J. Exp. Biomed. Sci. 2013, 19(3): 254~260 pissn : 1738-3226 Original Article The Effects of Karvonen Exercise Prescription in Acute Coronary Artery Disease Patients Reaching Age-Predicted Maximal Heart Rates with Exercise Stress Test Chul Kim and Young-Joo Kim 1, Department of Rehabilitation Medicine, Sanggye-Paik Hospital, Seoul 139-707, Korea The purpose of this study was to survey the effects of Karvonen exercise prescription in coronary artery disease patients reaching age-predicted maximal heart rates with the exercise stress test on hemodynamic responses and cardiorespiratory fitness. The subject group was comprised of acute coronary syndrome (ACS) patients, who were divided into the maximal heart rate (MHR) group that included those who completed the test with their heart rates reaching the number of 220-age and the maximal dyspnea (MD) group that included those who could not continue the test due to respiratory difficulty and were asked to stop the test. Both groups had the exercise stress test before and after the experiment. In the exercise stress test before the experiment, the exercise prescription intensity of Karvonen was set at the target heart rates of 50~85% with a six-week exercise monitoring arrangement. As a result, there were no interactive effects in rest heart rate (RHR) according to time and group, but interactive effects were observed in maximal heart rate (MHR) (P=0.000). Both rest systolic blood pressure (RSBP) and rest diastolic blood pressure (RDBP) had no interactive effects according to time and group. Maximal systolic blood pressure (MSBP) showed significant interactive effects according to time and group (P=0.017). Maximal diastolic blood pressure (MDBP) showed no interactive effects according to time and group, while maximal rate pressure product (MRPP) showed significant interactive effects according to time and group (P=0.003). Maximal time (MT) had no interactive effects according to time and group. VO 2max and maximal metabolic equivalent (MMET) showed significant interactive effects according to time and group (P=0.000, P=0.002, respectively), whereas maximal respiratory exchange ratio (MRER) and maximal rating