Original Article 운동과학, 2015 년, 제 24 권제 4 호. Exercise Science, 2015, Vol.24, No.4. http://dx.doi.org/10.15857/ksep.2015.24.4.399 pissn 1226-1726 eissn 2384-0544 숙련자와비숙련자의벤치프레스운동중에강도별근활성도, 근피로도및반복횟수의비교 전현식 1), 이호성 1) * 1) 단국대학교일반대학원운동의과학과 Hyun-Sik Jeon, Ho-Seong Lee (2015). Comparison of Varying Intensities on Activation and Fatigue of Muscle, and Number of Repetitions during Bench Press in Trained and Untrained Men. Exercise Science, 24(4): 399-405. PURPOSE: This study tested the hypothesis that low-intensity resistance exercise would not be different in activation and fatigue of muscle and number of repetitions between trained and untrained men, but high-intensity resistance exercise would more decrease muscle activity, increase muscle fatigue and lower number of repetitions in the untrained men when compared with those in the trained men. METHODS: Eight trained males (TG) and 8 healthy untrained males (UTG) participated in this study. TG had undertaken a continual, resistance weight training program at least twice a week for longer than 6 months using bench press exercises. UTG had not been previously involved in a formal resistance weight training program over the last year. All subjects were tested for 1RM strength, and then performed maximal number of repetitions at 3 different intensities (60, 80, and 90% of 1RM) during bench press. EMG signals were recorded from the pectoralis major, deltoid anterior, and triceps brachii for maximal voluntary contraction (%MVC) and median frequency (MDF). RESULTS: %MVC of pectoralis major was significantly higher at 60 (p=0.010), 70 (p=0.039) and 85% (p=0.000) of 1RM in the UTG than the TG. Number of repetitions was significantly lower with 3 sets (p=0.027) at the 60% of 1RM and, 2 (p=0.012) and 3 sets (p=0.049) at the 70% of 1RM in the UTG than the TG. However, no significant changes were found in %MVC of anterior deltoid and triceps