following acute myocardial infarction ( ami ) , recovery of exercise capacity and control of 
 coronary risk factors ( crfs ) are highly critical for prognosis post ami1 . long - term follow - up research has shown that the improvement 
 of exercise capacity is negatively related to future cardiac events2 , and that the improvement of crfs is beneficial for 
 preventing the development of atherosclerosis . supervised , hospital - based phase ii cardiac exercise therapy ( cet ) allows patients to 
 exercise safely following personalized exercise prescriptions and monitoring of crfs . home - based phase iii cet following hospital - based phase ii continues to prepare patients 
 with the ability and confidence to go back to the society as soon as possible . does supervised , hospital - based phase ii cet help patients to achieve levels of exercise 
 capacity equal to those of age - matched normal subjects with patent coronary arteries ? this study used 
 age - matched subjects with patent coronary arteries as a normal - control group ( ncg ) . it was 
 designed to investigate the effects of phase ii and iii cet on exercise capacity , and on the 
 long - term changes in crfs of patients with ami in comparison with age - matched normal 
 subjects . the subjects were patients with ami who had been admitted to tzu - chi medical center , and 
 had undergone coronary angiography ( cag ) for evaluation and treatment of coronary artery 
 lesions . subjects in the experimental group ( eg ) were defined as those who were admitted to 
 hospital after ami , who had participated in the phase ii hospital - based cet and continued to 
 do the phase iii home - based exercise program . subjects in the control group ( cg ) were 
 defined as those who were admitted to hospital after ami but did not participate in the 
 hospital - based phase ii cet because of inconvenience of travel or for personal reasons . after 
 discharge from hospital , eg patients participated in an 8-week cet program designed 
 specifically for each patient by the same experienced physical therapist . there was no 
 coronary artery bypass surgery ( cabg ) given to eg or cg , and no stroke during the period 
 when the study was conducted . another group , the normal control group ( ncg ) , took part in this study . subjects in ncg 
 were whose who had received cag and had proven patent coronary arteries . the reason for cag 
 was either suspicion of coronary artery lesions or pre - examination for possible congenital 
 heart disease . subjects in ncg were age - matched with the subjects with ami in eg and cg . the 
 criterion for age matching was an age within 3  years of the target subject . in order to carefully understand how the home - based exercise was performed , we used a 
 questionnaire to specifically ask subjects the mode , the frequency and duration of exercise . 
 subjects who performed the exercise at least 3 times a week , 30 minutes a time and reached 
 their target heart rate were defined as regular exercise performers . this study was approved by the institutional review board of tzu chi medical center , and 
 written informed consent to participation in the study was obtained from each subject . data for duration of hospital stay , medication , cigarette smoking , hypertension ( htn ) , 
 diabetes mellitus ( dm ) , body mass index ( bmi ) , and fasting plasma serum levels of total 
 cholesterol ( t - chol ) , triglyceride ( tg ) , high density lipoprotein cholesterol ( hdl - c ) and 
 low density lipoprotein cholesterol ( ldl - c ) were collected during hospitalization . severity 
 of disease , such as numbers of stenotic vessels , with or without q wave , and infarcted wall 
 are recorded shown in table 1table 1.test items examined at different times in the normal control group ( ncg ) , 
 exercise group ( eg ) , and control group ( cg)periodacute stagephase ii cetphase iii cetduring admissionbeginningendhome exercisetest itemdiseaseseveritycrfsmedicationmetsmetscrfscrfsmetsmedicationquestionnairegroupncg-*-*------eg**********cg**********crfs , coronary risk factors ; mets , metabolic equivalents ; cet , cardiac exercise 
 therapy . smoking habits , bmi and plasma serum lipids were re - evaluated at the times of 
 the second ( the 2nd test ) and third examinations ( the 3rd test ) . the 2nd and 3rd tests were 
 done at two and five months after discharge from hospital , respectively . crfs , coronary risk factors ; mets , metabolic equivalents ; cet , cardiac exercise 
 therapy all three groups performed the symptom - limited maximal exercise test . subjects blood was 
 collected to measure serum lipids , and anthropometric measurements were taken to calculate 
 bmi . the maximal exercise test was performed by both eg and cg at the beginning of phase ii 
 cet ( the 1st test ) , at the end of phase ii cet ( the 2nd test ) and at 3 months after the end 
 of phase ii cet ( the 3rd test ) . ncg only performed the maximal exercise test at the time of 
 the 1 test . eg and cg patients performed an exercise test on a treadmill ( marquette max1 , milwaukee wi , 
