Lack of age-related decreases in basal whole leg blood flow in resistance-trained men.

Reductions in basal leg blood flow have been implicated in the pathogenesis of metabolic syndrome and functional impairment in humans. We tested the hypothesis that reductions in basal whole leg blood flow with age are either absent or attenuated in those who perform regular strength training. A total of 104 normotensive men aged 20-34 yr (young) and 35-65 yr (middle aged), who were either sedentary or resistance trained, were studied. Mean and diastolic blood pressures were higher (P < 0.05-0.001) in the middle-aged compared with the young men, but there were no significant differences between the sedentary and resistance-trained groups. In the sedentary group, basal whole leg blood flow (duplex Doppler ultrasound) and vascular conductance were lower ( approximately 30 and approximately 38%, respectively; P < 0.01) in the middle-aged compared with the young men. There were no such age-related differences in the resistance-trained group. In the young men, basal whole leg blood flow and vascular conductance were not different between the two activity groups, but, in the middle-aged men, they were higher ( approximately 35 and approximately 36%, respectively; P < 0.01) in the resistance-trained men than in the sedentary men. When blood flow and vascular conductance were expressed relative to the leg muscle mass, the results were essentially the same. We concluded that the age-related reduction in basal whole leg blood flow is absent in resistance-trained men. These results suggest that resistance training may favorably influence leg perfusion in aging humans, independent of its impact on leg muscle mass.     

Systemic alpha-adrenergic and nitric oxide inhibition on basal limb blood flow: effects of endurance training in middle-aged and older adults

Endurance training improves endothelium-dependent vasodilation, yet it does not increase basal blood flow in the legs. We determined the effects of a 3-mo aerobic exercise intervention on basal leg blood flow and alpha-adrenergic vasoconstriction and nitric oxide (NO) release in seven apparently healthy middle-aged and older adults (60 +/- 3 yr). Basal femoral artery blood flow (via Doppler ultrasound) (pretraining: 354 +/- 29; posttraining: 335 +/- 34 ml/min) and vascular conductance did not change significantly with the exercise training. Before the exercise intervention, femoral artery blood flow increased 32 +/- 16% with systemic alpha-adrenergic blockade (with phentolamine) (P < 0.05), and the addition of nitric oxide synthase (NOS) inhibition using N(G)-monomethyl-L-arginine (L-NMMA) did not affect femoral artery blood flow. After training was completed, femoral artery blood flow increased 47 +/- 7% with alpha-adrenergic blockade (P < 0.01) and then decreased 18 +/- 7% with the subsequent administration of L-NMMA (P < 0.05). Leg vascular conductance showed a greater alpha-adrenergic blockade-induced vasodilation (+1.7 +/- 0.5 to +3.0 +/- 0.5 units, P < 0.05) as well as NOS inhibition-induced vasoconstriction (-0.8 +/- 0.4 to -2.7 +/- 0.7 units, P < 0.05) after the exercise intervention. Resting plasma norepinephrine concentration significantly increased after the training. These results suggest that regular aerobic exercise training enhances NO bioavailability in middle-aged and older adults and that basal limb blood flow does not change with exercise training because of the contrasting influences of sympathetic nervous system activity and endothelium-derived vasodilation on the vasculature.     

High-dose ascorbic acid infusion abolishes chronic vasoconstriction and restores resting leg blood flow in healthy older men.