of perceived exertion (MRPE) showed no interactive effects according to time and group. The exercise test that was discontinued as the subjects reached the predicted maximal heart rates considering age did not reach the maximal exercise intensity and accordingly showed low exercise effects when applied to Karvonen exercise prescription intensity. That is, the test should keep going by monitoring cardiac events, MRER and MRPE until the heart rates exceed the predicted MHR by up to 10~12 even after the subject reaches the predicted MHR considering age in the exercise stress test. Key Words: Exercise stess test, Coronary artery disease, Age-predicted maximal heart rates 서 관상동맥질환은고지혈증, 당뇨, 흡연, 고혈압같은위험요인에의해혈관내피세포의손상과염증반응을일으 * Received: April 3, 2013 / Revised: September 16, 2013 Accepted: September 16, 2013 Corresponding author: Young-Joo Kim. Department of Rehabilitation Medicine, Sanggye-Paik Hospital, Seoul 139-707, Korea. Tel: +82-950-1114, e-mail: christian6801@hanmail.net C The Korean Society for Biomedical Laboratory Sciences. All rights reserved. 론 키며이로인해동맥내의경화반증식으로발생된다 (Libby et al., 2002). 경화반은증식될수록불안정한상태가되며결국은파열되면서혈전생성에의한관상동맥혈류의완전폐색으로사망에이르게한다. 관상동맥질환이발병된이후치료는약물이나관상동맥스텐트삽입술로혈류의재관류가우선이며향후재발방지를위해지속적인약물요법, 식이요법, 운동요법을병행해야한다 (Ades, 2001; Leon et al., 2005). 이중운동요법은관상동맥질환자들에있어혈중지질개선 (Lavie & Milani, 1995; Lavie et al., 2009), 인슐린감수성의증가 (Perderson et al., 1980), - 254 -
생존률증가 (Vanhees et al., 1994) 같은유익한효과들을가져다주는것으로보고되었다. 심혈관질환자의운동요법중운동강도는전통적으로 Karvonen에의한 40~85% {( 최대심박수-안정시심박수 ) 목표심박수강도 % + 안정시심박수 } 의목표심박수범위안에서이루어져왔다 (Karvonen et al., 1957). 운동처방강도를결정하기위해허혈성심혈관질환자들의사전운동부하검사는매우중요하며일반적으로증상제한운동부하검사 (symptom limited GXT) 를실시한다. 증상제한운동부하검사란운동부하검사중환자의흉통, 어지러움, 더이상진행하기힘든호흡곤란, 다리의불편함같이환자의요구에의해검사를중단하는경우이다 (Fletcher et al., 2003). 그러나그외환자의심근허혈이나치명적부정맥같은심장사건과혈압및심박수의변동에따라운동부하검사를중단해야하는혈역학반응들은절대적중단과상대적중단같은기준들이잘정립되어있다 (Gibons et al., 2002). 이중운동부하검사를중단해야하는조건중최대심박수가 220-연령에도달하거나호흡교환율 (RER) 이 1.1~ 1.13에도달하였을경우최대운동능력에도달한것으로간주하여검사를중단할수있다 (ACSM, 1998). 운동부하검사의종료기준은환자스스로가중단을요청하기전안전을고려한것이기때문에이러한규정준수는매우중요하다. 그러나최대심박수예측공식 (220-연령) 은연령과절대적상관관계가있는것으로보고되었지만개인간 10~12박정도차이를보인것으로알려져있다 (Londeree & Moeschberger, 1984). 이러한편차가있기때문에심혈관질환자들에게최대운동상태인호흡교환율같은지표를고려하지않고최대예상심박수에도달한것만으로운동부하검사를중단시켰을경우실제운동처방강도를설정하였을때더적은운동강도로설정될수도있을것이다. 