 usa ) . the symptom - limited maximal exercise capacity , expressed in metabolic equivalent 
 ( mets ) , was obtained at the end of the exercise test4 . the ecg was monitored continuously , with hr , bp and rate - pressure 
 product ( rpp ) measured every three minutes during the exercise test , and throughout the 
 five - minute recovery period . the borg scale of rating of perceived exertion ( rpe ) , which is 
 reported to be highly related to maximal oxygen consumption and metabolic demand , were 
 quantified at the same time . we requested the patients to abstain from food , coffee , and cigarettes for a minimum 
 of two hours before each test . they watched a real test to learn how the maximal exercise 
 test is conducted before they performed the test . before the maximal exercise test started , 
 subjects were asked to lie supine for 3 minute so that we could collect measurements of 
 their resting state . the bruce protocol starts at an intensity of 4.6 mets , and increases by 23 mets every 3 
 minutes , and it is considered unsuitable for patients with ami5 . therefore , the modified naughton protocol was adopted as the 1st 
 test for its lower beginning intensity ( 3 mets ) and smaller increment ( 1 met every 3 
 minutes ) . criteria for terminating the 1st exercise test included ischemic signs and/or symptoms , 
 inability to continue the exercise due to fatigue , hr reaching 140 bpm for subjects under 
 40  years old , or hr reaching 130 bpm for subjects over 40  years old . for the 2nd and 3rd 
 exercise tests , criteria for terminating the exercise test included ventricular arrhythmia 
 ( such as ventricular tachycardia and fibrillation ) , st segment depression (  2  mm ) or 
 elevation (  1  mm ) , target hr exceeded ( 90% of the predicted age - adjusted maximal hr ) , or bp 
 over 220 /hg or lower than that determined at the beginning of the 
 test . venous blood samples were collected after a 12-hour fast and used for the determination of 
 lipids ( serum t chol , tg , hdl - c , and ldl - c ) . serum t chol was measured using the enzymatic 
 method and automatic multi - channel chemical analyzer ( 747 automatic analyzer , hitachi , 
 tokyo , japan ) , with the au500/550 t - chol reagent kit ( katayama , osaka , japan ) . serum hdl - c 
 levels were determined using the precipitation method with phosphotungstic acid and 
 magnesium chloride6 . serum ldl - c was calculated using the values of t - chol , tg and hdl - c 
 in the following formula : ldl - c= t - chol  ( ( 1/5tg)+ hdl - c ) phase ii cet began 19(9 ) ( range 639 ) days after ami , and continued for eight weeks at a 
 frequency of two times per week . a warm - up was 
 performed of 1015 minutes of calisthenics ( gentle stretching ) . the main exercise was 
 performed on a treadmill , at an exercise intensity individually prescribed on the basis of 
 baseline data , and the graded treadmill exercise test results . the exercise intensity was 
 gradually increased to a goal of 60 to 79% of the predicted age - adjusted maximum heart rate 
 ( hr ) , and the exercise continued for 20 minutes at an intensity below that which would cause 
 symptomatic or silent ischemia . a cool - down , consisting of ten minutes of calisthenics was 
 also performed . during the period of cet , subjects were often given real - time feedback of hr as exercise proceeded , and 
 learned to monitor their own hr . after phase ii cet finished , phase iii cet programs were 
 designed specifically for each individual , and data were collected for 3 months . during phase iii cet , patients were asked to continue leisure - time physical activities 
 chosen by themselves , with an exercise formula prescribed according to the results of the 
 second of the exercise tests performed at the end of phase ii cet . based on the over - riding 
 emphasis on safety , an exercise type familiar to each individual was chosen for phase iii 
 cet . all eg patients were telephoned by the same investigator each month to provide relevant 
 information and personal support . subjects in cg performed the 1st and 2nd maximal exercise test and were given an exercise 
 prescription based on the results of the tests . subjects were telephoned by the same 
 investigator each month to provide relevant information and personal support , and if needed , 
 to change the exercise intensity to ensure its effectiveness and safety . subjects in cg were advised to exercise regularly after discharge , and were followed for 
 the status of home - based exercise during phase ii and phase iii by questionnaire . two - way repeated measures anova was used 
 to compare the differences in crfs for group effect ( two levels : eg vs. cg ) and training 
 effect ( three levels : 1st test , 2nd test and 3rd test ) with repeated measures of the second 
 factor . significant interaction effects were analyzed using univariate repeated measures and 
 mean comparisons with the lsd method . sixty subjects completed the study , 20 ami patients in eg ( age : 55.310.6  years ) , 10 ami 
 patients in cg ( age : 56.69.5  years ) , and the 30 age - matched normal subjects with patent 
