본 연구는 자유형 스트로크를 교정하기 위해 수영장 바닥 거울을 사용한 코칭이 효과적인지 분석하는데 목적이 있다, 1년 이상 수영 강습을 받은 성인 30명을 무작위로 Mirror group(MG)과 No mirror group(NMG)으로 나누어 실시하였다. MG(men=12, 32.25±8.2 yrs, 175±5.5 ㎝, 70.9±9.2 ㎏; women=3, 37.6±13.7 yrs, 160.0±3.4 ㎝, 55.6±3.5 ㎏), NMG(men=7, 28.7±6.1 yrs, 176.2±3.7 ㎝, 72.4±14.4 ㎏; women=8, 38.8±14.6 yrs, 162.1±4.4 ㎝, 54.1±7.3 ㎏)은 2.43 m x 4.57 m x 1.37 m 크기의 인공 수조에서 자유형 1분을 실시하였다. 거울제공 여부와 시간의 상호작용이 스트로크 기준점과의 차이에 미치는 효과는 1차 검사에서 NMG: 6.0±3.982 ㎝, MG: 7.67±3.266 ㎝로 집단 간 차이가 1.67 ㎝인 반면, 2차 검사결과 NMG: 5.07±3.788 ㎝, MG: 2.47±3.502 ㎝ 로 집단 간 차이가 2.6 cm 로 나타나 통계적으로 유의하였다(F=20.627, p<.001). 거울 제공 여부와 시간에 따른 스트로크 빈도에 대한 분산분석 결과, 피드백 종류와 1차, 2차 검사의 상호작용이 스트로크 빈도에 미치는 효과는 1차 결과 NMG: 57.67±6.821 score, MG: 60.73±7.294 score에서 2차 결과 NMG: 56.33±6.586 score, MG: 53.67±5.447 score로 통계적으로 유의한 차이가 있는 것으로 나타났다(F=24.807, p<.001). 거울 제공 여부와 사전사후 검사 따른 스트로크 시간에 대한 분산분석을 실시한 결과, 피드백 종류와 1차, 2차 검사의 상호작용이 스트로크 시간에 미치는 효과는 1차 NMG: 2.04±.208 sec, MG: 2.05±.250sec에서 2차 NMG: 2.15±.287 sec, MG: 2.39±.307 sec로 통계적으로 유의한 차이가 나타났다(F=10.813, p<.01).
This study analyzed whether coaching recreational swimmers using pool bottom mirror for correcting front crawl stroke is effective in achieving an intended stroke. Thirty adults who enrolled swimming lessons for more than 1 year participated and were randomly divided into two groups; mirror group (MG: 12 men; 32.3±8.2 yrs, 175.0±5.5 ㎝, 70.9±9.2 ㎏: 3 women; 37.6±13.7 yrs, 160.0±3.4 ㎝, 55.6±3.5 ㎏) and control group (CG: 7 men; 28.7±6.1 yrs, 176.2±3.7 ㎝, 72.4±14.4 ㎏: 8 women; 38.8±14.6 yrs, 162.1±4.4 ㎝, 54.1±7.3 ㎏). They performed front crawl twice in a swimming flume (2.43 × 4.57 × 1.37 meter) at their chosen speed (pace of 87.9±4.2 for men, 102.7±4.7 sec/100 meter for women). Their stroke was video recorded by an underwater camera (xnb-6001, Samsung, Korea) and dry land camera (gnd-6020R, Samsung, Korea). After their first trial and recording, individual stroke was evaluated and verbal feedback was given for correction targeting full arm range stroking. During second trial, MG had a mirror (81 × 151 ㎝) installed under the bottom of flume so that they could check their stroke. CG did not use mirror during second trial. An image analyzer (Dartfish, Swiss) was used to analyze the distance between reference point (RP: where fingertip was reached over Vastus lateralis during standing till on land) and fingertip as well as stroke time (time between left hand immersion cycle). Stroke frequency was counted cycles of both arms. Two trials were compared. The distance between RP and fingertip was 7.7±3.3 and 2.5±3.5 ㎝ in MG in 1st and 2nd trial, respectively (p<0.001) while it was 6.0±4.0 and 5.1±3.8 ㎝ in CG. The stroke frequency was 60.7±7.3 in MG and 57.7±6.8 freq/min in CG at 1st trial. It was decreased to 53.7±5.4 in MG (p<0.001), but not in CG (56.3±6.6 freq/min). The stroke time was increased from 2.1±0.3 to 2.4±0.3 sec in MG (p<0.01), but it was not changed in CG (2.1±0.2 vs. 2.2±0.3 sec)(F=10.813, p<.01).