography (CT) for measuring changes in total thigh skeletal muscle (SM) mass with strength training (ST) in older adults. SUBJECTS: Fifty previously sedentary, relatively healthy older men (n=23, 60 (s.d.=7.5) years) and women (n=27, 60 (s.d.=9.3) years). RESULTS: Results indicate that there was a significant increase in thigh SM mass with ST measured by both CT (3.9+/-0.4%) and DXA (2.9+/-0.6%) methods (both P<0.001), and there was not a significant difference in percent change between the two methods, although there was a substantial absolute difference ( approximately 2 kg) at baseline between the two methods. Although Bland-Altman plots indicate overall agreement between the percent thigh SM mass changes of DXA vs CT methods, the 3.4% error associated with DXA was greater than the thigh SM mass change from DXA. However, the CT measured change in thigh SM mass was greater than its error (0.6%). CONCLUSIONS: DXA overestimates baseline and after ST thigh SM mass, and may not be able to detect small changes in thigh SM mass with ST due to its higher error. Although DXA has certain advantages that warrant is used in epidemiologic and intervention studies, improvements to DXA are needed for the accurate assessment of small changes in thigh SM mass.

Resistance training alters cytokine gene expression in skeletal muscle of adults with type 2 diabetes.

Resistance training results in muscle hypertrophy and improves glycemic control in patients with type 2 diabetes. Whether resistance training modulates inflammation in muscles of diabetic patients remains unknown. We examined the expression of genes encoding the cytokines, tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and transforming growth factor-beta1 (TGF-beta1) as well as the pan-leukocyte marker CD18. Thirty men and women (67+/-7 years) were randomized to either 16 weeks of resistance training and usual diabetes care (EX) or to usual diabetes care only (CON). Muscle biopsies were obtained from the vastus lateralis muscle prior to the 16-week intervention, and 72 h following the maximal strength test post-intervention. Fiber cross-sectional area (CSA) was determined following ATPase staining. Cytokine and CD18 transcript levels were assessed by real-time PCR. Resistance training increased CSA of type I and II fibers (both P <0.05) and IL-1beta transcript levels (P = 0.05). TNF-alpha (P<0.05) and TGF-beta1 transcripts (P<0.05) increased over time in the EX group, but these increases did not differ from those in the CON group. In both groups, the increase in CD18 transcripts remained minimal. The two groups differ by the relationship between changes in CD18 and changes in cytokine transcripts, suggesting that resistance training affects the source of cytokines in muscle. Our studies establish that resistance training in older adults with type 2 diabetes results in muscle fiber hypertrophy, despite a greater accumulation of inflammatory cytokine transcripts in muscle.

Elevated high-density lipoprotein cholesterol levels in older endurance athletes.

To ascertain whether older (masters) athletes exhibit a more favorable plasma lipoprotein/lipid profile than sedentary men of similar age, 14 endurance-trained masters athletes (mean age 60 +/- 2 years [+/- standard error of the mean]), 12 older, untrained-not lean men (mean age 62 +/- 1 years), 9 older untrained-lean men (mean age 61 +/- 2 years), 15 young endurance-trained athletes (mean age 26 +/- 1 years) and 15 young untrained men (mean age 28 +/- 1 years) were studied. The athletes had higher values for maximal oxygen uptake and lower levels of body fatness compared with the untrained men, regardless of age (p less than 0.05). High-density lipoprotein (HDL) cholesterol was markedly higher in the masters athletes than in the other groups (66 vs 42 to 55 mg/dl, p less than 0.05). The total cholesterol (TC) and low-density lipoprotein cholesterol concentrations of the masters athletes generally were higher than those of the younger groups, similar to those of the older lean men, and lower than those of the older-not lean men (p less than 0.05). The TC/HDL cholesterol ratios were similarly low (2.8 to 3.4) for the athletes and the young untrained men compared with the older untrained men (4.0 to 5.6) (p less than 0.05). Thus, some older endurance athletes exhibit markedly higher HDL cholesterol levels and lower TC/HDL cholesterol ratios compared with their sedentary peers. This favorable plasma lipoprotein profile may indicate a reduced risk of developing coronary artery disease for older men who exercise regularly.