일반적으로심혈관질환자들에게서유산소운동은최대산소섭취량을 11~36% 정도증가시킨다고하였다 (Ades, 2001). 이러한결과들은운동의기간이나운동강도같은요인들에영향을받기때문에달라질수있지만아직까지운동부하검사에서종료된다양성을고려하여실험된연구는전무하다. 즉호흡교환율이최대에도달하지않은상태에서예상최대심박수에도달한것만으로검사를중단한심혈관질환자들의경우운동효과가다르게나타나는지검증할필요가있다. 본연구의목적은운동부하검사에서최대예상심박수에도달하여검사를중단한관상동맥질환자에게 Karvonen 운동처방강도범위에서트레이닝을시켰을경우이들에게나타나는혈역 학반응과심폐체력의변화에미치는영향에대해서실제적으로구명하기위함이다. 연구대상 Table 1. Demographic characteristic of subjects Variable MHRG (n=25) MDG (n=25) P-value Age (yrs) 58.24 ± 11.30 55.40 ± 9.96 0.351 Sex (male/female) 19/6 21/4 0.480 Height (cm) 164.88 ± 7.44 164.32 ± 6.81 0.782 Weight (kg) 65.78 ± 9.83 68.96 ± 7.79 0.211 BMI (kg/m 2 ) 24.05 ± 2.63 25.56 ± 2.74 0.053 Diagnosis UA 10 (40%) 10 (40%) AMI 15 (60%) 15 (60%) 1.000 DM 2 (8%) 1 (4%) 0.552 Medication Aspirin 25 (100%) 25 (100%) Plavix 23 (92%) 25 (100%) 0.149 BB 0 (0%) 0 (0%) CCB 5 (20%) 4 (16%) 0.713 ACEI 15 (60%) 16 (64%) 0.771 ATII 2 (8%) 2 (8%) 1.000 Nitrates 19 (76%) 23 (92%) 0.123 Niuretics 1 (4%) 1 (4%) 1.000 Statin 16 (64%) 14 (56%) 0.564 MHRG, maximal heart rate group; MDG, maximal dyspnea group; BMI, body mass index; UA, unstable angina; AMI, acute myocardial infarction; DM, diabetes mellitus; BB, beta-blocker; CCB, calcium channel blocker; ACEI, angiotensin converting enzyme inhibitor; ATII, angiotensin II receptor antagonist. 재료및방법 이연구는인제대학교생명윤리위원회에승인을받았으며환자의정보와실험에대한동의를얻어연구되어졌다. 이연구대상자들은 S병원응급실을내원한불안정협심증및급성심근경색증으로내과적인시술 ( 경피적관상동맥성형술 ) 과약물처치를받은급성관상동맥증후군 (Acute coronary syndrome: ACS) 환자들은총 98명이었다. 연구대상그룹의분류는심박수가 220-나이에도달하여검사를마친집단 (MHR군; maximal heart rate group, n=25) 과더이상호흡곤란으로운동부하검사를수행하지못한집단 (MD군; maximal dyspnea group, n=25) 으로구분하였다 (Table 1). 두집단간의신장, 체중, 성별, 약물, - 255 -
병명등신체적특징과임상적특성간에는차이가없었다. 운동부하검사시기는급성관상동맥질환으로내과적인관상동맥중재술을받은후약물복용을시작한지일주일정도지난후시행하였다. 이들대상자중심각한심장사건 ( 심근허혈, 부정맥 ), 좌심실박출률 (ejection fraction) 이 40% 이하의심부전증, 운동부하검사를받기어려운만성폐쇄성폐질환과근골격계질환, 운동부하검사중다리의통증으로중단한경우, 발병전 1개월이상지속적인운동경험이있는환자, 그리고심박수에영향을미치는베타차단제와칼슘채널차단제 (non-dihydropyidines 계통 ) 를복용중인환자는본연구에서제외시켰다. 그러나칼슘체널차단제중심박수에영향을미치지않는 dihydropyridines 계통은포함시켰다. 측정항목및방법신체계측측정 : 신장은 STDK-AD (Shintokyo Desshikizai Co., Japan) 를이용하였으며, 체중은 Autobody Weight (YK-150N, Korea) 기기를이용하여계측하였다. 