Resting whole leg blood flow and vascular conductance decrease linearly with advancing age in healthy adult men. The potential role of age-related increases in oxidative stress in these changes is unknown. Resting leg blood flow during saline and ascorbic acid infusion was studied in 10 young (25 +/- 1 yr) and 11 older (63 +/- 2 yr) healthy normotensive men. Plasma oxidized LDL, a marker of oxidative stress, was greater in the older men (P < 0.05). Absolute resting femoral artery blood flow at baseline (iv saline control infusion) was 25% lower in the older men (238 +/- 25 vs. 316 +/- 38 ml/min; P < 0.05), and it was inversely related to plasma oxidized LDL (r = -0.56, P < 0.01) in all subjects. Infusion of supraphysiological concentrations of ascorbic acid increased femoral artery blood flow by 37% in the older men (to 327 +/- 52 ml/min; P < 0.05), but not in the young men (352 +/- 41 ml/min; P = 0.28), thus abolishing group differences (P = 0.72). Mean arterial blood pressure was greater in the older men at baseline (86 +/- 4 vs. 78 +/- 2 mmHg; P < 0.05), but it was unaffected by ascorbic acid infusion (P >/= 0.70). As a result, the lower baseline femoral artery blood flow in the older men was mediated solely by a 32% lower femoral artery vascular conductance (P < 0.05). Baseline femoral vascular conductance also was inversely related to plasma oxidized LDL (r = -0.65, P < 0.01). Ascorbic acid increased femoral vascular conductance by 36% in the older men (P < 0.05) but not in the young men (P = 0.31). In conclusion, ascorbic acid infused at concentrations known to scavenge reactive oxygen species restores resting femoral artery blood flow in healthy older adult men by increasing vascular conductance. These results support the hypothesis that oxidative stress plays a major role in the reduced resting whole leg blood flow and increased leg vasoconstriction observed with aging in men.     

Arterial compliance of rowers: implications for combined aerobic and strength training on arterial elasticity

Regular endurance exercise increases central arterial compliance, whereas resistance training decreases it. It is not known how the vasculature adapts to a combination of endurance and resistance training. Rowing is unique, because its training encompasses endurance- and strength-training components. We used a cross-sectional study design to determine arterial compliance of 15 healthy, habitual rowers [50 +/- 9 (SD) yr, 11 men and 4 women] and 15 sedentary controls (52 +/- 8 yr, 10 men and 5 women). Rowers had been training 5.4 +/- 1.2 days/wk for 5.7 +/- 4.0 yr. The two groups were matched for age, body composition, blood pressure, and metabolic risk factors. Central arterial compliance (simultaneous ultrasound and applanation tonometry on the common carotid artery) was higher (P < 0.001) and carotid beta-stiffness index was lower (P < 0.001) in rowers than in sedentary controls. There were no group differences for measures of peripheral (femoral) arterial stiffness. The higher central arterial compliance in rowers was associated with a greater cardiovagal baroreflex sensitivity, as estimated during a Valsalva maneuver (r = 0.54, P < 0.005). In conclusion, regular rowing exercise in middle-aged and older adults is associated with a favorable effect on the elastic properties of the central arteries. Our results suggest that simultaneously performed endurance training may negate the stiffening effects of strength training.     

Resistance exercise training improves age-related declines in leg vascular conductance and rejuvenates acute leg blood flow responses to feeding and exercise

One manifestation of age-related declines in vascular function is reduced peripheral (limb) blood flow and vascular conduction at rest and in response to vasodilatory stimuli such as exercise and feeding. Since, even in older age, resistance exercise training (RET) represents an efficacious strategy for increasing muscle mass and function, we hypothesized that likewise RET would improve age-related declines in leg blood flow (LBF) and vascular conductance (LVC). We studied three mixed-sex age groups (young: 18-28 yr, n = 14; middle aged: 45-55 yr, n = 20; older: 65-75 yr, n = 17) before and after 20 wk of whole body RET in the postabsorptive state (BASAL) and after unilateral leg extensions (6 × 8 repetitions; 75% 1 repetition maximum) followed by intermittent mixed-nutrient liquid feeds (～6.5 kJ·kg(-1)·30 min(-1)), which allowed us to discern the acute effects of feeding (nonexercised leg; FED) and exercise plus feeding (exercised leg; FEDEX) on vascular function. We measured LBF using Doppler ultrasound and recorded mean arterial pressure (MAP) to calculate LVC. Our results reveal that although neither age nor RET influenced BASAL LBF, age-related declines in LBF responses to FED were eradicated by RET. Moreover, increases in LBF after FEDEX, which occurred only in young and middle-aged groups before RET (+73 ± 9%, and +90 ± 13%, P < 0.001, respectively), increased in all groups after RET (young +78 ± 10%, middle-aged +96 ± 15%, older +80 ± 19%, P < 0.001). Finally, RET robustly improved LVC under FASTED, FED, and FEDEX conditions in the older group. These data provide novel information that supports the premise that RET represents a valuable strategy to counter age-related impairments in LBF/LVC.     

