| Summary: | 博士 === 國立臺灣科技大學 === 工業管理系 === 88 === Isostation B-200 had been identified to be a valid and reliable measurement apparatus. It can sufficiently response to the mechanism of static and dynamic testing by measuring indexes of low back function of range of motion (ROM), isometric strength, velocity, and endurance. Firstly, this study established a database of low back function for healthy subjects to provide the reference for clinical diagnosis, labor screening, and exercise training. And then, we evaluated the various indexes of low back function using a factor analysis. In addition, we collected simultaneously the surface EMG (electromyography) during isometric and isoinertial testing on the B-200 to explore the coactivation pattern of trunk muscles. The patterns are helpful to understand the alternative behaviors and loading mechanisms of trunk muscles during various conditions of resistance, axis, and trunk angle movements.
ROM has been used as a clinical sign to assess disability in low back pain (LBP). Maximal isometric strength is a good method for assessing lumbar strength. Isoinertial velocity was proved to be a sensitive indicator of the differences between a normative and a LBP population. Endurance has shown to be a reference of the occurrence of LBP. In the study, we collected ROM, isometric strength, velocity, and endurance data from 71 males and females subjects on B-200. Results have shown that ROM has greater difference in flexion between males and females. ROM of our subject is greater than that of western population. Strength of the males are two times than that of the females. Strength of our subject is smaller than that of western population. The sequences of strength is extension, bending, flexion, and rotation. Fatigue in left and right rotation is greater than that of flexion and extension during 25% MIS (maximal isometric strength) endurance testing. Fatigue of the males increases when resistance increases.
It remains unclear what are the relationships between indexes and what indexes are needed to realize a true performance of low back. A total of 22 performance scores were collected and their relationships were examined by a factor analysis. The major loading on different factors indicated that: Factor 1 could be labeled as a static strength measure and it can explain 33.2% of total variance; Factor 2 was velocity and it can explain 29.8% of total variance; Factor 3 was flexibility and it can explain 15.4% of total variance; and Factor 4 and 5 were fatigue-resistance and they can explain 17.9% of total variance. Factor structure indicated that strength and velocity are the most sensitive indexes.
To understand alternation behavior and intensity of trunk muscles during axial movements. Twenty subjects were recruited and their isometric strength during trunk flexion, extension, lateral bending (left and right), and rotation (left and right) on B200 were measured. Musculature activities on both sides of the rectus abdominis (RAB-L and RAB-R), anterior adbominal oblique (AAO-L and AAO-R), latissimus dorsi (LAT-L and LAT-R), and erectus spinae (ERS-L and ERS-R) were collected simultaneously by using a surface EMG. The coactivation pattern was established and was discussed. Results indicated that the RAB-L and RAB-R were the primary contributors in flexion, and their NEMG (Normalization Electromyography) all are 43.9% MVC (Maximal Voluntary Contraction); the ERS-L and ERS-R in extension (47.5 and 46.1% MVC); the AAO-L in left bending (41.5% MVC); the AAO-R in right bending (45.3% MVC); the LAT-L in left rotation (38.3% MVC ); and the LAT-R in right rotation (39.7% MVC). In addition, the coactivation patterns of the weak and the strong samples were compared (two samples, 5 weak strength subjects and 5 strong strength subjects , from 20 subjects, respectively). Even if the axial strength were significantly different (sagittal and transverse movements involve in trunk bending), but both samples have similar prime movers during axial movements. In general, the sample of the weak and the strong subjects have similar coactivation pattern during maximal isometric testing.
To understand alternation behavior and intensity of trunk muscles during different resistances, axis, and trunk angle movements, we recruited ten subjects and measured their isoinertial velocities during different resistances, axis, and trunk angles on B-200. Musculature activities on both sides of the rectus abdominis, anterior adbominal oblique, latissimus dorsi, and erectus spinae were collected simultaneously by using surface EMG electrodes. The coactivation pattern was established and was discussed. Results indicated that the coactivation patterns of trunk muscles are similar between the low resistance(25% MIS) isoinertial testing and the maximal isometric testing (prime mover is consistent for each axial movement). There was “posture effect” during high resistance (50 and 75% MIS) isoinertial testing. High resistance testing leads to transfer of the prime to other muscles. It seems that the low resistance isoinertial testing is an adequate measurement item of low back function due to no “posture effect”. This result is consistent with other researches. So we suggest that isoinertial testing should adopt low resistance (25% MIS) measurement. The muscle NEMG, ipsilateral with the movement direction , were increased with the trunk angle. Contralateral muscles NEMG were not. The NEMG of the trunk muscles are not significantly changed in rotation except for ipsilateral erectus spinae which was increased slightly.
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