Exercise Science Vol.26, No.4, November 2017: 239-247 https://doi.org/10.15857/ksep.2017.26.4.239 ISSN(Online) 2384-0544 ORIGINAL ARTICLE 유산소성및무산소성최대운동후혈중젖산생성및제거율비교 김창선 1, 김지연 1, 김효진 1, 김지원 1, 민석기 2, 박동호 3 1 동덕여자대학교체육학과, 2 한국스포츠개발원스포츠과학실, 3 인하대학교스포츠과학과 The Comparisons of Blood Lactate Concentration and Removal Rate after Aerobic and Anaerobic Maximal Exercise Chang-Sun Kim 1, Ji-Yeon Kim 1, Hyo-Jin Kim 1, Ji-Won Kim 1, Seok-Ki Min 2, Dong-Ho Park 3 1 Department of Physical Education, Dongduck Women s University, Seoul; 2 Department of Sport Science, Korea Institute of Sport Science (KISS), Seoul; 3 Department of Kinesiology, Inha University, Incheon, Korea PURPOSE: This study examined blood lactate concentration and removal rate after aerobic and anaerobic maximal exercise test in sedentary middle-age women. METHODS: Ten sedentary middle-age women (aged 52.7±3.3 years) were performed after aerobic (Aero group) and anaerobic maximal exercise (Anaero group) test, VO2max test and Wingate test, by cross-over repeated design with biweekly. The blood was collected from cardinal veins at before and immediately after test for measurement of lactate and lactate dehydrogenase (LDH). And it was also collected from fingertip at before, immediately after and then recovery 5, 10, 15, 30 minutes after each maximal test. Lactate removal rate (%) were calculated by bellow formulas: ={1-[(Lactate at 30 minutes. after test-resting lactate)/increased lactate]} 100. RESULTS: The blood lactate concentration from fingertip after both maximal test significantly increased immediately after test (p<.001 respectively), and maintained until recovery of 30 minutes. after test (p<.01, p<.001 respectively) in spite of there were no significant differences between both Aero and Anaero group. There were also no significant differences between both test groups in blood maximum lactate (p=.090) and increased lactate concentration (p=.058). No significant differences were also observed between the two groups in lactate removal rate (p>.05). There are positive correlationship among muscle mass and blood maximum lactate and increased lactate concentration (p<.01). CONCLUSIONS: These results indicate that exercise was performed by anaerobic at end of test in VO2max test. Also suggested that the greater muscle mass may induce the more lactate accumulation, thereby increasing lactate tolerance. Key words: Aerobic, Anaerobic, Maximal exercise, Blood lactate, LDH 서론 지금까지젖산 (lactate) 은무산소성운동중에생성되어근육수축을방해하는피로물질로알려져있다 [1]. 