Effects of training on systolic time intervals at rest and during isometric exercise in men and women 61 to 64 years old.

To determine whether regular exercise improves left ventricular (LV) contractile function in persons 60 years and older, systolic time intervals (STIs) were measured in 10 healthy men and women (mean age 62 +/- 1 year [+/- standard deviation]) before and after 6 months of intense endurance training. STIs, systolic and diastolic blood pressure (BP) and heart rate (HR) were determined at rest and in response to isometric handgrip exercise. Systolic BP, diastolic BP and HR increased acutely from rest in response to handgrip (p less than 0.002). The indexes of total electromechanical systole and LV ejection time (ET) index increased (p less than 0.01), preejection period (PEP) index increased (p less than 0.05) or remained unchanged and PEP/LVET did not change from values at rest in response to handgrip. Training resulted in an 18% increase in maximal oxygen uptake (p less than 0.01). After training, systolic and diastolic BP were reduced at rest (p less than 0.002) and, along with HR, were lower in response to handgrip (p less than 0.002). However, training did not alter STIs at rest or during handgrip. These findings indicate that healthy persons in their 60s have a normal LV response to isometric exercise. Prolonged, intense endurance training does not alter LV contractile function at rest or in response to isometric exercise. However, training can significantly reduce BP at rest, and markedly lower the HR-systolic BP product attained during acute isometric stress, even in normotensive older subjects.

Insulin action after resistive training in insulin resistant older men and women.

OBJECTIVES: To determine the effects of resistive training (RT) on insulin action and assess the determinants of the changes in insulin action. DESIGN: Longitudinal study. SETTING: Outpatient setting. PARTICIPANTS: Eighteen older men and older postmenopausal women (65-74 years) with normal (6 men and 5 women) or impaired glucose tolerance (4 men and 3 women). INTERVENTION: Six months of progressive whole-body RT. MEASUREMENTS: Upper and lower body strength was assessed by the one repetition maximum test. Total body fat and fat-free mass (FFM) were determined by dual-energy x-ray absorptiometry before and after 6 months of RT. Insulin sensitivity was estimated from the relationship of glucose utilization (M) to the concentration of insulin (I) during the last 30 minutes of 3-hour hyperinsulinemic-euglycenic clamps (240 pmol x min(-2) x min(-1)) (M/I) before and after RT. RESULTS: RT significantly improved upper- and lower-body muscular strength (P < .005). FFM increased after RT in the entire group (P < .01) with no significant change in body fat. Although the change in M was larger in men (13%) than women (3%), the difference was not significant. The change in M was a function of initial M (r = -0.53, P < .05). There was a trend (0.060+/-0.006 vs 0.066+/-0.006 micromol x kg(-1) x min(-1)/pmol/l, n = 18) for M/I to increase after RT in the combined group of men and women (P = .06). There were no significant relationships between changes in M or M/I with changes in body composition or strength. CONCLUSION: A 6-month RT program tends to improve insulin action in insulin-resistant older adults. These results suggest that RT may be useful in ameliorating insulin resistance that often occurs with physical inactivity, obesity, and loss of muscular strength in older insulin resistant men and women.

Strength training normalizes resting blood pressure in 65- to 73-year-old men and women with high normal blood pressure.