운동부하검사 : 운동부하검사는수정된브루스프로토콜 (modified Bruce protocol) 을이용하여점진적증상제한운동부하검사 (symptom limited GXT) 를실시하였다. 운동부하검사를통하여안정시및최대운동까지심박수 (HR; heart rate), 혈압 (BP; blood pressure), 자각도 (RPE: rating of perceived exertion), 호흡교환율 (RER: respiratory exchange ratio), 산소소모량 (oxygen consumption, VO 2 ) 을기록하였다. 검사는 12채널실시간운동부하검사용심전도검사기 Q4500 및호흡가스분석기 QMC (Quinton, USA), 자동혈압및맥박측정기 (Model 412, USA) 그리고운동부하검사용트레드밀 (Medtrack ST 55, Quinton, USA) 를사용하였다. 운동부하검사검사종료는환자가더이상운동부하검사를수행하지못하는흉통의증가, 피로, 호흡곤란, 파행, 하지근육경련외 Q파없는 ST 분절의 1 mm 이상상승, 허혈증상을동반하면서수축기혈압이 10 mmhg 이상하강하는경우, ST 분절의 1 mm 이상 horizontal 하강과 downslope 하강일경우, 그리고수축기와이완기혈압이 250/115 mmhg 이상일경우, 220-연령에도달한경우, 호흡교환율 (RER) 이 1.15 이상인경우등 ACC/AHA 지침에의해종료했다 (Gibobons et al., 2002). 운동자각도는 6-20 Borg's scale을이용하였으며운동부하검사전운동자각도에대한설명을충분히하였으며힘든정도가변할때마다 Borg's scale을즉시표현하게하였다. 운동프로그램절차 : 연구대상자들은급성관상동맥증후군 (acute coronary syndrome; ACS) 으로내원하여경피적관상동맥중재술 (percutaneous coronary intervention; PCI) 을받은환자를대상으로하였으며, 운동강도는 [( 최대심박수 -안정시심박수 ) % 강도 + 안정시심박수 ] 을적용하였다 (Karvonen et al., 1957). 목표심박수 % 강도는첫 2주는 60% 강도에서수행하다가 3주째부터 4주끝날때까지 70%, 5주째부터 6주끝날때까지 85% 강도로시행하였다. 운동중무선송수신심전도감시기 (Q-Tel ECG telemetry system, Quinton Instrument Co., Boston, USA) 로심박수와심전도 ( 심근허혈, 부정맥 ) 를감시하였고혈압은운동시작전과운동종료마지막 2분전에측정하였다. 운동순서는준비운동 10분 ( 스트레칭 5분후가볍게걷기 5분 ), 본운동 30분 ( 트레드밀과고정식자전거 ), 정리운동으로 10분 ( 가볍게걷기 5분후스트레칭 5분 ) 으로구성하였다 (Fletcher 등, 2003). 본운동은트레드밀 (Quinton MED-TRACK SR 60, Quinton Instrument Co., Boston, USA) 을시행한후 3분간가볍게걸으면서휴식한후다시고정식자전거 (Quinton CORIVAL 400, Quinton Instrument Co., Boston, USA) 에서각각 15분씩시행하였다. 운동강도증강은 85% 에도달할때까지 5분간격으로 3차례로나누어운동강도를증가시켰다. 6주간의감시하에수행된운동프로그램을마친후운동부하검사를다시수행하여재평가하였다. 자료처리방법 : 본연구에서얻어진결과는 SPSS/PC 17.0 통계프로그램을이용하여모든항목에대해평균 (Mean) 과표준편차 (SD) 를산출하였다. 집단간평균차이와시기간평균차이를검증하기위하여 two-way repeated ANOVA 분석을통해상호작용효과를검증하였다. 상호작용효과가있을경우주효과검증을위해독립및종속 t-test를실시하였다. 그리고성별, 진단명, 약물복용의집단간빈도차이에대한분석은교차분석 (χ 2 test) 으로실시하였으며모든통계적유의수준은 P<0.05로설정하였다. 결과 BMI (body mass index) 와혈역학반응 BMI와혈역학반응에대한연구결과는 (Table 2) 에나타난바와같다. 체질량지수 (BMI) 와안정시심박수 (RHR) 는운동전후시기와집단간상호작용효과가없 - 256 -
