이 연구의 목적은 6주간의 엉덩관절 강화 훈련이 근력, 동적 자세 조절 및 하체 손상 준거에 미치는 영향을 보고자 하였다. 운동선수 20명을 운동군과 통제군으로 분류하여, 운동군은 주 3회, 60분, 6주간 엉덩관절 강화훈련을 하였다. 이 연구의 측정 변인은 유연성, 근력, 동적 자세 조절 및 하체 부상 준거로 하였다. 연구 결과 유연성에서 운동의 효과가 유의하지 않았으나 배근력에서는 유의하였다. 동적 자세 조절 결과, 좌·우 후방 가쪽 및 안쪽에서 운동의 효과가 유의하였다. 또한 종합점수에서도 운동의 효과가 유의하였고, 좌·우 다리 간의 차이는 없었다. 결론적으로 엉덩관절 강화 운동은 근력과 동적 자세 조절 능력의 증가와 하체 손상의 우려는 감소시키는 것으로 나타났다.
이 연구의 목적은 6주간의 플라이오메트릭 트레이닝이 태권 시범선수의 서전트 점프, 자세 조절 및 하체 부상 준거에 미치는 영향을 보고자 하였다. 이 연구에 참여한 대상자는 대학 태권 시범선수 20 명을 대상으로 운동군 10명과 통제군 10명을 무작위로 분류하였다. 운동군은 주 3회, 60분, 6주간 실시하였고, 통제군은 일반적인 훈련을 하였으며, 사전 사후 서전트 점프, 배근력, 자세 조절 및 하체 부상 준거를 측정하였다. 연구 결과, 배근력에서는 유의하지 않았으나 서전트 점프에서는 유의한 증가가 있었다. 자세 조절에서는 앞쪽은 경우 유의하지 않았으나 좌·우 후방 외쪽과 안쪽에서는 유의한 증가가 있었고, 종합점수 결과 하체 부상의 위험성은 없는 것으로 나타났다. 결론적으로 플라이오메트릭 트레이닝은 순발력, 자세 조절, 하체 부상 방지 및 재활에 적극적으로 활용할 필요가 있는 훈련 방법이다.
Background: Visual and somatosensory integration processing is needed to reduce pusher behavior (PB) and improve postural control in hemiplegic patients with acute stroke.
Objects: This study aimed to investigate the effects of game-based postural vertical training (GPVT) on PB, postural control, and activity daily living (ADL) in acute stroke patients.
Methods: Fourteen participants with acute stroke (<2 months post-stroke) who had PB according to the Burke lateropulsion scale (BLS) (score>2) were randomly divided into the GPVT group (n1=7) and conventional postural vertical training (CPVT) group (n2=7). The GPVT group performed game-based postural vertical training using a whole-body tilt apparatus. while the CPVT group performed conventional postural vertical training to reduce PB (30 minutes/session, 2 times/day, 5 days/week for 3 consecutive weeks). The BLS was evaluated to assess the severity of PB. And each subject’s postural control ability and ADL level were assessed using the postural assessment scale for stroke (PASS), balance posture ratio (BPR), and Korean-modified Barthel index (K-MBI). Outcomes were measured preand post-intervention.
Results: Comparison of the pre- and post-intervention assessment results showed that both interventions led to the following significant changes: decreased severity of PB scores and increased PASS, BPR, and K-MBI scores (p<.05). In particular, statistical analysis between the two groups, the BLS score was significantly decreased in the GPVT group (p<.05). And PASS, BPR, and K-MBI scores were significantly improved in the GPVT group than in the CPVT group (p<.01, respectively). Conclusion: This study demonstrated that GPVT lessened PB severity and improved postural control ability and ADL levels in acute stroke patients.
The purpose of this study was to evaluate the changes in the electromyographic (EMG) activity of the trunk and the lower limb muscles during quiet standing on an unstable surface while wearing low-heeled shoes (3 ㎝), high-heeled shoes (7 ㎝) and without footwear (0 ㎝) in 20 young healthy women. The subjects stood on an unstable surface for 30 seconds. We examined the differences in the EMG data of the erector spinae, rectus abdominis, biceps femoris, rectus femoris, tibialis anterior, and the gastrocnemius medialis muscle. A one-way repeated analysis of variance was used to compare the effects of shoe heel height on the EMG activity with the level of significance set at α=.05. The EMG activity of the erector spinae and the rectus femoris were significantly increased (p<.05) in the subjects who wore elevated heel height, while the tibialis anterior and the gastrocnemius medialis were significantly decreased (p<.05). However, the rectus abdominis and the biceps femoris exhibited no significant difference among the three conditions. The above results indicate that wearing high-heeled shoes may change the postural strategy. The findings of this study suggest that excessive heel height could contribute to an increased fall risk during quiet standing.