국내에서도 Kim et al. [2] 의연구를통하여젖산은운동피로를발생시키는가장중요한물질로보고되면서많은연구자들이피로물질로오해하고있는경우가많다. 이로인해최근까지도혈중젖산을보다빨리제거하면피로회복이빨리된다는생각을앞세워, 젖산제거를보다빠르게진행하기위한운동강도 [3] 또는마사지방법 [4] 등에대한연구가진행되고있는실정이다. 그러나 lactate shuttle theory를발표한 Brooks et al. [5] 의연구이래로젖산은피로물질이아니라는연구들이다수보고되면서기존의학설이수정되고있다. 즉, 젖산은피로물질이아니라세포내의산증 (acidosis) 으로부터근섬유를보호하는보호물질 [6] 로, 포도당이분해되는과정의일시적인상태 [7,8] 이며, 더빨리에너지를공급할수있는에너지원이라고보고되고있다 [9]. 더나아가서운동에의한적응을조절하는신호분자로정의 [10] 되고있으며, 운동후의젖산의섭취가글리 Corresponding author: Dong-Ho Park Tel +82-32-860-8182 Fax +82-32-860-8188 E-mail dparkosu@inha.ac.kr Keywords 유산소, 무산소, 최대운동, 혈중젖산, LDH Received 23 May 2017 Revised 29 May 2017 Accepted 28 Jun 2017 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Copyright 2017 Korean Society of Exercise Physiology 239
Vol.26, No.4, November 2017: 239-247 코겐의농도와젖산수송체 (monocarboxylate transporters, MCT) 를증가시켜운동능력을향상시킨다 [11] 고까지보고되고있다. 따라서젖산에대하여지금까지알려져있던피로물질이라는인식에서벗어나운동시운동능력을향상시킬수있는유용한물질로서의접근이필요하다고생각된다. 한편, 젖산은신진대사및운동중해당과정에서생성된피루브산 (pyruvate) 이젖산탈수소효소 (lactate dehydrogenase, LDH) 의작용을통하여생성된다. 일반적으로근육에서의젖산생성속도가젖산제거속도를초과할때농도가증가하며, 젖산감소속도는 MCT [12], LDH 의농도 [13] 및조직의산화능력 [14] 등많은요인에의해좌우된다. 안정시혈중젖산농도는 0.5-2 mmol/l 이지만, 격렬한운동시에는 20 mmol/l 이상으로상승한다 [15]. 안정시에는무산소성에너지대사는잘일어나지않아근육에서는젖산생성이안될것이라생각되기쉽지만, 미토콘드리아가없는적혈구의대사와높은해당능력을갖는근섬유의효소활성에의해서젖산이생성되기때문에안정시에도혈중에소량이생성되고있다 [16]. 또한강한무산소성운동이나스프린트파워운동과같이짧은시간에많은에너지가필요할경우에는근육에서의해당과정을통한젖산생성이증가되고 [17], 혈중으로배출되어혈중농도가급격하게상승하며 [18], 운동시혈중젖산수치의증가는운동강도와비례하는것으로알려져있다 [19]. 또한유산소성운동능력지표로젖산역치가이용되어왔으며 [20,21], 운동시또는회복시의혈중젖산제거능력은운동수행능력과정의상관관계를나타낸다고보고되고있다 [22]. 이처럼혈중젖산대사특성을이용하여운동수행능력을평가하는방법으로이용되고있으며, 트레드밀을이용한유산소성최대운동부하 [23] 부터 30초-2분등의단시간고강도의무산소성최대운동부하 [4] 까지다양한운동부하방법이적용되고있다. 그러나이러한운동부하방법및운동시간에따라서혈중젖산반응은다르게나타날가능성이있으나이를직접검토한연구는미흡한실정이다. 따라서본연구에서는정기적인운동경험이없는좌업중년여성을대상으로하여동일피험자에의한반복측정을실시하였다. 즉, 최대산소섭취량 (VO 2max) 테스트에의한유산소성최대운동부하와 Wingate 테스트에의한무산소성최대운동부하를실시하고, 운동에의해생성된혈중젖산생성량및젖산제거율을비교검토하여유산소성최대운동과무산소성최대운동에따른혈중젖산대사에있어서의차이를밝히는것을목적으로하였다. 연구방법 1. 연구대상자및실험절차연구대상자는자율적으로실험에참여를희망하는좌업중년여성 중, 48-59 세 ( 평균연령 52.7± 3.3 세 ) 10 명을무작위로선정하였다. 본실 험은 cross-over repeated design 에의하여, 유산소성최대운동으로점증 부하에의한최대산소섭취량 (VO 2max) 테스트와무산소성최대운동 으로 Wingate 테스트를 1 주일기간을두고총 2 회실시하였다. 실험시 작에앞서대상자에게 D 대학교의실험에대한규정에따라, 실험내용 및피해점, 실험중지의자유등에대하여자세히설명한후동의를얻었 다. 1 차실험당일대상자들은실험실에도착하여신장, 체중및신체조 성 (InBody 620, Biospace, Korea) 등의신체적특성을측정한후, 5 명씩 무작위로나누어 VO 2max 테스트와무산소성최대운동으로 Wingate 테스트를실시하였다. 1 주일후에 1 차시측정하지않았던테스트를동 일한방법에의하여진행하였다. 연구기간동안식사와신체활동을평 소생활을유지하도록하며, 활발한운동이나신체활동은금지하였다. 대상자들의신체적특징및각테스트결과는 Table 1 과같다. 2. 채혈및혈액분석 대상자들은 8 시간이상의공복상태에서실험실에도착한후 30 분간 안정을취하고나서상완정맥에서안정시 (resting) 혈액을채혈하였다 (5 ml). 