brachii and MDF of pectoralis major, anterior deltoid and triceps brachii. CONCLUSIONS: These results did not support the hypothesis, and differences in activation and fatigue of muscle between the trained and untrained men were important in number of repetitions and recruitment ratio of agonist and synergist rather than exercise intensity. Key words: bench press, muscle activation, muscle fatigue, number of repetitions 주요어 : 벤치프레스, 근활성도, 근피로도, 반복횟수 Ⅰ. 서론 스포츠현장에서근전도 (electromyogram) 는근육의활동, 즉근활성도 (muscle activity) 및근피로도 (muscle fatigue) 를분석하는데주로사용되며 [1,11], 또한근육에서발생하는 ( 근수축 ) 활동전위 (action potential) 의증폭을기록하는데이용되고있다 [17]. 저항운동프로그램구성은운동의형태, 세트수, 휴식시간, 기간및강도등으로구분되며 [9,20], 그중에서저항운동의강도에관한많은연구들이활발히진행되고있다 [10,14,22,26,27,30]. 일반적으로저항운동강도의설정은최대반복횟수또는 one repetition maximum(1rm) 을기반으로이루어지며 [29], 1RM 측정 을통한운동강도의설정은 1RM 간접추정식을이용하는것보다더욱정확하고효과적으로목적에맞는운동강도를설정할수있다고보고하였다 [9]. 또한최대반복횟수는운동강도에따라수행할수있는연속적인동작의횟수를의미하는것으로서, 저항운동의강도설정방법중에서도 %1RM 과밀접한관련성이있다고보고하였다 [4,7]. 즉, %1RM 의증가는최대반복횟수의감소를나타낸다고할수있다 [14]. Gotshalk et al [10] 은 1RM의 85% 이상의고강도는근력, 70-80% 의중강도는근비대 [12], 그리고 65% 이하의저강도는근지구력향상에효과적이라고보고하면서 [2], 운동강도의차이에따라근기능개선에도차이가있다고보고하였다. 교신저자 : 이호성, hoseh28@dankook.ac.kr Tel: +82-41-550-3838, Fax: +82-41-559-7915 Received 17 Oct. 2015, Revised 2 Nov. 2015, Accepted 11 Nov. 2015
운동과학, 2015 년, 제 24 권제 4 호, 399-405 선행연구에따르면근기능개선의차이는운동강도의차이뿐만아니라주동근 (agonist) 과협응근 (synergist) 의동원비율 (recruitment ratio) 차이에의해서도나타난다고보고하였다 [27]. 예를들어벤치프레스의경우, Lehman [23] 의연구에서는위팔세갈래근 (Triceps brachii) 의근활성도가가장높게나타났다고한반면에, Welsch et al [31] 은앞쪽세모근 (Deltoid anterior) 과큰가슴근 (Pectoralis major) 의근활성도가높게나타났다고보고하였다. 따라서주동근의근력강화를위해서는주동근과협응근의동원비율을보다명확하게검토할필요가있다고생각된다. 한편, 저항운동은운동경력, 즉숙련자 (trained men) 와비숙련자 (untrained men) 에따라사용하는근육군 (muscle group)( 주동근 ) 이다르며 [14], 근활성및근피로에서도차이가있다고보고하였다 [13]. 선행연구에의하면, 태권도발차기동작시숙련자의경우넙다리곧은근- 가쪽넓은근-안쪽넓은근-넙다리두갈래근순으로근활성도가높게나타났으나, 비숙련자의경우안쪽넓은근-넙다리곧은근-가쪽넓은근- 넙다리두갈래근순으로근활성도가높게나타났다고보고하였다 [16]. 