In daily activities, people often perform two or more tasks simultaneously. This is referred to as dual-tasking or multi-tasking. The purpose of this study was to examine the effects of performing dual tasks while using a mobile phone on static and dynamic postural stability. Twenty-four subjects were asked to stand on a force plate and then instructed to perform a balance task only (BT), a balance task while listening to music (BTL), a balance task while talking on the mobile phone (BTT), and a balance task while sending text messages (BTS). We used the BioRescue to measure postural sway and limit of stability for static and dynamic postural stability. Also the star excursion balance test (SEBT) was used to measure dynamic postural stability. A one-way ANOVA with repeated measures was used to compare the effects of the BT, BTL, BTT, and BTS. The Bonferroni's post hoc test was used to determine the differences among four tasks. Carrying out the BTS significantly decreased the limit of stability compared with carrying out the BT, BTL, and BTT (p<.05). In limit of stability, total surface area of BTT was more significantly decreased than that of BT and total surface area of BTS was more decreased than that of BT, BTL and BTT (p<.05). In the SEBT, the BTS displayed significantly smaller reach distance values compared with the BT or BTL (p<.05). These findings suggest that performing the balance task while sending text message on the mobile phone decreases dynamic postural stability, whereas performing the same task while listening to music using the mobile phone does not. Therefore, it requires more attention to maintain dynamic balance while sending text messages.
The purpose of this study was to investigate the effect of visual feedback on the postural control of stroke patients, by systematically varying conditions of visual feedback [eye-open condition (EO) vs. eye-closed condition (EC)], and base-support (both-side support, affected-side support, and unaffected-side support). In this study, we allocated 41 stroke patients with no damage in the cerebellum and visual cortex who can walk at least 10 meters independently, and 35 normal adults who have no experience of stroke to the control group. Both groups were asked to perform a "sit-to-stand" task three to five times, and their postural control ability was measured and compared in terms of asymmetric dependence (AD) instead of the traditional symmetric index (SI) in the literature. The results showed that although both subject groups maintained better postural control in the EO condition than in the EC condition, the patient group appeared to be more stable in EC than in EO when they were required to perform the task of the support condition given on the affected side. These results implied that visual feedback can impair stroke patients' postural control when it is combined with a specific support condition.
목적 : 자세조절과 시지각 능력은 일상생활 및 학습을 하는 데 있어 기초가 되고 이러 한 요소는 뇌성마비 아동을 치 료하는데 주된 목표가 된다. 따라서 본 연구를 통해 경직형 뇌성마비 아동에서 안구운동프로그램이 자세조절과 시 지각 능력에 미치는 영향을 알아보고자 한다. 연구방법 : 2010년 5월 1일부터 2010년 8월 31일까지 부산에 위치한 P복지관에 내원하는 만4세~8세 경직형 뇌 성마비 아동을 대상으로 하였다. 10명의 경직형 뇌성마비 아동을 무작위로 실험군과 대조군으로 각각 5명씩 배정 하였다. 실험군에게는 안구운동프로그램과 함께 일반적 작업치료를 제공하고 대조군에게는 일반적 작업치료를 시 행하였다. 안구운동 프로그램은 단속성안구운동, 이접안구운동, 추적안구운동, 전정안구운동 4가지로 구성되어 있 다. 활동 중재는 1회 40분씩 주 3회로 8주 동안 제공되었다. 중재 전∙후에 대한 평가는 대동작기능평가(GMFM), 소아균형척도(PBS), 소아뻗기검사(PRT)와 한국판시지각발달검사(K-DTVP)를 사용하였다. 결과 : 안구운동프로그램을 수행한 실험군에서는 GMFM, PBS, PRT와 시각통합을 제외한 K-DTVP 모든 하위평 가항목에서 중재 전과 후의 점수가 통계적으로 유의한 차이가 있는 것으로 나타났으나(p<.05), 대조군에서는 PRT와 K-DTVP의 눈손협응과 공간위치를 제외하고는 통계적으로 유의한 차이를 보이지 않았다. 또한 두 집단 의 평가 점수의 변화량을 비교하였을 때 모든 평가항목에서 실험군이 대조군에 비해 유의한 차이를 보여 자세조절 과 시지각 기능 향상이 대조군보다 더 좋음을 나타냈다(p<.05). 결론 : 본 연구는 경직형 뇌성마비 아동에서 안구운동프로그램 중재가 자세조절 및 시지각능력 향상에 효과적임을 시사한다.