 coronary arteries in ncg ( age : 57.19.6  years ) . table 
 2table 2.hemodynamic parameters , exercise capacity and crfs of each groupvariablesncg ( n=30)eg ( n=20)cg ( n=10)1st test2nd test3rd test1st test2nd test3rd testage ( yrs)57.19.655.310.6 - -56.69.5 - -exercise capacitymets9.42.16.51.510.01.49.71.57.11.28.51.79.81.0hemodynamic parametersrpp*100024.55.119.36.522.34.124.44.921.83.026.03.725.11.6maximal hr140.120.7126.820.4139.913.1149.516.5137.68.1146.516.5148.910.4maximal bp174.422.4149.928.0159.123.6162.822.7159.114.3181.615.2171.018.1borg scale-13.80.814.11.014.30.813.81.013.91.114.51.1crfssmoking ( % ) 3378617562222 dm ( % ) 1722 - -22 - -htn ( % ) 5033 - -36 - -total cholesterol ( mg / dl)179.945.2184.043.4178.430.9196.649.3208.855.4207.557.0207.048.6triglyceride ( mg / dl)178.4110.4164.282.0182.9134.5155.1103.9154.6120.3178.0157.1153.6121.2hdl - c ( mg / dl)43.212.438.110.838.49.142.510.344.910.046.710.346.27.3ldl - c ( mg / dl)103.343.8113.036.4102.835.5124.551.8139.551.1126.260.8133.146.3bmi27.54.325.24.025.24.125.33.925.44.824.23.324.53.6disease severityadmission days-10.45.5 - -8.73.3 - -number of stenotic vessels01.50.8 - -2.00.9 - -ekgq wave ( n)-16 - -8 - -non - q wave ( n)-4 - -2 - -infarcted wallanterior ( n)-8 - -3 - -lower / posterior ( n)-7 - -5 - -lateral ( n)-1 - -0 - -angioplastyphase i ( n)-9 - -5 - -phase ii ( n)-0 - -0 - -phase iii ( n)-2 - -1 - -crfs : coronary risk factors , phase i : acute stage during the admission , phase ii : 
 supervised , hospital - based phase ii cardiac exercise therapy , phase iii : home - based 
 phase iii cardiac exercise therapy . * : significantly lower than ncg ( p<0.05 ) :  : 
 significantly higher than ncg ( p<0.05 ) . : significantly higher than the 1st test ( p<0.05 ) ; & : significantly lower 
 than the 1st test ( p<0.05 ) ;  : significantly higher than the 2nd test ( p<0.05 ) ; 
 # : significant difference between groups ( p<0.05 ) . shows the subjects , anthropometric characteristics . mets , rpp and systolic bp 
 of ncg were significantly higher than those of eg and cg . the percentage of smokers was lower in ncg than in the other two 
 groups . crfs : coronary risk factors , phase i : acute stage during the admission , phase ii : 
 supervised , hospital - based phase ii cardiac exercise therapy , phase iii : home - based 
 phase iii cardiac exercise therapy . * : significantly lower than ncg ( p<0.05 ) :  : 
 significantly higher than ncg ( p<0.05 ) . : significantly higher than the 1st test ( p<0.05 ) ; & : significantly lower 
 than the 1st test ( p<0.05 ) ;  : significantly higher than the 2nd test ( p<0.05 ) ; 
 # : significant difference between groups ( p<0.05 ) . as shown in table 2 , exercise capacity 
 increased 54% ( 6.5 vs. 10.0 mets , p<0.01 ) in eg from the 1st to the 2nd test without any 
 increase in rpe . both eg and cg showed improvements 
 in their exercise capacities ( eg : 6.5 to 9.7 mets ; cg : 7.1 to 9.8 mets ) from the 1st to the 
 3rd test , with improvements of approximately 49% and 38% , respectively . the only significant difference found between eg and cg appeared in systolic bp at the stop 
 point of the maximal exercise test . the 2nd test of hdl - c is significantly higher than the 
 first in eg . there were no differences in blocker , ace - i , diuretics , ca channel 
 blocker and hypolipemic drug use among the groups . in eg , six subjects chose walking as their home exercise , six chose walking / jogging , five 
 chose cycling and one each chose table - tennis , golf and rope skipping . a well designed phase ii 
 cet not only increases the confidence of patients to proceed to phase iii , but also 
 increases compliance and safety during phase iii . mets are 
 calculated from oxygen consumption during exercise and they are easy to convert to the 
 energy consumption for activities . the values of mets are related to genetics , fitness , 
 disease level , age , and gender , and it is one of the best indexes for measuring exercise 
 capacity and cardiovascular function8 . mets and hr / sbp at the point of maximal exercise are highly correlated with left ventrical 
 perfusion and abnormal left ventrical function , which have been proven to be highly 
 important in predicting the prognosis after ami9 . the hemodynamic parameter , rpp , the product of hr and sbp , can be 
 used to evaluate both dynamic and static exercise , and is not influenced by the use of 
 blockers . it is agreed that hr and sbp are increased by the increase of exercise intensity ; 
 however , the degree of increase can be reduced by proper exercise therapy10 . as shown in table 2 , phase 
 ii cet also stabilizes the autonomic nervous system and this is reflected in hemodynamic 
 parameters11 . in the present study , , there was no 
 significant difference in maximal mets , medication or the successful rate of percutaneous 
 coronary intervention . however , between the 1st and the 2nd test , mets increased only in eg 
 and without any change in rpe or rpp . cg did 
 not show an improvement in mets until the 3rd test , while rpp increased in the 2nd test . 