그후각각의최대운동테스트를수행하고테스트종료직후 Table 1. The characteristics of the subjects Variables (n = 10) Anthropometric characteristics Age (yr) Height (cm) Weight (kg) BMI (kg/m 2 ) Body composition TFM (kg) %FM (%) TMM (kg) SMM (kg) FFM (kg) Aerobic index from VO2max test VO2max (ml/kg/min) HRmax (beat/min) Running time (sec) VE (L/min) METs (score) Anaerobic index from Wingate test Total work (kpm) Total work (kpm/kg) Mean power (watt) Mean power (watt/kg) Peak power (watt) Peak power (watt/kg) Fatigue index (%) Mean ± SD 52.70 ± 3.30 155.09 ± 3.57 59.18 ± 4.90 24.65 ± 2.25 19.89 ± 3.97 33.39 ± 4.65 37.10 ± 2.62 22.01 ± 2.93 39.29 ± 2.76 34.29 ± 4.10 169.30 ± 10.80 419.00 ± 48.62 68.16 ± 8.74 9.80 ± 1.17 668.96 ± 85.25 11.36 ± 0.99 221.52 ± 26.82 3.77 ± 0.35 262.12 ± 41.53 4.44 ± 0.44 25.10 ± 9.17 Values are mean ± SD. BMI, body mass index; TFM, total fat mass; %FM, % fat mass; TMM, total muscle mass; SMM, skeletal muscle mass; FFM, fat free mass; VO2max, maximal oxygen consumption; HRmax, maximum heart rate; VE, minute ventilation; METs, metabolic equivalents. 240 Chang-Sun Kim, et al. Comparisons of Blood Lactate after Aerobic and Anaerobic Maximal Exercise
https://doi.org/10.15857/ksep.2017.26.4.239 (maximum) 다시채혈하였다. 정맥에서채취한혈액은전문혈액분석회사에의뢰하여젖산및젖산탈수소효소 (lactate dehydrogenase, LDH) 의농도를분석하였다. 한편테스트종료후회복시의혈중젖산 (lactate) 변화를관찰하기위하여, 정맥혈 (vein) 과동일한안정시 (pre) 에손가락끝 (fingertip) 에서채혈침에의하여채혈하였으며, 종료직후 (0 minutes), 5분 (5 minutes), 10분 (10 minutes), 15분 (15 minutes), 30분 (30 minutes) 후에동일한방법으로채혈하였다. Fingertip 샘플은 0.1 ml 모세관에옮겨젖산전용측정기 (YSI1500, Instruments, USA) 로젖산을측정하였다. 젖산증가량및젖산회복률은다음식을이용하여계산하였다. 젖산증가량 (mmol/l) = 최대젖산농도 안정시젖산농도 ; 젖산제거율 (%) = {1- [( 회복 30 minute 젖산농도-안정시젖산농도 )/ 젖산증가량 ]} 100. 3. VO 2max 테스트최대유산소성운동을부하하고, 유산소성관련지표를측정하기위하여점증부하에의한 VO 2max 테스트를실시하였다. 점증부하방법은운동경험이없는중년여성인점을감안하여한국스포츠개발원에서개발한 KISS 프로토콜을토대로변경하여실시하였다. 프로토콜은 0:00-1:00까지경사도 0%, 3.0 km/hr로시작하여, -3:00까지경사도 2%, 4.8 km/hr로하였으며그이후부터는 2분간격으로경사도는 2%, 속도는 1.2 km/hr를증가시켜측정하였다. VO 2max의결정은대상자스스로가더이상운동을지속하지못하거나, 운동강도가증가하더라도심박수또는산소섭취량이유의하게증가하지않을때, 호흡교환률 1.10 이상, 운동자각도 (RPE) 17 이상중 2가지이상이충족된경우로하였다 [24]. 트레드밀 (Technogym run race 10, Technogym, Italy) 과호흡가스분석기 (Cosmed, Quark b 2, USA) 를사용하였다. 4. Wingate 테스트 Wingate 테스트는전용측정기 (Excaliber Sport, Sweden) 를이용하여 2분이상사전운동후 30초간최대운동부하를실시하였다 [25]. 페달의상대적부하는피험자체중의약 0.05% (kp) 로하였다. 측정시에는대상자들이자의적으로최대무산소성능력을발휘하도록격려하였으며, 측정결과로부터 fatigue index 및 total work, peak power, mean power를환산하였다. 5. 자료분석및통계방법모든자료는 SPSS 22.0 통계프로그램을이용하여요인별평균과표준편차, 표준오차를산출하였다. 두가지최대운동부하후 30분간의회복시의변화를비교하기위하여이원변량반복측정분산분석 (2-way repeated measure ANOVA) 을실시하여 2가지최대운동방법 (VO 2max 테스트와 Wingate 테스트 ) 에따른시기간 (6시기: 운동전, 운동직후및회복 0, 5, 10, 15, 30분후 ) 의차이 (2 by 6) 를분석하였다. ANOVA 검사후주효과에유의한차이가있을경우시기간의사후검증은일원변량분산분석 (one way ANOVA) 를이용하였다. 