Leg blood flow during submaximal cycle ergometry is not reduced in healthy older normally active men.

The purpose of the present study was to test the hypothesis that leg blood flow responses during submaximal cycle ergometry are reduced with age in healthy normally active men. Eleven younger (20-25 yr) and eight older (62-73 yr) normotensive, nonendurance-trained men performed both graded and constant-load bouts of leg cycling at the same absolute and relative [% of peak O(2) consumption (Vo(2 peak))] exercise intensities while leg blood flow (femoral vein thermodilution), mean arterial pressure (MAP; radial artery), cardiac output (acetylene rebreathing), blood O(2) content, and plasma catecholamines were measured. Leg blood flow responses at the same absolute submaximal power outputs (20-100 W) and at a fixed systemic O(2) demand (1.1 l/min) did not differ between groups (P = 0.14-0.19), despite lower absolute levels of cardiac output in the older men (P < 0.05). MAP at the same absolute power outputs was 8-12 mmHg higher (P < 0.05) in the older men, but calculated leg vascular conductance responses (leg blood flow/MAP) were identical in the two groups (P > 0.9). At the same relative intensity (60% Vo(2 peak)), leg norepinephrine spillover rates were approximately twofold higher in the older men (P = 0.38). Exercise-induced increases in leg arterial-venous O(2) difference were identical between groups (P > 0.9) because both arterial and venous O(2) contents were lower in the older vs. younger men. These results suggest that the ability to augment active limb blood flow and O(2) extraction during submaximal large muscle mass exercise is not impaired but is well preserved with age in healthy men who are normally active.     

Impaired leg vasodilation during dynamic exercise in healthy older women.

The purpose of the present study was to test the hypothesis that leg blood flow responses during leg cycle ergometry are reduced with age in healthy non-estrogen-replaced women. Thirteen younger (20-27 yr) and thirteen older (61-71 yr) normotensive, non-endurance-trained women performed both graded and constant-load bouts of leg cycling at the same absolute exercise intensities. Leg blood flow (femoral vein thermodilution), mean arterial pressure (MAP; radial artery), mean femoral venous pressure, cardiac output (acetylene rebreathing), and blood O2 contents were measured. Leg blood flow responses at light workloads (20-40 W) were similar in younger and older women. However, at moderate workloads (50-60 W), leg blood flow responses were significantly attenuated in older women. MAP was 20-25 mmHg higher (P < 0.01) in the older women across all work intensities, and calculated leg vascular conductance (leg blood flow/estimated leg perfusion pressure) was lower (P < 0.05). Exercise-induced increases in leg arteriovenous O2 difference and O2 extraction were identical between groups (P > 0.6). Leg O2 uptake was tightly correlated with leg blood flow across all workloads in both subject groups (r2 = 0.80). These results suggest the ability of healthy older women to undergo limb vasodilation in response to submaximal exercise is impaired and that the legs are a potentially important contributor to the augmented systemic vascular resistance seen during dynamic exercise in older women.     

Enhanced endothelin-1-mediated leg vascular tone in healthy older subjects.