또다른선행연구에서는동일한운동강도에따른반복횟수를숙련자와비숙련자를대상으로비교한결과, 숙련자는큰근육군뿐만아니라작은근육군의근활성도도높게나타났으며, 반복횟수도증가하였다고보고하면서, 이러한차이는훈련습관에서나온다고추론하였다 [14]. 또한 Shimano et al [29] 은동일한강도의 Free weight 운동시반복횟수, 평균파워및운동자각도 (RPE) 를비교한결과, 숙련자는비숙련자에비해모든지표에서긍정적인결과를나타냈다고보고하였다. 하지만운동강도의차이, 즉저강도, 중강도및고강도등다양한강도에서숙련자와비숙련자의근활성, 근피로및반복횟수를비교 검토한연구는찾아볼수없다. 일반적으로저강도의저항운동은자세및사용하는근육군에있어서훈련의영향을적게받지만, 고강도의저항운동에서는자세, 근육군및피로등의영향을많이받는다고보고되어있다 [26]. Sakamoto & Sinclair [27] 은건강한성인남성을대상으로벤치프레스운동시 1RM의 40, 50, 60, 70 및 80% 의점진적강도증가에따른근활성도및근피로도의변화를관찰한결과, 큰가슴근, 앞쪽어깨세모근및위팔세갈래근에서강도가증가할수록근활성도및근피로도가증가하는것을확인하였다. Snyder & Fry [30] 의연구에서는 11명의축구선수를대상으로 1RM의 50 및 80% 운동시큰가슴근, 앞쪽어깨세모근및위팔세갈래근의근활성도를비교한결과, 1RM 50% 에서는큰가슴근의근활성도가유의하게증가하였지만, 앞쪽어깨세모근및위팔세갈래근에서는유의한차이가나타나지않았고, 1RM 80% 에서는큰가슴근과앞쪽어깨세모근의근활성도가유의하게증가하는것으로나타났다. 이와같이일반성인및운동선수를대상으로단일집단에서운동강도의차이에따른근활성도를비교한연구는있지만, 전술한바와같이숙련자와비숙련자를대상으로다양한강도에서근활성도, 근피로도및반복횟수를상세히검토한연구는전무한실정이다. 이에이연구에서는저강도의저항운동은숙련자와비숙련자간에근활성도, 근피로도및반복횟수에차이를나타내지않지만, 고강도의저항운동은숙련자에비해비숙련자가주동근의근활성도의감소, 근피로도의증가및반복횟수가낮을것이라는가설을세우고, 이러한가설을검증하기위하여실제로건강한숙련자와비숙련자를대상으로벤치프레스운동중에강도별근활성도, 근피로도및반복횟수를비교 검토하고자하는데목적이있다. Ⅱ. 연구방법 1. 연구대상 연구대상은건강한성인남성숙련자 (Trained group; TG, n=8) 와비숙련자 (Untrained group; UTG, n=8) 를모집하였다. TG는 1주일에두번이상, 적어도 6개월이상의고강도 (Intensity < 6RM) 저항운동프로그램을수행한자로설정하였으며, UTG는지난 1년동안에웨이트트레이닝프로그램을수행하지않은자로설정하였다 [29]. 피험자의신체적특성은 <Table 1> 에제시하였으며, 벤치프레스의 1RM의근력에서 TG가 UTG보다유의하게높게나타났다 (p<.05). 모든피험자에게는연구의취지내용을충분히설명한후자발적으로참가동의를얻었다. Table 1. Subject characteristics TG UTG Age (years) 28.0±6.1 29.3±4.4 Height (cm) 173.7±3.8 173.7±4.5 Weight (kg) 75.0±6.5 75.8±12.2 Muscle mass (kg) 36.1±2.6 35.5±6.3 1RM bench press 105.0±16.5 *** 78.0±15.2 1RM: one repetition maximum *** p<.001 vs. UTG 2. 실험절차 이연구에서는벤치프레스 20 kg의바벨을이용하여 15회 1세트의준비운동을실시한후에 1RM의 60, 70 및 85% 의무게에서메트로놈 60 bpm의속도에맞춰자신이최대로반복할수있는 400 전현식, 이호성