기타변인의집단간에차이의검토는 paired t-test를실시하였다. 통계적유의수준은 p <.05로설정하였다. 연구결과 1. 최대운동부하전후의혈청젖산변화 Table 2에는두집단간의최대운동부하전후의손가락끝 (fingertip) 혈액의평균젖산변화를각측정시기별로나타냈다. 이원변량반복측정분산분석결과시기간에유의한차이가나타났다 (p <.001). 사후검증결과유산소성최대운동부하집단 (Aero) 에서는운동전 (pre) 과비교하여운동직후 (0 minute) 에최대치를나타냈으며 (p <.01), 회복 10분이후에최대치에비교하여유의하게감소하였다 (p <.001). 무산소성최대운동부하집단 (Anaero) 에서는운동전 (pre) 과비교하여운동직후에증가하였으나 (p <.001), 회복 5분후에운동직후보다더증가 (p <.05) 하여최대치를나타냈다 (p <.01). 회복 15분이후에는최대치에비교하여유의하게감소하였다 (p <.01). Fig. 1에는두집단의운동전 (pre) 을기준으로한상대적변화율을나타냈다. Aero 집단의최대치는 0 minute 에나타나안정시 (mean ±SD) 의 6.50 ± 2.79 배까지증가하였으며, Anaero 집단의최대치는 5 minutes에나타나안정시의 5.98 ± 2.44 배까지증가하였다. Table 2. The comparison of fingertip lactate concentration after each maximal test between aerobic and anaerobic group Group pre Recovery times (min) 0 5 10 15 30 Aero 0.94 ± 0.15 5.40 ± 0.45 a 5.23 ± 0.49 a 4.40 ± 0.41 a,c 3.92 ± 0.37 a,c 2.69 ± 0.25 a,c G.041 (.843) T 32.09 (.001) Anaero 0.98 ± 0.13 4.47 ± 0.22 b 5.06 ± 0.26 b,d 4.85 ± 0.38 b 4.02 ± 0.31 b,e 2.85 ± 0.16 b,d,e G T 2.451 (.174) Mean±SD. Aerobic maximal test was performed by VO2max test and anaerobic maximal test was performed by Wingate test. Aero, aerobic maximal test group; Anaero, anaerobic maximal test group. a p<.001 vs. pre VO2max test; b p<.001 vs. pre Wingate test; c p<.001 vs. 0 minute after VO2max test; d p<.05 vs. 0 minute after Wingate test; e p<.01 vs. 5 minutes after Wingate test. source F (p) 김창선외 유산소성및무산소성최대운동후혈중젖산 241
Vol.26, No.4, November 2017: 239-247 2. 최대운동부하전후의정맥과 fingertip 혈액에서의젖산변화 Table 3 에는두집단간의최대운동부하전후의정맥과 fingertip 혈 액에서의젖산변화를나타냈다. 최대젖산농도 (Maximum lactate) 는 Aero 집단에서는대부분 0 minute 에나타났으나, 2 명은 5 minutes 에 나타났다. Anaero 집단의최대젖산농도는각각 2 명은 0 minute 에, 4 명 Lactate change rate (ratio) 8 7 6 5 4 3 2 1 0 aaa bbb Aerobic max test aaa bbb, d Max test pre 0 5 10 15 30 Recovery time (min) Fig. 1. The comparison of change rate of fingertip lactate concentration at recovery period between aerobic and anaerobic maximal test. Values are mean±se. An aerobic maximal test was performed by VO2max test and anaerobic maximal test was performed by Wingate test. aaa p<.001, aa p<.01 vs. pre VO2max test; bbb p<.001, bb p<.01 vs. pre Wingate test; ccc p<.001 vs. 0 minute after VO2max test; d p<.05 vs. 0 minute after Wingate test, eee p<.001, ee p<.01 vs. 5 minutes after Wingate test. bbb aaa, ccc Anaerobic max test aa, ccc bbb, ee bb, eee aa, ccc 은 5 minutes에, 4명은 10 minutes에나타났다. 정맥에서의안정시젖산농도는 Anaero 집단이높았으나 (p <.05), 최대젖산농도에서는두집단간의유의한차이는나타나지않았다. 