Advanced age is associated with a decreased leg blood flow and reduced physical activity. Endothelin (ET-1), a powerful vasoconstrictor, may play a role in the increased leg vascular tone in older men. objectives: to assess the ET-1-mediated vascular tone in the legs of healthy sedentary older men, both before and after 8 wk of exercise training. methods: in 8 younger subjects (19-50 yr) and 8 older men (67-76 yr), bilateral leg blood flow was measured using venous occlusion plethysmography before and after antagonizing ET-1 (using selective ET(A/B)-receptor antagonists). In older men, reversibility of the observations was assessed after 8 wk of cycling. results: ET-receptor inhibition increased leg blood flow significantly more in older men compared with younger individuals (29 +/- 9% and 10 +/- 4%, respectively, P < 0.05). Eight-week cycling training increased baseline blood flow in older men. The blood flow response to ET-receptor inhibition in older men was not affected by the training program (25 +/- 8%, P > 0.05 for comparison with pretraining). The flow ratio (blood flows infused leg/noninfused leg) decreased significantly by training from 26 +/- 8% to 7+3% (P < 0.05). CONCLUSION: the increased baseline vascular tone in aging is at least in part mediated by the endothelin. Eight-weeks cycling training in older sedentary men decreased leg vascular tone and seems to partly decrease the ET-1-mediated vascular tone.     

Age-specific modification of local cutaneous vasodilation by capsaicin-sensitive primary afferents

Age-related changes in neurogenic vasodilation mediated by sensory nerves may alter local skin blood flow (SkBF) responses in older individuals. The purpose of this study was to determine the age-specific modification of cutaneous vasodilation by capsaicin-sensitive primary afferent (CSPA) nerves during local heating. Nine young (18-30 yr), eight middle-aged (40-55 yr), and eight older (65-80 yr) healthy men participated in the experiments. Two local-heating protocols (rapid and slow) were performed before and after 1 wk of capsaicin pretreatment (CP), used to desensitize CSPAs. All temperatures were below those that elicit pain. SkBF was measured with a laser-Doppler imager and indexed to percentage of maximal cutaneous vascular conductance (%CVCmax). CP caused a significant reduction in %CVCmax in the middle-aged and older groups during slow heating (P < 0.05), without affecting %CVCmax in the young group. During rapid heating, CP significantly reduced (53.9 +/- 4.4 vs. 74.4 +/- 7.4% CVCmax, P < 0.05), but did not abolish, the initial sensory nerve-mediated rise in SkBF in the young group. No significant effects of CP on SkBF were observed during rapid heating in the middle-aged or older groups. These results indicate that, with advanced age, CSPA activity is more important to the maximal SkBF response during prolonged local heating, whereas it has a reduced role in the initial SkBF peak elicited by rapid local heating. In summary, CSPA activity contributes modestly to the overall SkBF response to local heating in an age-specific manner.     

Oxidative stress contributes to chronic leg vasoconstriction in estrogen-deficient postmenopausal women.

Basal whole leg blood flow and vascular conductance are reduced in estrogen-deficient postmenopausal compared with premenopausal women. The underlying mechanisms are unknown, but oxidative stress could be involved. We studied 9 premenopausal [23 +/- 1 yr (mean +/- SE)] and 20 estrogen-deficient postmenopausal (55 +/- 1 yr) healthy women. During baseline control, oxidized low-density lipoprotein (LDL), a marker of oxidative stress, was 50% greater in the postmenopausal women (P < 0.001). Basal whole leg blood flow (duplex ultrasound of femoral artery) was 34% lower in the postmenopausal women because of a 38% lower leg vascular conductance (P < 0.0001); mean arterial pressure was not different. Intravenous administration of a supraphysiological dose of the antioxidant ascorbic acid increased leg blood flow by 15% in the postmenopausal women as a result of an increase in leg vascular conductance (both P < 0.001), but it did not affect leg blood flow in premenopausal controls or mean arterial pressure in either group. In the pooled subjects, the changes in leg blood flow and leg vascular conductance with ascorbic acid were related to baseline plasma oxidized LDL (r = 0.46 and 0.53, P < 0.01) and waist-to-hip ratio and total body fat (r = 0.41-0.44, all P < 0.05). Our results are consistent with the hypothesis that oxidative stress contributes to chronic leg vasoconstriction and reduced basal whole leg blood flow in estrogen-deficient postmenopausal women. This oxidative stress-related suppression of leg vascular conductance and blood flow may be linked in part to increased total and abdominal adiposity.     