횟수를수행하는것을 1세트로설정하여각각의강도에서 3세트씩수행하였다. 세트당휴식시간은 3분, 1RM의강도별휴식시간은 48시간으로설정하였다 [29]. TG와 UTG 모두동일한방법으로실험을진행하였다. 순서에따른영향을최소화하기위하여 1RM의강도별 (60%, 70%, 85%) 에따른운동의순서는무선배정하였다. EMG 신호는피험자의큰가슴근, 앞쪽어깨세모근및위팔세갈레근의근활성도 (maximal voluntary contraction: %MVC) 및근피로도 (median frequency: MDF) 를기록하였다. 3. 측정항목 1) 신체조성 신체조성은생체전기저항분석기 (Bioelectrical Impedance Analysis : Inbody 770, Biospace, Korea) 를이용한생체전기저항법으로체중 (kg) 및골격근량 (kg) 을측정하였다. 2) 최대반복횟수 1RM은 Kraemer et al [21] 의연구에서사용한실험절차를수정및보완하여측정하였다. 피험자는저강도의무게를설정하여반복횟수 8-10회를수행하여준비운동을실시하고, 중강도의무게를설정하여반복횟수 3-5회를수행한후에고강도의무게로 1-3회의반복횟수를수행하였다. 준비운동후에피험자들은자신이최대로수행할수있는각도와기술을사용하여더이상무게를증가시키지못하는지점까지운동을수행하여자신의최대반복횟수 (1RM) 를측정하였다. 측정간의휴식시간은 3 5분으로설정하였다. TG은 1RM을 1회수행하였으나 UTG은정확한측정을위하여 1RM을 2회수행하였다 [29]. 3) 최대수의적등척성수축력 개인별근력차이로인한자료분석의오류를최소화하기위해최대수의적등척성수축력 (Maximal voluntary iosmetric contraction: MVIC) 을측정하여정량화하였다 [6]. MVIC 는한번에약 3초간실시하여총 3회의측정값에대한평균값을실측치로활용하였으며, 근피로를최소화하기위하여측정간의휴식시간은 3분으로설정하였다. 큰가슴근의 MVIC는벤치프레스에서어깨관절을 90 로수평벌림 (horizontal abduction) 하고, 팔꿈치관절각도를 90 로굽힘 (flexion) 한상태에서최대근력을측정하였으며, 앞쪽어깨세모근의 MVIC는편하게선자세에서어깨관절을 90 굽힘한상태를유지하도록하여측정하였다. 또한위팔세갈래근의 MVIC는앉은자세에서팔을 90 굽힌뒤팔꿈치관절의 90 굽힘을유지하면서최대근력을측정하였다. 4) 근전도분석 근활성도및근피로도는무선근전도 (Delsys Trigno Wireless EMG Surface Electrodes, Delsys, Boston, MA) 를이용하여분석하였다. 전극은피부저항으로생기는오차를줄이기위하여제모를시행한후에알코올솜으로소독하여근육섬유방향과평행하게부착하였다. 앞쪽세모근과위팔세갈래근의전극은 Zipp [33] 의연구에서제시한부위와동일하게부착하였으며, 큰가슴근의전극은 Clemons & Aaron [5] 의연구에서사용한부위와동일하게부착하였다. 전극의부착은동일한연구자가수행하였다. EMG 신호의샘플링주파수 (sample frequency) 는 1,000 Hz 2,000 Hz 로설정하였으며, 20 Hz 500 Hz에서 Filter하여 Passband 하였다 [15]. 근활성도는벤치프레스운동시근육이수축되는전체동작을적분하여산출하게되는데이연구에서는강도의차이에따른각강도및세트의반복횟수에서발현되는신호를각각분석하여평균화하였으며, 총 3세트분석후평균값을근활성도값으로사용하였다. 또한근피로도는각신호에서 length를지정하여 0.15초동안 power spectrum을지정한면적의중앙값을사용하였으며, 이를분석하기위하여 Falvo et al [8] 이사용한근피로도분석방법을수정 보완하여각세트의첫번째반복횟수의신호와마지막반복횟수의신호에서발현된근피로도값의감소율의차이를분석하였다. 총 3세트분석후에평균값을근피로도값으로사용하였다. RMS = RMS - Root Mean Square Window Length (Points) - Data within the window Percent fatigue = [(Work first rap Work last rap ) / Work first rap ] 100 5) 반복횟수 숙련자와비숙련자의벤치프레스운동중에강도별반복횟수를비교하기위하여각강도및세트의최대로수행한반복횟수를기록하였으며, 세트에따른평균값을사용하였다. 4. 자료처리방법 SPSS 20.0(SPSS Inc., Chicago, IL, USA) 을사용하여벤치프레스 숙련자와비숙련자의벤치프레스운동중에강도별근활성도, 근피로도및반복횟수의비교 401