Table 2. Changes of BMI and hemodynamic response Variable Group Pre Post P-value BMI RHR (beats/min) MHR (beats/min) RSBP RDBP MSBP MDBP MRPP MHRG 24.05 ± 2.63 24.10 ± 3.15 0.243a 0.115b MDG 25.56 ± 2.74 25.14 ± 2.89 0.136c MHRG 80.16 ± 11.22 79.64 ± 14.71 0.211a 0.171b MDG 77.20 ± 13.87 73.24 ± 13.70 0.336c MHRG 156.36 ± 11.20 154.20 ± 12.59 0.036a 0.080b MDG 145.68 ± 13.05 153.24 ± 12.32 * 0.000c MHRG 124.32 ± 14.25 121.12 ± 10.60 0.624a 0.054b MDG 116.48 ± 15.73 117.52 ± 9.76 0.338c MHRG 82.72 ± 9.17 82.84 ± 8.72 0.727a 0.158b MDG 80.36 ± 7.51 79.36 ± 8.31 0.657c MHRG 186.92 ± 21.73 179.92 ± 22.75 * 0.596a 0.267b MDG 174.52 ± 22.02 179.04 ± 23.21 0.017c MHRG 80.76 ± 12.89 85.44 ± 12.26 0.073a 0.207b MDG 78.68 ± 11.21 79.84 ± 11.65 0.274c MHRG 29091.64 ± 4447.27 27799.84 ± 4507.94 * 0.736a 0.056b MDG 25416.88 ± 4062.74 27026.16 ± 4353.89 * 0.003c BMI, body mass index; MHRG, maximal heart rate group; MDG, maximal dyspnea group; RHR, rest heart rate; MHR, maximal heart rate; RSBP, rest systolic blood pressure; RDBP, rest diastolic blood pressre; MSBP, maximal systolic blood pressre; MDBP, maximal diastolic blood pressure; MRPP, maximal rate pressure product. a, time; b, group; c, time group. *: pre vs post (P<.05), : MHRG vs MDG (P<.05) 었다. 최대심박수 (MHR) 에서는운동전후시기와집단간상호작용효과가있었다 (P=0.000). 즉 MHR군에서운동전 156.36 ± 11.20 에서운동후 154.20 ± 12.59로유의한차이가없는반면 MD군에서는운동전 145.68 ± 13.05에서운동후 153.24 ± 12.32로유의하게증가하였다. 안정시수축기혈압 (RSBP) 과이완기혈압 (RDBP) 은시기와집단간유의한상호작용효과가없었다. 최대수축기혈압 (MSBP) 은운동전후시기와집단간유의한상호작용효과가있었다 (P=0.017). 즉 MHR군에서운동전 186.92 ± 21.73에서운동후 179.92 ± 22.75로유의하게감소한반면 MD군에서는운동전 174.52 ± 22.02에서 179.04 ± 23.21로유의한차이가없었다. 최대이완기혈압 (MDBP) 에서는운동전후시기와집단간유의한상호작용효과가없었다. 최대심근부담율 (MRPP) 는운동전후시기와집단간유의한상호작용효과가나타났다 (P= 0.003). 즉 MHR군에서운동전 29091.64 ± 4447.27에서운동후 27799.84 ± 4507.94로유의한감소를보였으며 MDG에서는운동전 25416.88 ± 4062.74에서운동후 27026.16 ± 4353.89로유의한증가를보였다. 심폐체력과 MRER 및 MRPE 반응심폐체력과 MRER 및 MRPE 반응에대한연구결과는 (Table 3) 에나타난바와같다. 최대운동수행시간 (MT) 은운동전후시기와집단간유의한상호작용효과는없었다. VO 2max 는운동전후시기와집단간유의한상호작용효과가있었다 (P=0.000). 즉 MHR군에서운동전 28.48 ± 5.91에서운동후 30.00 ± 6.90로증가하였으며 MD군에서도운동전 29.44 ± 5.51에서운동후 34.18 ± 6.68로더크게증가한것으로나타났다 (P=0.000). 또한최대대사당량 (MMET) 에서도운동전후시기와집단간유의한상호작용효과가나타났다 (P=0.002). 즉 MHR군에서운동전 8.19 ± 1.84에서운동후 8.54 ± 2.01로유의한증가를보였으며 MDG에서도운동전 8.48 ± 1.51 에서운동후 9.83 ± 1.92로더높은증가를보였다 (P= - 257 -