정맥의젖산증가량에서는 Aero 집단이 Anaero 집단에비교하여약 1.3배높은경향을나타냈으나통계적유의차는나타나지않았다 (p =.058). 한편, fingertip에서의안정시및최대치, 증가량, 회복 30 minutes의젖산농도, 젖산제거율은두집단간의유의한차이는나타나지않았다. 젖산탈수소효소 (LDH) 에있어서도두집단간의유의한차이는나타나지않았으며, 두집단내의안정시와최대치의비교에있어서도유의한차이는나타나지않았다. 3. 정맥과 fingertip 혈액간의젖산농도비교 Table 4에는정맥과 fingertip 혈액간의젖산농도비교를나타냈다. 정맥과 fingertip 혈액의젖산농도를비교하기위하여 Aero 집단과 Anaero 집단을더하여산출하였다 (n =20). 안정시에는두집단간의유의한차이는나타나지않았으나, 최대젖산농도에서는정맥이 fingertip에비교하여약 1.14배유의하게높았다 (p <.01). Table 3. The comparisons of vein and fingertip lactate index between aerobic and anaerobic group Variables Drawing blood from Vein (n=10) Resting lactate (mmol/l) Maximum lactate (mmol/l) Increased lactate (mmol/l) Resting LDH (U/L) Maximum LDH (U/L) Drawing blood from fingertip (n=10) Resting lactate (mmol/l) Maximum lactate (mmol/l) Increased lactate (mmol/l) Lactate at recovery 30 min (mmol/l) Lactate removal rate (%) Aero 0.65 ± 0.13 6.88 ± 1.96 6.23 ± 1.99 197.6 ± 21.5 207.6 ± 19.6 0.94 ± 0.51 5.64 ± 1.62 4.70 ± 1.45 2.69 ± 0.85 63.16 ± 16.13 Group Anaero 0.94 ± 0.21 5.73 ± 1.24 4.79 ± 1.23 207.2 ± 27.3 231.0 ± 38.3 1.01 ± 0.44 5.40 ± 0.89 4.38 ± 0.88 2.93 ± 0.48 56.47 ± 13.82 Values are mean±sd. Aero, aerobic maximal test group; Anaero, anaerobic maximal test group; LDH, Lactate dehydrogenase. Increased lactate volume and lactate removal rate (%) were calculated by bellow formulas: Increased lactate volume (mmol/l) = Maximum lactate - Resting lactate Lactate removal rate (%) = {1-[(Lactate at 30 minutes after test-resting lactate)/increased lactate]} 100. Table 4. The comparison of lactate index in draw point between vein and fingertip (n=20) t -2.567 1.897 2.163-1.244-1.460 -.194.619.904 -.528.891 p.030.090.058.245.178.851.551.389.610.398 Variables Vein (n=20) Draw point Fingertip (n=20) Resting lactate (mmol/l) 0.79±0.23 0.96±0.44-1.488.153 Maximum lactate (mmol/l) 6.23±1.63 5.47±1.22 3.446.003 Values are mean ± SD. Aero, aerobic maximal test group; Anaero, anaerobic maximal test group. t p 242 Chang-Sun Kim, et al. Comparisons of Blood Lactate after Aerobic and Anaerobic Maximal Exercise
https://doi.org/10.15857/ksep.2017.26.4.239 Table 5. The relationship among lactate index from both vein and fingertip, body composition, aerobic and anaerobic capacity index Body composition BW TMM SMM FFM TFM %FM BMI Aerobic index from VO2max test VO2max HRmax Running time VE METs Anaerobic index from Wingate test Total work Total work/bw Mean power Mean power/bw Peak power Peak power/bw Fatigue index Vein Fingertip Max. lactate Inc. lactate Max. lactate Inc. lactate.051.336.512.358 -.186 -.302 -.251.729*.661*.839**.351.730*.253.470.510.784**.245.493 -.129.067.322.523.343 -.156 -.270 -.224.700*.668*.853**.377.701*.266.363.549.722*.313.489 -.062.475.660*.618.677*.115 -.147.095.296.580.668*.596 -.049 -.264 -.048 Lactate removal rate Max. lactate, maximal lactate concentration; Inc. lactate, increased lactate concentration; BW, Body weight; TMM, total muscle mass; SMM, skeletal muscle mass; FFM, fat free mass; TFM, total fat mass; %FM, % fat mass; BMI, body mass index; VO2max, maximal oxygen consumption; HRmax, maximum heart rate; VE, minute ventilation; METs, metabolic equivalents. **p<.01; *p<.05..403.748*.772**.310.404.024.157.259.472 -.003.115 -.328.535.783*.824**.210.536.273.515.416.666*.167.374 -.176.686*.407.148.392.574.376.584 -.610.040 -.171.160 -.610 -.211 -.525 -.011 -.201.003 -.176.003 4. 젖산관련지표와신체조성, 유산소성지표, 무산소성지표와의상관관계 Table 5에는정맥과 fingertip 혈액에있어서의젖산관련지표와신체조성, 유산소성지표, 무산소성지표와의상관관계를나타냈다. 신체조성과의관계에있어서는체중은젖산제거율과정적상관관계를나타냈으며 (p <.05), 총근육량및골격근량, 제지방량은 fingertip의최대젖산농도와정적상관관계 (p <.05) 를, 골격근량과 fingertip의젖산증가량과정적상관관계를나타냈다 (p <.05). 유산소성지표와의관계에있어서는 VO 2max와 HRmax, Running time, METs는정맥의최대젖산농도및젖산증가량과정적상관관계를나타냈다 (p <.05, p <.01). 또한, HRmax와 Running time은 fingertip의최대젖산농도및젖산증가량과정적상관관계를나타냈다 (p <.05, p <.01). 무산소성지표와의관계에있어서는 Mean power/bw은정맥의최대젖산농도및젖산증가량과정적상관관계를나타냈다 (p <.05). 또한, Mean power/bw은 fingertip의젖산증가량과정적상관관계를나타냈다 (p <.05). 논의 본연구에서는유산소성최대운동후와무산소성최대운동후에 생성된혈중젖산생성량및젖산제거율을비교검토하였다. 그결과유산소성 (Aero) 최대운동후의정맥혈중젖산농도는 6.88 ±1.96 mmol/l로무산소성 (Anaero) 최대운동후의 5.73 ± 1.24 mmol/l와통계적인유의한차이는없는것으로나타났다. 6-7분지속되는 VO 2max 테스트와 30초로끝나는 Wingate 테스트에의한젖산생성량에는큰차이가없는것으로나타났다. VO 2max 테스트시, 운동강도가낮을때에는유산소성대사에의해에너지생산이진행되므로젖산의생성은거의일어나지않지만운동강도가높아지면서에너지수요가증가하게되고이에따라포도당분해가증가하면서혈중젖산농도도증가한다. 일반적으로무산소성경로를통한근육의 ATP 공급능력은동적운동의마지막약 3분동안에최대로나타나며, 건조근육중량 (dm) 당약 370 mmol/kg을생산하는것으로알려져있다. 또한무산소성해당과정을통하여약 80%, 포스포크레아틴 (PC) 분해를통하여약 16%, 저장 ATP를통하여약 4% 공급되는것으로알려져있다 [26]. VO 2max 테스트의초 중반에는운동강도가그다지높지않지만운동후반부에급격히증가하게되고피험자는더이상그운동부하를유지하지못하는운동피로가유발된다. 이러한테스트의특성이반영되기때문에 VO 2max 테스트와 Wingate 테스트사이의젖산생성량에는큰차이가없었던것으로판단된다. 김창선외 유산소성및무산소성최대운동후혈중젖산 243
Vol.26, No.4, November 2017: 239-247 또한, 최대혈중젖산농도는운동강도는물론이고대상자나운동방법에따라다르게나타나며최대 25 mmol/l까지증가하는것으로알려져있다 [15]. Smith et al. [27] 의연구에서는평균연령 22.5세의건강한남성을대상으로점증부하자전거에르고미터최대운동후의혈중젖산농도가약 9 mmol/l이었다고보고되고있으며, 우리나라마라톤선수의경우본연구와유사한 VO 2max 테스트를실시한결과 12.7± 2.7 mmol/l까지증가하는것이보고되고있다 [23]. 본연구에서최대약 6.9 mmol/l이었던점을감안하면일반젊은남성의약 77%, 남자마라톤선수의약 50% 의젖산밖에생성하지못하는것으로나타났다. 한편, Simon et al. [28] 은운동능력이좋을수록젖산확산율이높아운동종료후혈중젖산농도가빠르게증가한다고보고하고있고, 이러한혈중젖산의빠른증가는트레이닝으로인한모세혈관의밀도증가에따라서교환면적이증가하기때문이라고알려져있으며, 이러한모세혈관의밀도증가는젖산생성위치로부터혈관으로의확산거리를단축시켜젖산교환능력이향상되기때문으로알려져있다 [29]. 