***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Current ACSM guidelines recommend that adults should exercise for 20 - 60 min on 3 - 5 days.week(-1 ) ( M.L. Pollock , et al. , The recommended quantity and quality of exercise for developing and maintaining cardiorespiratory and muscular fitness , and flexibility in healthy adults . Medicine and Science in Sports and Exercise , 30 ( 6 ) ( 1998 ) 975 - 991 . ) . For individuals constrained by a busy lifestyle , an exercise prescription that delivers benefits with the minimum investment of time is attractive . The purpose of the present study , therefore , was to examine the effect of instructing sedentary individuals to undertake 20 min of brisk walking , in two different patterns , 3 days per week , on fitness and other cardiovascular disease ( CVD ) risk factors . METHODS Forty-eight subjects ( 31 women ) mean ( + /-SD ) age 45.7 + /- 9.4 year were r and omly assigned to either one 20-min walk ( single bout ) , two 10-min walks ( accumulated bouts ) 3 days week(-1 ) for 12-week , or no training ( control ) . Oxygen consumption ( VO2 ) , heart rate ( HR ) , and ratings of perceived exertion ( RPE ) were measured during a 4-stage treadmill test at pre- and post-intervention . Body composition , resting blood pressure and fasting lipoproteins were also assessed . Thirty-two subjects completed the study . RESULTS There was a significant difference between single-bout and accumulated-bout walkers in the reduction of HR at stages 2 and 3 of the treadmill test from pre- to post-intervention ( P < 0.05 ) . There were no differences between groups for changes in VO2 or RPE from pre- to post-intervention . There were also no changes in body mass , adiposity , blood pressure , waist and hip circumferences , or lipid/lipoproteins . CONCLUSION Brisk walking for 20 min on 3 days of the week fails to alter cardiovascular disease risk factors in previously sedentary adults Endothelial function deteriorates with aging . On the other h and , exercise training improves the function of vascular endothelial cells . Endothelin-1 ( ET-1 ) , which is produced by vascular endothelial cells , has potent constrictor and proliferative activity in vascular smooth muscle cells and , therefore , has been implicated in regulation of vascular tonus and progression of atherosclerosis . We previously reported significantly higher plasma ET-1 concentration in middle-aged than in young humans , and recently we showed that plasma ET-1 concentration was significantly decreased by aerobic exercise training in healthy young humans . We hypothesized that plasma ET-1 concentration increases with age , even in healthy adults , and that lifestyle modification ( i.e. , exercise ) can reduce plasma ET-1 concentration in previously sedentary older adults . We measured plasma ET-1 concentration in healthy young women ( 21 - 28 yr old ) , healthy middle-aged women ( 31 - 47 yr old ) , and healthy older women ( 61 - 69 yr old ) . The plasma level of ET-1 significantly increased with aging ( 1.02 + /- 0.08 , 1.33 + /- 0.11 , and 2.90 + /- 0.20 pg/ml in young , middle-aged , and older women , respectively ) . Thus plasma ET-1 concentration was markedly higher in healthy older women than in healthy young or middle-aged women ( by approximately 3- and 2-fold , respectively ) . In healthy older women , we also measured plasma ET-1 concentration after 3 mo of aerobic exercise ( cycling on a leg ergometer at 80 % of ventilatory threshold for 30 min , 5 days/wk ) . Regular exercise significantly decreased plasma ET-1 concentration in the healthy older women ( 2.22 + /- 0.16 pg/ml , P < 0.01 ) and also significantly reduced their blood pressure . The present study suggests that regular aerobic-endurance exercise reduces plasma ET-1 concentration in older humans , and this reduction in plasma ET-1 concentration may have beneficial effects on the cardiovascular system ( i.e. , prevention of progression of hypertension and /or atherosclerosis by endogenous ET-1 ) Aerobic endurance training increases insulin action in skeletal muscle , but the effect of resistance training has not been well described . Controversy exists about whether the effect of resistance training is merely due to an increase in muscle mass . We studied the effect of cessation of resistance training in young , healthy subjects by taking muscle biopsies and measuring insulin-mediated whole body and leg