 without the intervention of phase ii cet , the hemodynamic parameters at the maximal mets in 
 cg were poorer than those of eg , especially sbp at the point of maximal exercise . this shows 
 that sustainable regular exercise is helpful for the improvement of mets , and for the same 
 reason , that phase ii cet successfully shortens the natural recovery time of exercise 
 capacity . besides , hr is representative of 
 the physical load exacted on the heart11 . 
 in the present study , 6079% of maximal target hr 
 was determined based on the results of ecg , hemodynamic parameters , exercise capacity and 
 rpe obtained in the symptom - limited maximal exercise test . this helped to ensure the phase iii home exercise program 
 was feasible and safe . cet , based on exercise training , has changed the emphasis from 
 long - term prognosis to short - term effects . however , long - term prognosis is highly correlated 
 to lifelong regular exercise and control of crfs12 . eg chose an exercise activity they were familiar with , and trained 
 at 6079% of their maximal hr in the phase iii home cet . one of the authors called all the 
 subjects every month to ask if they had any difficulty in continuing their exercise program . found that the benefits of a 12-week phase ii cet were not maintained after 
 6 months13 . in the present study , subjects in eg continued to show improvements in their maximal mets until 3 months after the 
 end of phase ii cet . it would have been better to have performed a longer follow - up , but it 
 is difficult to control subjects in long - term clinical studies . the authors wish to further 
 investigate phase iii cet in the future , and hopefully as time proceeds , there will be more 
 subjects and longer periods of follow - up providing data which will allow a better 
 understanding of the mechanism behind the outcomes . we found that maximal mets in cg 
 increased during the phase iii cet and eventually reached the same level as the shown by ncg 
 in the 1st test . using an exercise that subjects are already familiar with can provide fitness and 
 wellbeing . it has been reported to be of physiological benefit14 . according to the questionnaire regarding exercise status , 
 67% of subjects in eg chose to do walking - related activities , such as walking ( 6 subjects ) , 
 and brisk walking/ jogging ( 6 subjects ) . all the subjects in cg chose to walk as their home 
 exercise program ( walking : 7 , brisk walk : 1 , jogging : 1 , and treadmill walking : 1 ) . we found 
 that moderate intensity of home exercise , 3 times a week with a duration of at least 30 
 minutes , was safe , flexible and did not discourage the subjects so it would be well accepted 
 by most people . previous research has shown that walking can prevent recurrence of heart 
 attack and has been used as a secondary prevention method for patients with ami15 . there were no reinfarction or cardiac events in either eg or cg during phases ii and iii 
 cet , and maximal mets were improved and maintained , the effects of exercise therapy on total cholesterol ( t - cho ) and low density lipoprotein 
 ( ldl - c ) are controversial16 , but it is 
 agreed that exercise is mostly beneficial for controlling triglyceride no matter how long 
 the training period is . possible mechanisms for this include lowering the synthesis of very 
 low density lipoprotein ( vldl ) , speeding up catabolism , and greater metabolism of free fatty 
 acids to provide energy source for skeletal muscles16 . we note that neither eg nor cg had high triglyceride to begin 
 with , and this is likely why there was not much exercise effect on triglyceride . possible 
 reasons why sustainable walking training increased high density lipoprotein cholesterol 
 ( hdl - c ) by 2030% are overactive lipoprotein lipase and lecithin - cholesterol - acyltransferase 
 induce greater catabolism of vldl , and lower the activity of hepatic lipase . in the present 
 study , there was no significant change in hdl - c although it did increase in eg . in taiwan , the impact of crfs on cad is similar to that reported for the united states and 
 japan17 . especially , hdl - c has been 
 shown to be highly correlated with cad18 . hdl - c is influenced by gender , age , medication , smoking , obesity , and the parameters of the 
 exercise prescription19 . nicotine increases 
 epinephrine and norepinephrine in the circulation speeding up the development of 
 atherosclerosis . compared to non - smokers , smokers have 5.7% lower hdl - c and quitting smoking 