즉트레이닝에의해체력이좋아질수록혈중으로의젖산이빠르게증가하는것을의미한다. 본연구에서의피험자들의 VO 2max는약 34.3 ± 4.1 ml/kg/min 정도로, 위의 Smith et al. [27] 의연구의피험자들 42.8 ± 2.0 ml/kg/min, 마라톤선수약 70.9 ±1.0 ml/kg/min 이었던점을고려해보면, 각각 80.1% 와 48.4% 의체력수준에불과하고, 젖산생성비율과유사한비율이라는것을알수있다. 즉, 심폐체력수준에따라젖산생성량이달라질가능성이있으며추가연구를통하여검토할사항이라생각된다. 또한, 두집단의최대운동후의혈중젖산농도를살펴보면, 두집단사이의통계적인유의차는없었지만 Aero가 Anaero에비교하여약 1, 2배높은경향을나타내고있으며 (p =.090), 젖산증가량또한약 1.3배높은경향을나타내고있다 (p =.058). 통계적으로유의차는없으나대상자수에의해영향을받으므로 0.1 이하의유의수준은주의깊게검토할필요가있다고판단된다. 즉, Aero와 Anaero의최대운동시모든대상자들은자신의최대노력으로운동을수행하였기때문에, 두집단의최대젖산농도의차이는무산소성으로실시한운동시간, 즉최대로노력한시간에의한차이라고판단된다. 본연구에서 Aero의경우운동시간은평균 419.0 ± 48.6초이었으며, Anaero는 30초이었다. Aero의경우운동시작 60초이후부터는 120초간격으로부하강도를높였으므로평균적으로 4번째스테이지이후부터최대운동을수행하였을것이다. 최대로노력한시간을정확하게알수는없지만, 평균약 7분정도의운동시간을고려할때적어도 1분이상은최선의노력으로고강도의운동을수행하고있는것으로판단되었다. 반면 Anaero는테스트초반에가장높은파워가도출되는특성을반영하여테스트를시작하여 10-15초내외까지최대운동을수행하고나머지시 간까지그것을유지하는운동을수행하였을것이라고판단된다. 이러한운동특성은 fingertip 젖산농도에반영되어, Aero에서는운동직후 (0 minute) 에최대치를나타내는것에반하여 Anaero에서는회복 5분후에최대치를나타내는것으로판단된다. 즉, Aero에서는운동시간이긴만큼운동에따른근육에서의젖산생성이혈액에그대로반영되어, 운동종료직후나타나는것에반하여, Anaero에서는운동시간이짧은만큼근육에서생성된젖산이혈액에반영되기까지시간적으로지연되는것을의미하는것이라판단된다. Withers et al. [30] 의연구에서도 30-90초정도의단시간고강도 all out 운동시의혈중최대젖산수치는운동종료후몇분정도뒤에나타난다고보고하고있으며, Goodwin et al. [15] 도 30초에서 120초정도지속하는 all out 최대운동시에는혈중최대젖산수치가운동종료후 3분에서 8분사이에나타난다고보고하고있다. 한편, 지금까지운동후의젖산생성은운동강도에비례한다고알려져있다. Kelleher et al. [31] 의연구에서도전통적인근력트레이닝 (TRAD) 과여러세트를번갈아가며고강도로작용-길항근육의근력트레이닝을수행하는상호적슈퍼세트 (SUPERs) 를부하한후검토한결과, SUPERs 집단의운동후초과산소섭취량 (excess postexercise oxygen consumption, EPOC) 증가와함께혈중젖산도 TRAD 집단 (3.8± 0.6 mmol/l) 에비교하여 SUPER 집단 (5.1 ± 0.9 mmol/l) 에서유의하게증가하게증가하는것을보고하고있다. 최근의 Jones et al. [32] 과 Park et al. [33] 의연구에서도근력트레이닝집단 (ST) 과근력트레이닝후에지구력트레이닝 (ST-END), 지구력트레이닝후에근력트레이닝집단 (END-ST), 트레이닝없는대조집단 (CON) 으로나누어검토한결과, 운동후 1시간뒤의 END-ST와 ST의혈중젖산농도는 ST-END 에비교하여유의하게높은것으로나타나마지막에수행한운동강도가젖산농도에영향을미치는것을제안하고있다. 그러나 Thornton et al. [34] 의연구에서는저항성운동강도를저강도와고강도로나누고운동량을일정하게하여운동후의혈중젖산농도를검토한결과, 두집단간의유의한차이가없음을밝히면서, 혈중젖산의생성은운동강도보다는운동량 (work volume) 에비례한다는것을보고하고있다. 본연구에서도단순히운동강도로만비교할때에는 Anaero가 Aero에비교하여운동강도는더높았다. 그러나혈중젖산농도는운동강도가낮았던 Aero 후에더높은경향을나타냈으며, 젖산농도는어느수준을넘는운동강도에서는최대로발휘한운동시간과같이운동량에영향을받을가능성이시사하는것이라생각된다. 혈중젖산농도는 fingertip에비교하여정맥에서더높게나타날가능성이시사되었다 (Table 4). 젖산의생성은사용되는근육의세포질에서생성되어혈류를타고혈중으로배출된다. 정맥혈은다양한조직으로부터생성된물질들이포함되기때문에채혈부위에따라서혈중젖산농도는달라질수있고, 가능한동맥혈에서젖산농도를측정하는 244 Chang-Sun Kim, et al. Comparisons of Blood Lactate after Aerobic and Anaerobic Maximal Exercise