Aerobic training and cutaneous vasodilation in young and older men.

To determine the effect and underlying mechanisms of exercise training and the influence of age on the skin blood flow (SkBF) response to exercise in a hot environment, 22 young (Y; 18-30 yr) and 21 older (O; 61-78 yr) men were assigned to 16 wk of aerobic (A; YA, n = 8; OA, n = 11), resistance (R; YR, n = 7; OR, n = 3), or no training (C; YC, n = 7; OC, n = 7). Before and after treatment, subjects exercised at 60% of maximum oxygen consumption (VO2 max) on a cycle ergometer for 60 min at 36 degrees C. Cutaneous vascular conductance, defined as SkBF divided by mean arterial pressure, was monitored at control (vasoconstriction intact) and bretylium-treated (vasoconstriction blocked) sites on the forearm using laser-Doppler flowmetry. Forearm vascular conductance was calculated as forearm blood flow (venous occlusion plethysmography) divided by mean arterial pressure. Esophageal and skin temperatures were recorded. Only aerobic training (functionally defined a priori as a 5% or greater increase in VO2 max) produced a decrease in the mean body temperature threshold for increasing forearm vascular conductance (36.89 +/- 0.08 to 36.63 +/- 0.08 degrees C, P < 0.003) and cutaneous vascular conductance (36.91 +/- 0.08 to 36.65 +/- 0.08 degrees C, P < 0.004). Similar thresholds between control and bretylium-treated sites indicated that the decrease was mediated through the active vasodilator system. This shift was more pronounced in the older men who presented greater training-induced increases in VO2 max than did the young men (22 and 9%, respectively). In summary, older men improved their SkBF response to exercise-heat stress through the effect of aerobic training on the cutaneous vasodilator system.     

Aging and the skin blood flow response to the unloading of baroreceptors during heat and cold stress.

Control of skin blood flow (SkBF) is on the efferent arm of both thermoregulatory and nonthermoregulatory reflexes. To what extent aging may affect the SkBF response when these two reflex systems interact is unknown. To determine the response of aged skin to the unloading of baroreceptors in thermoneutral, cold stress, and heat stress conditions, sequential bouts of nonhypotensive lower body negative pressure (LBNP) were applied at -10, -20, and -30 mmHg in 14 young (18-25 yr) and 14 older (63-78 yr) men. SkBF was measured by laser-Doppler velocimetry (averaged over 2 forearm sites), and data are expressed as percentage of maximal cutaneous vascular conductance (%CVC(max)). Total forearm blood flow was measured by venous occlusion plethysmography, and forearm vascular conductance (FVC) was calculated as the ratio of forearm blood flow to mean arterial pressure. In young men, all three intensities of LBNP in thermoneutrality decreased FVC significantly (P < 0.05), but FVC at -10 mmHg did not change in the older men. There were no significant LBNP effects on %CVC(max). Application of LBNP during cold stress did not significantly change %CVC(max) or FVC in either age group. During heat stress, -10 to -30 mmHg of LBNP decreased FVC significantly (P < 0.05) in both age groups, but these decreases were attenuated in the older men (P < 0.05). %CVC(max) decreased at -30 mmHg in the younger men only. These results suggest that older men have an attenuated skin vasoconstrictor response to the unloading of baroreceptors in heat stress conditions. Furthermore, the forearm vasoconstriction elicited by LBNP in older men reflects that of underlying tissue (i.e., muscle) rather than that of skin, whereas -30 mmHg LBNP also decreases SkBF in young hyperthermic men.     