OBJECTIVE: To determine the effects of heavy resistance strength training (ST) on resting blood pressure (BP) in older men and women. DESIGN: Prospective intervention study. SETTING: University of Maryland Exercise Science Laboratory. PARTICIPANTS: Twenty-one sedentary, healthy older men (69 +/- 1 year, n = 11) and women (68 +/- 1 year, n = 10) served as subjects for the study. INTERVENTION: Six months of progressive whole body ST performed 3 days per week using Keiser K-300 air-powered resistance machines. MEASUREMENTS: One-repetition maximum (1 RM) strength was measured for seven different exercises before and after the ST program. Resting BP was measured on six separate occasions before and after ST for each subject. RESULTS: Substantial increases in 1 RM strength were observed for upper body (UB) and lower body (LB) muscle groups for men (UB: 215 vs 265 kg; LB: 694 vs 838 kg; P < .001) and women (UB: 128 vs 154 kg; LB: 441 vs 563 kg; P < .001). The ST program led to reductions in both systolic (131 +/- 2 vs 126 +/- 2 mm Hg, P < .010) and diastolic (79 +/- 2 vs 75 +/- 1 mm Hg, P < .010) BP. Systolic BP was reduced significantly in men (134 +/- 3 vs 127 +/- 2 mm Hg, P < .01) but not in women (128 +/- 3 vs 125 +/- 3 mm Hg, P < .01), whereas diastolic BP was reduced following training in both men (81 +/- 3 vs 77 +/- 1, mm Hg, P = .054) and women (78 +/- 2 vs 74 +/- 2 mm Hg, P = .055). CONCLUSIONS: Six months of heavy resistance ST may reduce resting BP in older persons. According to the latest guidelines from the Joint National Committee for the Detection, Evaluation, and Treatment of Hypertension, the changes in resting BP noted in the present study represent a shift from the high normal to the normal category.

Muscle size responses to strength training in young and older men and women.

OBJECTIVES: To examine the possible influences of age and gender on muscle volume responses to strength training (ST). DESIGN: Prospective intervention study. SETTING: University of Maryland Exercise Science and Wellness Research Laboratories. PARTICIPANTS: Eight young men (age 20-30 years), six young women (age 20-30 years), nine older men (age 65-75 years), and ten older women (age 65-75 years). INTERVENTION: A 6-month whole-body ST program that exercised all major muscle groups of the upper and lower body 3 days/week. MEASUREMENTS: Thigh and quadriceps muscle volumes and mid-thigh muscle cross-sectional area (CSA) were assessed by magnetic resonance imaging before and after the ST program. RESULTS: Thigh and quadriceps muscle volume increased significantly in all age and gender groups as a result of ST (P < .001), with no significant differences between the groups. Modest correlations were observed between both the change in quadriceps versus the change in total thigh muscle volume (r = 0.65; P < .001) and the change in thigh muscle volume versus the change in mid-thigh CSA (r = 0.76, P < .001). CONCLUSIONS: The results indicate that neither age nor gender affects muscle volume response to whole-body ST. Muscle volume, rather than muscle CSA, is recommended for studying muscle mass responses to ST.

Age, gender, and muscular strength.

Muscular strength can be measured by cable tensiometry, non-motorized dynamometry (e.g., handgrip dynamometer), motorized dynamometry, or with free weights or exercise machines. Advantages and disadvantages of each are discussed. Cross-sectional studies indicate that isometric and concentric strength levels peak between the second and third decade, remain unchanged until the fourth or fifth decade, and start to decline from about the fifth decade at a rate of 12% to 15% per decade until the eighth decade in men. Greater strength losses in both men and women have been suggested from the few longitudinal studies available on this topic. However, concentric strength levels in women tend to peak sooner, start to decline earlier, and decrease at a slightly slower rate than men. Age- and inactivity-induced sarcopenia explains some but not all of the losses in strength with age. There is a need to determine the separate roles of disease, inactivity, and normal aging on these losses. New findings from the Baltimore Longitudinal Study of Aging suggest a preservation of eccentric strength levels with age in women.

Effects of strength training and detraining on muscle quality: age and gender comparisons.