glucose uptake rates after 90 days of heavy resistance training ( T ) and again after 90 days of de-training ( dT ) . Data on leg glucose uptake were expressed relative to accurate measures of leg muscle mass by MRI scanning . Muscle strength ( 239 + /- 43 vs. 208 + /- 33 N m ) , quadriceps area ( 8463 + /- 453 vs. 7763 + /- 329 mm2 ) and glycogen content ( 458 + /- 22 vs. 400 + /- 26 mmol ( kg dry weight muscle)(-1 ) ) decreased , while myosin heavy chain isoform IIX increased 4-fold in dT vs. T , respectively ( all P < 0.05 ) . GLUT4 mRNA levels and enzyme activities and mRNA levels of glycolytic , lipolytic and glyconeogenic enzymes did not change with de-training . Likewise , capillary density did not change . Whole body glucose uptake decreased 11 % and leg glucose uptake decreased from 75 + /- 11 ( T ) to 50 + /- 6 ( dT ) nmol min(-1 ) ( mm muscle)(-2 ) ( P < 0.05 ) at maximal insulin , the latter decrease being due to decreased arterio-femoral venous glucose extraction . The decrease was mainly due to reduced non-oxidative glucose disposal . We have thus shown that 90 days after the termination of heavy resistance training , insulin-mediated glucose uptake rates per unit of skeletal muscle have decreased significantly BACKGROUND Several nonpharmacological interventions , including exercise , are recommended in primary prevention of hypertension and other cardiovascular diseases in which the pathogenetic role of endothelial dysfunction has been suggested . We studied the effects of long-term aerobic exercise on endothelial function in patients with essential hypertension . METHODS AND RESULTS The forearm blood flow was measured by strain-gauge plethysmography . The responses of forearm vasculature to acetylcholine were smaller in the hypertensive patients than in the normotensive subjects . There was no significant difference in forearm vascular responses to isosorbide dinitrate in the normotensive and hypertensive subjects . We evaluated the effects of physical exercise for 12 weeks on forearm hemodynamics in untreated patients with mild essential hypertension who were divided r and omly into an  exercise group ( n=10 ) and a control group ( n=7 ) . After 12 weeks , the forearm blood flow response to acetylcholine increased significantly , from 25.8+/-9.8 to 32.3+/-11.2 mL. min(-1 ) . 100 mL tissue(-1 ) ( P<0.05 ) , in the exercise group but not in the control group . The increase in the forearm blood flow after isosorbide dinitrate was similar before and after 12 weeks of follow-up in both groups . The infusion of N(G)-monomethyl-L-arginine abolished the exercise-induced enhancement of forearm vasorelaxation evoked by acetylcholine in the exercising group . In normotensive subjects also , long-term aerobic exercise augmented acetylcholine-stimulated nitric oxide release . CONCLUSIONS These findings suggest that long-term physical exercise improves endothelium-dependent vasorelaxation through an increase in the release of nitric oxide in normotensive as well as hypertensive subjects BACKGROUND Aging is associated with increased cardiovascular risk and endothelial dysfunction . Since exercise can improve endothelium-dependent vasodilation , in the present study we tested whether long-term physical activity could prevent aging-related endothelial dysfunction . METHODS AND RESULTS In 12 young and elderly ( age 26.9+/-2.3 and 62.9+/-5.8 years , respectively ) healthy sedentary subjects and 11 young and 14 elderly matched athletes ( age 27.5+/-1.9 and 66.4+/-6.1 years , respectively ) , we studied ( with strain-gauge plethysmography ) forearm blood flow modifications induced by intrabrachial acetylcholine ( 0.15 , 0.45 , 1.5 , 4.5 , and 15 microg/100 mL per minute ) , an endothelium-dependent vasodilator , at baseline , during infusion of N(G)-monomethyl-L-arginine ( L-NMMA ) ( 100 microg/100 mL forearm tissue per minute ) , a nitric oxide-synthase inhibitor , vitamin C ( 8 mg/100 mL forearm tissue per minute ) , an antioxidant , and finally under simultaneous infusion of L-NMMA and vitamin C. The response to  sodium nitroprusside ( 1 , 2 , and 4 microg/100 mL forearm tissue per minute ) was also evaluated . In young athletes and sedentary subgroups , vasodilation to acetylcholine was inhibited by L-NMMA and was not changed by vitamin C. In elderly subjects , vasodilation to acetylcholine was blunted as compared with young subjects in both control subjects and