Table 3. Changes of cardiopulmornary fitness, MRER and MRPE Variable Group Pre Post P-value MT (sec) VO 2max (ml/kg/min) MMET MRER MRPE MHRG 762.16 ± 206.04 859.80 ± 159.92 0.000a 0.093b MDG 828.84 ± 149.60 941.68 ± 118.09 0.597c MHRG 28.48 ± 5.91 30.00 ± 6.90 * 0.000a 0.144b MDG 29.44 ± 5.51 34.18 ± 6.68 * 0.000c MHRG 8.19 ± 1.84 8.54 ± 2.01 * 0.000a 0.117b MDG 8.48 ± 1.51 9.83 ± 1.92 * 0.002c MHRG 1.04 ± 0.07 1.05 ± 0.07 0.192a 0.000b MDG 1.10 ± 0.04 1.12 ± 0.06 0.669c MHRG 15.00 ± 1.82 15.28 ± 1.42 0.714a 0.000b MDG 17.32 ± 0.74 17.24 ± 0.66 0.158c Values are mean ± SD. MHRG, maximal heart rate group; MDG, maximal dyspnea group; MT, maximal time; MMET, maximal metabolic equivalent; MRER, maximal respiratory exchange ratio; MRPE, maximal rating of perceived exertion. a, time; b, group; c, time group. *: pre vs post (P<.05), : MHRG vs MDG (P<.05) 0.002). 최대호흡교환율 (MRER) 과최대자각도 (MRPE) 는운동전후시기와집단간유의한상호작용효과가나타나지않았다. 고찰본연구는관상동맥질환자를대상으로운동부하검사상최대예상심박수에도달하여검사를중단한집단 (MHRG) 과호흡곤란으로더이상운동을수행하지못한집단 (MD군) 을대상으로 6주간의유산소운동효과를조사하였다. 우선혈역학반응에서최대심박수 (MHR), 최대수축기혈압 (MSBP), 최대심근부담률에서시기와집단간유의한상호작용효과가나타났다. 운동부하검사에서 220-연령에해당하는예상최대심박수에도달할수있다는의미는첫째, 환자의운동유발성심근허혈과부정맥을진단하기위한목적이나환자의운동능력평가목적으로충분하며, 둘째, 심혈관질환자에게서예상최대심박수에도달후더이상진행하지않는것은환자의안전을위하여검사를중단해야하는요인중하나이다 (ACSM, 2009). 그러나반대로베타차단제를복용하는환자를제외하고최대심박수가예상최대심박수의 85% 이하로낮은심박수를보이거나심박수의증가가현저히낮을수록심혈관질환자의생존율도낮아진다 (Kligfield et al., 2006; Lauer et al., 2005). 본연구에서운동전후인위적으로예상최대심박수에도달하여운동부하검사를중단한 MHR군은최대심박수에서운동전후차이가없었으나자발적인최대운동부하검사를수행한 MD군은운동후거의예상최대심박수가까이증가한것으로나타났다. 이러한원인으로 MHR군에서는운동전예상최대심박수에도달하여운동부하검사를인위적으로중단하였고운동후에도마찬가지조건에서대부분운동부하검사가중단되었다. 결국환자의최대운동능력과상관없이운동부하검사가예상최대심박수에도달된조건만으로검사를중단시킨다면이들에게서최대운동상태가정확히측정될수없으며운동처방을설정할때낮게설정될수있음을알수있다. 반면 MD군에서는환자가예상최대심박수에도달하기전에환자의호흡곤란으로운동부하검사중단을요청했기때문에최대한운동능력을수행할수있었고여기서처방된운동강도설정은 6주간의운동후더높은심박수까지증가된것으로나타났다. 즉이러한증거를가장잘설명할수있는결과로 MD 군에서 MHR군보다높은최대산소섭취량 (VO max2 ) 의증가를보인것은주목할만한결과이다. 산소섭취량 (VO 2 ) 은심박출량 (cardiac output) 과동정맥간의산소농도차이에의해결정되며심박출량은 1회박출량 (stoke volume) 과심박수에의해결정된다 (ACSM, 1995). 유산소운동은최대심박수와 1회박출량을증가시켜최대심박출량과최대산소섭취량을증가시킨다 (Fletcher et al., 2003). 이러한효과가더욱충분하게나타나려면운동강도의안전한계로 Karvonen 등 (1957) 의공식에서제시하 - 258 -