Exercise training enhances leg vasodilatory capacity of 65-yr-old men and women

To determine whether extremity vasodilatory capacity may be augmented in older persons by endurance exercise training, lower leg blood flow and conductance were characterized plethysmographically at rest and during maximal hyperemia in 9 men and 10 women aged 64 +/- 3 (SD) yr before and after 31 +/- 6 wk of walking and jogging at 70-90% of maximal oxygen uptake for 45 min 3-5 days/wk. Maximal oxygen uptake expressed as milliliters per kilogram per minute improved 25% in men and 21% in women (P less than 0.01). Maximal leg blood flow and conductance increased in all nine men by an average of 39 +/- 33 (P less than 0.001) and 42 +/- 44% (P less than 0.004), respectively. Results were more variable in women and achieved unequivocal statistical significance only for maximal blood flow (+33 +/- 54% for blood flow and +29 +/- 55% for conductance; P less than 0.02 and P = 0.05, respectively). Body weight and skinfold adiposity declined in both sexes (P less than 0.05). Enhancement of vasodilatory capacity was related to weight loss in men and adipose tissue loss in women (r = 0.61 and 0.51, respectively; P less than 0.05). There were no significant changes in exercise capacity, body weight, or maximal blood flow in four male and three female controls aged 66 +/- 4 yr. Thus adaptability of the lower limb circulation to endurance exercise training is retained to at least age 65 yr.     

Sex differences in leg vasodilation during graded knee extensor exercise in young adults.

Limb vascular conductance responses to pharmacological and nonexercise vasodilator stimuli are generally augmented in women compared with men. In the present investigation, we tested the hypothesis that exercise-induced vasodilator responses are also greater in women than men. Sixteen women and 15 men (20-30 yr) with similar fitness and activity levels performed graded quadriceps exercise (supine, single-leg knee extensions, 40 contractions/min) to maximal exertion. Active limb hemodynamics (left common femoral artery diameter and volumetric blood flow), heart rate (ECG), and beat-to-beat mean arterial blood pressure (MAP; radial artery tonometry) were measured during each 3-min workload (4.8 and 8 W/stage for women and men, respectively). The hyperemic response to exercise (slope of femoral blood flow vs. workload) was greater (P < 0.01) in women as was femoral blood flow at workloads >15 W. The leg vasodilatory response to exercise (slope of calculated femoral vascular conductance vs. absolute workload) was also greater in women than in men (P < 0.01) because of the sex difference in hyperemia and the women's lower MAP ( approximately 10-15 mmHg) at all workloads (P < 0.05). The femoral artery dilated to a significantly greater extent in the women ( approximately 0.5 mm) than in the men ( approximately 0.1 mm) across all submaximal workloads. At maximal exertion, femoral vascular conductance was lower in the men (men, 18.0 +/- 0.6 ml.min(-1)xmmHg(-1); women, 22.6 +/- 1.4 mlxmin(-1)xmmHg(-1); P < 0.01). Collectively, these findings suggest that the vasodilatory response to dynamic leg exercise is greater in young women vs. men.     

Reduced leg blood flow during dynamic exercise in older endurance-trained men

It is currentlyunclear whether aging alters the perfusion of active muscles duringlarge-muscle dynamic exercise in humans. To study this issue, directmeasurements of leg blood flow (femoral vein thermodilution) andsystemic arterial pressure during submaximal cycle ergometry (70, 140, and 210 W) were compared between six younger (Y; 22-30 yr) and sixolder (O; 55-68 yr) chronically endurance-trainedmen. Whole body O₂uptake, ventilation, and arterial and femoral venous samples forblood-gas, catecholamine, and lactate determinations were alsoobtained. Training duration (min/day), estimated leg muscle mass(dual-energy X-ray absorptiometry; Y, 21.5 ± 1.2 vs. O, 19.9 ± 0.9 kg), and blood hemoglobin concentration (Y, 14.9 ± 0.4 vs. O, 14.7 ± 0.2 g/dl) did not significantly differ (P > 0.05) between groups. Leg bloodflow, leg vascular conductance, and femoral venousO₂ saturation were ~20-30%lower in the older men at each work rate (allP < 0.05), despite similarlevels of whole body O₂ uptake. At210 W, leg norepinephrine spillover rates and femoral venous lactateconcentrations were more than twofold higher in the older men.Pulmonary ventilation was also higher in the older men at 140 (+24%)and 210 (+39%) W. These results indicate that leg blood flow andvascular conductance during cycle ergometer exercise are significantlylower in older endurance-trained men in comparison to their youngercounterparts. The mechanisms responsible for this phenomenon and theextent to which they operate in other groups of older subjects deservefurther attention.