운동과학, 2015 년, 제 24 권제 4 호, 399-405 운동중에강도별에따른큰가슴근, 앞쪽어깨세모근및위팔세갈래근의근활성도및근피로도의차이를숙련자와비숙련자를비교분석하기위하여 t-test를실시하고, 통계적유의수준 (α) 은 5% 이하로설정하였다. Fig. 2. Changes in the muscle fatigue during bench press in trained and untrained group. Ⅲ. 연구결과 1. 근활성도의변화 숙련자와비숙련자의벤치프레스운동중에강도별근활성도의변화는 <Fig 1> 에제시한바와같다. 큰가슴근의근활성도는 TG와비교해서 UTG의 85%(p=.000), 70%(p=.039) 및 60%(p=.010) 에서각각유의하게높게나타났다. 앞쪽어깨세모근및위팔세갈래근의근활성도는집단간에있어서유의한차이를보이지않았다. 3. 반복횟수의변화 숙련자와비숙련자의벤치프레스운동중에강도별반복횟수의변화는 <Fig 3> 에제시한바와같다. 반복횟수는 TG와비교해서 UTG의 70% 2세트 (p=.012), 3세트 (p=.049), 및 60% 의 3세트 (p=.027) 에서각각유의하게낮게나타났다. 하지만 85% 에서는세트및집단간에있어서유의한차이를보이지않았다. Fig. 1. Changes in the muscle activities during bench press in trained and untrained group. Values are means±sd *p<.05, ***p<.001 Fig. 3. Changes in the repetition during bench press in trained and untrained group. Values are means±sd *p<.05 Ⅳ. 논의 2. 근피로도의변화숙련자와비숙련자의벤치프레스운동중에강도별근피로도의변화는 <Fig 2> 에제시한바와같다. 큰가슴근, 앞쪽어깨세모근및위팔세갈래근의근피로도는집단간에있어서유의한차이를보이지않았다. 이연구에서는숙련자와비숙련자의벤치프레스운동중에강도별근활성도, 근피로도및반복횟수를비교한결과, 큰가슴근의근활성도는모든강도에서숙련자에비해비숙련자가높게나타났다. 또한운동강도가낮아지고강도별세트가증가할수록비숙련자에비해숙련자의반복횟수는높게나타났지만근피로도는차이를보이지않았다. 이는비숙련자의경우는주동근을보다많이사용하였고, 반면에숙련자의경우는주동근및협응근을효율적으로사용하였기때문이라고생각된다. 따라서이연구의가설이성립되지않았다. 즉이연구에서숙련자와비숙련자간의근활성도및근피로도의차이는운동강도가아니라반복횟수및주동근과협응근의동원비율이중요할것으로생각된다. 402 전현식, 이호성
일반적으로벤치프레스운동은큰가슴근을발달시키기위한목적으로가장대표적인근력운동으로 [32], 주동근인큰가슴근과협응근인어깨세모근및위팔세갈래근의단축성수축 (concentric contraction) 과신장성 (eccentric contraction) 수축이반복적으로이루어지게되는복합관절운동이다 [25]. 이러한복합관절운동은주동근과협응근이동원되는비율이중요하며, 이는 1RM의무게와반복횟수에도영향을미치게된다. 벤치프레스의주동근과협응근의근활성도에관한연구에서 Junior et al [15] 은건강한성인남성 13명을대상으로 10RM의벤치프레스운동시큰가슴근, 앞쪽세모근및위팔세갈레근의근활성도를비교한결과, 큰가슴근의근활성도가높게나타났다고보고하였다. 또한 Kohler et al [18] 은저강도의벤치프레스운동을실시한결과, 큰가슴근의근활성도가높게나타났다고보고하였다. 