This study examined whether any changes by mental task types on postural control in chronic stroke persons. Sixteen chronic stroke persons (mean age=53.75 yr) and sixteen age-and gender-matched healthy controls (mean age=54.44 yr) took part in this study. Participants randomly performed three different tasks on the stable and unstable surfaces. The no mental task was to stand while holding a 100 g weight in each hand, the arithmetic task (mental task) was to perform a silent 1-backwards counting while standing and holding a 100 g weight in each hand, and the simple task (mental task) was to stand and hold with both hands a tray (200 g) on which a glass filled with water has been placed. Sway path and sway velocity of the center of pressure (COP) were measured to assess standing postural control by task performance using the force platform. According to the results, in stroke group, total sway path and total sway velocity of COP was significantly decreased during arithmetic and simple task compared to no mental task on the stable surface (p<.05), and sway path (anteroposterior AP, mediolateral ML) of COP, total and sway velocity (AP, ML, total) of COP was significantly decreased during arithmetic and simple task compared to no mental task on the unstable surface (p<.05). Especially, sway path (AP, total) of COP and sway velocity (AP, ML, total) of COP was significantly decreased under the simple task when compared to the arithmetic task on the unstable surface (p<.05). In healthy control group, sway path (AP, ML, total) of COP and sway velocity (AP, ML, total) of COP was significantly decreased during arithmetic and simple task compared to no mental task on the stable and unstable surface (p<.05), and sway path (AP, total) of COP and sway velocity (AP, ML, total) of COP was significantly decreased under the simple task when compared to the arithmetic task on the unstable surface (p<.05). In conclusion, the findings of this study showed that arithmetic and simple task improved standing postural control for chronic stroke patients and the type of arithmetic and simple tasks were critical factor that reduced standing postural sway in dual-task conditions. Future research should determine whether dual-task conditions, including simple task, would be effective as a training program for standing postural control of stroke patients.
The purpose of this study was to investigate the effects postural changes on respiratory muscles and acoustic parameters of the children with spastic cerebral palsy. Nine children with spastic cerebral palsy who required assistance when walking were selected. The ages of the children ranged from 6 to 9 years old. The phonation of the sustained vowel /a/ and the voice qualities of each child such as fundamental frequency(F0; Hz), pitch variation (Jitter; %), amplitude variation (Shimmer; %) and noise to harmonic ratio (NHR) were analyzed by Multi-Dimensional Voice Program (MDVP). The muscle activity of three major respiratory muscles: pectoralis major muscle, upper trapezius muscle and rectus abdorminalis muscle, were measured by examining the root mean square (RMS) of the surface EMG to investigate the impact of changes in the adjusted sitting posture of each subject. However, the RMS of pectoralis major muscle showed a significant differences (p<.05). Secondly, there were no significant differences in , Jitter and Shimmer between pre and post posture change, but there was a significant difference in NHR (p<.05). The data were collected in each individual; once prior and once after the sitting posture change. The data were analyzed by Wilcoxon signed ranks-test using SPSS version 14.0 for Windows. The findings of this study were as follows; Firstly, the RMS of upper trapezius and rectus abdorminalis muscle were not significant different between pre and post sitting posture changes. From the result, it is concluded that changes in the adjusted sitting posture decreases the abnormal respiratory patterns in the children with spastic cerebral palsy which is characterized by the hyperactivity of the respiratory muscles in breathing. Also, there is increased on the voice qualities in children with spastic cerebral palsy.