 can make hdl - c more normal20 . our results show that the cessation of smoking rate increased at 
 the 2nd test , and continued to increase at the 3rd test . however , a significant increase in 
 hdl - c was only seen in the 3rd test . this shows that quitting smoking alone is not enough to 
 explain the increase in hdl - c . our results show that the maximal mets increased in eg 
 during the phase ii cet , but bmi did not change . this could explain why hdl - c did not 
 increase during the phase ii cet . in addition to smoking and bmi , the intensity , duration , and frequency of exercise during 
 cet also affect hdl - c22 , 23 . mendoza et al . showed that 312 months of exercise are 
 needed to elicit an increase in hdl - c16 . berg et al . showed that at least 3 months is required to improve hdl - c . therefore , the 
 reason that hdl - c did not improve during the phase ii cet might be because exercise , 2 times 
 a week for a total of 8 weeks is insufficient . in contrast , exercise , 2 times a week 
 elicited a difference in exercise capacity in the present study . after phase ii and phase 
 iii cet possible reasons for this 
 could be that exercise capacity continued to improve and the cessation of smoking rate was 
 maintained , with no change in bmi . it is also possible that the combination of phase ii and 
 iii cet was beneficial for maintaining cessation of smoking and bmi , creating an environment 
 in which an increase of hdl - c could occur . hdl - c in cg did not change with improvement of 
 exercise capacity , despite the fact that bmi was maintained and there was a stop in the 
 smoking cessation rate . the small sample size could be another reason why no change in hdl - c 
 was observed . the authors hope to enroll more subjects in the future to better investigate 
 the temporal change of hdl - c during phase iii cet . one limitation of our research was the relatively large number of days before exercise was 
 initiated after myocardial infarction . we recognize that this makes the interpretation of 
 the training effect more difficult . however , considering the substantial area and rugged 
 travel conditions of hualien county and the difficulty of making transportation arrangements 
 for some patients , this was perhaps the best result achievable . it is our hope that this 
 limitation is offset by the fact that this research presents a contribution to clinical 
 medicine from an under - represented corner of taiwan and of the world . this study pioneered the enrolment of subjects with patent coronary arteries as a normal 
 control group , and we believe it will provide valuable insights for clinical medicine . in conclusion , a supervised , hospital - based phase ii cet performed twice a week for 8 weeks 
 shortened the recovery time of exercise capacity in patients with ami . successful and 
 regular exercise during phase iii home - based cet maintained the exercise capacity gains of 
 phase ii , improved hdl - c , and also continued to increase exercise capacity in the control 
 group .
[ purpose ] to investigate the effects of phase ii cardiac exercise therapy ( cet ) on 
 exercise capacity and changes in coronary risk factors ( crfs ) of patients with acute 
 myocardial infarction ( ami ) . 
 [ subjects ] thirty male subjects with ami were divided into an 
 experimental group ( eg ) and a control group ( cg ) . 
 another 30 age - matched subjects with 
 patent coronary arteries served as a normal - control group ( ncg ) . 
 [ methods ] subjects in eg 
 ( n=20 ) trained using a stationary bicycle for 30  min at their target heart rate twice a 
 week for 8 weeks . 
 exercise capacity was defined as the maximal metabolic equivalents 
 ( mets ) that subjects reached during the symptom - limited maximal exercise test . 
 hr , bp and 
 rpp were recorded . 
 subjects in eg and cg received exercise tests and screening for crfs at 
 the beginning of , end of , and 3 months after phase ii cet , while subjects in ncg 
 participated only in the 1st test . 
 [ results ] mets of cg did not improve until the 3rd 
 test , while rpp at the 2nd test showed a significant increase . 
 however , eg showed 
 increased mets at the 2nd test without increase of rpp , and increased their high density 
 lipoprotein cholesterol ( hdl - c ) during the follow - up period between the 2nd and 3rd tests . 
 [ conclusion ] phase ii cet shortens the recovery time of exercise capacity , helps to 
 maintain the gained exercise capacity and increases hdl - c in phase iii .