     

Long-term estrogen deficiency lowers regional blood flow, resting systolic blood pressure, and heart rate in exercising premenopausal women

The cardiovascular consequences of hypoestrogenism in premenopausal women are unclear. Accordingly, the influence of menstrual status and endogenous estrogen (E(2)) exposure on blood pressure (BP), heart rate (HR), and calf blood flow in young (18-35 yr) regularly exercising premenopausal women with exercise-associated menstrual aberrations was investigated. Across consecutive menstrual cycles, daily urinary ovarian steroid levels were analyzed, and the area under the curve was calculated to determine menstrual status and E(2) exposure. BP, HR, blood flow, vascular conductance, and resistance were measured at baseline and following ischemic calf exercise. Exercising subjects consisted of 14 ovulatory (ExOv), 10 short-term (anovulatory and 100 days amenorrhea; LT-E(2) Def) E(2)-deficient women. Nine sedentary ovulatory subjects (SedOv) were also studied. All groups were similar in age (24.8 +/- 0.7 yr), height (164.8 +/- 1.3 cm), weight (57.9 +/- 0.9 kg), and body mass index (21.3 +/- 0.3 kg/m(2)). E(2)-deficient groups had lower (P < 0.002) E(2) exposure compared with ovulatory groups. Resting systolic BP, HR, blood flow, and vascular conductance were lower (P < 0.05) and vascular resistance higher (P < 0.05) in LT-E(2) Def compared with both ovulatory groups. Peak ischemic blood flow, vascular conductance, and HR were also lower (P < 0.05) and vascular resistance higher (P < 0.05) in LT-E(2) Def compared with all other groups. Our findings show that exercising women with long-term E(2) deficiency have impaired regional blood flow and lower systolic BP and HR compared with exercising and sedentary ovulatory women. These cardiovascular alterations represent markers of altered vascular function and autonomic regulation of which the long-term effects remain unknown.     

Ultrastructural muscle damage in young vs. older men after high-volume, heavy-resistance strength training.

This study assessed ultrastructural muscle damage in young (20-30 yr old) vs. older (65-75 yr old) men after heavy-resistance strength training (HRST). Seven young and eight older subjects completed 9 wk of unilateral leg extension HRST. Five sets of 5-20 repetitions were performed 3 days/wk with variable resistance designed to subject the muscle to near-maximal loads during every repetition. Biopsies were taken from the vastus lateralis of both legs, and muscle damage was quantified via electron microscopy. Training resulted in a 27% strength increase in both groups (P < 0.05). In biopsies before training in the trained leg and in all biopsies from untrained leg, 0-3% of muscle fibers exhibited muscle damage in both groups (P = not significant). After HRST, 7 and 6% of fibers in the trained leg exhibited damage in the young and older men, respectively (P < 0.05, no significant group differences). Myofibrillar damage was primarily focal, confined to one to two sarcomeres. Young and older men appear to exhibit similar levels of muscle damage at baseline and after chronic HRST.     