Anticipatory postural adjustments is an example of the ability of the central nervous system to predict the consequence of the mechanical effect of movement on posture and helps minimize a forth coming disturbance. The aim of this study was to evaluate the sequence of activation of the trunk muscles during the performance of hip and shoulder movement and to determine the relationship between anticipatory activity and subjects' motor and functional status in subjects with hemiplegia post stroke. Twenty-four poststroke hemiparetic patients enrolled in this study. Electromyographic activity of the lumbar erector spinae, latissimus dorsi, and of the obliquus internus muscles was recorded bilaterally during flexion of both arm and from the rectus abdominis, obliquus externus, and obliquus internus muscles during flexion of both hip. Onset latencies of trunk muscles were partially delayed in the subjects with hemiplegia post stroke (p<.05). With upper limb flexion, the onset of erector spinae muscle and latissimus dorsi muscle activity preceded the onset of deltoid on both side respectively (p<.05). A similar sequence of activation occurred with lower limb flexion. Also the onset of external oblique muscle and rectus abdominis muscle activity preceded the onset of rectus femoris muscle on both side (p<.05). Major impairments in the activity of trunk muscles in hemiparetic subjects were manifested in delayed onset between activation of pertinent muscular pairs. These problems were associated with motor and functional deficits and warrant specific consideration during physical rehabilitation of post stroke hemiparetic patients.
Anticipatory postural adjustments are pre-planned by the central nervous system (CNS) before the activation of agonist muscles in the limbs, and minimize postural sway. Most previous studies on this topic have focused on upper-limb movement, and little research has been conducted on lower-limb movement. The purpose of this study was to investigate the recruitment order of left and right trunk muscles during limb movement. Fifteen healthy subjects (10 male, 5 female) were enrolled. Electro-myographic signals were recorded on the muscles of: (1) deltoid, lumbar erector spinae, latissimus dorsi and internal oblique during shoulder flexion, (2) rectus femoris, rectus abdominis, external oblique and internal oblique during hip flexion. During right upper limb flexion, the onset of left erector spinae muscle and left internal oblique muscle activity preceded the onset of right deltoid by 8.09 ms and 19.83 ms, respectively. But these differences were not significant (p>.05). A similar sequence of activation occurred with lower limb flexion. The onset of left internal oblique muscle activity preceded the onset of right rectus femoris muscle by 28.29 ms (p<.05). The onset of right internal oblique muscle activity preceded the onset of left rectus femoris muscles by 23.24 ms (p<.05). The internal oblique muscle was the first activated during limb movement. Our study established the recruitment order of trunk muscles during limb movement, and explained the postural control strategy of the trunk muscles in healthy people. We expect that this study will be used to evaluate patients with an asymmetric recruitment order of muscle activation due to impaired CNS.
The purpose of this study was to find any correlations among Postural Assessment Scale for Stroke (PASS), Modified Barthel Index (MBI), Tone Assessment Scale (TAS), Motor Assessment Scale-Gait (MAS-G), Fugl Meyer-Balance (FM-B), and to predict MBI from subscales of the PASS. The subjects were 41 stroke patients of the Korea National Rehabilitation Center in Seoul. The main outcome measures were postural control (PASS), gait (MAS-G), Balance (FM-B), Tone (TAS), ADL (MBI). The data was analyzed using the Pearson product correlation. PASS scale was used between other clinical and instrumental indexes, multiple stepwise regression analyses were performed to identify prognostic factors for ADL incline, and Cronbach's alpha coefficient was used to identify internal consistency on PASS scale. The results of this study areas follows: 1. The highest level was sitting without support, the lowest level was standing on paretic leg on PASS scale. The highest level was chair/bed transfer, the lowest level was bathing on MBI. 2. All items of the PASS, except postural tone were significantly correlated with Gait, Balance, MBI (p<.01), 3. The Internal Consistency (Cronbach's alpha coefficient=.85) was very high, indicating that the PASS is homogeneous and is likely to produce consistent response. Furthermore, the sums of maintaining position items and of changing-position items were strongly correlated (r=.64, p<.05) and there were significant correlations between sums of PASS, sums of maintaining position items (r=.87, p<.01), and changing-position items (r=.93, p<.01). 4. The standing without support of the PASS items was the strongest variance (R²=.85) of the predicting ADL function. These findings provide strong evidence of the predictive value of the postural control on gait, Balance, ADL function in stroke patients and to can provide a reference for the successful therapeutic program and more improved functional recovery.