Maximal force production per unit of muscle mass (muscle quality, or MQ) has been used to describe the relative contribution of non-muscle-mass components to the changes in strength with age and strength training (ST). To compare the influence of age and gender on MQ response to ST and detraining, 11 young men (20-30 years), nine young women (20-30 years), 11 older men (65-75 years), and 11 older women (65-75 years), were assessed for quadriceps MQ at baseline, after 9 weeks of ST, and after 31 weeks of detraining. MQ was calculated by dividing quadriceps one repetition maximum (IRM) strength by quadriceps muscle volume determined by magnetic resonance imaging. All groups demonstrated significant increases in IRM strength and muscle volume after training (all p < .05). All groups also increased their MQ with training (all p < .01), but the gain in MQ was significantly greater in young women than in the other three groups (p < .05). After 31 weeks of detraining, MQ values remained significantly elevated above baseline levels in all groups (p < .05), except the older women. These results indicate that factors other than muscle mass contribute to strength gains with ST in young and older men and women, but those other factors may account for a higher portion of the strength gains in young women. These factors continue to maintain strength levels above baseline for up to 31 weeks after cessation of training in young men and women, and in older men.

Skeletal muscle satellite cell characteristics in young and older men and women after heavy resistance strength training.

Skeletal muscle satellite cell proportions and morphology were assessed in healthy, sedentary young and older men and women in response to heavy resistance strength training (HRST). Fourteen young (20-30 years) men (n = 7) and women (n = 7) and 15 older (65-75 years) men (n = 8) and women (n = 7) completed 9 weeks of unilateral knee extension exercise training 3 days per week. Muscle biopsies were obtained from each vastus lateralis before and after training, with the nondominant leg serving as an untrained control. All four groups demonstrated a significant increase in satellite cell proportion in response to HRST (2.3 +/- 0.4% vs 3.1 +/- 0.4% for all subjects combined, before and after training, respectively; p < .05), with older women demonstrating the greatest increase (p < .05). Morphology data indicated a significant increase in the proportion of active satellite cells in after-training muscle samples compared with before-training samples and with control leg samples (31% vs 6% and 7%, respectively; p < .05). The present results indicate that the proportion of satellite cells is increased after HRST in young and older men and women, with an exaggerated response in older women. Furthermore, the proportion of satellite cells that appear morphologically active is increased as a result of HRST.

Effects of age, gender, and myostatin genotype on the hypertrophic response to heavy resistance strength training.

BACKGROUND: Because of the scarcity of data available from direct comparisons of age and gender groups using the same relative training stimulus, it is unknown whether older individuals can increase their muscle mass as much as young individuals and whether women can increase as much as men in response to strength training (ST). In addition, little is known about whether the hypertrophic response to ST is affected by myostatin genotype, a candidate gene for muscle hypertrophy. METHODS: Eleven young men (25 +/- 3 years, range 21-29 years), 11 young women (26 +/- 2 years, range 23-28 years), 12 older men (69 +/- 3 years, range 65-75 years), and 11 older women (68 +/- 2 years, range 65-73 years) had bilateral quadriceps muscle volume measurements performed using magnetic resonance imaging (MRI) before and after ST and detraining. Training consisted of knee extension exercises of the dominant leg three times per week for 9 weeks. The contralateral limb was left untrained throughout the ST program. Following the unilateral training period, the subjects underwent 31 weeks of detraining during which no regular exercise was performed. Myostatin genotype was determined in a subgroup of 32 subjects, of which five female subjects were carriers of a myostatin gene variant. RESULTS: A significantly greater absolute increase in muscle volume was observed in men than in women (204 +/- 20 vs 101 +/- 13 cm3, p < .01), but there was no significant difference in muscle volume response to ST between young and older individuals. The gender effect remained after adjusting for baseline muscle volume. In addition, there was a significantly greater loss of absolute muscle volume after 31 weeks of detraining in men than in women (151 +/- 13 vs 88 +/- 7 cm3, p < .05), but no significant difference between young and older individuals. Myostatin genotype did not explain the hypertrophic response to ST when all 32 subjects were assessed. However, when only women were analyzed, those with the less common myostatin allele exhibited a 68% larger increase in muscle volume in response to ST (p = .056). CONCLUSIONS: Aging does not affect the muscle mass response to either ST or detraining, whereas gender does, as men increased their muscle volume about twice as much in response to ST as did women and experienced larger losses in response to detraining than women. Young men were the only group that maintained muscle volume adaptation after 31 weeks of detraining. Although myostatin genotype may not explain the observed gender difference in the hypertrophic response to ST, a role for myostatin genotype may be indicated in this regard for women, but future studies are needed with larger subject numbers in each genotype group to confirm this observation.

