Background: Although various exercises have been performed for patients with chronic low back pain (CLBP), the effects of these exercises including joint mobilization, gym ball exercises, and breathing exercises on flexion relaxation ratio (FRR) have not been compared. Objective: To compare the effects of joint mobilization, gym ball exercises, and breathing exercises on the flexion relaxation phenomenon (FRP) and pain in patients with chronic low back pain. Design: Randomized pretest-posttest control group design. Methods: Thirty-six patients with chronic low back pain who were undergoing rehabilitation at a rehabilitation center were included. The patients were randomly divided into three groups: joint mobilization group (JMG; n=12), gym ball exercise group (GBG; n=12), and breathing exercise group (BEG; n=12). The exercises were performed for 40 minutes a day, twice a week, for a total of 12 weeks. Results: There were no significant differences in FRR between the three groups (P>.05). Significant decreases in the modified visual analog scale (MVAS) scores after intervention between the groups were found (P<.05). The GBG was significantly decreases from the JMG in the MVAS (P<.05). However, there were significant improvements between the pre- and post-interventional findings on FRR and MVAS in the three groups (P<.05). Conclusion: We demonstrated that intervention using joint mobilization, gym ball exercises, and breathing exercises improve FRP and pain in patients with CLBP.

Background: Squatting is one of the best functional exercises to strengthen the quadriceps muscle in independent gait and activities of daily living. Although the use of a gym ball during squat exercise is the most common way of strengthening the vastus medialis oblique (VMO) muscle, published data on this subject are limited. Objects: The purpose of this study was to compare the sequential muscle activation of the VMO and vastus lateralis (VL) muscles during squat exercise using a gym ball at different knee flexion angles. Methods: Forty healthy adults were randomly divided into experimental (squat exercise using a gym ball) and control (squat exercise alone) groups, in which squats were performed at 45° and 90° knee flexion. Electromyographic (EMG) activity data were collected over 10 seconds under the 2 angles of knee flexion (45° and 90°). Results: There was significant group and time interaction effect for VMO and VL muscle activation at 45° knee flexion. This was similarly demonstrated at 90° knee flexion. No significant group main effect and time main effect for VMO and VL muscle activation were noted at 45° knee flexion, respectively. In contrast, there was significant group main effect and time main effect for VMO and VL muscle activation at 90° knee flexion. These significant differences were demonstrated through two-way analysis of variance over repeated measurements, suggesting that the EMG activity of the VMO muscle during squatting with a gym ball showed remarkable improvement compared to that of the VL muscle. Conclusion: This research suggests that squat exercise using a gym ball may be more beneficial in improving the activity of VMO than of the VL muscle at both 45° and 90° of knee flexion, respectively. We highly recommend squat exercises with a gym ball for selective strengthening of the VMO muscle in knee rehabilitation.

대공간구조에서 접합부의 신뢰도는 매우 중요하다. 접합부에 사용되는 고력볼트의 나사부 유효단면적은 축부단면적보다 작고 볼트 축부에 락핀용 구멍이 있기 때문에 볼트 나사부 또는 락핀용 구멍에 응력집중 현상이 발생하여 취성 파단이 발생할 우려가 높다. 특히 접합부는 직렬형 구조로 이루어져 있다. 따라서 접합부에서의 극한상황시 파괴유형은 필히 취성파괴를 피해야 하며 연성파손으로 유도해야 한다. 따라서 본 연구에서는 볼 조인트 접합부의 소성변형능력을 향상시키고 현장에서 발생할 수 있는 시공오차의 흡수가 가능하도록, 볼트의 나사부나 핀부의 취성파단 없이 소성변형능력 향상을 목표로 하였다. 에너지흡수형 볼트를 사용함으로써 소성변형능력이 향상된 스페이스 프레임의 접합상세를 제안하였다.

The purpose of this study is to analyze the characteristics of the connector having an influence on the elasto-plastic buckling load of ball-jointed single layer latticed domes. As an analytic model, domes are composed of tubular member elements, balls and connectors. The joint system of members in single layer latticed domes has influence on the buckling load. Therefore, in this paper, the variation of the elasto-plastic buckling load by effects of the connectors characteristics is analyzed. The structural behavior of the connector is investigated by following points: (1) the length of rigid zone, (2) looseness of screw and (3) the diameter of connector. In addition, the elasto-plastic buckling analysis is carried out through the variation of the connectors section of yielding part, and then the buckling mode of the dome is examined. As a result, it is emphasized that the characteristics of the connector have significant effects on the buckling load of latticed domes.