목적 : 본 연구는 만성 뇌졸중 환자를 대상으로 자세 조절이 일상생활동작 수행능력과 근 긴장도 변화 및 상지기 능 수행에 어떠한 영향을 미치는지 알아보고자 하였다.
연구방법 : 본 연구를 위하여 국립재활원에 입원한 41명의 뇌졸중 환자를 대상으로 모든 환자들은 자세조절 평가 척도(Postural Assessment Scale stroke, PASS), 일상생활동작 수행능력 측정 도구(Modified Barthel Index, MBI), 긴장도 사정 척도(Tone Assessment scale, TAS), Fugl-Meyer 평가 척도(Fugl-Meyer Assessment scale-upper extremity) 등을 이용하였고 자료 분석은 피어슨 상관분석(pearson correlation coefficient), 단계적 다중 회귀분석(stepwise multiple regression)을 실시하였으며 내적 일치도를 알아보기 위하여 Cronbach's alpha Coefficient를 구하였다.
결과 : PASS항목에서 가장 기능이 좋은 것은 지지하여 서기로 나타났으며,가장 기능이 낮은 것은 환측으로 서기였고,MBI항목에서 가장 기능이 좋은 것은 의자/침상 이동이며, 가장 기능이 낮은 것은 목욕하기로 나타났다.PASS의 모든 항목은 MBI, FM-UE, TAS와 유의한 상관관계(r=-33~91, p<.05~01)가 있으며,FM-U/E와 MBI(r=.35, p<.05), TAS- 안정(r=.-40, p,<.0.1), 연합항목(r=-.39,p<.05)에서 유의한 상관관계가 있는 것으로 나타났다.내적 일치도는 Cronbach's a=.86로 높게 나타났으며,PASS의 합과 자세유지 항목 (r=.90 p<.01)의 합,자세변화 항목(r=.93,p<.01)의 합은 유의한 상관관계가 있었으며,자세유지 항목의 합과 자세변화 항목의 합 간에는 유의한 상관관계(r=.69,p<.01)가 있었다.PASS 항목 중 누운자세에서 건측으로 돌기와 바닥에서 볼펜집어 올리기가 각각 ADL과 상지 기능을 예견하는데 가장 중요한 변수(R2=.95, R2=.56)임을 알 수 있었다.
결론 : PASS는 일상생활동작 수행 능력과 근 긴장도 및 상지기능수행 간에 유의한 상관관계가 있는 것으로 나타나 뇌졸중 환자의 기능적 독립성을 예측할 수 있는 지표가 될 수 있을 것이다.
Objective: To explore the effectiveness of sensory integrative procedures in promoting postural control, bilateral coordination and motor planning outcomes in child with developmental delay.
Design: A single-subject ABA research design.
Setting: Early Intervention Center of University.
Participant: A 7-year-old boy with developmental delay.
Interventions: Sensory integrative procedure. The subject was tested four times before, four times during, and three times after intervention.
Main Outcome Measure: Part of subtests of DeGangi-Berl Test of Sensory Integration, Bruininks-Oseretsky Motor Proficiency and Sensory Integration and Praxis Test.
Result: Postural control and motor planning are effected on sensory integrative procedure. Bilateral coordination did not change by this study. The quality of performance was increased by the therapy.
The purposes of this study were 1) to determine the relationship between antigravity control(supine flexion and prone extension) and postural control(static and dynamic balance) by age, 2) to determine the quality of antigravity and postural control, and 3) to determine whether sex difference correlates with differences in antigravity and postural control in young normal children. We tested 120 children aged 4 to 7 years. The study results showed a significant relationship between antigravity and postural control by age. Quality scale measurements(r=0.90) indicated that the children in this study had not yet developed full antigravity or postural control. The study results revealed differences between sexes(f>m in 5 of 7 tests) and a significant relationship by age in antigravity and postural control.