Maximal vascular leg conductance in trained and untrained men

Lower leg blood flow and vascular conductance were studied and related to maximal oxygen uptake in 15 sedentary men (28.5 +/- 1.2 yr, mean +/- SE) and 11 endurance-trained men (30.5 +/- 2.0 yr). Blood flows were obtained at rest and during reactive hyperemia produced by ischemic exercise to fatigue. Vascular conductance was computed from blood flow measured by venous occlusion plethysmography, and mean arterial blood pressure was determined by auscultation of the brachial artery. Resting blood flow and mean arterial pressure were similar in both groups (combined mean, 3.0 ml X min-1 X 100 ml-1 and 88.2 mmHg). After ischemic exercise, blood flows were 29- and 19-fold higher (P less than 0.001) than rest in trained (83.3 +/- 3.8 ml X min-1 X 100 ml-1) and sedentary subjects (61.5 +/- 2.3 ml X min-1 X 100 ml-1), respectively. Blood pressure and heart rate were only slightly elevated in both groups. Maximal vascular conductance was significantly higher (P less than 0.001) in the trained compared with the sedentary subjects. The correlation coefficients for maximal oxygen uptake vs. vascular conductance were 0.81 (trained) and 0.45 (sedentary). These data suggest that physical training increases the capacity for vasodilation in active limbs and also enables the trained individual to utilize a larger fraction of maximal vascular conductance than the sedentary subject.     

Effects of age on testosterone responses to resistance exercise and musculoskeletal variables in men

This study compared serum total testosterone (TT) and free testosterone (FT) responses of young (20-26 years, n = 8), middle-aged (38-53 years, n = 7), and older (59-72 years, n = 9) men to resistance exercise. We also examined the relationships between testosterone (T) levels and strength, bone mineral density (BMD), and body composition variables for each age group. Subjects were tested for isotonic muscular strength (1 repetition maximum [1RM]), BMD (dual-energy x-ray absorptiometry [DXA]) and body composition (DXA). Each group performed an acute exercise protocol (3 sets, 10 repetitions, 80% of 1RM, 6 exercises). Blood samples were obtained at baseline, immediately postexercise, and 15 minutes postexercise for the TT and FT assays. The older age group had significantly (p < 0.05) lower T levels than the young group, but each group exhibited an increase (p < 0.05) in TT and FT immediately postexercise. Total T and FT were significantly correlated (p < 0.05) with strength in middle-aged and older men and with bone-free lean tissue mass in older men. In conclusion, middle-aged and older men showed similar relative T responses to those of younger men to a single bout of high-intensity resistance exercise. However, T levels were related to strength and muscle mass only in middle-aged or older men. On a practical application level, older men can complete a high-intensity resistance exercise program resulting in spikes in T that may attenuate age-related muscle and BMD loss.     

Mechanism of reduced maximal expiratory flow with aging.

To investigate the determinants of maximal expiratory flow (MEF) with aging, 17 younger (7 men and 10 women, 39 +/- 4 yr, mean +/- SD) and 19 older (11 men and 8 women, 69 +/- 3 yr) subjects with normal pulmonary function were studied. For further comparison, we also studied 10 middle-aged men with normal lung function (54 +/- 6 yr) and 15 middle-aged men (54 +/- 7 yr) with mild chronic airflow limitation (CAL; i.e., forced expiratory volume in 1 s/forced vital capacity = 63 +/- 8%). MEF, static lung elastic recoil pressure (Pst), and the minimal pressure for maximal flow (Pcrit) were determined in a pressure-compensated, volume-displacement body plethysmograph. Values were compared at 60, 70, and 80% of total lung capacity. In the older subjects, decreases in MEF (P < 0.01) and Pcrit (P < 0.05), compared with the younger subjects, were explained mainly by loss of Pst (P < 0.05). In the CAL subjects, MEF and Pcrit were lower (P < 0.05) than in the older subjects, but Pst was similar. Thus decreases in MEF and Pcrit were greater than could be explained by the loss of Pst and appeared to be related to increased upstream resistance. These data indicate that the loss of lung recoil explains the decrease in MEF with aging subjects, but not in the mild CAL patients that we studied.