Lactate threshold and distance-running performance in young and older endurance athletes.

Many well-trained elite older runners have performances comparable to those of much younger nonelite runners. We sought to determine whether the physiological determinants of endurance performance in two groups of such athletes were the same. Eight master athletes (age 56 +/- 5 yr) were matched on the basis of 10-km performance and training to younger runners (age 25 +/- 3 yr). The master athletes had a 9% lower maximum O2 uptake (VO2max) (P less than 0.05) than the matched young runners, despite the similarity in their performance. Running economy was not different between these groups. However, the master athletes attained a 2.5-mM blood lactate level during steady-state exercise at a higher percentage of their VO2max (P less than 0.05), although both groups attained this lactate level at the same running speed and VO2. Thus, despite having significantly lower VO2max values, the older athletes were able to perform as well as the younger runners because they were able to work closer to their VO2max for the duration of the race.

Strength training increases insulin action in healthy 50- to 65-yr-old men.

The insulin resistance associated with aging may be due, in part, to reduced levels of physical activity in the elderly. We hypothesized that strength training increases insulin action in older individuals. To test this hypothesis, 11 healthy men 50-63 yr old [mean 58 +/- 1 (SE) yr] underwent a two-step hyperinsulinemic-euglycemic glucose clamp with concurrent indirect calorimetry and an oral glucose tolerance test (OGTT) before and after 16 wk of strength training. The training program increased overall strength by 47% (P < 0.001). Fat-free mass (FFM; measured by hydrodensitometry) increased (62.4 +/- 2.1 vs. 63.6 +/- 2.1 kg; P < 0.05) and body fat decreased (27.2 +/- 1.8 vs. 25.6 +/- 1.9%; P < 0.001) with training. Fasting plasma glucose levels and glucose levels during the OGTT were not significantly lower after training. In contrast, fasting plasma insulin levels decreased (85 +/- 25 vs. 55 +/- 10 pmol/l; P < 0.05) and insulin levels decreased (P < 0.05, analysis of variance) during the OGTT. Glucose infusion rates during the hyperinsulinemic-euglycemic glucose clamp increased 24% (13.5 +/- 1.7 vs. 16.7 +/- 2.2 mumol.kg FFM-1.min-1; P < 0.05) during the low (20 mU.m-2.min-1) insulin infusion and increased 22% (55.7 +/- 3.3 vs. 67.7 +/- 3.9 mumol.kg FFM-1.min-1; P < 0.05) during the high (100 mU.m-2.min-1) insulin infusion. These increases were accompanied by a 40% increase (n = 7; P < 0.08) in nonoxidative glucose metabolism during the high insulin infusion. These results demonstrate that strength training increases insulin action and lowers plasma insulin levels in middle-aged and older men.

Muscle triglyceride utilization during exercise: effect of training.

The respiratory exchange ratio (RER) is lower during exercise of the same intensity in the trained compared with the untrained state, even though plasma free fatty acids (FFA) and glycerol levels are lower, suggesting reduced availability of plasma FFA. In this context, we evaluated the possibility that lipolysis of muscle triglycerides might be higher in the trained state. Nine adult male subjects performed a prolonged bout of exercise of the same absolute intensity before and after adapting to a strenuous 12-wk program of endurance exercise. The exercise test required 64% of maximum O2 uptake before training. Plasma FFA and glycerol concentrations and RER during the exercise test were lower in the trained than in the untrained state. The proportion of the caloric expenditure derived from fat, calculated from the RER, during the exercise test increased from 35% before training to 57% after training. Muscle glycogen utilization was 41% lower, whereas the decrease in quadriceps muscle triglyceride concentration was roughly twice as great (12.7 +/- 5.5 vs. 26.1 +/- 9.3 mmol/kg dry wt, P less than 0.001) in the trained state. These results suggest that the greater utilization of FFA in the trained state is fueled by increased lipolysis of muscle triglyceride.