이와같이다수의선행연구에서벤치프레스운동시주동근 ( 큰가슴근 ) 의근활성도가높게나타났으며, 주동근의발달에효과적이라고보고하고있지만, 협응근의근활성도에서도유의한차이가있었다는연구결과도보고되어지고있다. Schick et al [28] 의연구에의하면 1RM 70 및 90% 의벤치프레스운동시 1RM의 90% 에서큰가슴근과어깨세모근이높은근활성도를보인다고보고하였으며, 이러한결과는벤치프레스운동이주동근보다협응근의동원비율이높게나타날수있다는것을의미하며, 이러한동원비율은저항운동의숙련자와비숙련자사이에도차이가있다고추측하였다. 이에이연구에서는숙련자와비숙련자를대상으로벤치프레스운동시저강도, 중강도및고강도에서근활성도를비교한결과, 비숙련자의경우, 모든강도에서숙련자에비해큰가슴근의근활성도가높게나타났다. 전술한바와같이, 숙련자의경우에는주동근과협응근을효율적으로사용하여운동시수행되는동작및운동강도에따른부하량을안정적으로조절하는반면에, 비숙련자의경우에는주동근및협응근을효율적으로사용하기보다상대적으로큰근육군을사용하여운동동작및부하량을조절하였기때문이라고생각된다. 또한이연구에서숙련자의경우에는 1RM의 60, 70 및 85% 강도에서거의동일한근활성도를보이는반면에, 비숙련자의경우에는 1RM의 85% 강도에서근활성도가가장높고, 운동강도가낮아질수록근활성도가낮아지는것을확인할수있다. Hoeger et al [14] 은동일한강도의저항운동을실시할경우에비숙련자는작은근육군보다큰근육군을보다많이사용한다고보고하였으며, Kraemer et al [20] 의연구결과에의하면 Free weight 운동을수행할때에는힘의균등한조절이필요하다고보고하였다. 이러한선행연구의결과는이연구에서숙련자에비해비숙련자의주동근 ( 큰가슴근 ) 의근활성도가높은이유를뒷받침해주는결과라고생각된다. 일반적으로저항운동에따른근피로의유발은부하량의증가 [24] 와속근섬유 (fast-twitch muscles) 의비율이중요하며 [19], 운동단위 (motor unit) 의동원및신경전도 (nerve conduction) 속도가저하하여발생한다고알려져있다 [3]. 또한근피로도는최대반복횟수와관련이있으며, 최대반복횟수, 즉연속적인동작의횟수는근기능의차이에서비롯된다고보고하였다 [4,7]. Hoeger et al [14] 은동일한강도의저항운동시근기능이우수한숙련자는비숙련자에비해반복횟수를보다많이수행한다고보고하였으며, Shimano et al [29] 은숙련자와비숙련자간에 1RM의 60, 80 및 90% 의강도에서벤치프레스, 스쿼트및암컬의최대반복횟수를비교한결과, 1RM 의 60% 강도의스쿼트운동에서숙련자가비숙련자에비해더많은반복횟수를수행하였지만, 다른운동강도및운동간에는유의한차이가나타나지않았다고보고하였다. 이연구에서 1RM의 85% 의고강도에서의반복횟수는집단간에차이를보이지않았다. 1RM 의 85% 와같은고강도의저항운동은숙련자및비숙련자모두에서많은반복횟수를수행하지못하였기때문이라고생각되며, 특히비숙련자의경우에는큰근육군을이용하여단시간동안에근력발휘가가능하여집단간에반복횟수의차이가나타나지않았을가능성이있다고생각된다. 따라서이연구에서는고강도의저항운동은근기능의차이와관계없이반복횟수에차이가없다는사실을증명하였다. 반면에, 이연구에서 1RM의 75% 의중강도와 60% 의저강도에서는세트가증가할수록비숙련자에비해숙련자의반복횟수는높게나타났지만, 근피로도는차이를보이지않았다. 전술한바와같이, 이것은주동근과협응근의동원비율, 즉상대적으로많은반복횟수가요구되는저항운동의운동강도에서는주동근과협응근을효율적으로사용할필요가있다는것을시사하는것이다. Ⅴ. 결론 이연구에서는숙련자와비숙련자의벤치프레스운동중에강도별근활성도, 근피로도및반복횟수를비교한결과, 큰가슴근의근활성도는모든강도에서숙련자에비해비숙련자가높게나타났다. 또한운동강도가낮아지고강도별세트가증가할수록비숙련자에비해숙련자의반복횟수는높게나타났지만근피로도는차이를보이지않았다. 따라서이연구에서숙련자와비숙련자간의근활성도및근피로도의차이는운동강도가아니라반복횟수및주동근과협응근의동원비율이중요할것으로생각된다. 향후에는숙련자와비숙련자의벤치프레스운동중및기간등에따른반복횟수및주동근과협응근의동원비율의차 숙련자와비숙련자의벤치프레스운동중에강도별근활성도, 근피로도및반복횟수의비교 403
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