는것처럼여유심박수 (HRR; heart rate reserve) 나여유산소섭취량 (VO 2 R) 의 85% 까지를허용범위로제시하고있으며, 심혈관질환자일경우안전한계를 80~85% 까지허용하도록하고있다 (ACSM, 2009). 그러나운동부하검사상 MHR군에서최대자각도 (MRPE) 가운동전 15.00 ± 1.82에서운동후 15.28 ± 1.42로 " 힘들다 " 의느낌에서중단되어졌고최대호흡교환율 (MRER) 도최대도달강도범위인 1.1~1.13 (ACSM, 1998) 이아닌 1.04 ± 0.07에서 1.05 ± 0.07로차이를보이지않았다. 반면 MD군에서의 MRPE은운동전 17.32 ± 0.74에서운동후 17.24 ± 0.66로 " 매우힘들다 " 로나타났고 MRER도최대강도도달범위인운동전 1.10 ± 0.04에서운동후 1.12 ± 0.06 로최대까지도달된것으로나타났다. 이러한결과는실제생리학적인신체반응이최대에도달하지않은상태에서예상최대심박수만으로운동부하검사를중단하였다는것은실제로최대강도로도달하지못했기때문에운동강도가처음부터낮게설정될수밖에없다. 즉운동강도가처음부터낮게설정되어운동에참여하였기때문에본연구결과에서나타난것과같이 MHR군의 VO 2max 이증가는생리학적으로최대로수행된 MD군보다효과적이지못했다. 220-연령에의해예상최대심박수를결정할때개인간의표준편차는 10~12박정도차이를보인다 (Londeree & Moeschberger, 1984) 따라서최대예상심박수에도달하더라도 RER값이 1.15에도달하지못했거나심장사건과혈역학반응에특별한이상반응이없다면이런환자들은운동효과를더높이기위해 10~12박까지의검사종료범위를늘려야할것이다. VO 2max 는운동선수들에게는선수들의심폐체력을평가할수있는지표로사용되지만심혈관질환자들에게는향후생존율과관련이깊다. VO 2max 를안정시산소섭취량인 3.5 ml/kg/min로나눈값을 1 MET (metabolic equivalents) 이라는용어로사용한다. 1 MET는안정시 3.5 ml/kg/min의산소를섭취하며최대운동시 1 MET가증가할때마다심장사의감소와생존율증가와관련있다. Laukkanen 등 (2004) 은대규모연구에서관상동맥질환자와건강인에게서 1 MET 증가는치명적심장사의 28~51% 가감소하였으며비치명적심장사에서는 17~29% 평균감소를보여최대산소섭취량이장례치명적심장사건에강력한예후평가요인으로이용될수있다고하였다. 또한 Dorn 등 (1999) 은운동을통해 1 MET 증가할때마다 10% 의사망률감소를가져왔으며, Myers 등 (2002) 도 1MET 증가할때마다 12% 의생존이증가하는것으로보고하였다. 이러한결과들을바탕으로본연구에서나타난최대대사당량 (MMET) 의증가는향후생존율에있어서도예상최대심박수에도달하여운동부하검사를종료한 MHR군이최대로수행된 MD군보다더낮을것으로예상되어진다. 따라서운동부하검사에서최대예상심박수를기준으로개인적인최대운동량에도달했다는호흡교환율이나최대자각도같은요인을배제한상태에서검사를중단하는것은낮은운동강도를설정할수있게되며이낮은운동강도에서운동을진행한환자는운동효과를얻는데있어최대로수행한집단보다약간의제한이있을것으로사료된다. 과거운동강도설정에있어심혈관질환자일경우최대안전한계를 80~85% 까지제시하고있지만, 최근연구결과들에의하면최대운동부하검사상심장사건같은위험성이없는심혈관질환자들에게도인터벌트레이닝과함께안전한계의허용범위를최대산소섭취량의 90~95% 까지증가시키는것이심폐능력과혈관내피세포기능, 염증반응같은요인들을개선하는데더효과적인것으로보고되고있다 (Moholdt et al., 2011; Munk et al., 2009; Wisløff et al., 2007) 이러한선행연구들을보더라도호흡교환율이나운동자각도를고려하지않고예상최대심박수에도달하였다고하여검사를중단하는것은충분한심폐체력과그밖에유익한운동의효과를보는데상대적으로낮은효율성을보일것으로생각된다. 운동부하검사의중단에있어안전을위하여설정된절대적중단요인과상대적중단요인의안내조건들을반드시지켜져야한다 (Gibons et al., 2002). 그러나이러한고위험군환자들을제외하고최대예상심박수에도달하더라도심장사건이없으면서최대호흡교환율 (MRER) 과최대자각도 (MRPE) 에미치지않았다면예상최대심박수에서 10~12박까지지켜보면서진행해야할것이다. 결론적으로개개인마다다른체력을예상최대심박수로제한하여운동부하검사를중단한다면운동처방설정이더낮게책정되어운동효과에제한이따르는것으로나타났다. 따라서최대운동부하검사를유도하여개인에따른정확한운동처방을설정하는것이환자들의향후예후개선을위해도움이될것이다. REFERENCES Ades PA. Cardiac rehabilitation and secondary prevention of coronary heart disease. NEJM. 2001. 345: 892-902. American College of Sports Medicine. ACSM' s Guidelines for - 259 -
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