High-volume, heavy-resistance strength training and muscle damage in young and older women.

To determine possible age differences in muscle damage response to strength training, ultrastructural muscle damage was assessed in seven 20- to 30-yr-old and six 65- to 75-yr-old previously sedentary women after heavy-resistance strength training (HRST). Subjects performed unilateral knee-extension exercise 3 days/wk for 9 wk. Bilateral muscle biopsies from the vastus lateralis were assessed for muscle damage via electron microscopy. HRST resulted in a 38 and 25% increase in strength in the young and older women, respectively (P < 0.05), but there were no between-group differences. In the young women, 2-4% of muscle fibers exhibited damage before and after training in both the trained and untrained legs (P = not significant). In contrast, muscle damage increased significantly after HRST, from 5 to 17% of fibers damaged (P < 0.01), in the older women in the trained leg compared with only 2 and 5% of fibers damaged in the untrained leg before and after training, respectively. The present results indicate that older women exhibit higher levels of muscle damage after chronic HRST than do young women.

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

To assess age and gender differences in muscle strength, isometric, concentric (Con), and eccentric (Ecc) peak torque was measured in the knee extensors at a slow (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 Longitudinal Study of Aging. Regression analysis revealed significant (P < 0.001) age-related reductions in Con and Ecc peak torque for men and women at both velocities, but no differences were observed between the gender groups or velocities. Age explained losses in 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. To assess age and gender differences in the ability to store and utilize elastic energy, the stretch-shortening cycle was determined in a subset of subjects (n = 47). The older women (mean age = 70 yr) showed a significantly greater enhancement in the stretch-shortening cycle, compared with men of similar age (P < 0.01) and compared with younger men and women (each P < 0.05). Both men and women showed significant declines in muscle quality for Con peak 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 extensor peak torque; however, age accounted for less of the variance in Ecc peak torque in women, and women tend to better preserve muscle quality with age for Ecc peak torque. In addition, older women have an enhanced capacity to store and utilize elastic energy compared with similarly aged men as well as with younger women and men.

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

To determine the differences between arm and leg muscle quality (MQ) across the adult life span in men and women, concentric (Con) and eccentric (Ecc) peak torque (PT) were measured in 703 subjects (364 men and 339 women, age range 19-93 yr) and appendicular skeletal muscle mass (MM) was determined in the arm 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 of MM, was significantly higher in the arm ( approximately 30%) than in the leg across age in both genders (P < 0.01). Arm and leg MQ declined at a similar rate with age in men, whereas leg MQ declined approximately 20% more than arm MQ with increasing age in women (P

CNTF genotype is associated with muscular strength and quality in humans across the adult age span.

The relationship between ciliary neurotrophic factor (CNTF) genotype and muscle strength was examined in 494 healthy men and women across the entire adult age span (20-90 yr). Concentric (Con) and eccentric (Ecc) peak torque were assessed using a Kin-Com isokinetic dynamometer for the knee extensors (KE) and knee flexors (KF) at slow (0.52 rad/s) and faster (3.14 rad/s) velocities. The results were covaried for age, gender, and body mass or fat-free mass (FFM). Individuals heterozygous for the CNTF null (A allele) mutation (G/A) exhibited significantly higher Con peak torque of the KE and KF at 3.14 rad/s than G/G homozygotes when age, gender, and body mass were covaried (P < 0.05). When the dominant leg FFM (estimated muscle mass) was used in place of body mass as a covariate, Con peak torque of the KE at 3.14 rad/s was also significantly greater in the G/A individuals (P < 0.05). In addition, muscle quality of the KE (peak torque at 3.14 rad x s(-1) x leg muscle mass(-1)) was significantly greater in the G/A heterozygotes (P < 0.05). Similar results were seen in a subanalysis of subjects 60 yr and older, as well as in Caucasian subjects. In contrast, A/A homozygotes demonstrated significantly lower Ecc peak torque at 0.52 rad/s for both KE and KF compared with G/G and G/A groups (P < 0.05). No significant relationships were observed at 0.52 rad/s between genotype and Con peak torque. These data indicate that individuals exhibiting the G/A genotype possess significantly greater muscular strength and muscle quality at relatively fast contraction speeds than do G/G individuals. Because of high positive correlations between fast-velocity peak torque and muscular power, these findings suggest that further investigations should address the relationship between CNTF genotype and muscular power.