목적: 본 연구에서는 통증전문 운동치료인 SNPE(Self Natural Posture Exercise) 참여 후, 통증과 우울감소에 미치 는 직접영향력과 신체상 자기차이와 신체적 자기개념의 상호작용이 우울정서 경험에 미치는 간접영향력을 함께 검증하였다. 방법: 반복측정실험설계를 통해 만성통증을 겪고 있는 참여자 104명(여자=93명)을 대상으로 12주간 SNPE 프로그램 참여 전/후 통증, 우울, 신체상과 신체적 자기개념을 측정하였다. 결과: SNPE 참여 전과 비교했 을 때, 통증과 우울은 감소하였고, 더 마른 체형을 원하는 갈망 또한 줄어들었으며, 신체적 자기개념은 좋아졌다. SNPE 참여 전 통증과 우울의 부적관련성이 SNPE 참여 후 낮아졌으므로 SNPE 참여 후 감소된 통증이 우울감소에 긍정적 영향을 미쳤을 것으로 예상할 수 있다. 그리고 참여자의 체지방이 감소할 때, 신체상 자기차이가 우울 정서 감소로 이어지는 간접효과도 함께 존재하는 것으로 나타났다. 논의: SNPE와 같은 운동치료법은 통증감소는 물론, 신체상 자기차이로 인하여 유발되는 우울감 개선에도 도움이 되므로 운동치료법이 지닌 여러 장점을 재확인 할 수 있었다. 본 연구결과로 실용적으로 현장에 적용할 수 있는 방안과 함께 연구의 한계점과 향후 연구방향에 대해서도 논하였다.
Purpose: This study investigated whether there is a correspondence between linear and non-linear analysis for postural stability. Specifically, the focus on this study was to examine whether standard deviation could represent postural stability of whole body and each foot. Methods: 12 young adults participated in the experiment and had to maintain their balance with eyes open in 5 postures: side-by-side (SS), staggered (left (SL) or right (SR) foot forward), and tandem (left (TL) or right (TR) foot forward). Each subject had two 65s trials in each condition. Under two force platform protocol, center of pressure of left (COPL) and right (COPR) was measured and total body center of pressure (COPNET) was finally measured in both the anterior-posterior (AP) and medio-lateral (ML) direction. Standard deviation (SD) of linear analysis and the largest Lyapunov expoenent (LyE) of non-linear analysis were measured for COPL, COPR, and COPNET across whole standing conditions. Results: SD of COPNET was larger in AP than ML in SR and SL conditions, whereas LyE of COPNET in AP and ML were not significantly different. In addition, SD of COPNET in AP was not significantly different from that in ML in TR and TL conditions, while LyE of COPNET in ML was larger than that in AP. Lastly, SD of COPL and COPR in ML was larger than that of COPR and COPL in TR and TL condition, respectively, on the other hand, there was no difference in LyE between COPL and COPR in ML in those conditions. Conclusion: Overall, there is an inconsistency between the SD and LyE during postural dynamics. The findings support the position that SD is not a representative measure of postural stability.
척추변형의 치료는 수술을 통하거나 보조기 등의 교정기를 착용하는 것을 일반적인 방법으로 하나, 후유증의 위험과 성장과 함께 재환원 되는 문제가 있다. 이 연구의 목적은 자세교정의 환원문제를 해결하기 위해 자동적-통제적 정보처리 모형을 적용하여 의식적 자세조절 프로그램을 개발하고 그 효과를 검증하는데 있다. 이를 위해, Feldenkrais (1903~1984), Pilates (1880-1967)의 이론들과 국선도와 합기도의 호홉 기법을 적용하여 16개 동작으로 구성된 의식적 자세조절 프로그램을 개발하였다. 개발된 의식적 자세조절 프로그램의 효과를 검증하기 위해서 초등학교 4-6학년 학생 총 45명의 참가자를 세 집단으로 나누어 의식적 자세조절 운동에 15명(남 10명, 여 5명), 자세조절 운동에 15명(남 8명, 여 7명) 그리고 통제집단 15명(남 8명, 여 7명)으로 무선 할당하였다. 의식적 자세조절 프로그램은 10주가 진행되었으며, 측정은 사전, 10주 운동 직후, 4주 휴식기 후에 어깨각도, 척추각도, 발란스, 전방굴곡이 측정되었다. 그 결과, 처치 전에 실시한 어깨각도, 척추각도, 발란스, 전방굴곡 모두에서 실험집단과 비교집단은 통제집단에 비해 유의미한 효과가 있었으며, 특히 휴식기에 실험집단이 비교집단에 비해 유의미한 효과가 있는 것으로 나타났다. 이러한 결과는 자세조절 운동시에 동작에 대한 의식적 집중이 자세조절의 자동화를 촉진시킨 것으로 해석된다.