athletes , whereas the response to sodium nitroprusside was similar . Moreover , in elderly athletes , vitamin C did not change the vasodilation to acetylcholine . In contrast , in elderly sedentary subjects , the response to acetylcholine was resistant to L-NMMA . In this subgroup , vitamin C increased the vasodilation to acetylcholine and restored the inhibiting effect of L-NMMA . CONCLUSIONS These results suggest that regular physical activity can at least in part prevent the age-induced endothelial dysfunction , probably the restoration of nitric oxide availability consequent to prevention of production of oxidative stress Objective : To compare the effects of aerobic and resistance exercise on weight , muscle strength , cardiovascular fitness , blood pressure and mood in obese women who were not on an energy-restricted diet . Design : R and omized , prospect i ve , controlled trial . Setting : Department of Physical Medicine and Rehabilitation , University Hospital . Subjects : Sixty obese women were assigned to one of three groups : aerobic exercise ( n=20 ) , resistance exercise ( n=20 ) and control group ( n=20 ) . Interventions : The aerobic exercise group performed both walking and leg cycle exercise with increasing duration and frequency . The resistance exercise group performed progressive weight-resistance exercises for the upper and lower body . Main outcome measures : Before and after a 12-week period , all subjects were evaluated by anthropometric measurement , rating of mood , cardiorespiratory capacity and maximum strength of trained muscles . Results : After a 12-week training period , subjects in the resistance group showed significant improvement in one-repetition maximum test of hip abductors ( 7.95±3.58 kg ) , quadriceps ( 14±7.18 kg ) , biceps ( 3.37± 2.84 kg ) and pectorals ( 8.75±5.09 kg ) compared with those in the control group ( P<0.001 ) . VO2 max increased ( 0.51±0.40 ) and Beck Depression Scale scores decreased ( -5.40±4.27 ) in the aerobic exercise group compared with the control group , significantly ( P<0.001 ) . Only in hip abductor muscle strength was there a significant increase in the resistance exercise group compared with the aerobic exercise group ( P < 0.05 ) . Conclusion : Both aerobic exercise and resistance exercise result ed in improved performance and exercise capacity in obese women .  While aerobic exercise appeared to be beneficial with regard to improving depressive symptoms and maximum oxygen consumption , resistance exercise was beneficial in increasing muscle strength The effects of exercise training on baroreflex control of sympathetic nerve activity in human hypertension are unknown . We hypothesized that exercise training would improve baroreflex control of muscle sympathetic nerve activity ( MSNA ) and heart rate ( HR ) in patients with hypertension and that exercise training would reduce MSNA and blood pressure ( BP ) in hypertensive patients . Twenty never-treated hypertensive patients were r and omly divided into 2 groups :  exercise-trained ( n=11 ; age : 46±2 years ) and untrained ( n=9 ; age : 42±2 years ) patients . An age-matched normotensive exercise-trained group ( n=12 ; age : 42±2 years ) was also studied . Baroreflex control of MSNA ( microneurography ) and HR ( ECG ) was assessed by stepwise intravenous infusions of phenylephrine and sodium nitroprusside and analyzed by linear regression . BP was monitored on a beat-to-beat basis . Exercise training consisted of three 60-minute exercise sessions per week for 4 months . Under baseline conditions ( before training ) 
    Output:
    
Physical activity seems to enhance cardiovascular fitness during the course of the lifecycle , improve blood pressure , and is associated with decreased prevalence of hypertension and coronary heart disease .
In summary , aerobic exercise ( 30 to 40 minutes of training at 60 % to 85 % of predicted maximal heart rate , most days of the week ) appears to significantly improve blood pressure and reduce augmentation index .
Resistance training ( three to four sets of eight to 12 repetitions at 10 repetition maximum , 3 days a week ) appears to significantly improve blood pressure , whereas combination exercise training ( 15 minutes of aerobic and 15 minutes of resistance , 5 days a week ) is beneficial to vascular function , but at a lower scale .
Aerobic exercise seems to better benefit blood pressure and vascular function