https://doi.org/10.15857/ksep.2017.26.4.239 것이바람직하다 [35]. 그러나동맥혈의경우, 운동시에빠르게채혈하는것이힘들기때문에보통정맥혈이나 fingertip에서채혈하고있다. 그러나 Foxdal et al. [36] 은 10명의남성을 20-25분간최대하운동수행전후의혈장및정맥혈, fingertip 혈액에서각각젖산농도를비교한결과, 각각유의한차이가있기때문에직접비교해서는안된다고보고하였다. 또한혈중젖산농도가 4.0 mmol/l이되는운동강도를비교한다른연구 [37] 에서는유의하게혈장 < fingertip < 정맥혈혈액순으로나타나는것을보고하고있다. 즉, 운동강도가같다고가정할때정맥혈에비교하여 fingertip의젖산농도가더높다는것을의미하는것으로, 본연구결과와같이최대강도의운동후의젖산농도는정맥혈이 fingertip 혈액보다더높게나타날수있다는것을의미한다. 따라서, 운동후의젖산농도의비교는채혈부위별로나누어검토해야할것이라판단되었다. 혈중젖산탈수소효소 (LDH) 은운동종료후 Aero와 Anaero는각각약 5.0% 와 11.4% 정도증가하는경향을보였으나유의한차이는나타나지않았다 (Table 3). 젖산농도는두집단모두운동전에비교하여운동후에 6.1-10.6배증가한것에비교해서는 LDH의변화는미비한편이라할수있다. LDH는근조직내에서피루브산을젖산으로변화시킬때작용하는효소로서젖산증가와동반하여 LDH도증가할것이라생각했지만유의한변화는나타나지않았다. 한편, LDH는일반혈액검사에서는근손상지표로사용된다. Koch et al. [38] 은저항운동과혈중근손상지표와관련한리뷰논문에서저항성운동이근육조직에있어세포골격및수축미세섬유, 기저판등에서국소적인손상을초래하며, 이때젖산탈수소효소및크레아틴키나제 (CK), 미오글로빈등이혈액으로방출된다고제안하고있다. 또한 Neto et al. [39] 은남성군인을대상으로저강도의저항운동과혈류제한조건에따른근손상과산화적스트레스를검토한연구에서도 LDH의증가를근손상지표로사용하고있다. 추후운동방법이나인원수등을조정하여추가적으로검토할필요가있을것이라생각된다. 한편, 두집단의회복 30 minutes의젖산농도에서는유의한차이는나타나지않았다. 젖산제거율에있어서도 Aero와 Anaero는각각약 63% 와약 56% 까지회복되는것으로나타났으나두집단간의유의한차이는나타나지않았다. 이로써평소에운동을수행하지않은중년여성이라할지라도최대운동후약 30분정도안정을취하면약 60% 까지젖산이제거되는것으로나타났다. 서론에서도언급한바와같이지금까지젖산회복에대한연구는운동에의하여빨리젖산을제거하는것이피로회복에효과적이라고보고하고있다 [3,4]. Neric et al. [40] 의단시간최대운동후생성된젖산제거에미치는운동효과를검토한연구에서도운동종료후 20분에수동적인안정상태는약 4.1 mmol/l이었지만, 최대하수영회복은약 1.6 mmol/l까지감소하여능동적으로운동을수행하는것이젖산제거에효과적이라고보고하고 있다. 즉, 운동후혈중젖산이높은상태에서회복처치로써유산소운동을수행하면젖산의간에서의포도당신생 ( 일부분 ) 과피루브산으로의전환을통한크렙스사이클의에너지원으로이용 ( 대부분 ) 모두가높아지기때문이다 [9]. 일반적으로젖산제거능력은지구성운동수행능력이나상대적으로더고강도로운동을지속할수있는능력과관련이있다 [41]. 같은조건에서젖산제거능력이좋다고한다면, 운동막바지의고강도운동시의근육내의젖산축적을줄일수있고, 더높은강도에서의내성이증가하는것이므로운동수행력의예측인자로활용할수있을것이다. 이를평가하기위한전제조건은회복시의운동강도는일정해야한다. 본연구에서는회복기에운동을수행하지않고안정상태에서제거율을비교하였다. 동일인에의한실험이었던만큼거의비슷한회복률을보였다고판단된다. 한편, 체중과젖산제거율은정적상관관계가있는것으로나타나, 체중이많을수록젖산제거가빠를가능성이있는것으로나타났다. 그러나근육량및골격근량과젖산제거율간관련성이없는것으로나타나, 이에대해서는추가적인검토가필요할것으로판단된다. 총근육량및골격근량, 제지방량은 fingertip의최대젖산농도와, 골격근량은 fingertip의젖산증가량과정적관련성이있는것으로나타나근육량이많을수록젖산축적량이많을것으로생각되었다. Beneke et al. [42] 의연구에의하면 Wingate 테스트후의젖산농도는평균연령약 12세소년, 약 16세청소년, 약 27세성인에서각각약 10.2, 12.7, 13,7 mmol/l 를나타낸다는보고와같이, 연령증가와함께전신의근육량이증가하고이에따라서최대젖산치도증가하는것이라고판단된다. 또한, VO 2max와 HRmax, Running time, METs 등의유산소성지표는정맥또는 fingertip의최대젖산농도및젖산증가량과정적상관관계를나타냈다. 즉유산소운동중막바지에는무산소성에너지대사비율이증가하게되어젖산생성량이증가하고, 축적되는젖산에대한내성이높을수록유산소성운동수행력도높다는것을반증하는것이라고생각된다. McLellan & Jacobs [43] 의운동강도와근육글리코겐이용률을외측광근 (m. vastus lateralis) 의생검으로검토한연구에의하면근육글리코겐이용은 %VO 2max와 %OBLA와높은정상관이있는것으로알려져있다. 이는유산소성운동수행력이높을수록글리코겐이용율이높고, 근육중의젖산농도도높을가능성을시사하는것이다. 무산소성지표인 Mean power/bw은정맥또는 fingertip의최대젖산농도및젖산증가량과정상관을나타내, 평균파워의경우도젖산내성과관련성이높다는것을의미하는것이라고판단되었다. 결론 정기적인운동경험이없는좌업중년여성을대상으로 VO 2max 테스트와 Wingate 테스트에의한유산소성최대운동과무산소성최대 김창선외 유산소성및무산소성최대운동후혈중젖산 245
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