A hemodynamic comparison of young and older endurance athletes during exercise.

This study assessed the hemodynamic responses to exercise of master athletes (56 +/- 5 yr of age) who placed in the top 10% of their age groups in local 10-km competitive events, competitive young runners (26 +/- 3 yr), young runners matched in training and performance to the master athletes (25 +/- 3 yr), and healthy older sedentary subjects (58 +/- 5 yr). The maximal O2 consumption (VO2max) of the master athletes was 9 and 19% lower than that of the matched young and competitive young runners, respectively. When compared at the same relative submaximal work rates, these three groups had similar stroke volumes and arteriovenous O2 (aVO2) differences, though the master athletes had lower VO2, cardiac output, and heart rate, and higher vascular resistance. The older sedentary group had a lower stroke volume, aVO2 difference, and higher vascular resistance than the master athletes. Maximal stroke volume and estimated aVO2 difference were the same in the three groups of athletes; the lower maximal heart rate of the master athletes appears to account for their lower VO2max. The older sedentary subjects' VO2max was 47% lower than that of the master athletes; this difference was almost equally the result of a lower stroke volume and a lower a-VO2 difference. Thus these older athletes did not exhibit the decline in maximum stroke volume and aVO2 difference that occurs with aging in sedentary individuals; they also appear to have retained a greater peripheral vasodilatory response than their sedentary peers.

Effects of strength training on total and regional body composition in older men.

The effects of a 16-wk strength-training program on total and regional body composition were assessed by dual-energy X-ray absorptiometry (DEXA), magnetic resonance imaging (MRI), and hydrodensitometry in 13 untrained healthy men [60 +/- 4 (SD) yr]. Nine additional men (62 +/- 6 yr) served as inactive controls. The strength-training program resulted in substantial increases in both upper (39 +/- 8%; P < 0.001) and lower (42 +/- 14%; P < 0.001) body strength. Total fat-free mass (FFM) increased by 2 kg (62.0 +/- 7.1 to 64.0 +/- 7.2 kg; P < 0.001), and total fat mass decreased by the same amount (23.8 +/- 6.7 to 21.8 +/- 6.0 kg; P < 0.001) when measured by DEXA. When measured by hydrodensitometry, similar increases in FFM (61.3 +/- 7.8 to 63.0 +/- 7.6 kg; P < 0.01) and decreases in fat mass (23.8 +/- 7.9 to 22.1 +/- 7.7 kg; P < 0.001) were observed. When measured by DEXA, FFM was increased in the arms (6.045 +/- 0.860 to 6.418 +/- 0.803 kg; P < 0.01), legs (19.416 +/- 2.228 to 20.131 +/- 2.303 kg; P < 0.001), and trunk (29.229 +/- 4.108 to 30.134 +/- 4.184 kg; P < 0.01), whereas fat mass was reduced in the arms (2.383 +/- 0.830 to 2.128 +/- 0.714 kg; P < 0.01), legs (7.583 +/- 1.675 to 6.945 +/- 1.551 kg; P < 0.001), and trunk (12.216 +/- 4.143 to 11.281 +/- 3.653 kg; P < 0.01) as a result of training.(ABSTRACT TRUNCATED AT 250 WORDS)